Merge branch 'direct-calls' into zefuzz-dc

140 files changed, 5424 insertions, 4572 deletions

diff --git a/src/core/ext/census/trace_context.c b/src/core/ext/census/trace_context.c
new file mode 100644
index 0000000000..fbb20d3448
--- /dev/null
+++ b/src/core/ext/census/trace_context.c
@@ -0,0 +1,86 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/ext/census/trace_context.h"
+
+#include <grpc/census.h>
+#include <grpc/support/log.h>
+#include <stdbool.h>
+
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+// This function assumes the TraceContext is valid.
+size_t encode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                            const size_t buf_size) {
+  // Create a stream that will write to our buffer.
+  pb_ostream_t stream = pb_ostream_from_buffer(buffer, buf_size);
+
+  // encode message
+  bool status = pb_encode(&stream, google_trace_TraceContext_fields, ctxt);
+
+  if (!status) {
+    gpr_log(GPR_DEBUG, "TraceContext encoding failed: %s",
+            PB_GET_ERROR(&stream));
+    return 0;
+  }
+
+  return stream.bytes_written;
+}
+
+bool decode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                          const size_t nbytes) {
+  // Create a stream that reads nbytes from the buffer.
+  pb_istream_t stream = pb_istream_from_buffer(buffer, nbytes);
+
+  // decode message
+  bool status = pb_decode(&stream, google_trace_TraceContext_fields, ctxt);
+
+  if (!status) {
+    gpr_log(GPR_DEBUG, "TraceContext decoding failed: %s",
+            PB_GET_ERROR(&stream));
+    return false;
+  }
+
+  // check fields
+  if (!ctxt->has_trace_id) {
+    gpr_log(GPR_DEBUG, "Invalid TraceContext: missing trace_id");
+    return false;
+  }
+  if (!ctxt->has_span_id) {
+    gpr_log(GPR_DEBUG, "Invalid TraceContext: missing span_id");
+    return false;
+  }
+
+  return true;
+}
diff --git a/src/core/ext/census/trace_context.h b/src/core/ext/census/trace_context.h
new file mode 100644
index 0000000000..ee71fef460
--- /dev/null
+++ b/src/core/ext/census/trace_context.h
@@ -0,0 +1,68 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* Functions for manipulating trace contexts as defined in
+   src/proto/census/trace.proto */
+#ifndef GRPC_CORE_EXT_CENSUS_TRACE_CONTEXT_H
+#define GRPC_CORE_EXT_CENSUS_TRACE_CONTEXT_H
+
+#include "src/core/ext/census/gen/trace_context.pb.h"
+
+/* Maximum number of bytes required to encode a TraceContext (31)
+1 byte for trace_id field
+1 byte for trace_id length
+1 byte for trace_id.hi field
+8 bytes for trace_id.hi (uint64_t)
+1 byte for trace_id.lo field
+8 bytes for trace_id.lo (uint64_t)
+1 byte for span_id field
+8 bytes for span_id (uint64_t)
+1 byte for is_sampled field
+1 byte for is_sampled (bool) */
+#define TRACE_MAX_CONTEXT_SIZE 31
+
+/* Encode a trace context (ctxt) into proto format to the buffer provided.  The
+size of buffer must be at least TRACE_MAX_CONTEXT_SIZE.  On success, returns the
+number of bytes successfully encoded into buffer.  On failure, returns 0. */
+size_t encode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                            const size_t buf_size);
+
+/* Decode a proto-encoded TraceContext from the provided buffer into the
+TraceContext structure (ctxt).  The function expects to be supplied the number
+of bytes to be read from buffer (nbytes).  This function will also validate that
+the TraceContext has a span_id and a trace_id, and will return false if either
+of these do not exist. On success, returns true and false otherwise. */
+bool decode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                          const size_t nbytes);
+
+#endif
diff --git a/src/core/ext/census/tracing.c b/src/core/ext/census/tracing.c
index 3b5d6dab2b..8f0e12296d 100644
--- a/src/core/ext/census/tracing.c
+++ b/src/core/ext/census/tracing.c
@@ -31,15 +31,19 @@
  *
  */
 
+//#include "src/core/ext/census/tracing.h"
+
 #include <grpc/census.h>
 
 /* TODO(aveitch): These are all placeholder implementations. */
 
-int census_trace_mask(const census_context *context) {
-  return CENSUS_TRACE_MASK_NONE;
-}
+// int census_trace_mask(const census_context *context) {
+//   return CENSUS_TRACE_MASK_NONE;
+// }
+
+// void census_set_trace_mask(int trace_mask) {}
 
-void census_set_trace_mask(int trace_mask) {}
+// void census_trace_print(census_context *context, uint32_t type,
+//                         const char *buffer, size_t n) {}
 
-void census_trace_print(census_context *context, uint32_t type,
-                        const char *buffer, size_t n) {}
+// void SetTracerParams(const Params& params);
diff --git a/src/core/ext/client_config/client_channel.c b/src/core/ext/client_config/client_channel.c
index 61e012578e..63797bfa1e 100644
--- a/src/core/ext/client_config/client_channel.c
+++ b/src/core/ext/client_config/client_channel.c
@@ -42,6 +42,7 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/useful.h>
 
+#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/subchannel.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/connected_channel.h"
@@ -63,6 +64,8 @@ typedef struct client_channel_channel_data {
   grpc_resolver *resolver;
   /** have we started resolving this channel */
   bool started_resolving;
+  /** client channel factory */
+  grpc_client_channel_factory *client_channel_factory;
 
   /** mutex protecting client configuration, including all
       variables below in this data structure */
@@ -173,20 +176,26 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_error *state_error = GRPC_ERROR_CREATE("No load balancing policy");
 
   if (chand->resolver_result != NULL) {
-    lb_policy = grpc_resolver_result_get_lb_policy(chand->resolver_result);
+    grpc_lb_policy_args lb_policy_args;
+    lb_policy_args.addresses =
+        grpc_resolver_result_get_addresses(chand->resolver_result);
+    lb_policy_args.additional_args =
+        grpc_resolver_result_get_lb_policy_args(chand->resolver_result);
+    lb_policy_args.client_channel_factory = chand->client_channel_factory;
+    lb_policy = grpc_lb_policy_create(
+        exec_ctx,
+        grpc_resolver_result_get_lb_policy_name(chand->resolver_result),
+        &lb_policy_args);
     if (lb_policy != NULL) {
-      GRPC_LB_POLICY_REF(lb_policy, "channel");
       GRPC_LB_POLICY_REF(lb_policy, "config_change");
       GRPC_ERROR_UNREF(state_error);
       state =
           grpc_lb_policy_check_connectivity(exec_ctx, lb_policy, &state_error);
     }
-
     grpc_resolver_result_unref(exec_ctx, chand->resolver_result);
+    chand->resolver_result = NULL;
   }
 
-  chand->resolver_result = NULL;
-
   if (lb_policy != NULL) {
     grpc_pollset_set_add_pollset_set(exec_ctx, lb_policy->interested_parties,
                                      chand->interested_parties);
@@ -346,6 +355,9 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
     grpc_resolver_shutdown(exec_ctx, chand->resolver);
     GRPC_RESOLVER_UNREF(exec_ctx, chand->resolver, "channel");
   }
+  if (chand->client_channel_factory != NULL) {
+    grpc_client_channel_factory_unref(exec_ctx, chand->client_channel_factory);
+  }
   if (chand->lb_policy != NULL) {
     grpc_pollset_set_del_pollset_set(exec_ctx,
                                      chand->lb_policy->interested_parties,
@@ -387,13 +399,15 @@ typedef struct client_channel_call_data {
   grpc_connected_subchannel *connected_subchannel;
   grpc_polling_entity *pollent;
 
-  grpc_transport_stream_op *waiting_ops;
+  grpc_transport_stream_op **waiting_ops;
   size_t waiting_ops_count;
   size_t waiting_ops_capacity;
 
   grpc_closure next_step;
 
   grpc_call_stack *owning_call;
+
+  grpc_linked_mdelem lb_token_mdelem;
 } call_data;
 
 static void add_waiting_locked(call_data *calld, grpc_transport_stream_op *op) {
@@ -404,7 +418,7 @@ static void add_waiting_locked(call_data *calld, grpc_transport_stream_op *op) {
         gpr_realloc(calld->waiting_ops,
                     calld->waiting_ops_capacity * sizeof(*calld->waiting_ops));
   }
-  calld->waiting_ops[calld->waiting_ops_count++] = *op;
+  calld->waiting_ops[calld->waiting_ops_count++] = op;
   GPR_TIMER_END("add_waiting_locked", 0);
 }
 
@@ -413,14 +427,14 @@ static void fail_locked(grpc_exec_ctx *exec_ctx, call_data *calld,
   size_t i;
   for (i = 0; i < calld->waiting_ops_count; i++) {
     grpc_transport_stream_op_finish_with_failure(
-        exec_ctx, &calld->waiting_ops[i], GRPC_ERROR_REF(error));
+        exec_ctx, calld->waiting_ops[i], GRPC_ERROR_REF(error));
   }
   calld->waiting_ops_count = 0;
   GRPC_ERROR_UNREF(error);
 }
 
 typedef struct {
-  grpc_transport_stream_op *ops;
+  grpc_transport_stream_op **ops;
   size_t nops;
   grpc_subchannel_call *call;
 } retry_ops_args;
@@ -429,7 +443,7 @@ static void retry_ops(grpc_exec_ctx *exec_ctx, void *args, grpc_error *error) {
   retry_ops_args *a = args;
   size_t i;
   for (i = 0; i < a->nops; i++) {
-    grpc_subchannel_call_process_op(exec_ctx, a->call, &a->ops[i]);
+    grpc_subchannel_call_process_op(exec_ctx, a->call, a->ops[i]);
   }
   GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, a->call, "retry_ops");
   gpr_free(a->ops);
@@ -437,6 +451,10 @@ static void retry_ops(grpc_exec_ctx *exec_ctx, void *args, grpc_error *error) {
 }
 
 static void retry_waiting_locked(grpc_exec_ctx *exec_ctx, call_data *calld) {
+  if (calld->waiting_ops_count == 0) {
+    return;
+  }
+
   retry_ops_args *a = gpr_malloc(sizeof(*a));
   a->ops = calld->waiting_ops;
   a->nops = calld->waiting_ops_count;
@@ -566,9 +584,11 @@ static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
     int r;
     GRPC_LB_POLICY_REF(lb_policy, "pick_subchannel");
     gpr_mu_unlock(&chand->mu);
-    r = grpc_lb_policy_pick(exec_ctx, lb_policy, calld->pollent,
-                            initial_metadata, initial_metadata_flags,
-                            connected_subchannel, on_ready);
+    const grpc_lb_policy_pick_args inputs = {calld->pollent, initial_metadata,
+                                             initial_metadata_flags,
+                                             &calld->lb_token_mdelem};
+    r = grpc_lb_policy_pick(exec_ctx, lb_policy, &inputs, connected_subchannel,
+                            NULL, on_ready);
     GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "pick_subchannel");
     GPR_TIMER_END("pick_subchannel", 0);
     return r;
@@ -759,10 +779,12 @@ const grpc_channel_filter grpc_client_channel_filter = {
     "client-channel",
 };
 
-void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
-                                      grpc_channel_stack *channel_stack,
-                                      grpc_resolver *resolver) {
+void grpc_client_channel_finish_initialization(
+    grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
+    grpc_resolver *resolver,
+    grpc_client_channel_factory *client_channel_factory) {
   /* post construction initialization: set the transport setup pointer */
+  GPR_ASSERT(client_channel_factory != NULL);
   grpc_channel_element *elem = grpc_channel_stack_last_element(channel_stack);
   channel_data *chand = elem->channel_data;
   gpr_mu_lock(&chand->mu);
@@ -776,6 +798,8 @@ void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
     grpc_resolver_next(exec_ctx, resolver, &chand->resolver_result,
                        &chand->on_resolver_result_changed);
   }
+  chand->client_channel_factory = client_channel_factory;
+  grpc_client_channel_factory_ref(client_channel_factory);
   gpr_mu_unlock(&chand->mu);
 }
 
diff --git a/src/core/ext/client_config/client_channel.h b/src/core/ext/client_config/client_channel.h
index 1e47ad34ad..abb5ac4d87 100644
--- a/src/core/ext/client_config/client_channel.h
+++ b/src/core/ext/client_config/client_channel.h
@@ -34,6 +34,7 @@
 #ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
 #define GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
 
+#include "src/core/ext/client_config/client_channel_factory.h"
 #include "src/core/ext/client_config/resolver.h"
 #include "src/core/lib/channel/channel_stack.h"
 
@@ -46,12 +47,12 @@
 
 extern const grpc_channel_filter grpc_client_channel_filter;
 
-/* post-construction initializer to let the client channel know which
-   transport setup it should cancel upon destruction, or initiate when it needs
-   a connection */
-void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
-                                      grpc_channel_stack *channel_stack,
-                                      grpc_resolver *resolver);
+/* Post-construction initializer to give the client channel its resolver
+   and factory. */
+void grpc_client_channel_finish_initialization(
+    grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
+    grpc_resolver *resolver,
+    grpc_client_channel_factory *client_channel_factory);
 
 grpc_connectivity_state grpc_client_channel_check_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect);
diff --git a/src/core/ext/client_config/lb_policy.c b/src/core/ext/client_config/lb_policy.c
index 8b980b2cca..903563ef6b 100644
--- a/src/core/ext/client_config/lb_policy.c
+++ b/src/core/ext/client_config/lb_policy.c
@@ -100,13 +100,11 @@ void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx,
 }
 
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                        grpc_polling_entity *pollent,
-                        grpc_metadata_batch *initial_metadata,
-                        uint32_t initial_metadata_flags,
-                        grpc_connected_subchannel **target,
+                        const grpc_lb_policy_pick_args *pick_args,
+                        grpc_connected_subchannel **target, void **user_data,
                         grpc_closure *on_complete) {
-  return policy->vtable->pick(exec_ctx, policy, pollent, initial_metadata,
-                              initial_metadata_flags, target, on_complete);
+  return policy->vtable->pick(exec_ctx, policy, pick_args, target, user_data,
+                              on_complete);
 }
 
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
diff --git a/src/core/ext/client_config/lb_policy.h b/src/core/ext/client_config/lb_policy.h
index a2f5446fc6..37c93d707c 100644
--- a/src/core/ext/client_config/lb_policy.h
+++ b/src/core/ext/client_config/lb_policy.h
@@ -53,23 +53,38 @@ struct grpc_lb_policy {
   grpc_pollset_set *interested_parties;
 };
 
+/** Extra arguments for an LB pick */
+typedef struct grpc_lb_policy_pick_args {
+  /** Parties interested in the pick's progress */
+  grpc_polling_entity *pollent;
+  /** Initial metadata associated with the picking call. */
+  grpc_metadata_batch *initial_metadata;
+  /** See \a GRPC_INITIAL_METADATA_* in grpc_types.h */
+  uint32_t initial_metadata_flags;
+  /** Storage for LB token in \a initial_metadata, or NULL if not used */
+  grpc_linked_mdelem *lb_token_mdelem_storage;
+} grpc_lb_policy_pick_args;
+
 struct grpc_lb_policy_vtable {
   void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
-
   void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 
-  /** implement grpc_lb_policy_pick */
+  /** \see grpc_lb_policy_pick */
   int (*pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-              grpc_polling_entity *pollent,
-              grpc_metadata_batch *initial_metadata,
-              uint32_t initial_metadata_flags,
-              grpc_connected_subchannel **target, grpc_closure *on_complete);
+              const grpc_lb_policy_pick_args *pick_args,
+              grpc_connected_subchannel **target, void **user_data,
+              grpc_closure *on_complete);
+
+  /** \see grpc_lb_policy_cancel_pick */
   void (*cancel_pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                       grpc_connected_subchannel **target);
+
+  /** \see grpc_lb_policy_cancel_picks */
   void (*cancel_picks)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                        uint32_t initial_metadata_flags_mask,
                        uint32_t initial_metadata_flags_eq);
 
+  /** \see grpc_lb_policy_ping_one */
   void (*ping_one)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                    grpc_closure *closure);
 
@@ -83,8 +98,7 @@ struct grpc_lb_policy_vtable {
 
   /** call notify when the connectivity state of a channel changes from *state.
       Updates *state with the new state of the policy. Calling with a NULL \a
-      state cancels the subscription.
-      */
+      state cancels the subscription.  */
   void (*notify_on_state_change)(grpc_exec_ctx *exec_ctx,
                                  grpc_lb_policy *policy,
                                  grpc_connectivity_state *state,
@@ -124,26 +138,34 @@ void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 void grpc_lb_policy_init(grpc_lb_policy *policy,
                          const grpc_lb_policy_vtable *vtable);
 
-/** Given initial metadata in \a initial_metadata, find an appropriate
-    target for this rpc, and 'return' it by calling \a on_complete after setting
-    \a target.
-    Picking can be asynchronous. Any IO should be done under \a pollent. */
+/** Find an appropriate target for this call, based on \a pick_args.
+    Picking can be synchronous or asynchronous. In the synchronous case, when a
+    pick is readily available, it'll be returned in \a target and a non-zero
+    value will be returned.
+    In the asynchronous case, zero is returned and \a on_complete will be called
+    once \a target and \a user_data have been set. Any IO should be done under
+    \a pick_args->pollent. The opaque \a user_data output argument corresponds
+    to information that may need be propagated from the LB policy. It may be
+    NULL. Errors are signaled by receiving a NULL \a *target. */
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                        grpc_polling_entity *pollent,
-                        grpc_metadata_batch *initial_metadata,
-                        uint32_t initial_metadata_flags,
-                        grpc_connected_subchannel **target,
+                        const grpc_lb_policy_pick_args *pick_args,
+                        grpc_connected_subchannel **target, void **user_data,
                         grpc_closure *on_complete);
 
+/** Perform a connected subchannel ping (see \a grpc_connected_subchannel_ping)
+    against one of the connected subchannels managed by \a policy. */
 void grpc_lb_policy_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                              grpc_closure *closure);
 
+/** Cancel picks for \a target.
+    The \a on_complete callback of the pending picks will be invoked with \a
+    *target set to NULL. */
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                                 grpc_connected_subchannel **target);
 
-/** Cancel all pending picks which have:
-    (initial_metadata_flags & initial_metadata_flags_mask) ==
-         initial_metadata_flags_eq */
+/** Cancel all pending picks for which their \a initial_metadata_flags (as given
+    in the call to \a grpc_lb_policy_pick) matches \a initial_metadata_flags_eq
+    when AND'd with \a initial_metadata_flags_mask */
 void grpc_lb_policy_cancel_picks(grpc_exec_ctx *exec_ctx,
                                  grpc_lb_policy *policy,
                                  uint32_t initial_metadata_flags_mask,
diff --git a/src/core/ext/client_config/lb_policy_factory.c b/src/core/ext/client_config/lb_policy_factory.c
index 70e46ef3cf..c17af91a09 100644
--- a/src/core/ext/client_config/lb_policy_factory.c
+++ b/src/core/ext/client_config/lb_policy_factory.c
@@ -31,8 +31,66 @@
  *
  */
 
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+
 #include "src/core/ext/client_config/lb_policy_factory.h"
 
+grpc_lb_addresses* grpc_lb_addresses_create(size_t num_addresses) {
+  grpc_lb_addresses* addresses = gpr_malloc(sizeof(grpc_lb_addresses));
+  addresses->num_addresses = num_addresses;
+  const size_t addresses_size = sizeof(grpc_lb_address) * num_addresses;
+  addresses->addresses = gpr_malloc(addresses_size);
+  memset(addresses->addresses, 0, addresses_size);
+  return addresses;
+}
+
+grpc_lb_addresses* grpc_lb_addresses_copy(grpc_lb_addresses* addresses,
+                                          void* (*user_data_copy)(void*)) {
+  grpc_lb_addresses* new_addresses =
+      grpc_lb_addresses_create(addresses->num_addresses);
+  memcpy(new_addresses->addresses, addresses->addresses,
+         sizeof(grpc_lb_address) * addresses->num_addresses);
+  for (size_t i = 0; i < addresses->num_addresses; ++i) {
+    if (new_addresses->addresses[i].balancer_name != NULL) {
+      new_addresses->addresses[i].balancer_name =
+          gpr_strdup(new_addresses->addresses[i].balancer_name);
+    }
+    if (user_data_copy != NULL) {
+      new_addresses->addresses[i].user_data =
+          user_data_copy(new_addresses->addresses[i].user_data);
+    }
+  }
+  return new_addresses;
+}
+
+void grpc_lb_addresses_set_address(grpc_lb_addresses* addresses, size_t index,
+                                   void* address, size_t address_len,
+                                   bool is_balancer, char* balancer_name,
+                                   void* user_data) {
+  GPR_ASSERT(index < addresses->num_addresses);
+  grpc_lb_address* target = &addresses->addresses[index];
+  memcpy(target->address.addr, address, address_len);
+  target->address.len = address_len;
+  target->is_balancer = is_balancer;
+  target->balancer_name = balancer_name;
+  target->user_data = user_data;
+}
+
+void grpc_lb_addresses_destroy(grpc_lb_addresses* addresses,
+                               void (*user_data_destroy)(void*)) {
+  for (size_t i = 0; i < addresses->num_addresses; ++i) {
+    gpr_free(addresses->addresses[i].balancer_name);
+    if (user_data_destroy != NULL) {
+      user_data_destroy(addresses->addresses[i].user_data);
+    }
+  }
+  gpr_free(addresses->addresses);
+  gpr_free(addresses);
+}
+
 void grpc_lb_policy_factory_ref(grpc_lb_policy_factory* factory) {
   factory->vtable->ref(factory);
 }
diff --git a/src/core/ext/client_config/lb_policy_factory.h b/src/core/ext/client_config/lb_policy_factory.h
index da1de3579a..54408c6308 100644
--- a/src/core/ext/client_config/lb_policy_factory.h
+++ b/src/core/ext/client_config/lb_policy_factory.h
@@ -36,9 +36,9 @@
 
 #include "src/core/ext/client_config/client_channel_factory.h"
 #include "src/core/ext/client_config/lb_policy.h"
-#include "src/core/lib/iomgr/resolve_address.h"
 
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/resolve_address.h"
 
 typedef struct grpc_lb_policy_factory grpc_lb_policy_factory;
 typedef struct grpc_lb_policy_factory_vtable grpc_lb_policy_factory_vtable;
@@ -47,9 +47,53 @@ struct grpc_lb_policy_factory {
   const grpc_lb_policy_factory_vtable *vtable;
 };
 
+/** A resolved address alongside any LB related information associated with it.
+ * \a user_data, if not NULL, contains opaque data meant to be consumed by the
+ * gRPC LB policy. Note that no all LB policies support \a user_data as input.
+ * Those who don't will simply ignore it and will correspondingly return NULL in
+ * their namesake pick() output argument. */
+typedef struct grpc_lb_address {
+  grpc_resolved_address address;
+  bool is_balancer;
+  char *balancer_name; /* For secure naming. */
+  void *user_data;
+} grpc_lb_address;
+
+typedef struct grpc_lb_addresses {
+  size_t num_addresses;
+  grpc_lb_address *addresses;
+} grpc_lb_addresses;
+
+/** Returns a grpc_addresses struct with enough space for
+ * \a num_addresses addresses. */
+grpc_lb_addresses *grpc_lb_addresses_create(size_t num_addresses);
+
+/** Creates a copy of \a addresses.  If \a user_data_copy is not NULL,
+ * it will be invoked to copy the \a user_data field of each address. */
+grpc_lb_addresses *grpc_lb_addresses_copy(grpc_lb_addresses *addresses,
+                                          void *(*user_data_copy)(void *));
+
+/** Sets the value of the address at index \a index of \a addresses.
+ * \a address is a socket address of length \a address_len.
+ * Takes ownership of \a balancer_name. */
+void grpc_lb_addresses_set_address(grpc_lb_addresses *addresses, size_t index,
+                                   void *address, size_t address_len,
+                                   bool is_balancer, char *balancer_name,
+                                   void *user_data);
+
+/** Destroys \a addresses.  If \a user_data_destroy is not NULL, it will
+ * be invoked to destroy the \a user_data field of each address. */
+void grpc_lb_addresses_destroy(grpc_lb_addresses *addresses,
+                               void (*user_data_destroy)(void *));
+
+/** Arguments passed to LB policies. */
+/* TODO(roth, ctiller): Consider replacing this struct with
+   grpc_channel_args.  See comment in resolver_result.h for details. */
 typedef struct grpc_lb_policy_args {
-  grpc_resolved_addresses *addresses;
+  grpc_lb_addresses *addresses;
   grpc_client_channel_factory *client_channel_factory;
+  /* Can be used to pass implementation-specific parameters to the LB policy. */
+  grpc_channel_args *additional_args;
 } grpc_lb_policy_args;
 
 struct grpc_lb_policy_factory_vtable {
diff --git a/src/core/ext/client_config/resolver_factory.h b/src/core/ext/client_config/resolver_factory.h
index f69bf79564..9ec5b9a70e 100644
--- a/src/core/ext/client_config/resolver_factory.h
+++ b/src/core/ext/client_config/resolver_factory.h
@@ -47,10 +47,7 @@ struct grpc_resolver_factory {
   const grpc_resolver_factory_vtable *vtable;
 };
 
-typedef struct grpc_resolver_args {
-  grpc_uri *uri;
-  grpc_client_channel_factory *client_channel_factory;
-} grpc_resolver_args;
+typedef struct grpc_resolver_args { grpc_uri *uri; } grpc_resolver_args;
 
 struct grpc_resolver_factory_vtable {
   void (*ref)(grpc_resolver_factory *factory);
diff --git a/src/core/ext/client_config/resolver_registry.c b/src/core/ext/client_config/resolver_registry.c
index e7a4abd568..b5308a140c 100644
--- a/src/core/ext/client_config/resolver_registry.c
+++ b/src/core/ext/client_config/resolver_registry.c
@@ -128,15 +128,13 @@ static grpc_resolver_factory *resolve_factory(const char *target,
   return factory;
 }
 
-grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_client_channel_factory *client_channel_factory) {
+grpc_resolver *grpc_resolver_create(const char *target) {
   grpc_uri *uri = NULL;
   grpc_resolver_factory *factory = resolve_factory(target, &uri);
   grpc_resolver *resolver;
   grpc_resolver_args args;
   memset(&args, 0, sizeof(args));
   args.uri = uri;
-  args.client_channel_factory = client_channel_factory;
   resolver = grpc_resolver_factory_create_resolver(factory, &args);
   grpc_uri_destroy(uri);
   return resolver;
diff --git a/src/core/ext/client_config/resolver_registry.h b/src/core/ext/client_config/resolver_registry.h
index 5ef1383cd3..92e248d548 100644
--- a/src/core/ext/client_config/resolver_registry.h
+++ b/src/core/ext/client_config/resolver_registry.h
@@ -55,8 +55,7 @@ void grpc_register_resolver_type(grpc_resolver_factory *factory);
     If a resolver factory was found, use it to instantiate a resolver and
     return it.
     If a resolver factory was not found, return NULL. */
-grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_client_channel_factory *client_channel_factory);
+grpc_resolver *grpc_resolver_create(const char *target);
 
 /** Find a resolver factory given a name and return an (owned-by-the-caller)
  *  reference to it */
diff --git a/src/core/ext/client_config/resolver_result.c b/src/core/ext/client_config/resolver_result.c
index c6c4166e83..59c9e7dc25 100644
--- a/src/core/ext/client_config/resolver_result.c
+++ b/src/core/ext/client_config/resolver_result.c
@@ -1,75 +1,87 @@
-/*
- *
- * Copyright 2015, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
+//
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
 
 #include "src/core/ext/client_config/resolver_result.h"
 
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/channel/channel_args.h"
 
 struct grpc_resolver_result {
   gpr_refcount refs;
-  grpc_lb_policy *lb_policy;
+  grpc_lb_addresses* addresses;
+  char* lb_policy_name;
+  grpc_channel_args* lb_policy_args;
 };
 
-grpc_resolver_result *grpc_resolver_result_create() {
-  grpc_resolver_result *c = gpr_malloc(sizeof(*c));
-  memset(c, 0, sizeof(*c));
-  gpr_ref_init(&c->refs, 1);
-  return c;
+grpc_resolver_result* grpc_resolver_result_create(
+    grpc_lb_addresses* addresses, const char* lb_policy_name,
+    grpc_channel_args* lb_policy_args) {
+  grpc_resolver_result* result = gpr_malloc(sizeof(*result));
+  memset(result, 0, sizeof(*result));
+  gpr_ref_init(&result->refs, 1);
+  result->addresses = addresses;
+  result->lb_policy_name = gpr_strdup(lb_policy_name);
+  result->lb_policy_args = lb_policy_args;
+  return result;
 }
 
-void grpc_resolver_result_ref(grpc_resolver_result *c) { gpr_ref(&c->refs); }
+void grpc_resolver_result_ref(grpc_resolver_result* result) {
+  gpr_ref(&result->refs);
+}
 
-void grpc_resolver_result_unref(grpc_exec_ctx *exec_ctx,
-                                grpc_resolver_result *c) {
-  if (gpr_unref(&c->refs)) {
-    if (c->lb_policy != NULL) {
-      GRPC_LB_POLICY_UNREF(exec_ctx, c->lb_policy, "resolver_result");
-    }
-    gpr_free(c);
+void grpc_resolver_result_unref(grpc_exec_ctx* exec_ctx,
+                                grpc_resolver_result* result) {
+  if (gpr_unref(&result->refs)) {
+    grpc_lb_addresses_destroy(result->addresses, NULL /* user_data_destroy */);
+    gpr_free(result->lb_policy_name);
+    grpc_channel_args_destroy(result->lb_policy_args);
+    gpr_free(result);
   }
 }
 
-void grpc_resolver_result_set_lb_policy(grpc_resolver_result *c,
-                                        grpc_lb_policy *lb_policy) {
-  GPR_ASSERT(c->lb_policy == NULL);
-  if (lb_policy) {
-    GRPC_LB_POLICY_REF(lb_policy, "resolver_result");
-  }
-  c->lb_policy = lb_policy;
+grpc_lb_addresses* grpc_resolver_result_get_addresses(
+    grpc_resolver_result* result) {
+  return result->addresses;
+}
+
+const char* grpc_resolver_result_get_lb_policy_name(
+    grpc_resolver_result* result) {
+  return result->lb_policy_name;
 }
 
-grpc_lb_policy *grpc_resolver_result_get_lb_policy(grpc_resolver_result *c) {
-  return c->lb_policy;
+grpc_channel_args* grpc_resolver_result_get_lb_policy_args(
+    grpc_resolver_result* result) {
+  return result->lb_policy_args;
 }
diff --git a/src/core/ext/client_config/resolver_result.h b/src/core/ext/client_config/resolver_result.h
index 402f7dbd7e..d4118b90e8 100644
--- a/src/core/ext/client_config/resolver_result.h
+++ b/src/core/ext/client_config/resolver_result.h
@@ -1,52 +1,71 @@
-/*
- *
- * Copyright 2015, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
+//
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
 
 #ifndef GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H
 #define GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H
 
-#include "src/core/ext/client_config/lb_policy.h"
+#include "src/core/ext/client_config/lb_policy_factory.h"
+#include "src/core/lib/iomgr/resolve_address.h"
 
-/** Results reported from a grpc_resolver. */
+// TODO(roth, ctiller): In the long term, we are considering replacing
+// the resolver_result data structure with grpc_channel_args.  The idea is
+// that the resolver will return a set of channel args that contains the
+// information that is currently in the resolver_result struct.  For
+// example, there will be specific args indicating the set of addresses
+// and the name of the LB policy to instantiate.  Note that if we did
+// this, we would probably want to change the data structure of
+// grpc_channel_args such to a hash table or AVL or some other data
+// structure that does not require linear search to find keys.
+
+/// Results reported from a grpc_resolver.
 typedef struct grpc_resolver_result grpc_resolver_result;
 
-grpc_resolver_result *grpc_resolver_result_create();
-void grpc_resolver_result_ref(grpc_resolver_result *client_config);
-void grpc_resolver_result_unref(grpc_exec_ctx *exec_ctx,
-                                grpc_resolver_result *client_config);
+/// Takes ownership of \a addresses and \a lb_policy_args.
+grpc_resolver_result* grpc_resolver_result_create(
+    grpc_lb_addresses* addresses, const char* lb_policy_name,
+    grpc_channel_args* lb_policy_args);
+void grpc_resolver_result_ref(grpc_resolver_result* result);
+void grpc_resolver_result_unref(grpc_exec_ctx* exec_ctx,
+                                grpc_resolver_result* result);
+
+/// Caller does NOT take ownership of result.
+grpc_lb_addresses* grpc_resolver_result_get_addresses(
+    grpc_resolver_result* result);
+
+/// Caller does NOT take ownership of result.
+const char* grpc_resolver_result_get_lb_policy_name(
+    grpc_resolver_result* result);
 
-void grpc_resolver_result_set_lb_policy(grpc_resolver_result *client_config,
-                                        grpc_lb_policy *lb_policy);
-grpc_lb_policy *grpc_resolver_result_get_lb_policy(
-    grpc_resolver_result *client_config);
+/// Caller does NOT take ownership of result.
+grpc_channel_args* grpc_resolver_result_get_lb_policy_args(
+    grpc_resolver_result* result);
 
 #endif /* GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H */
diff --git a/src/core/ext/client_config/subchannel.c b/src/core/ext/client_config/subchannel.c
index df35904b85..96595a38dd 100644
--- a/src/core/ext/client_config/subchannel.c
+++ b/src/core/ext/client_config/subchannel.c
@@ -33,6 +33,7 @@
 
 #include "src/core/ext/client_config/subchannel.h"
 
+#include <limits.h>
 #include <string.h>
 
 #include <grpc/support/alloc.h>
@@ -219,8 +220,8 @@ static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
                             : gpr_atm_no_barrier_fetch_add(&c->ref_pair, delta);
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
-          "SUBCHANNEL: %p % 12s 0x%08x -> 0x%08x [%s]", c, purpose, old_val,
-          old_val + delta, reason);
+          "SUBCHANNEL: %p %s 0x%08" PRIxPTR " -> 0x%08" PRIxPTR " [%s]", c,
+          purpose, old_val, old_val + delta, reason);
 #endif
   return old_val;
 }
@@ -347,21 +348,16 @@ grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
       }
       if (0 ==
           strcmp(c->args->args[i].key, GRPC_ARG_MAX_RECONNECT_BACKOFF_MS)) {
-        if (c->args->args[i].type == GRPC_ARG_INTEGER) {
-          if (c->args->args[i].value.integer >= 0) {
-            gpr_backoff_init(
-                &c->backoff_state, GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
-                GRPC_SUBCHANNEL_RECONNECT_JITTER,
-                GPR_MIN(c->args->args[i].value.integer,
-                        GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000),
-                c->args->args[i].value.integer);
-          } else {
-            gpr_log(GPR_ERROR, GRPC_ARG_MAX_RECONNECT_BACKOFF_MS
-                    " : must be non-negative");
-          }
-        } else {
-          gpr_log(GPR_ERROR,
-                  GRPC_ARG_MAX_RECONNECT_BACKOFF_MS " : must be an integer");
+        const grpc_integer_options options = {-1, 0, INT_MAX};
+        const int value =
+            grpc_channel_arg_get_integer(&c->args->args[i], options);
+        if (value >= 0) {
+          gpr_backoff_init(
+              &c->backoff_state, GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
+              GRPC_SUBCHANNEL_RECONNECT_JITTER,
+              GPR_MIN(value,
+                      GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000),
+              value);
         }
       }
     }
@@ -504,14 +500,13 @@ static void connected_subchannel_state_op(grpc_exec_ctx *exec_ctx,
                                           grpc_pollset_set *interested_parties,
                                           grpc_connectivity_state *state,
                                           grpc_closure *closure) {
-  grpc_transport_op op;
+  grpc_transport_op *op = grpc_make_transport_op(NULL);
   grpc_channel_element *elem;
-  memset(&op, 0, sizeof(op));
-  op.connectivity_state = state;
-  op.on_connectivity_state_change = closure;
-  op.bind_pollset_set = interested_parties;
+  op->connectivity_state = state;
+  op->on_connectivity_state_change = closure;
+  op->bind_pollset_set = interested_parties;
   elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
-  elem->filter->start_transport_op(exec_ctx, elem, &op);
+  elem->filter->start_transport_op(exec_ctx, elem, op);
 }
 
 void grpc_connected_subchannel_notify_on_state_change(
@@ -525,12 +520,11 @@ void grpc_connected_subchannel_notify_on_state_change(
 void grpc_connected_subchannel_ping(grpc_exec_ctx *exec_ctx,
                                     grpc_connected_subchannel *con,
                                     grpc_closure *closure) {
-  grpc_transport_op op;
+  grpc_transport_op *op = grpc_make_transport_op(NULL);
   grpc_channel_element *elem;
-  memset(&op, 0, sizeof(op));
-  op.send_ping = closure;
+  op->send_ping = closure;
   elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
-  elem->filter->start_transport_op(exec_ctx, elem, &op);
+  elem->filter->start_transport_op(exec_ctx, elem, op);
 }
 
 static void publish_transport_locked(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/ext/lb_policy/grpclb/grpclb.c b/src/core/ext/lb_policy/grpclb/grpclb.c
index af913d8a9d..36db8ab00d 100644
--- a/src/core/ext/lb_policy/grpclb/grpclb.c
+++ b/src/core/ext/lb_policy/grpclb/grpclb.c
@@ -76,9 +76,9 @@
  *    operations in progress over the old RR instance. This is done by
  *    decreasing the reference count on the old policy. The moment no more
  *    references are held on the old RR policy, it'll be destroyed and \a
- *    rr_connectivity_changed notified with a \a GRPC_CHANNEL_SHUTDOWN state.
- *    At this point we can transition to a new RR instance safely, which is done
- *    once again via \a rr_handover().
+ *    glb_rr_connectivity_changed notified with a \a GRPC_CHANNEL_SHUTDOWN
+ *    state. At this point we can transition to a new RR instance safely, which
+ *    is done once again via \a rr_handover().
  *
  *
  * Once a RR policy instance is in place (and getting updated as described),
@@ -96,6 +96,8 @@
  * - Implement LB service forwarding (point 2c. in the doc's diagram).
  */
 
+#include <errno.h>
+
 #include <string.h>
 
 #include <grpc/byte_buffer_reader.h>
@@ -105,22 +107,50 @@
 #include <grpc/support/string_util.h>
 
 #include "src/core/ext/client_config/client_channel_factory.h"
+#include "src/core/ext/client_config/lb_policy_factory.h"
 #include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/parse_address.h"
 #include "src/core/ext/lb_policy/grpclb/grpclb.h"
 #include "src/core/ext/lb_policy/grpclb/load_balancer_api.h"
+#include "src/core/lib/iomgr/sockaddr.h"
 #include "src/core/lib/iomgr/sockaddr_utils.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel.h"
+#include "src/core/lib/transport/static_metadata.h"
 
 int grpc_lb_glb_trace = 0;
 
+/* add lb_token of selected subchannel (address) to the call's initial
+ * metadata */
+static void initial_metadata_add_lb_token(
+    grpc_metadata_batch *initial_metadata,
+    grpc_linked_mdelem *lb_token_mdelem_storage, grpc_mdelem *lb_token) {
+  GPR_ASSERT(lb_token_mdelem_storage != NULL);
+  GPR_ASSERT(lb_token != NULL);
+  grpc_metadata_batch_add_tail(initial_metadata, lb_token_mdelem_storage,
+                               lb_token);
+}
+
 typedef struct wrapped_rr_closure_arg {
   /* the original closure. Usually a on_complete/notify cb for pick() and ping()
    * calls against the internal RR instance, respectively. */
   grpc_closure *wrapped_closure;
 
+  /* the pick's initial metadata, kept in order to append the LB token for the
+   * pick */
+  grpc_metadata_batch *initial_metadata;
+
+  /* the picked target, used to determine which LB token to add to the pick's
+   * initial metadata */
+  grpc_connected_subchannel **target;
+
+  /* the LB token associated with the pick */
+  grpc_mdelem *lb_token;
+
+  /* storage for the lb token initial metadata mdelem */
+  grpc_linked_mdelem *lb_token_mdelem_storage;
+
   /* The RR instance related to the closure */
   grpc_lb_policy *rr_policy;
 
@@ -141,9 +171,20 @@ static void wrapped_rr_closure(grpc_exec_ctx *exec_ctx, void *arg,
               (intptr_t)wc_arg->rr_policy);
     }
     GRPC_LB_POLICY_UNREF(exec_ctx, wc_arg->rr_policy, "wrapped_rr_closure");
+
+    /* if target is NULL, no pick has been made by the RR policy (eg, all
+     * addresses failed to connect). There won't be any user_data/token
+     * available */
+    if (wc_arg->target != NULL) {
+      initial_metadata_add_lb_token(wc_arg->initial_metadata,
+                                    wc_arg->lb_token_mdelem_storage,
+                                    GRPC_MDELEM_REF(wc_arg->lb_token));
+    }
   }
   GPR_ASSERT(wc_arg->wrapped_closure != NULL);
-  grpc_exec_ctx_sched(exec_ctx, wc_arg->wrapped_closure, error, NULL);
+
+  grpc_exec_ctx_sched(exec_ctx, wc_arg->wrapped_closure, GRPC_ERROR_REF(error),
+                      NULL);
   gpr_free(wc_arg->owning_pending_node);
 }
 
@@ -164,6 +205,9 @@ typedef struct pending_pick {
   /* the initial metadata for the pick. See grpc_lb_policy_pick() */
   grpc_metadata_batch *initial_metadata;
 
+  /* storage for the lb token initial metadata mdelem */
+  grpc_linked_mdelem *lb_token_mdelem_storage;
+
   /* bitmask passed to pick() and used for selective cancelling. See
    * grpc_lb_policy_cancel_picks() */
   uint32_t initial_metadata_flags;
@@ -180,20 +224,24 @@ typedef struct pending_pick {
   wrapped_rr_closure_arg wrapped_on_complete_arg;
 } pending_pick;
 
-static void add_pending_pick(pending_pick **root, grpc_polling_entity *pollent,
-                             grpc_metadata_batch *initial_metadata,
-                             uint32_t initial_metadata_flags,
+static void add_pending_pick(pending_pick **root,
+                             const grpc_lb_policy_pick_args *pick_args,
                              grpc_connected_subchannel **target,
                              grpc_closure *on_complete) {
   pending_pick *pp = gpr_malloc(sizeof(*pp));
   memset(pp, 0, sizeof(pending_pick));
   memset(&pp->wrapped_on_complete_arg, 0, sizeof(wrapped_rr_closure_arg));
   pp->next = *root;
-  pp->pollent = pollent;
+  pp->pollent = pick_args->pollent;
   pp->target = target;
-  pp->initial_metadata = initial_metadata;
-  pp->initial_metadata_flags = initial_metadata_flags;
+  pp->initial_metadata = pick_args->initial_metadata;
+  pp->initial_metadata_flags = pick_args->initial_metadata_flags;
+  pp->lb_token_mdelem_storage = pick_args->lb_token_mdelem_storage;
   pp->wrapped_on_complete_arg.wrapped_closure = on_complete;
+  pp->wrapped_on_complete_arg.target = target;
+  pp->wrapped_on_complete_arg.initial_metadata = pick_args->initial_metadata;
+  pp->wrapped_on_complete_arg.lb_token_mdelem_storage =
+      pick_args->lb_token_mdelem_storage;
   grpc_closure_init(&pp->wrapped_on_complete, wrapped_rr_closure,
                     &pp->wrapped_on_complete_arg);
   *root = pp;
@@ -252,6 +300,9 @@ typedef struct glb_lb_policy {
    * response has arrived. */
   grpc_grpclb_serverlist *serverlist;
 
+  /** addresses from \a serverlist */
+  grpc_lb_addresses *addresses;
+
   /** list of picks that are waiting on RR's policy connectivity */
   pending_pick *pending_picks;
 
@@ -279,58 +330,132 @@ struct rr_connectivity_data {
   glb_lb_policy *glb_policy;
 };
 
-static grpc_lb_policy *create_rr(grpc_exec_ctx *exec_ctx,
-                                 const grpc_grpclb_serverlist *serverlist,
-                                 glb_lb_policy *glb_policy) {
-  /* TODO(dgq): support mixed ip version */
-  GPR_ASSERT(serverlist != NULL && serverlist->num_servers > 0);
-  char **host_ports = gpr_malloc(sizeof(char *) * serverlist->num_servers);
-  for (size_t i = 0; i < serverlist->num_servers; ++i) {
-    gpr_join_host_port(&host_ports[i], serverlist->servers[i]->ip_address,
-                       serverlist->servers[i]->port);
+static bool is_server_valid(const grpc_grpclb_server *server, size_t idx,
+                            bool log) {
+  const grpc_grpclb_ip_address *ip = &server->ip_address;
+  if (server->port >> 16 != 0) {
+    if (log) {
+      gpr_log(GPR_ERROR,
+              "Invalid port '%d' at index %zu of serverlist. Ignoring.",
+              server->port, idx);
+    }
+    return false;
   }
 
-  size_t uri_path_len;
-  char *concat_ipports = gpr_strjoin_sep(
-      (const char **)host_ports, serverlist->num_servers, ",", &uri_path_len);
+  if (ip->size != 4 && ip->size != 16) {
+    if (log) {
+      gpr_log(GPR_ERROR,
+              "Expected IP to be 4 or 16 bytes, got %d at index %zu of "
+              "serverlist. Ignoring",
+              ip->size, idx);
+    }
+    return false;
+  }
+  return true;
+}
 
-  grpc_lb_policy_args args;
-  args.client_channel_factory = glb_policy->cc_factory;
-  args.addresses = gpr_malloc(sizeof(grpc_resolved_addresses));
-  args.addresses->naddrs = serverlist->num_servers;
-  args.addresses->addrs =
-      gpr_malloc(sizeof(grpc_resolved_address) * args.addresses->naddrs);
-  size_t out_addrs_idx = 0;
+/* Returns addresses extracted from \a serverlist. */
+static grpc_lb_addresses *process_serverlist(
+    const grpc_grpclb_serverlist *serverlist) {
+  size_t num_valid = 0;
+  /* first pass: count how many are valid in order to allocate the necessary
+   * memory in a single block */
   for (size_t i = 0; i < serverlist->num_servers; ++i) {
-    grpc_uri uri;
-    struct sockaddr_storage sa;
-    size_t sa_len;
-    uri.path = host_ports[i];
-    if (parse_ipv4(&uri, &sa, &sa_len)) { /* TODO(dgq): add support for ipv6 */
-      memcpy(args.addresses->addrs[out_addrs_idx].addr, &sa, sa_len);
-      args.addresses->addrs[out_addrs_idx].len = sa_len;
-      ++out_addrs_idx;
+    if (is_server_valid(serverlist->servers[i], i, true)) ++num_valid;
+  }
+  if (num_valid == 0) return NULL;
+
+  grpc_lb_addresses *lb_addresses = grpc_lb_addresses_create(num_valid);
+
+  /* second pass: actually populate the addresses and LB tokens (aka user data
+   * to the outside world) to be read by the RR policy during its creation.
+   * Given that the validity tests are very cheap, they are performed again
+   * instead of marking the valid ones during the first pass, as this would
+   * incurr in an allocation due to the arbitrary number of server */
+  size_t addr_idx = 0;
+  for (size_t sl_idx = 0; sl_idx < serverlist->num_servers; ++sl_idx) {
+    GPR_ASSERT(addr_idx < num_valid);
+    const grpc_grpclb_server *server = serverlist->servers[sl_idx];
+    if (!is_server_valid(serverlist->servers[sl_idx], sl_idx, false)) continue;
+
+    /* address processing */
+    const uint16_t netorder_port = htons((uint16_t)server->port);
+    /* the addresses are given in binary format (a in(6)_addr struct) in
+     * server->ip_address.bytes. */
+    const grpc_grpclb_ip_address *ip = &server->ip_address;
+    grpc_resolved_address addr;
+    memset(&addr, 0, sizeof(addr));
+    if (ip->size == 4) {
+      addr.len = sizeof(struct sockaddr_in);
+      struct sockaddr_in *addr4 = (struct sockaddr_in *)&addr.addr;
+      addr4->sin_family = AF_INET;
+      memcpy(&addr4->sin_addr, ip->bytes, ip->size);
+      addr4->sin_port = netorder_port;
+    } else if (ip->size == 16) {
+      addr.len = sizeof(struct sockaddr_in6);
+      struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)&addr.addr;
+      addr6->sin6_family = AF_INET;
+      memcpy(&addr6->sin6_addr, ip->bytes, ip->size);
+      addr6->sin6_port = netorder_port;
+    }
+
+    /* lb token processing */
+    void *user_data;
+    if (server->has_load_balance_token) {
+      const size_t lb_token_size =
+          GPR_ARRAY_SIZE(server->load_balance_token) - 1;
+      grpc_mdstr *lb_token_mdstr = grpc_mdstr_from_buffer(
+          (uint8_t *)server->load_balance_token, lb_token_size);
+      user_data = grpc_mdelem_from_metadata_strings(
+          GRPC_MDSTR_LOAD_REPORTING_INITIAL, lb_token_mdstr);
     } else {
-      gpr_log(GPR_ERROR, "Invalid LB service address '%s', ignoring.",
-              host_ports[i]);
+      gpr_log(GPR_ERROR,
+              "Missing LB token for backend address '%s'. The empty token will "
+              "be used instead",
+              grpc_sockaddr_to_uri((struct sockaddr *)&addr.addr));
+      user_data = GRPC_MDELEM_LOAD_REPORTING_INITIAL_EMPTY;
     }
+
+    grpc_lb_addresses_set_address(lb_addresses, addr_idx, &addr.addr, addr.len,
+                                  false /* is_balancer */,
+                                  NULL /* balancer_name */, user_data);
+    ++addr_idx;
   }
+  GPR_ASSERT(addr_idx == num_valid);
+
+  return lb_addresses;
+}
+
+/* A plugin for grpc_lb_addresses_destroy that unrefs the LB token metadata. */
+static void lb_token_destroy(void *token) {
+  if (token != NULL) GRPC_MDELEM_UNREF(token);
+}
+
+static grpc_lb_policy *create_rr(grpc_exec_ctx *exec_ctx,
+                                 const grpc_grpclb_serverlist *serverlist,
+                                 glb_lb_policy *glb_policy) {
+  GPR_ASSERT(serverlist != NULL && serverlist->num_servers > 0);
+
+  grpc_lb_policy_args args;
+  memset(&args, 0, sizeof(args));
+  args.client_channel_factory = glb_policy->cc_factory;
+  args.addresses = process_serverlist(serverlist);
 
   grpc_lb_policy *rr = grpc_lb_policy_create(exec_ctx, "round_robin", &args);
 
-  gpr_free(concat_ipports);
-  for (size_t i = 0; i < serverlist->num_servers; i++) {
-    gpr_free(host_ports[i]);
+  if (glb_policy->addresses != NULL) {
+    /* dispose of the previous version */
+    grpc_lb_addresses_destroy(glb_policy->addresses, lb_token_destroy);
   }
-  gpr_free(host_ports);
-  gpr_free(args.addresses->addrs);
-  gpr_free(args.addresses);
+  glb_policy->addresses = args.addresses;
+
   return rr;
 }
 
 static void rr_handover(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
                         grpc_error *error) {
-  GRPC_ERROR_REF(error);
+  GPR_ASSERT(glb_policy->serverlist != NULL &&
+             glb_policy->serverlist->num_servers > 0);
   glb_policy->rr_policy =
       create_rr(exec_ctx, glb_policy->serverlist, glb_policy);
 
@@ -345,8 +470,8 @@ static void rr_handover(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
       exec_ctx, glb_policy->rr_policy, &glb_policy->rr_connectivity->state,
       &glb_policy->rr_connectivity->on_change);
   grpc_connectivity_state_set(exec_ctx, &glb_policy->state_tracker,
-                              glb_policy->rr_connectivity->state, error,
-                              "rr_handover");
+                              glb_policy->rr_connectivity->state,
+                              GRPC_ERROR_REF(error), "rr_handover");
   grpc_lb_policy_exit_idle(exec_ctx, glb_policy->rr_policy);
 
   /* flush pending ops */
@@ -359,9 +484,12 @@ static void rr_handover(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
       gpr_log(GPR_INFO, "Pending pick about to PICK from 0x%" PRIxPTR "",
               (intptr_t)glb_policy->rr_policy);
     }
-    grpc_lb_policy_pick(exec_ctx, glb_policy->rr_policy, pp->pollent,
-                        pp->initial_metadata, pp->initial_metadata_flags,
-                        pp->target, &pp->wrapped_on_complete);
+    const grpc_lb_policy_pick_args pick_args = {
+        pp->pollent, pp->initial_metadata, pp->initial_metadata_flags,
+        pp->lb_token_mdelem_storage};
+    grpc_lb_policy_pick(exec_ctx, glb_policy->rr_policy, &pick_args, pp->target,
+                        (void **)&pp->wrapped_on_complete_arg.lb_token,
+                        &pp->wrapped_on_complete);
     pp->wrapped_on_complete_arg.owning_pending_node = pp;
   }
 
@@ -378,13 +506,13 @@ static void rr_handover(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
                             &pping->wrapped_notify);
     pping->wrapped_notify_arg.owning_pending_node = pping;
   }
-  GRPC_ERROR_UNREF(error);
 }
 
-static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
-                                    grpc_error *error) {
+static void glb_rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
+                                        grpc_error *error) {
   rr_connectivity_data *rr_conn_data = arg;
   glb_lb_policy *glb_policy = rr_conn_data->glb_policy;
+
   if (rr_conn_data->state == GRPC_CHANNEL_SHUTDOWN) {
     if (glb_policy->serverlist != NULL) {
       /* a RR policy is shutting down but there's a serverlist available ->
@@ -398,8 +526,8 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
     if (error == GRPC_ERROR_NONE) {
       /* RR not shutting down. Mimic the RR's policy state */
       grpc_connectivity_state_set(exec_ctx, &glb_policy->state_tracker,
-                                  rr_conn_data->state, error,
-                                  "rr_connectivity_changed");
+                                  rr_conn_data->state, GRPC_ERROR_REF(error),
+                                  "glb_rr_connectivity_changed");
       /* resubscribe */
       grpc_lb_policy_notify_on_state_change(exec_ctx, glb_policy->rr_policy,
                                             &rr_conn_data->state,
@@ -408,41 +536,63 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
       gpr_free(rr_conn_data);
     }
   }
-  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_lb_policy *glb_create(grpc_exec_ctx *exec_ctx,
                                   grpc_lb_policy_factory *factory,
                                   grpc_lb_policy_args *args) {
+  /* Count the number of gRPC-LB addresses. There must be at least one.
+   * TODO(roth): For now, we ignore non-balancer addresses, but in the
+   * future, we may change the behavior such that we fall back to using
+   * the non-balancer addresses if we cannot reach any balancers. At that
+   * time, this should be changed to allow a list with no balancer addresses,
+   * since the resolver might fail to return a balancer address even when
+   * this is the right LB policy to use. */
+  size_t num_grpclb_addrs = 0;
+  for (size_t i = 0; i < args->addresses->num_addresses; ++i) {
+    if (args->addresses->addresses[i].is_balancer) ++num_grpclb_addrs;
+  }
+  if (num_grpclb_addrs == 0) return NULL;
+
   glb_lb_policy *glb_policy = gpr_malloc(sizeof(*glb_policy));
   memset(glb_policy, 0, sizeof(*glb_policy));
 
   /* All input addresses in args->addresses come from a resolver that claims
-   * they are LB services. It's the resolver's responsibility to make sure this
+   * they are LB services. It's the resolver's responsibility to make sure
+   * this
    * policy is only instantiated and used in that case.
    *
    * Create a client channel over them to communicate with a LB service */
   glb_policy->cc_factory = args->client_channel_factory;
   GPR_ASSERT(glb_policy->cc_factory != NULL);
-  if (args->addresses->naddrs == 0) {
-    return NULL;
-  }
 
-  /* construct a target from the args->addresses, in the form
+  /* construct a target from the addresses in args, given in the form
    * ipvX://ip1:port1,ip2:port2,...
    * TODO(dgq): support mixed ip version */
-  char **addr_strs = gpr_malloc(sizeof(char *) * args->addresses->naddrs);
-  addr_strs[0] =
-      grpc_sockaddr_to_uri((const struct sockaddr *)&args->addresses->addrs[0]);
-  for (size_t i = 1; i < args->addresses->naddrs; i++) {
-    GPR_ASSERT(grpc_sockaddr_to_string(
-                   &addr_strs[i],
-                   (const struct sockaddr *)&args->addresses->addrs[i],
-                   true) == 0);
+  char **addr_strs = gpr_malloc(sizeof(char *) * num_grpclb_addrs);
+  size_t addr_index = 0;
+  for (size_t i = 0; i < args->addresses->num_addresses; i++) {
+    if (args->addresses->addresses[i].user_data != NULL) {
+      gpr_log(GPR_ERROR,
+              "This LB policy doesn't support user data. It will be ignored");
+    }
+    if (args->addresses->addresses[i].is_balancer) {
+      if (addr_index == 0) {
+        addr_strs[addr_index++] = grpc_sockaddr_to_uri(
+            (const struct sockaddr *)&args->addresses->addresses[i]
+                .address.addr);
+      } else {
+        GPR_ASSERT(grpc_sockaddr_to_string(
+                       &addr_strs[addr_index++],
+                       (const struct sockaddr *)&args->addresses->addresses[i]
+                           .address.addr,
+                       true) == 0);
+      }
+    }
   }
   size_t uri_path_len;
-  char *target_uri_str = gpr_strjoin_sep(
-      (const char **)addr_strs, args->addresses->naddrs, ",", &uri_path_len);
+  char *target_uri_str = gpr_strjoin_sep((const char **)addr_strs,
+                                         num_grpclb_addrs, ",", &uri_path_len);
 
   /* will pick using pick_first */
   glb_policy->lb_channel = grpc_client_channel_factory_create_channel(
@@ -450,7 +600,7 @@ static grpc_lb_policy *glb_create(grpc_exec_ctx *exec_ctx,
       GRPC_CLIENT_CHANNEL_TYPE_LOAD_BALANCING, NULL);
 
   gpr_free(target_uri_str);
-  for (size_t i = 0; i < args->addresses->naddrs; i++) {
+  for (size_t i = 0; i < num_grpclb_addrs; i++) {
     gpr_free(addr_strs[i]);
   }
   gpr_free(addr_strs);
@@ -463,7 +613,7 @@ static grpc_lb_policy *glb_create(grpc_exec_ctx *exec_ctx,
   rr_connectivity_data *rr_connectivity =
       gpr_malloc(sizeof(rr_connectivity_data));
   memset(rr_connectivity, 0, sizeof(rr_connectivity_data));
-  grpc_closure_init(&rr_connectivity->on_change, rr_connectivity_changed,
+  grpc_closure_init(&rr_connectivity->on_change, glb_rr_connectivity_changed,
                     rr_connectivity);
   rr_connectivity->glb_policy = glb_policy;
   glb_policy->rr_connectivity = rr_connectivity;
@@ -486,6 +636,7 @@ static void glb_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
     grpc_grpclb_destroy_serverlist(glb_policy->serverlist);
   }
   gpr_mu_destroy(&glb_policy->mu);
+  grpc_lb_addresses_destroy(glb_policy->addresses, lb_token_destroy);
   gpr_free(glb_policy);
 }
 
@@ -546,7 +697,6 @@ static void glb_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
       *target = NULL;
       grpc_exec_ctx_sched(exec_ctx, &pp->wrapped_on_complete,
                           GRPC_ERROR_CANCELLED, NULL);
-      gpr_free(pp);
     } else {
       pp->next = glb_policy->pending_picks;
       glb_policy->pending_picks = pp;
@@ -576,7 +726,6 @@ static void glb_cancel_picks(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
           exec_ctx, pp->pollent, glb_policy->base.interested_parties);
       grpc_exec_ctx_sched(exec_ctx, &pp->wrapped_on_complete,
                           GRPC_ERROR_CANCELLED, NULL);
-      gpr_free(pp);
     } else {
       pp->next = glb_policy->pending_picks;
       glb_policy->pending_picks = pp;
@@ -603,12 +752,21 @@ static void glb_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 static int glb_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                    grpc_polling_entity *pollent,
-                    grpc_metadata_batch *initial_metadata,
-                    uint32_t initial_metadata_flags,
-                    grpc_connected_subchannel **target,
+                    const grpc_lb_policy_pick_args *pick_args,
+                    grpc_connected_subchannel **target, void **user_data,
                     grpc_closure *on_complete) {
   glb_lb_policy *glb_policy = (glb_lb_policy *)pol;
+
+  if (pick_args->lb_token_mdelem_storage == NULL) {
+    *target = NULL;
+    grpc_exec_ctx_sched(
+        exec_ctx, on_complete,
+        GRPC_ERROR_CREATE("No mdelem storage for the LB token. Load reporting "
+                          "won't work without it. Failing"),
+        NULL);
+    return 1;
+  }
+
   gpr_mu_lock(&glb_policy->mu);
   int r;
 
@@ -620,29 +778,36 @@ static int glb_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     GRPC_LB_POLICY_REF(glb_policy->rr_policy, "glb_pick");
     memset(&glb_policy->wc_arg, 0, sizeof(wrapped_rr_closure_arg));
     glb_policy->wc_arg.rr_policy = glb_policy->rr_policy;
+    glb_policy->wc_arg.target = target;
     glb_policy->wc_arg.wrapped_closure = on_complete;
+    glb_policy->wc_arg.lb_token_mdelem_storage =
+        pick_args->lb_token_mdelem_storage;
+    glb_policy->wc_arg.initial_metadata = pick_args->initial_metadata;
+    glb_policy->wc_arg.owning_pending_node = NULL;
     grpc_closure_init(&glb_policy->wrapped_on_complete, wrapped_rr_closure,
                       &glb_policy->wc_arg);
-    r = grpc_lb_policy_pick(exec_ctx, glb_policy->rr_policy, pollent,
-                            initial_metadata, initial_metadata_flags, target,
+
+    r = grpc_lb_policy_pick(exec_ctx, glb_policy->rr_policy, pick_args, target,
+                            (void **)&glb_policy->wc_arg.lb_token,
                             &glb_policy->wrapped_on_complete);
     if (r != 0) {
-      /* the call to grpc_lb_policy_pick has been sychronous. Unreffing the RR
-       * policy and notify the original callback */
-      glb_policy->wc_arg.wrapped_closure = NULL;
+      /* synchronous grpc_lb_policy_pick call. Unref the RR policy. */
       if (grpc_lb_glb_trace) {
         gpr_log(GPR_INFO, "Unreffing RR (0x%" PRIxPTR ")",
                 (intptr_t)glb_policy->wc_arg.rr_policy);
       }
       GRPC_LB_POLICY_UNREF(exec_ctx, glb_policy->wc_arg.rr_policy, "glb_pick");
-      grpc_exec_ctx_sched(exec_ctx, glb_policy->wc_arg.wrapped_closure,
-                          GRPC_ERROR_NONE, NULL);
+
+      /* add the load reporting initial metadata */
+      initial_metadata_add_lb_token(
+          pick_args->initial_metadata, pick_args->lb_token_mdelem_storage,
+          GRPC_MDELEM_REF(glb_policy->wc_arg.lb_token));
     }
   } else {
-    grpc_polling_entity_add_to_pollset_set(exec_ctx, pollent,
+    grpc_polling_entity_add_to_pollset_set(exec_ctx, pick_args->pollent,
                                            glb_policy->base.interested_parties);
-    add_pending_pick(&glb_policy->pending_picks, pollent, initial_metadata,
-                     initial_metadata_flags, target, on_complete);
+    add_pending_pick(&glb_policy->pending_picks, pick_args, target,
+                     on_complete);
 
     if (!glb_policy->started_picking) {
       start_picking(exec_ctx, glb_policy);
@@ -702,9 +867,6 @@ typedef struct lb_client_data {
   /* called once initial metadata's been sent */
   grpc_closure md_sent;
 
-  /* called once initial metadata's been received */
-  grpc_closure md_rcvd;
-
   /* called once the LoadBalanceRequest has been sent to the LB server. See
    * src/proto/grpc/.../load_balancer.proto */
   grpc_closure req_sent;
@@ -741,7 +903,6 @@ typedef struct lb_client_data {
 } lb_client_data;
 
 static void md_sent_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
-static void md_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 static void req_sent_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 static void res_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 static void close_sent_cb(grpc_exec_ctx *exec_ctx, void *arg,
@@ -756,7 +917,6 @@ static lb_client_data *lb_client_data_create(glb_lb_policy *glb_policy) {
   gpr_mu_init(&lb_client->mu);
   grpc_closure_init(&lb_client->md_sent, md_sent_cb, lb_client);
 
-  grpc_closure_init(&lb_client->md_rcvd, md_recv_cb, lb_client);
   grpc_closure_init(&lb_client->req_sent, req_sent_cb, lb_client);
   grpc_closure_init(&lb_client->res_rcvd, res_recv_cb, lb_client);
   grpc_closure_init(&lb_client->close_sent, close_sent_cb, lb_client);
@@ -855,23 +1015,6 @@ static void md_sent_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   grpc_op ops[1];
   memset(ops, 0, sizeof(ops));
   grpc_op *op = ops;
-  op->op = GRPC_OP_RECV_INITIAL_METADATA;
-  op->data.recv_initial_metadata = &lb_client->initial_metadata_recv;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  grpc_call_error call_error = grpc_call_start_batch_and_execute(
-      exec_ctx, lb_client->lb_call, ops, (size_t)(op - ops),
-      &lb_client->md_rcvd);
-  GPR_ASSERT(GRPC_CALL_OK == call_error);
-}
-
-static void md_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  lb_client_data *lb_client = arg;
-  GPR_ASSERT(lb_client->lb_call);
-  grpc_op ops[1];
-  memset(ops, 0, sizeof(ops));
-  grpc_op *op = ops;
 
   op->op = GRPC_OP_SEND_MESSAGE;
   op->data.send_message = lb_client->request_payload;
@@ -886,11 +1029,18 @@ static void md_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
 
 static void req_sent_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   lb_client_data *lb_client = arg;
+  GPR_ASSERT(lb_client->lb_call);
 
-  grpc_op ops[1];
+  grpc_op ops[2];
   memset(ops, 0, sizeof(ops));
   grpc_op *op = ops;
 
+  op->op = GRPC_OP_RECV_INITIAL_METADATA;
+  op->data.recv_initial_metadata = &lb_client->initial_metadata_recv;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+
   op->op = GRPC_OP_RECV_MESSAGE;
   op->data.recv_message = &lb_client->response_payload;
   op->flags = 0;
@@ -909,8 +1059,7 @@ static void res_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   grpc_op *op = ops;
   if (lb_client->response_payload != NULL) {
     /* Received data from the LB server. Look inside
-     * lb_client->response_payload, for
-     * a serverlist. */
+     * lb_client->response_payload, for a serverlist. */
     grpc_byte_buffer_reader bbr;
     grpc_byte_buffer_reader_init(&bbr, lb_client->response_payload);
     gpr_slice response_slice = grpc_byte_buffer_reader_readall(&bbr);
@@ -947,7 +1096,7 @@ static void res_recv_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
         } else {
           /* unref the RR policy, eventually leading to its substitution with a
            * new one constructed from the received serverlist (see
-           * rr_connectivity_changed) */
+           * glb_rr_connectivity_changed) */
           GRPC_LB_POLICY_UNREF(exec_ctx, lb_client->glb_policy->rr_policy,
                                "serverlist_received");
         }
@@ -1010,8 +1159,8 @@ static void srv_status_rcvd_cb(grpc_exec_ctx *exec_ctx, void *arg,
             lb_client->status, lb_client->status_details,
             lb_client->status_details_capacity);
   }
-  /* TODO(dgq): deal with stream termination properly (fire up another one? fail
-   * the original call?) */
+  /* TODO(dgq): deal with stream termination properly (fire up another one?
+   * fail the original call?) */
 }
 
 /* Code wiring the policy with the rest of the core */
diff --git a/src/core/ext/lb_policy/grpclb/load_balancer_api.c b/src/core/ext/lb_policy/grpclb/load_balancer_api.c
index f4720a1345..a8881004a0 100644
--- a/src/core/ext/lb_policy/grpclb/load_balancer_api.c
+++ b/src/core/ext/lb_policy/grpclb/load_balancer_api.c
@@ -57,6 +57,7 @@ static bool decode_serverlist(pb_istream_t *stream, const pb_field_t *field,
   if (dec_arg->first_pass) { /* count how many server do we have */
     grpc_grpclb_server server;
     if (!pb_decode(stream, grpc_lb_v1_Server_fields, &server)) {
+      gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(stream));
       return false;
     }
     dec_arg->num_servers++;
@@ -69,6 +70,7 @@ static bool decode_serverlist(pb_istream_t *stream, const pb_field_t *field,
           gpr_malloc(sizeof(grpc_grpclb_server *) * dec_arg->num_servers);
     }
     if (!pb_decode(stream, grpc_lb_v1_Server_fields, server)) {
+      gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(stream));
       return false;
     }
     dec_arg->servers[dec_arg->decoding_idx++] = server;
@@ -118,6 +120,7 @@ grpc_grpclb_initial_response *grpc_grpclb_initial_response_parse(
   grpc_grpclb_response res;
   memset(&res, 0, sizeof(grpc_grpclb_response));
   if (!pb_decode(&stream, grpc_lb_v1_LoadBalanceResponse_fields, &res)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
     return NULL;
   }
   grpc_grpclb_initial_response *initial_res =
@@ -145,6 +148,7 @@ grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
   arg.first_pass = true;
   status = pb_decode(&stream, grpc_lb_v1_LoadBalanceResponse_fields, &res);
   if (!status) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
     return NULL;
   }
 
@@ -152,6 +156,7 @@ grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
   status =
       pb_decode(&stream_at_start, grpc_lb_v1_LoadBalanceResponse_fields, &res);
   if (!status) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
     return NULL;
   }
 
diff --git a/src/core/ext/lb_policy/grpclb/load_balancer_api.h b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
index 9726c87a37..c1e73d08ef 100644
--- a/src/core/ext/lb_policy/grpclb/load_balancer_api.h
+++ b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
@@ -45,6 +45,7 @@ extern "C" {
 
 #define GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH 128
 
+typedef grpc_lb_v1_Server_ip_address_t grpc_grpclb_ip_address;
 typedef grpc_lb_v1_LoadBalanceRequest grpc_grpclb_request;
 typedef grpc_lb_v1_InitialLoadBalanceResponse grpc_grpclb_initial_response;
 typedef grpc_lb_v1_Server grpc_grpclb_server;
diff --git a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
index 52e11c40bb..afecb716fb 100644
--- a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
+++ b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
@@ -31,10 +31,11 @@
  *
  */
 /* Automatically generated nanopb constant definitions */
-/* Generated by nanopb-0.3.5-dev */
+/* Generated by nanopb-0.3.7-dev */
 
 #include "src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h"
 
+/* @@protoc_insertion_point(includes) */
 #if PB_PROTO_HEADER_VERSION != 30
 #error Regenerate this file with the current version of nanopb generator.
 #endif
@@ -72,8 +73,8 @@ const pb_field_t grpc_lb_v1_LoadBalanceResponse_fields[3] = {
 };
 
 const pb_field_t grpc_lb_v1_InitialLoadBalanceResponse_fields[3] = {
-    PB_FIELD(  2, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v1_InitialLoadBalanceResponse, load_balancer_delegate, load_balancer_delegate, 0),
-    PB_FIELD(  3, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v1_InitialLoadBalanceResponse, client_stats_report_interval, load_balancer_delegate, &grpc_lb_v1_Duration_fields),
+    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v1_InitialLoadBalanceResponse, load_balancer_delegate, load_balancer_delegate, 0),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v1_InitialLoadBalanceResponse, client_stats_report_interval, load_balancer_delegate, &grpc_lb_v1_Duration_fields),
     PB_LAST_FIELD
 };
 
@@ -84,7 +85,7 @@ const pb_field_t grpc_lb_v1_ServerList_fields[3] = {
 };
 
 const pb_field_t grpc_lb_v1_Server_fields[5] = {
-    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v1_Server, ip_address, ip_address, 0),
+    PB_FIELD(  1, BYTES   , OPTIONAL, STATIC  , FIRST, grpc_lb_v1_Server, ip_address, ip_address, 0),
     PB_FIELD(  2, INT32   , OPTIONAL, STATIC  , OTHER, grpc_lb_v1_Server, port, ip_address, 0),
     PB_FIELD(  3, STRING  , OPTIONAL, STATIC  , OTHER, grpc_lb_v1_Server, load_balance_token, port, 0),
     PB_FIELD(  4, BOOL    , OPTIONAL, STATIC  , OTHER, grpc_lb_v1_Server, drop_request, load_balance_token, 0),
@@ -116,3 +117,4 @@ PB_STATIC_ASSERT((pb_membersize(grpc_lb_v1_LoadBalanceRequest, initial_request)
 #endif
 
 
+/* @@protoc_insertion_point(eof) */
diff --git a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h
index 46fe588f72..53fed22bae 100644
--- a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h
+++ b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h
@@ -31,11 +31,12 @@
  *
  */
 /* Automatically generated nanopb header */
-/* Generated by nanopb-0.3.5-dev */
+/* Generated by nanopb-0.3.7-dev */
 
-#ifndef GRPC_CORE_EXT_LB_POLICY_GRPCLB_PROTO_GRPC_LB_V1_LOAD_BALANCER_PB_H
-#define GRPC_CORE_EXT_LB_POLICY_GRPCLB_PROTO_GRPC_LB_V1_LOAD_BALANCER_PB_H
+#ifndef PB_GRPC_LB_V1_LOAD_BALANCER_PB_H_INCLUDED
+#define PB_GRPC_LB_V1_LOAD_BALANCER_PB_H_INCLUDED
 #include "third_party/nanopb/pb.h"
+/* @@protoc_insertion_point(includes) */
 #if PB_PROTO_HEADER_VERSION != 30
 #error Regenerate this file with the current version of nanopb generator.
 #endif
@@ -52,6 +53,7 @@ typedef struct _grpc_lb_v1_ClientStats {
     int64_t client_rpc_errors;
     bool has_dropped_requests;
     int64_t dropped_requests;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_ClientStats) */
 } grpc_lb_v1_ClientStats;
 
 typedef struct _grpc_lb_v1_Duration {
@@ -59,22 +61,26 @@ typedef struct _grpc_lb_v1_Duration {
     int64_t seconds;
     bool has_nanos;
     int32_t nanos;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_Duration) */
 } grpc_lb_v1_Duration;
 
 typedef struct _grpc_lb_v1_InitialLoadBalanceRequest {
     bool has_name;
     char name[128];
+/* @@protoc_insertion_point(struct:grpc_lb_v1_InitialLoadBalanceRequest) */
 } grpc_lb_v1_InitialLoadBalanceRequest;
 
+typedef PB_BYTES_ARRAY_T(16) grpc_lb_v1_Server_ip_address_t;
 typedef struct _grpc_lb_v1_Server {
     bool has_ip_address;
-    char ip_address[46];
+    grpc_lb_v1_Server_ip_address_t ip_address;
     bool has_port;
     int32_t port;
     bool has_load_balance_token;
-    char load_balance_token[64];
+    char load_balance_token[65];
     bool has_drop_request;
     bool drop_request;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_Server) */
 } grpc_lb_v1_Server;
 
 typedef struct _grpc_lb_v1_InitialLoadBalanceResponse {
@@ -82,6 +88,7 @@ typedef struct _grpc_lb_v1_InitialLoadBalanceResponse {
     char load_balancer_delegate[64];
     bool has_client_stats_report_interval;
     grpc_lb_v1_Duration client_stats_report_interval;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_InitialLoadBalanceResponse) */
 } grpc_lb_v1_InitialLoadBalanceResponse;
 
 typedef struct _grpc_lb_v1_LoadBalanceRequest {
@@ -89,12 +96,14 @@ typedef struct _grpc_lb_v1_LoadBalanceRequest {
     grpc_lb_v1_InitialLoadBalanceRequest initial_request;
     bool has_client_stats;
     grpc_lb_v1_ClientStats client_stats;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_LoadBalanceRequest) */
 } grpc_lb_v1_LoadBalanceRequest;
 
 typedef struct _grpc_lb_v1_ServerList {
     pb_callback_t servers;
     bool has_expiration_interval;
     grpc_lb_v1_Duration expiration_interval;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_ServerList) */
 } grpc_lb_v1_ServerList;
 
 typedef struct _grpc_lb_v1_LoadBalanceResponse {
@@ -102,6 +111,7 @@ typedef struct _grpc_lb_v1_LoadBalanceResponse {
     grpc_lb_v1_InitialLoadBalanceResponse initial_response;
     bool has_server_list;
     grpc_lb_v1_ServerList server_list;
+/* @@protoc_insertion_point(struct:grpc_lb_v1_LoadBalanceResponse) */
 } grpc_lb_v1_LoadBalanceResponse;
 
 /* Default values for struct fields */
@@ -114,7 +124,7 @@ typedef struct _grpc_lb_v1_LoadBalanceResponse {
 #define grpc_lb_v1_LoadBalanceResponse_init_default {false, grpc_lb_v1_InitialLoadBalanceResponse_init_default, false, grpc_lb_v1_ServerList_init_default}
 #define grpc_lb_v1_InitialLoadBalanceResponse_init_default {false, "", false, grpc_lb_v1_Duration_init_default}
 #define grpc_lb_v1_ServerList_init_default       {{{NULL}, NULL}, false, grpc_lb_v1_Duration_init_default}
-#define grpc_lb_v1_Server_init_default           {false, "", false, 0, false, "", false, 0}
+#define grpc_lb_v1_Server_init_default           {false, {0, {0}}, false, 0, false, "", false, 0}
 #define grpc_lb_v1_Duration_init_zero            {false, 0, false, 0}
 #define grpc_lb_v1_LoadBalanceRequest_init_zero  {false, grpc_lb_v1_InitialLoadBalanceRequest_init_zero, false, grpc_lb_v1_ClientStats_init_zero}
 #define grpc_lb_v1_InitialLoadBalanceRequest_init_zero {false, ""}
@@ -122,7 +132,7 @@ typedef struct _grpc_lb_v1_LoadBalanceResponse {
 #define grpc_lb_v1_LoadBalanceResponse_init_zero {false, grpc_lb_v1_InitialLoadBalanceResponse_init_zero, false, grpc_lb_v1_ServerList_init_zero}
 #define grpc_lb_v1_InitialLoadBalanceResponse_init_zero {false, "", false, grpc_lb_v1_Duration_init_zero}
 #define grpc_lb_v1_ServerList_init_zero          {{{NULL}, NULL}, false, grpc_lb_v1_Duration_init_zero}
-#define grpc_lb_v1_Server_init_zero              {false, "", false, 0, false, "", false, 0}
+#define grpc_lb_v1_Server_init_zero              {false, {0, {0}}, false, 0, false, "", false, 0}
 
 /* Field tags (for use in manual encoding/decoding) */
 #define grpc_lb_v1_ClientStats_total_requests_tag 1
@@ -135,8 +145,8 @@ typedef struct _grpc_lb_v1_LoadBalanceResponse {
 #define grpc_lb_v1_Server_port_tag               2
 #define grpc_lb_v1_Server_load_balance_token_tag 3
 #define grpc_lb_v1_Server_drop_request_tag       4
-#define grpc_lb_v1_InitialLoadBalanceResponse_load_balancer_delegate_tag 2
-#define grpc_lb_v1_InitialLoadBalanceResponse_client_stats_report_interval_tag 3
+#define grpc_lb_v1_InitialLoadBalanceResponse_load_balancer_delegate_tag 1
+#define grpc_lb_v1_InitialLoadBalanceResponse_client_stats_report_interval_tag 2
 #define grpc_lb_v1_LoadBalanceRequest_initial_request_tag 1
 #define grpc_lb_v1_LoadBalanceRequest_client_stats_tag 2
 #define grpc_lb_v1_ServerList_servers_tag        1
@@ -161,7 +171,8 @@ extern const pb_field_t grpc_lb_v1_Server_fields[5];
 #define grpc_lb_v1_ClientStats_size              33
 #define grpc_lb_v1_LoadBalanceResponse_size      (98 + grpc_lb_v1_ServerList_size)
 #define grpc_lb_v1_InitialLoadBalanceResponse_size 90
-#define grpc_lb_v1_Server_size                   127
+/* grpc_lb_v1_ServerList_size depends on runtime parameters */
+#define grpc_lb_v1_Server_size                   98
 
 /* Message IDs (where set with "msgid" option) */
 #ifdef PB_MSGID
@@ -174,5 +185,6 @@ extern const pb_field_t grpc_lb_v1_Server_fields[5];
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
+/* @@protoc_insertion_point(eof) */
 
 #endif
diff --git a/src/core/ext/lb_policy/pick_first/pick_first.c b/src/core/ext/lb_policy/pick_first/pick_first.c
index 9decf70692..09df92dd99 100644
--- a/src/core/ext/lb_policy/pick_first/pick_first.c
+++ b/src/core/ext/lb_policy/pick_first/pick_first.c
@@ -199,10 +199,8 @@ static void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 static int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                   grpc_polling_entity *pollent,
-                   grpc_metadata_batch *initial_metadata,
-                   uint32_t initial_metadata_flags,
-                   grpc_connected_subchannel **target,
+                   const grpc_lb_policy_pick_args *pick_args,
+                   grpc_connected_subchannel **target, void **user_data,
                    grpc_closure *on_complete) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   pending_pick *pp;
@@ -225,13 +223,13 @@ static int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     if (!p->started_picking) {
       start_picking(exec_ctx, p);
     }
-    grpc_polling_entity_add_to_pollset_set(exec_ctx, pollent,
+    grpc_polling_entity_add_to_pollset_set(exec_ctx, pick_args->pollent,
                                            p->base.interested_parties);
     pp = gpr_malloc(sizeof(*pp));
     pp->next = p->pending_picks;
-    pp->pollent = pollent;
+    pp->pollent = pick_args->pollent;
     pp->target = target;
-    pp->initial_metadata_flags = initial_metadata_flags;
+    pp->initial_metadata_flags = pick_args->initial_metadata_flags;
     pp->on_complete = on_complete;
     p->pending_picks = pp;
     gpr_mu_unlock(&p->mu);
@@ -443,20 +441,34 @@ static grpc_lb_policy *create_pick_first(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(args->addresses != NULL);
   GPR_ASSERT(args->client_channel_factory != NULL);
 
-  if (args->addresses->naddrs == 0) return NULL;
+  /* Find the number of backend addresses. We ignore balancer
+   * addresses, since we don't know how to handle them. */
+  size_t num_addrs = 0;
+  for (size_t i = 0; i < args->addresses->num_addresses; i++) {
+    if (!args->addresses->addresses[i].is_balancer) ++num_addrs;
+  }
+  if (num_addrs == 0) return NULL;
 
   pick_first_lb_policy *p = gpr_malloc(sizeof(*p));
   memset(p, 0, sizeof(*p));
 
-  p->subchannels =
-      gpr_malloc(sizeof(grpc_subchannel *) * args->addresses->naddrs);
-  memset(p->subchannels, 0, sizeof(*p->subchannels) * args->addresses->naddrs);
+  p->subchannels = gpr_malloc(sizeof(grpc_subchannel *) * num_addrs);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * num_addrs);
   grpc_subchannel_args sc_args;
   size_t subchannel_idx = 0;
-  for (size_t i = 0; i < args->addresses->naddrs; i++) {
+  for (size_t i = 0; i < args->addresses->num_addresses; i++) {
+    /* Skip balancer addresses, since we only know how to handle backends. */
+    if (args->addresses->addresses[i].is_balancer) continue;
+
+    if (args->addresses->addresses[i].user_data != NULL) {
+      gpr_log(GPR_ERROR,
+              "This LB policy doesn't support user data. It will be ignored");
+    }
+
     memset(&sc_args, 0, sizeof(grpc_subchannel_args));
-    sc_args.addr = (struct sockaddr *)(args->addresses->addrs[i].addr);
-    sc_args.addr_len = (size_t)args->addresses->addrs[i].len;
+    sc_args.addr =
+        (struct sockaddr *)(&args->addresses->addresses[i].address.addr);
+    sc_args.addr_len = args->addresses->addresses[i].address.len;
 
     grpc_subchannel *subchannel = grpc_client_channel_factory_create_subchannel(
         exec_ctx, args->client_channel_factory, &sc_args);
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.c b/src/core/ext/lb_policy/round_robin/round_robin.c
index 7bcf608ab9..0feb0740a2 100644
--- a/src/core/ext/lb_policy/round_robin/round_robin.c
+++ b/src/core/ext/lb_policy/round_robin/round_robin.c
@@ -66,6 +66,7 @@
 #include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/transport/connectivity_state.h"
+#include "src/core/lib/transport/static_metadata.h"
 
 typedef struct round_robin_lb_policy round_robin_lb_policy;
 
@@ -76,15 +77,32 @@ int grpc_lb_round_robin_trace = 0;
  * Once a pick is available, \a target is updated and \a on_complete called. */
 typedef struct pending_pick {
   struct pending_pick *next;
+
+  /* polling entity for the pick()'s async notification */
   grpc_polling_entity *pollent;
+
+  /* output argument where to store the pick()ed user_data. It'll be NULL if no
+   * such data is present or there's an error (the definite test for errors is
+   * \a target being NULL). */
+  void **user_data;
+
+  /* bitmask passed to pick() and used for selective cancelling. See
+   * grpc_lb_policy_cancel_picks() */
   uint32_t initial_metadata_flags;
+
+  /* output argument where to store the pick()ed connected subchannel, or NULL
+   * upon error. */
   grpc_connected_subchannel **target;
+
+  /* to be invoked once the pick() has completed (regardless of success) */
   grpc_closure *on_complete;
 } pending_pick;
 
 /** List of subchannels in a connectivity READY state */
 typedef struct ready_list {
   grpc_subchannel *subchannel;
+  /* references namesake entry in subchannel_data */
+  void *user_data;
   struct ready_list *next;
   struct ready_list *prev;
 } ready_list;
@@ -102,12 +120,17 @@ typedef struct {
   ready_list *ready_list_node;
   /** last observed connectivity */
   grpc_connectivity_state connectivity_state;
+  /** the subchannel's target user data */
+  void *user_data;
 } subchannel_data;
 
 struct round_robin_lb_policy {
   /** base policy: must be first */
   grpc_lb_policy base;
 
+  /** total number of addresses received at creation time */
+  size_t num_addresses;
+
   /** all our subchannels */
   size_t num_subchannels;
   subchannel_data **subchannels;
@@ -166,16 +189,19 @@ static void advance_last_picked_locked(round_robin_lb_policy *p) {
 
   if (grpc_lb_round_robin_trace) {
     gpr_log(GPR_DEBUG, "[READYLIST] ADVANCED LAST PICK. NOW AT NODE %p (SC %p)",
-            p->ready_list_last_pick, p->ready_list_last_pick->subchannel);
+            (void *)p->ready_list_last_pick,
+            (void *)p->ready_list_last_pick->subchannel);
   }
 }
 
 /** Prepends (relative to the root at p->ready_list) the connected subchannel \a
  * csc to the list of ready subchannels. */
 static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
-                                           grpc_subchannel *sc) {
+                                           subchannel_data *sd) {
   ready_list *new_elem = gpr_malloc(sizeof(ready_list));
-  new_elem->subchannel = sc;
+  memset(new_elem, 0, sizeof(ready_list));
+  new_elem->subchannel = sd->subchannel;
+  new_elem->user_data = sd->user_data;
   if (p->ready_list.prev == NULL) {
     /* first element */
     new_elem->next = &p->ready_list;
@@ -189,7 +215,8 @@ static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
     p->ready_list.prev = new_elem;
   }
   if (grpc_lb_round_robin_trace) {
-    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (SC %p)", new_elem, sc);
+    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (Conn. SC %p)",
+            (void *)new_elem, (void *)sd->subchannel);
   }
   return new_elem;
 }
@@ -216,8 +243,8 @@ static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
   }
 
   if (grpc_lb_round_robin_trace) {
-    gpr_log(GPR_DEBUG, "[READYLIST] REMOVED NODE %p (SC %p)", node,
-            node->subchannel);
+    gpr_log(GPR_DEBUG, "[READYLIST] REMOVED NODE %p (SC %p)", (void *)node,
+            (void *)node->subchannel);
   }
 
   node->next = NULL;
@@ -229,9 +256,8 @@ static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
 
 static void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
-  size_t i;
   ready_list *elem;
-  for (i = 0; i < p->num_subchannels; i++) {
+  for (size_t i = 0; i < p->num_subchannels; i++) {
     subchannel_data *sd = p->subchannels[i];
     GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
     gpr_free(sd);
@@ -251,6 +277,7 @@ static void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
     gpr_free(elem);
     elem = tmp;
   }
+
   gpr_free(p);
 }
 
@@ -337,7 +364,7 @@ static void start_picking(grpc_exec_ctx *exec_ctx, round_robin_lb_policy *p) {
   p->started_picking = 1;
 
   if (grpc_lb_round_robin_trace) {
-    gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%" PRIuPTR, p,
+    gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%" PRIuPTR, (void *)p,
             p->num_subchannels);
   }
 
@@ -361,38 +388,43 @@ static void rr_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                   grpc_polling_entity *pollent,
-                   grpc_metadata_batch *initial_metadata,
-                   uint32_t initial_metadata_flags,
-                   grpc_connected_subchannel **target,
+                   const grpc_lb_policy_pick_args *pick_args,
+                   grpc_connected_subchannel **target, void **user_data,
                    grpc_closure *on_complete) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   pending_pick *pp;
   ready_list *selected;
   gpr_mu_lock(&p->mu);
   if ((selected = peek_next_connected_locked(p))) {
+    /* readily available, report right away */
     gpr_mu_unlock(&p->mu);
     *target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
+
+    if (user_data != NULL) {
+      *user_data = selected->user_data;
+    }
     if (grpc_lb_round_robin_trace) {
       gpr_log(GPR_DEBUG,
-              "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)", *target,
-              selected);
+              "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)",
+              (void *)*target, (void *)selected);
     }
     /* only advance the last picked pointer if the selection was used */
     advance_last_picked_locked(p);
     return 1;
   } else {
+    /* no pick currently available. Save for later in list of pending picks */
     if (!p->started_picking) {
       start_picking(exec_ctx, p);
     }
-    grpc_polling_entity_add_to_pollset_set(exec_ctx, pollent,
+    grpc_polling_entity_add_to_pollset_set(exec_ctx, pick_args->pollent,
                                            p->base.interested_parties);
     pp = gpr_malloc(sizeof(*pp));
     pp->next = p->pending_picks;
-    pp->pollent = pollent;
+    pp->pollent = pick_args->pollent;
     pp->target = target;
     pp->on_complete = on_complete;
-    pp->initial_metadata_flags = initial_metadata_flags;
+    pp->initial_metadata_flags = pick_args->initial_metadata_flags;
+    pp->user_data = user_data;
     p->pending_picks = pp;
     gpr_mu_unlock(&p->mu);
     return 0;
@@ -421,7 +453,7 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                     "connecting_ready");
         /* add the newly connected subchannel to the list of connected ones.
          * Note that it goes to the "end of the line". */
-        sd->ready_list_node = add_connected_sc_locked(p, sd->subchannel);
+        sd->ready_list_node = add_connected_sc_locked(p, sd);
         /* at this point we know there's at least one suitable subchannel. Go
          * ahead and pick one and notify the pending suitors in
          * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
@@ -433,12 +465,16 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
         }
         while ((pp = p->pending_picks)) {
           p->pending_picks = pp->next;
+
           *pp->target =
               grpc_subchannel_get_connected_subchannel(selected->subchannel);
+          if (pp->user_data != NULL) {
+            *pp->user_data = selected->user_data;
+          }
           if (grpc_lb_round_robin_trace) {
             gpr_log(GPR_DEBUG,
                     "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
-                    selected->subchannel, selected);
+                    (void *)selected->subchannel, (void *)selected);
           }
           grpc_polling_entity_del_from_pollset_set(exec_ctx, pp->pollent,
                                                    p->base.interested_parties);
@@ -571,19 +607,31 @@ static grpc_lb_policy *round_robin_create(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(args->addresses != NULL);
   GPR_ASSERT(args->client_channel_factory != NULL);
 
+  /* Find the number of backend addresses. We ignore balancer
+   * addresses, since we don't know how to handle them. */
+  size_t num_addrs = 0;
+  for (size_t i = 0; i < args->addresses->num_addresses; i++) {
+    if (!args->addresses->addresses[i].is_balancer) ++num_addrs;
+  }
+  if (num_addrs == 0) return NULL;
+
   round_robin_lb_policy *p = gpr_malloc(sizeof(*p));
   memset(p, 0, sizeof(*p));
 
-  p->subchannels =
-      gpr_malloc(sizeof(*p->subchannels) * args->addresses->naddrs);
-  memset(p->subchannels, 0, sizeof(*p->subchannels) * args->addresses->naddrs);
+  p->num_addresses = num_addrs;
+  p->subchannels = gpr_malloc(sizeof(*p->subchannels) * num_addrs);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * num_addrs);
 
   grpc_subchannel_args sc_args;
   size_t subchannel_idx = 0;
-  for (size_t i = 0; i < args->addresses->naddrs; i++) {
+  for (size_t i = 0; i < args->addresses->num_addresses; i++) {
+    /* Skip balancer addresses, since we only know how to handle backends. */
+    if (args->addresses->addresses[i].is_balancer) continue;
+
     memset(&sc_args, 0, sizeof(grpc_subchannel_args));
-    sc_args.addr = (struct sockaddr *)(args->addresses->addrs[i].addr);
-    sc_args.addr_len = (size_t)args->addresses->addrs[i].len;
+    sc_args.addr =
+        (struct sockaddr *)(&args->addresses->addresses[i].address.addr);
+    sc_args.addr_len = args->addresses->addresses[i].address.len;
 
     grpc_subchannel *subchannel = grpc_client_channel_factory_create_subchannel(
         exec_ctx, args->client_channel_factory, &sc_args);
@@ -595,12 +643,14 @@ static grpc_lb_policy *round_robin_create(grpc_exec_ctx *exec_ctx,
       sd->policy = p;
       sd->index = subchannel_idx;
       sd->subchannel = subchannel;
+      sd->user_data = args->addresses->addresses[i].user_data;
       ++subchannel_idx;
       grpc_closure_init(&sd->connectivity_changed_closure,
                         rr_connectivity_changed, sd);
     }
   }
   if (subchannel_idx == 0) {
+    /* couldn't create any subchannel. Bail out */
     gpr_free(p->subchannels);
     gpr_free(p);
     return NULL;
diff --git a/src/core/ext/resolver/dns/native/dns_resolver.c b/src/core/ext/resolver/dns/native/dns_resolver.c
index 79682e78b5..1b85d2d634 100644
--- a/src/core/ext/resolver/dns/native/dns_resolver.c
+++ b/src/core/ext/resolver/dns/native/dns_resolver.c
@@ -37,7 +37,6 @@
 #include <grpc/support/host_port.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
@@ -58,8 +57,6 @@ typedef struct {
   char *name;
   /** default port to use */
   char *default_port;
-  /** subchannel factory */
-  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -166,24 +163,20 @@ static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
                             grpc_error *error) {
   dns_resolver *r = arg;
   grpc_resolver_result *result = NULL;
-  grpc_lb_policy *lb_policy;
   gpr_mu_lock(&r->mu);
   GPR_ASSERT(r->resolving);
   r->resolving = 0;
-  grpc_resolved_addresses *addresses = r->addresses;
-  if (addresses != NULL) {
-    grpc_lb_policy_args lb_policy_args;
-    result = grpc_resolver_result_create();
-    memset(&lb_policy_args, 0, sizeof(lb_policy_args));
-    lb_policy_args.addresses = addresses;
-    lb_policy_args.client_channel_factory = r->client_channel_factory;
-    lb_policy =
-        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
-    if (lb_policy != NULL) {
-      grpc_resolver_result_set_lb_policy(result, lb_policy);
-      GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "construction");
+  if (r->addresses != NULL) {
+    grpc_lb_addresses *addresses =
+        grpc_lb_addresses_create(r->addresses->naddrs);
+    for (size_t i = 0; i < r->addresses->naddrs; ++i) {
+      grpc_lb_addresses_set_address(
+          addresses, i, &r->addresses->addrs[i].addr,
+          r->addresses->addrs[i].len, false /* is_balancer */,
+          NULL /* balancer_name */, NULL /* user_data */);
     }
-    grpc_resolved_addresses_destroy(addresses);
+    grpc_resolved_addresses_destroy(r->addresses);
+    result = grpc_resolver_result_create(addresses, r->lb_policy_name, NULL);
   } else {
     gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
     gpr_timespec next_try = gpr_backoff_step(&r->backoff_state, now);
@@ -244,7 +237,6 @@ static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   if (r->resolved_result) {
     grpc_resolver_result_unref(exec_ctx, r->resolved_result);
   }
-  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   gpr_free(r->name);
   gpr_free(r->default_port);
   gpr_free(r->lb_policy_name);
@@ -271,10 +263,8 @@ static grpc_resolver *dns_create(grpc_resolver_args *args,
   grpc_resolver_init(&r->base, &dns_resolver_vtable);
   r->name = gpr_strdup(path);
   r->default_port = gpr_strdup(default_port);
-  r->client_channel_factory = args->client_channel_factory;
   gpr_backoff_init(&r->backoff_state, BACKOFF_MULTIPLIER, BACKOFF_JITTER,
                    BACKOFF_MIN_SECONDS * 1000, BACKOFF_MAX_SECONDS * 1000);
-  grpc_client_channel_factory_ref(r->client_channel_factory);
   r->lb_policy_name = gpr_strdup(lb_policy_name);
   return &r->base;
 }
diff --git a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
index 3807522d2b..ced4fb024c 100644
--- a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
+++ b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
@@ -40,7 +40,6 @@
 #include <grpc/support/port_platform.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/parse_address.h"
 #include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
@@ -52,18 +51,16 @@ typedef struct {
   grpc_resolver base;
   /** refcount */
   gpr_refcount refs;
-  /** subchannel factory */
-  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
   /** the addresses that we've 'resolved' */
-  grpc_resolved_addresses *addresses;
+  grpc_lb_addresses *addresses;
 
   /** mutex guarding the rest of the state */
   gpr_mu mu;
   /** have we published? */
-  int published;
+  bool published;
   /** pending next completion, or NULL */
   grpc_closure *next_completion;
   /** target result address for next completion */
@@ -102,7 +99,7 @@ static void sockaddr_channel_saw_error(grpc_exec_ctx *exec_ctx,
                                        grpc_resolver *resolver) {
   sockaddr_resolver *r = (sockaddr_resolver *)resolver;
   gpr_mu_lock(&r->mu);
-  r->published = 0;
+  r->published = false;
   sockaddr_maybe_finish_next_locked(exec_ctx, r);
   gpr_mu_unlock(&r->mu);
 }
@@ -122,17 +119,10 @@ static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
 static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
                                               sockaddr_resolver *r) {
   if (r->next_completion != NULL && !r->published) {
-    grpc_resolver_result *result = grpc_resolver_result_create();
-    grpc_lb_policy_args lb_policy_args;
-    memset(&lb_policy_args, 0, sizeof(lb_policy_args));
-    lb_policy_args.addresses = r->addresses;
-    lb_policy_args.client_channel_factory = r->client_channel_factory;
-    grpc_lb_policy *lb_policy =
-        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
-    grpc_resolver_result_set_lb_policy(result, lb_policy);
-    GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "sockaddr");
-    r->published = 1;
-    *r->target_result = result;
+    r->published = true;
+    *r->target_result = grpc_resolver_result_create(
+        grpc_lb_addresses_copy(r->addresses, NULL /* user_data_copy */),
+        r->lb_policy_name, NULL);
     grpc_exec_ctx_sched(exec_ctx, r->next_completion, GRPC_ERROR_NONE, NULL);
     r->next_completion = NULL;
   }
@@ -141,8 +131,7 @@ static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
 static void sockaddr_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   sockaddr_resolver *r = (sockaddr_resolver *)gr;
   gpr_mu_destroy(&r->mu);
-  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
-  grpc_resolved_addresses_destroy(r->addresses);
+  grpc_lb_addresses_destroy(r->addresses, NULL /* user_data_destroy */);
   gpr_free(r->lb_policy_name);
   gpr_free(r);
 }
@@ -175,7 +164,7 @@ static void do_nothing(void *ignored) {}
 static grpc_resolver *sockaddr_create(
     grpc_resolver_args *args, const char *default_lb_policy_name,
     int parse(grpc_uri *uri, struct sockaddr_storage *dst, size_t *len)) {
-  int errors_found = 0; /* GPR_FALSE */
+  bool errors_found = false;
   sockaddr_resolver *r;
   gpr_slice path_slice;
   gpr_slice_buffer path_parts;
@@ -216,21 +205,18 @@ static grpc_resolver *sockaddr_create(
   gpr_slice_buffer_init(&path_parts);
 
   gpr_slice_split(path_slice, ",", &path_parts);
-  r->addresses = gpr_malloc(sizeof(grpc_resolved_addresses));
-  r->addresses->naddrs = path_parts.count;
-  r->addresses->addrs =
-      gpr_malloc(sizeof(grpc_resolved_address) * r->addresses->naddrs);
-
-  for (size_t i = 0; i < r->addresses->naddrs; i++) {
+  r->addresses = grpc_lb_addresses_create(path_parts.count);
+  for (size_t i = 0; i < r->addresses->num_addresses; i++) {
     grpc_uri ith_uri = *args->uri;
     char *part_str = gpr_dump_slice(path_parts.slices[i], GPR_DUMP_ASCII);
     ith_uri.path = part_str;
-    if (!parse(&ith_uri,
-               (struct sockaddr_storage *)(&r->addresses->addrs[i].addr),
-               &r->addresses->addrs[i].len)) {
-      errors_found = 1; /* GPR_TRUE */
+    if (!parse(&ith_uri, (struct sockaddr_storage *)(&r->addresses->addresses[i]
+                                                          .address.addr),
+               &r->addresses->addresses[i].address.len)) {
+      errors_found = true;
     }
     gpr_free(part_str);
+    r->addresses->addresses[i].is_balancer = lb_enabled;
     if (errors_found) break;
   }
 
@@ -238,7 +224,7 @@ static grpc_resolver *sockaddr_create(
   gpr_slice_unref(path_slice);
   if (errors_found) {
     gpr_free(r->lb_policy_name);
-    grpc_resolved_addresses_destroy(r->addresses);
+    grpc_lb_addresses_destroy(r->addresses, NULL /* user_data_destroy */);
     gpr_free(r);
     return NULL;
   }
@@ -246,8 +232,6 @@ static grpc_resolver *sockaddr_create(
   gpr_ref_init(&r->refs, 1);
   gpr_mu_init(&r->mu);
   grpc_resolver_init(&r->base, &sockaddr_resolver_vtable);
-  r->client_channel_factory = args->client_channel_factory;
-  grpc_client_channel_factory_ref(r->client_channel_factory);
 
   return &r->base;
 }
diff --git a/src/core/ext/transport/chttp2/client/insecure/channel_create.c b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
index cbaa75a90a..ddc00bd79f 100644
--- a/src/core/ext/transport/chttp2/client/insecure/channel_create.c
+++ b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
@@ -160,7 +160,6 @@ typedef struct {
   grpc_client_channel_factory base;
   gpr_refcount refs;
   grpc_channel_args *merge_args;
-  grpc_channel *master;
 } client_channel_factory;
 
 static void client_channel_factory_ref(
@@ -173,10 +172,6 @@ static void client_channel_factory_unref(
     grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory) {
   client_channel_factory *f = (client_channel_factory *)cc_factory;
   if (gpr_unref(&f->refs)) {
-    if (f->master != NULL) {
-      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
-                                  "client_channel_factory");
-    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
@@ -210,15 +205,15 @@ static grpc_channel *client_channel_factory_create_channel(
   grpc_channel *channel = grpc_channel_create(exec_ctx, target, final_args,
                                               GRPC_CLIENT_CHANNEL, NULL);
   grpc_channel_args_destroy(final_args);
-  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  grpc_resolver *resolver = grpc_resolver_create(target);
   if (!resolver) {
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
                                 "client_channel_factory_create_channel");
     return NULL;
   }
 
-  grpc_client_channel_set_resolver(
-      exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+  grpc_client_channel_finish_initialization(
+      exec_ctx, grpc_channel_get_channel_stack(channel), resolver, &f->base);
   GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create_channel");
 
   return channel;
@@ -250,12 +245,8 @@ grpc_channel *grpc_insecure_channel_create(const char *target,
 
   grpc_channel *channel = client_channel_factory_create_channel(
       &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
-  if (channel != NULL) {
-    f->master = channel;
-    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_insecure_channel_create");
-  }
-  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
 
+  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
   grpc_exec_ctx_finish(&exec_ctx);
 
   return channel != NULL ? channel : grpc_lame_client_channel_create(
diff --git a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
index 9e2bdd758f..f36fbbfc57 100644
--- a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
+++ b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
@@ -220,7 +220,6 @@ typedef struct {
   gpr_refcount refs;
   grpc_channel_args *merge_args;
   grpc_channel_security_connector *security_connector;
-  grpc_channel *master;
 } client_channel_factory;
 
 static void client_channel_factory_ref(
@@ -235,10 +234,6 @@ static void client_channel_factory_unref(
   if (gpr_unref(&f->refs)) {
     GRPC_SECURITY_CONNECTOR_UNREF(&f->security_connector->base,
                                   "client_channel_factory");
-    if (f->master != NULL) {
-      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
-                                  "client_channel_factory");
-    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
@@ -276,10 +271,10 @@ static grpc_channel *client_channel_factory_create_channel(
                                               GRPC_CLIENT_CHANNEL, NULL);
   grpc_channel_args_destroy(final_args);
 
-  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  grpc_resolver *resolver = grpc_resolver_create(target);
   if (resolver != NULL) {
-    grpc_client_channel_set_resolver(
-        exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+    grpc_client_channel_finish_initialization(
+        exec_ctx, grpc_channel_get_channel_stack(channel), resolver, &f->base);
     GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create");
   } else {
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
@@ -356,10 +351,6 @@ grpc_channel *grpc_secure_channel_create(grpc_channel_credentials *creds,
 
   grpc_channel *channel = client_channel_factory_create_channel(
       &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
-  if (channel != NULL) {
-    f->master = channel;
-    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_secure_channel_create");
-  }
 
   grpc_client_channel_factory_unref(&exec_ctx, &f->base);
   grpc_exec_ctx_finish(&exec_ctx);
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_plugin.c b/src/core/ext/transport/chttp2/transport/chttp2_plugin.c
index 7d5279b9da..bd87253ed3 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_plugin.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_plugin.c
@@ -36,14 +36,11 @@
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/transport/metadata.h"
 
-extern int grpc_http_write_state_trace;
-
 void grpc_chttp2_plugin_init(void) {
   grpc_chttp2_base64_encode_and_huffman_compress =
       grpc_chttp2_base64_encode_and_huffman_compress_impl;
   grpc_register_tracer("http", &grpc_http_trace);
   grpc_register_tracer("flowctl", &grpc_flowctl_trace);
-  grpc_register_tracer("http_write_state", &grpc_http_write_state_trace);
 }
 
 void grpc_chttp2_plugin_shutdown(void) {}
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index 00999e3b94..d46656ce81 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -33,6 +33,7 @@
 
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 
+#include <limits.h>
 #include <math.h>
 #include <stdio.h>
 #include <string.h>
@@ -46,6 +47,7 @@
 #include "src/core/ext/transport/chttp2/transport/http2_errors.h"
 #include "src/core/ext/transport/chttp2/transport/internal.h"
 #include "src/core/ext/transport/chttp2/transport/status_conversion.h"
+#include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/http/parser.h"
 #include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
@@ -63,40 +65,27 @@
 #define MAX_CLIENT_STREAM_ID 0x7fffffffu
 int grpc_http_trace = 0;
 int grpc_flowctl_trace = 0;
-int grpc_http_write_state_trace = 0;
-
-#define TRANSPORT_FROM_WRITING(tw)                                        \
-  ((grpc_chttp2_transport *)((char *)(tw)-offsetof(grpc_chttp2_transport, \
-                                                   writing)))
-
-#define TRANSPORT_FROM_PARSING(tp)                                        \
-  ((grpc_chttp2_transport *)((char *)(tp)-offsetof(grpc_chttp2_transport, \
-                                                   parsing)))
-
-#define TRANSPORT_FROM_GLOBAL(tg)                                         \
-  ((grpc_chttp2_transport *)((char *)(tg)-offsetof(grpc_chttp2_transport, \
-                                                   global)))
-
-#define STREAM_FROM_GLOBAL(sg) \
-  ((grpc_chttp2_stream *)((char *)(sg)-offsetof(grpc_chttp2_stream, global)))
-
-#define STREAM_FROM_PARSING(sg) \
-  ((grpc_chttp2_stream *)((char *)(sg)-offsetof(grpc_chttp2_stream, parsing)))
 
 static const grpc_transport_vtable vtable;
 
 /* forward declarations of various callbacks that we'll build closures around */
-static void writing_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
-static void reading_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
-static void parsing_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
-static void initiate_writing(grpc_exec_ctx *exec_ctx, void *t,
+static void write_action_begin_locked(grpc_exec_ctx *exec_ctx, void *t,
+                                      grpc_error *error);
+static void write_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
+static void write_action_end(grpc_exec_ctx *exec_ctx, void *t,
                              grpc_error *error);
+static void write_action_end_locked(grpc_exec_ctx *exec_ctx, void *t,
+                                    grpc_error *error);
 
-static void start_writing(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t);
-static void end_waiting_for_write(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t, grpc_error *error,
-                                  const char *reason);
+static void read_action_begin(grpc_exec_ctx *exec_ctx, void *t,
+                              grpc_error *error);
+static void read_action_locked(grpc_exec_ctx *exec_ctx, void *t,
+                               grpc_error *error);
 
+static void complete_fetch_locked(grpc_exec_ctx *exec_ctx, void *gs,
+                                  grpc_error *error);
+static void complete_fetch(grpc_exec_ctx *exec_ctx, void *gs,
+                           grpc_error *error);
 /** Set a transport level setting, and push it to our peer */
 static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                          grpc_chttp2_setting_id id, uint32_t value);
@@ -105,56 +94,28 @@ static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 static void drop_connection(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                             grpc_error *error);
 
-/** Perform a transport_op */
-static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
-                                     grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s, void *transport_op);
-
-/** Cancel a stream: coming from the transport API */
-static void cancel_from_api(grpc_exec_ctx *exec_ctx,
-                            grpc_chttp2_transport_global *transport_global,
-                            grpc_chttp2_stream_global *stream_global,
-                            grpc_error *error);
-
-static void close_from_api(grpc_exec_ctx *exec_ctx,
-                           grpc_chttp2_transport_global *transport_global,
-                           grpc_chttp2_stream_global *stream_global,
-                           grpc_error *error);
-
-/** Add endpoint from this transport to pollset */
-static void add_to_pollset_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_ignored, void *pollset);
-static void add_to_pollset_set_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s_ignored,
-                                      void *pollset_set);
+static void close_from_api(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                           grpc_chttp2_stream *s, grpc_error *error);
 
 /** Start new streams that have been created if we can */
-static void maybe_start_some_streams(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global);
-
-static void finish_global_actions(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t);
-
-static void connectivity_state_set(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_connectivity_state state, grpc_error *error, const char *reason);
+static void maybe_start_some_streams(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t);
 
-static void check_read_ops(grpc_exec_ctx *exec_ctx,
-                           grpc_chttp2_transport_global *transport_global);
-
-static void incoming_byte_stream_update_flow_control(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, size_t max_size_hint,
-    size_t have_already);
+static void connectivity_state_set(grpc_exec_ctx *exec_ctx,
+                                   grpc_chttp2_transport *t,
+                                   grpc_connectivity_state state,
+                                   grpc_error *error, const char *reason);
+
+static void incoming_byte_stream_update_flow_control(grpc_exec_ctx *exec_ctx,
+                                                     grpc_chttp2_transport *t,
+                                                     grpc_chttp2_stream *s,
+                                                     size_t max_size_hint,
+                                                     size_t have_already);
 static void incoming_byte_stream_destroy_locked(grpc_exec_ctx *exec_ctx,
-                                                grpc_chttp2_transport *t,
-                                                grpc_chttp2_stream *s,
-                                                void *byte_stream);
+                                                void *byte_stream,
+                                                grpc_error *error_ignored);
 static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport_global *transport_global,
-                                grpc_chttp2_stream_global *stream_global,
+                                grpc_chttp2_transport *t, grpc_chttp2_stream *s,
                                 grpc_error *error);
 
 /*******************************************************************************
@@ -165,39 +126,33 @@ static void destruct_transport(grpc_exec_ctx *exec_ctx,
                                grpc_chttp2_transport *t) {
   size_t i;
 
-  gpr_mu_lock(&t->executor.mu);
-
-  GPR_ASSERT(t->ep == NULL);
+  grpc_endpoint_destroy(exec_ctx, t->ep);
 
-  gpr_slice_buffer_destroy(&t->global.qbuf);
+  gpr_slice_buffer_destroy(&t->qbuf);
 
-  gpr_slice_buffer_destroy(&t->writing.outbuf);
-  grpc_chttp2_hpack_compressor_destroy(&t->writing.hpack_compressor);
+  gpr_slice_buffer_destroy(&t->outbuf);
+  grpc_chttp2_hpack_compressor_destroy(&t->hpack_compressor);
 
-  gpr_slice_buffer_destroy(&t->parsing.qbuf);
   gpr_slice_buffer_destroy(&t->read_buffer);
-  grpc_chttp2_hpack_parser_destroy(&t->parsing.hpack_parser);
-  grpc_chttp2_goaway_parser_destroy(&t->parsing.goaway_parser);
+  grpc_chttp2_hpack_parser_destroy(&t->hpack_parser);
+  grpc_chttp2_goaway_parser_destroy(&t->goaway_parser);
 
   for (i = 0; i < STREAM_LIST_COUNT; i++) {
     GPR_ASSERT(t->lists[i].head == NULL);
     GPR_ASSERT(t->lists[i].tail == NULL);
   }
 
-  GPR_ASSERT(grpc_chttp2_stream_map_size(&t->parsing_stream_map) == 0);
-  GPR_ASSERT(grpc_chttp2_stream_map_size(&t->new_stream_map) == 0);
+  GPR_ASSERT(grpc_chttp2_stream_map_size(&t->stream_map) == 0);
 
-  grpc_chttp2_stream_map_destroy(&t->parsing_stream_map);
-  grpc_chttp2_stream_map_destroy(&t->new_stream_map);
+  grpc_chttp2_stream_map_destroy(&t->stream_map);
   grpc_connectivity_state_destroy(exec_ctx, &t->channel_callback.state_tracker);
 
-  gpr_mu_unlock(&t->executor.mu);
-  gpr_mu_destroy(&t->executor.mu);
+  grpc_combiner_destroy(exec_ctx, t->combiner);
 
   /* callback remaining pings: they're not allowed to call into the transpot,
      and maybe they hold resources that need to be freed */
-  while (t->global.pings.next != &t->global.pings) {
-    grpc_chttp2_outstanding_ping *ping = t->global.pings.next;
+  while (t->pings.next != &t->pings) {
+    grpc_chttp2_outstanding_ping *ping = t->pings.next;
     grpc_exec_ctx_sched(exec_ctx, ping->on_recv,
                         GRPC_ERROR_CREATE("Transport closed"), NULL);
     ping->next->prev = ping->prev;
@@ -205,37 +160,40 @@ static void destruct_transport(grpc_exec_ctx *exec_ctx,
     gpr_free(ping);
   }
 
+  while (t->write_cb_pool) {
+    grpc_chttp2_write_cb *next = t->write_cb_pool->next;
+    gpr_free(t->write_cb_pool);
+    t->write_cb_pool = next;
+  }
+
   gpr_free(t->peer_string);
   gpr_free(t);
 }
 
-/*#define REFCOUNTING_DEBUG 1*/
-#ifdef REFCOUNTING_DEBUG
-#define REF_TRANSPORT(t, r) ref_transport(t, r, __FILE__, __LINE__)
-#define UNREF_TRANSPORT(cl, t, r) unref_transport(cl, t, r, __FILE__, __LINE__)
-static void unref_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                            const char *reason, const char *file, int line) {
-  gpr_log(GPR_DEBUG, "chttp2:unref:%p %d->%d %s [%s:%d]", t, t->refs.count,
-          t->refs.count - 1, reason, file, line);
+#ifdef GRPC_CHTTP2_REFCOUNTING_DEBUG
+void grpc_chttp2_unref_transport(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_transport *t, const char *reason,
+                                 const char *file, int line) {
+  gpr_log(GPR_DEBUG, "chttp2:unref:%p %" PRIdPTR "->%" PRIdPTR " %s [%s:%d]", t,
+          t->refs.count, t->refs.count - 1, reason, file, line);
   if (!gpr_unref(&t->refs)) return;
   destruct_transport(exec_ctx, t);
 }
 
-static void ref_transport(grpc_chttp2_transport *t, const char *reason,
-                          const char *file, int line) {
-  gpr_log(GPR_DEBUG, "chttp2:  ref:%p %d->%d %s [%s:%d]", t, t->refs.count,
-          t->refs.count + 1, reason, file, line);
+void grpc_chttp2_ref_transport(grpc_chttp2_transport *t, const char *reason,
+                               const char *file, int line) {
+  gpr_log(GPR_DEBUG, "chttp2:  ref:%p %" PRIdPTR "->%" PRIdPTR " %s [%s:%d]", t,
+          t->refs.count, t->refs.count + 1, reason, file, line);
   gpr_ref(&t->refs);
 }
 #else
-#define REF_TRANSPORT(t, r) ref_transport(t)
-#define UNREF_TRANSPORT(cl, t, r) unref_transport(cl, t)
-static void unref_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t) {
+void grpc_chttp2_unref_transport(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_transport *t) {
   if (!gpr_unref(&t->refs)) return;
   destruct_transport(exec_ctx, t);
 }
 
-static void ref_transport(grpc_chttp2_transport *t) { gpr_ref(&t->refs); }
+void grpc_chttp2_ref_transport(grpc_chttp2_transport *t) { gpr_ref(&t->refs); }
 #endif
 
 static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
@@ -251,74 +209,67 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 
   t->base.vtable = &vtable;
   t->ep = ep;
-  /* one ref is for destroy, the other for when ep becomes NULL */
-  gpr_ref_init(&t->refs, 2);
-  /* ref is dropped at transport close() */
-  gpr_ref_init(&t->shutdown_ep_refs, 1);
-  gpr_mu_init(&t->executor.mu);
+  /* one ref is for destroy */
+  gpr_ref_init(&t->refs, 1);
+  t->combiner = grpc_combiner_create(grpc_endpoint_get_workqueue(ep));
   t->peer_string = grpc_endpoint_get_peer(ep);
   t->endpoint_reading = 1;
-  t->global.next_stream_id = is_client ? 1 : 2;
-  t->global.is_client = is_client;
-  t->writing.outgoing_window = DEFAULT_WINDOW;
-  t->parsing.incoming_window = DEFAULT_WINDOW;
-  t->global.stream_lookahead = DEFAULT_WINDOW;
-  t->global.connection_window_target = DEFAULT_CONNECTION_WINDOW_TARGET;
-  t->global.ping_counter = 1;
-  t->global.pings.next = t->global.pings.prev = &t->global.pings;
-  t->parsing.is_client = is_client;
-  t->parsing.deframe_state =
-      is_client ? GRPC_DTS_FH_0 : GRPC_DTS_CLIENT_PREFIX_0;
-  t->parsing.is_first_frame = true;
-  t->writing.is_client = is_client;
+  t->next_stream_id = is_client ? 1 : 2;
+  t->is_client = is_client;
+  t->outgoing_window = DEFAULT_WINDOW;
+  t->incoming_window = DEFAULT_WINDOW;
+  t->stream_lookahead = DEFAULT_WINDOW;
+  t->connection_window_target = DEFAULT_CONNECTION_WINDOW_TARGET;
+  t->ping_counter = 1;
+  t->pings.next = t->pings.prev = &t->pings;
+  t->deframe_state = is_client ? GRPC_DTS_FH_0 : GRPC_DTS_CLIENT_PREFIX_0;
+  t->is_first_frame = true;
   grpc_connectivity_state_init(
       &t->channel_callback.state_tracker, GRPC_CHANNEL_READY,
       is_client ? "client_transport" : "server_transport");
 
-  gpr_slice_buffer_init(&t->global.qbuf);
+  gpr_slice_buffer_init(&t->qbuf);
 
-  gpr_slice_buffer_init(&t->writing.outbuf);
-  grpc_chttp2_hpack_compressor_init(&t->writing.hpack_compressor);
-  grpc_closure_init(&t->writing_action, writing_action, t);
-  grpc_closure_init(&t->reading_action, reading_action, t);
-  grpc_closure_init(&t->parsing_action, parsing_action, t);
-  grpc_closure_init(&t->initiate_writing, initiate_writing, t);
+  gpr_slice_buffer_init(&t->outbuf);
+  grpc_chttp2_hpack_compressor_init(&t->hpack_compressor);
 
-  gpr_slice_buffer_init(&t->parsing.qbuf);
-  grpc_chttp2_goaway_parser_init(&t->parsing.goaway_parser);
-  grpc_chttp2_hpack_parser_init(&t->parsing.hpack_parser);
+  grpc_closure_init(&t->write_action_begin_locked, write_action_begin_locked,
+                    t);
+  grpc_closure_init(&t->write_action, write_action, t);
+  grpc_closure_init(&t->write_action_end, write_action_end, t);
+  grpc_closure_init(&t->write_action_end_locked, write_action_end_locked, t);
+  grpc_closure_init(&t->read_action_begin, read_action_begin, t);
+  grpc_closure_init(&t->read_action_locked, read_action_locked, t);
+
+  grpc_chttp2_goaway_parser_init(&t->goaway_parser);
+  grpc_chttp2_hpack_parser_init(&t->hpack_parser);
 
-  grpc_closure_init(&t->writing.done_cb, grpc_chttp2_terminate_writing,
-                    &t->writing);
   gpr_slice_buffer_init(&t->read_buffer);
 
-  if (is_client) {
-    gpr_slice_buffer_add(
-        &t->global.qbuf,
-        gpr_slice_from_copied_string(GRPC_CHTTP2_CLIENT_CONNECT_STRING));
-    grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "initial_write");
-  }
   /* 8 is a random stab in the dark as to a good initial size: it's small enough
      that it shouldn't waste memory for infrequently used connections, yet
      large enough that the exponential growth should happen nicely when it's
      needed.
      TODO(ctiller): tune this */
-  grpc_chttp2_stream_map_init(&t->parsing_stream_map, 8);
-  grpc_chttp2_stream_map_init(&t->new_stream_map, 8);
+  grpc_chttp2_stream_map_init(&t->stream_map, 8);
 
   /* copy in initial settings to all setting sets */
   for (i = 0; i < GRPC_CHTTP2_NUM_SETTINGS; i++) {
-    t->parsing.settings[i] = grpc_chttp2_settings_parameters[i].default_value;
     for (j = 0; j < GRPC_NUM_SETTING_SETS; j++) {
-      t->global.settings[j][i] =
-          grpc_chttp2_settings_parameters[i].default_value;
+      t->settings[j][i] = grpc_chttp2_settings_parameters[i].default_value;
     }
   }
-  t->global.dirtied_local_settings = 1;
+  t->dirtied_local_settings = 1;
   /* Hack: it's common for implementations to assume 65536 bytes initial send
      window -- this should by rights be 0 */
-  t->global.force_send_settings = 1 << GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
-  t->global.sent_local_settings = 0;
+  t->force_send_settings = 1 << GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
+  t->sent_local_settings = 0;
+
+  if (is_client) {
+    gpr_slice_buffer_add(&t->outbuf, gpr_slice_from_copied_string(
+                                         GRPC_CHTTP2_CLIENT_CONNECT_STRING));
+    grpc_chttp2_initiate_write(exec_ctx, t, false, "initial_write");
+  }
 
   /* configure http2 the way we like it */
   if (is_client) {
@@ -332,701 +283,430 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 
   if (channel_args) {
     for (i = 0; i < channel_args->num_args; i++) {
-      if (0 ==
-          strcmp(channel_args->args[i].key, GRPC_ARG_MAX_CONCURRENT_STREAMS)) {
-        if (is_client) {
-          gpr_log(GPR_ERROR, "%s: is ignored on the client",
-                  GRPC_ARG_MAX_CONCURRENT_STREAMS);
-        } else if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_MAX_CONCURRENT_STREAMS);
-        } else {
-          push_setting(exec_ctx, t, GRPC_CHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS,
-                       (uint32_t)channel_args->args[i].value.integer);
-        }
-      } else if (0 == strcmp(channel_args->args[i].key,
-                             GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER);
-        } else if ((t->global.next_stream_id & 1) !=
-                   (channel_args->args[i].value.integer & 1)) {
-          gpr_log(GPR_ERROR, "%s: low bit must be %d on %s",
-                  GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER,
-                  t->global.next_stream_id & 1,
-                  is_client ? "client" : "server");
-        } else {
-          t->global.next_stream_id =
-              (uint32_t)channel_args->args[i].value.integer;
+      if (0 == strcmp(channel_args->args[i].key,
+                      GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER)) {
+        const grpc_integer_options options = {-1, 0, INT_MAX};
+        const int value =
+            grpc_channel_arg_get_integer(&channel_args->args[i], options);
+        if (value >= 0) {
+          if ((t->next_stream_id & 1) != (value & 1)) {
+            gpr_log(GPR_ERROR, "%s: low bit must be %d on %s",
+                    GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER,
+                    t->next_stream_id & 1, is_client ? "client" : "server");
+          } else {
+            t->next_stream_id = (uint32_t)value;
+          }
         }
       } else if (0 == strcmp(channel_args->args[i].key,
                              GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES);
-        } else if (channel_args->args[i].value.integer <= 5) {
-          gpr_log(GPR_ERROR, "%s: must be at least 5",
-                  GRPC_ARG_HTTP2_STREAM_LOOKAHEAD_BYTES);
-        } else {
-          t->global.stream_lookahead =
-              (uint32_t)channel_args->args[i].value.integer;
-        }
-      } else if (0 == strcmp(channel_args->args[i].key,
-                             GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_DECODER)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_DECODER);
-        } else if (channel_args->args[i].value.integer < 0) {
-          gpr_log(GPR_ERROR, "%s: must be non-negative",
-                  GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_DECODER);
-        } else {
-          push_setting(exec_ctx, t, GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE,
-                       (uint32_t)channel_args->args[i].value.integer);
+        const grpc_integer_options options = {-1, 5, INT_MAX};
+        const int value =
+            grpc_channel_arg_get_integer(&channel_args->args[i], options);
+        if (value >= 0) {
+          t->stream_lookahead = (uint32_t)value;
         }
       } else if (0 == strcmp(channel_args->args[i].key,
                              GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_ENCODER)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_ENCODER);
-        } else if (channel_args->args[i].value.integer < 0) {
-          gpr_log(GPR_ERROR, "%s: must be non-negative",
-                  GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_ENCODER);
-        } else {
-          grpc_chttp2_hpack_compressor_set_max_usable_size(
-              &t->writing.hpack_compressor,
-              (uint32_t)channel_args->args[i].value.integer);
-        }
-      } else if (0 == strcmp(channel_args->args[i].key,
-                             GRPC_ARG_MAX_METADATA_SIZE)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_MAX_METADATA_SIZE);
-        } else if (channel_args->args[i].value.integer < 0) {
-          gpr_log(GPR_ERROR, "%s: must be non-negative",
-                  GRPC_ARG_MAX_METADATA_SIZE);
-        } else {
-          push_setting(exec_ctx, t, GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE,
-                       (uint32_t)channel_args->args[i].value.integer);
+        const grpc_integer_options options = {-1, 0, INT_MAX};
+        const int value =
+            grpc_channel_arg_get_integer(&channel_args->args[i], options);
+        if (value >= 0) {
+          grpc_chttp2_hpack_compressor_set_max_usable_size(&t->hpack_compressor,
+                                                           (uint32_t)value);
         }
-      } else if (0 == strcmp(channel_args->args[i].key,
-                             GRPC_ARG_HTTP2_MAX_FRAME_SIZE)) {
-        if (channel_args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s: must be an integer",
-                  GRPC_ARG_HTTP2_MAX_FRAME_SIZE);
-        } else if (channel_args->args[i].value.integer < 16384 ||
-                   channel_args->args[i].value.integer > 16777215) {
-          gpr_log(GPR_ERROR, "%s: must be between 16384 and 16777215",
-                  GRPC_ARG_HTTP2_MAX_FRAME_SIZE);
-        } else {
-          push_setting(exec_ctx, t, GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE,
-                       (uint32_t)channel_args->args[i].value.integer);
+      } else {
+        static const struct {
+          const char *channel_arg_name;
+          grpc_chttp2_setting_id setting_id;
+          grpc_integer_options integer_options;
+          bool availability[2] /* server, client */;
+        } settings_map[] = {
+            {GRPC_ARG_MAX_CONCURRENT_STREAMS,
+             GRPC_CHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS,
+             {-1, 0, INT_MAX},
+             {true, false}},
+            {GRPC_ARG_HTTP2_HPACK_TABLE_SIZE_DECODER,
+             GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE,
+             {-1, 0, INT_MAX},
+             {true, true}},
+            {GRPC_ARG_MAX_METADATA_SIZE,
+             GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE,
+             {-1, 0, INT_MAX},
+             {true, true}},
+            {GRPC_ARG_HTTP2_MAX_FRAME_SIZE,
+             GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE,
+             {-1, 16384, 16777215},
+             {true, true}},
+        };
+        for (j = 0; j < (int)GPR_ARRAY_SIZE(settings_map); j++) {
+          if (0 == strcmp(channel_args->args[i].key,
+                          settings_map[j].channel_arg_name)) {
+            if (!settings_map[j].availability[is_client]) {
+              gpr_log(GPR_DEBUG, "%s is not available on %s",
+                      settings_map[j].channel_arg_name,
+                      is_client ? "clients" : "servers");
+            } else {
+              int value = grpc_channel_arg_get_integer(
+                  &channel_args->args[i], settings_map[j].integer_options);
+              if (value >= 0) {
+                push_setting(exec_ctx, t, settings_map[j].setting_id,
+                             (uint32_t)value);
+              }
+            }
+            break;
+          }
         }
       }
     }
   }
+
+  grpc_chttp2_initiate_write(exec_ctx, t, false, "init");
 }
 
-static void destroy_transport_locked(grpc_exec_ctx *exec_ctx,
-                                     grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s_ignored,
-                                     void *arg_ignored) {
+static void destroy_transport_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                     grpc_error *error) {
+  grpc_chttp2_transport *t = tp;
   t->destroying = 1;
   drop_connection(exec_ctx, t, GRPC_ERROR_CREATE("Transport destroyed"));
+  GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "destroy");
 }
 
 static void destroy_transport(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, NULL, destroy_transport_locked,
-                                   NULL, 0);
-  UNREF_TRANSPORT(exec_ctx, t, "destroy");
-}
-
-/** block grpc_endpoint_shutdown being called until a paired
-    allow_endpoint_shutdown is made */
-static void prevent_endpoint_shutdown(grpc_chttp2_transport *t) {
-  GPR_ASSERT(t->ep);
-  gpr_ref(&t->shutdown_ep_refs);
-}
-
-static void allow_endpoint_shutdown_locked(grpc_exec_ctx *exec_ctx,
-                                           grpc_chttp2_transport *t) {
-  if (gpr_unref(&t->shutdown_ep_refs)) {
-    if (t->ep) {
-      grpc_endpoint_shutdown(exec_ctx, t->ep);
-    }
-  }
-}
-
-static void destroy_endpoint(grpc_exec_ctx *exec_ctx,
-                             grpc_chttp2_transport *t) {
-  grpc_endpoint_destroy(exec_ctx, t->ep);
-  t->ep = NULL;
-  /* safe because we'll still have the ref for write */
-  UNREF_TRANSPORT(exec_ctx, t, "disconnect");
+  grpc_combiner_execute(exec_ctx, t->combiner,
+                        grpc_closure_create(destroy_transport_locked, t),
+                        GRPC_ERROR_NONE, false);
 }
 
 static void close_transport_locked(grpc_exec_ctx *exec_ctx,
                                    grpc_chttp2_transport *t,
                                    grpc_error *error) {
   if (!t->closed) {
-    if (grpc_http_write_state_trace) {
-      gpr_log(GPR_DEBUG, "W:%p close transport", t);
-    }
     t->closed = 1;
-    connectivity_state_set(exec_ctx, &t->global, GRPC_CHANNEL_SHUTDOWN,
+    connectivity_state_set(exec_ctx, t, GRPC_CHANNEL_SHUTDOWN,
                            GRPC_ERROR_REF(error), "close_transport");
-    if (t->ep) {
-      allow_endpoint_shutdown_locked(exec_ctx, t);
-    }
+    grpc_endpoint_shutdown(exec_ctx, t->ep);
 
     /* flush writable stream list to avoid dangling references */
-    grpc_chttp2_stream_global *stream_global;
-    grpc_chttp2_stream_writing *stream_writing;
-    while (grpc_chttp2_list_pop_writable_stream(
-        &t->global, &t->writing, &stream_global, &stream_writing)) {
-      GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2_writing");
+    grpc_chttp2_stream *s;
+    while (grpc_chttp2_list_pop_writable_stream(t, &s)) {
+      GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:close");
     }
   }
   GRPC_ERROR_UNREF(error);
 }
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
-void grpc_chttp2_stream_ref(grpc_chttp2_stream_global *stream_global,
-                            const char *reason) {
-  grpc_stream_ref(STREAM_FROM_GLOBAL(stream_global)->refcount, reason);
+void grpc_chttp2_stream_ref(grpc_chttp2_stream *s, const char *reason) {
+  grpc_stream_ref(s->refcount, reason);
 }
-void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx,
-                              grpc_chttp2_stream_global *stream_global,
+void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx, grpc_chttp2_stream *s,
                               const char *reason) {
-  grpc_stream_unref(exec_ctx, STREAM_FROM_GLOBAL(stream_global)->refcount,
-                    reason);
+  grpc_stream_unref(exec_ctx, s->refcount, reason);
 }
 #else
-void grpc_chttp2_stream_ref(grpc_chttp2_stream_global *stream_global) {
-  grpc_stream_ref(STREAM_FROM_GLOBAL(stream_global)->refcount);
+void grpc_chttp2_stream_ref(grpc_chttp2_stream *s) {
+  grpc_stream_ref(s->refcount);
 }
-void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx,
-                              grpc_chttp2_stream_global *stream_global) {
-  grpc_stream_unref(exec_ctx, STREAM_FROM_GLOBAL(stream_global)->refcount);
+void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx, grpc_chttp2_stream *s) {
+  grpc_stream_unref(exec_ctx, s->refcount);
 }
 #endif
 
-static void finish_init_stream_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s,
-                                      void *arg_ignored) {
-  grpc_chttp2_register_stream(t, s);
-}
-
 static int init_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                        grpc_stream *gs, grpc_stream_refcount *refcount,
                        const void *server_data) {
+  GPR_TIMER_BEGIN("init_stream", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
 
   memset(s, 0, sizeof(*s));
 
+  s->t = t;
   s->refcount = refcount;
   /* We reserve one 'active stream' that's dropped when the stream is
      read-closed. The others are for incoming_byte_streams that are actively
      reading */
-  gpr_ref_init(&s->global.active_streams, 1);
-  GRPC_CHTTP2_STREAM_REF(&s->global, "chttp2");
+  gpr_ref_init(&s->active_streams, 1);
+  GRPC_CHTTP2_STREAM_REF(s, "chttp2");
 
-  grpc_chttp2_incoming_metadata_buffer_init(&s->parsing.metadata_buffer[0]);
-  grpc_chttp2_incoming_metadata_buffer_init(&s->parsing.metadata_buffer[1]);
-  grpc_chttp2_incoming_metadata_buffer_init(
-      &s->global.received_initial_metadata);
-  grpc_chttp2_incoming_metadata_buffer_init(
-      &s->global.received_trailing_metadata);
-  grpc_chttp2_data_parser_init(&s->parsing.data_parser);
-  gpr_slice_buffer_init(&s->writing.flow_controlled_buffer);
-  s->global.deadline = gpr_inf_future(GPR_CLOCK_MONOTONIC);
+  grpc_chttp2_incoming_metadata_buffer_init(&s->metadata_buffer[0]);
+  grpc_chttp2_incoming_metadata_buffer_init(&s->metadata_buffer[1]);
+  grpc_chttp2_data_parser_init(&s->data_parser);
+  gpr_slice_buffer_init(&s->flow_controlled_buffer);
+  s->deadline = gpr_inf_future(GPR_CLOCK_MONOTONIC);
+  grpc_closure_init(&s->complete_fetch, complete_fetch, s);
+  grpc_closure_init(&s->complete_fetch_locked, complete_fetch_locked, s);
 
-  REF_TRANSPORT(t, "stream");
+  GRPC_CHTTP2_REF_TRANSPORT(t, "stream");
 
   if (server_data) {
-    GPR_ASSERT(t->executor.parsing_active);
-    s->global.id = (uint32_t)(uintptr_t)server_data;
-    s->parsing.id = s->global.id;
-    s->global.outgoing_window =
-        t->global.settings[GRPC_PEER_SETTINGS]
-                          [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
-    s->parsing.incoming_window = s->global.max_recv_bytes =
-        t->global.settings[GRPC_SENT_SETTINGS]
-                          [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
+    s->id = (uint32_t)(uintptr_t)server_data;
+    s->outgoing_window = t->settings[GRPC_PEER_SETTINGS]
+                                    [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
+    s->incoming_window = s->max_recv_bytes =
+        t->settings[GRPC_SENT_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
     *t->accepting_stream = s;
-    grpc_chttp2_stream_map_add(&t->parsing_stream_map, s->global.id, s);
-    s->global.in_stream_map = true;
+    grpc_chttp2_stream_map_add(&t->stream_map, s->id, s);
   }
 
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, finish_init_stream_locked,
-                                   NULL, 0);
+  GPR_TIMER_END("init_stream", 0);
 
   return 0;
 }
 
-static void destroy_stream_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s, void *arg) {
+static void destroy_stream_locked(grpc_exec_ctx *exec_ctx, void *sp,
+                                  grpc_error *error) {
   grpc_byte_stream *bs;
+  grpc_chttp2_stream *s = sp;
+  grpc_chttp2_transport *t = s->t;
 
   GPR_TIMER_BEGIN("destroy_stream", 0);
 
-  GPR_ASSERT((s->global.write_closed && s->global.read_closed) ||
-             s->global.id == 0);
-  GPR_ASSERT(!s->global.in_stream_map);
-  if (grpc_chttp2_unregister_stream(t, s) && t->global.sent_goaway) {
-    close_transport_locked(
-        exec_ctx, t,
-        GRPC_ERROR_CREATE("Last stream closed after sending goaway"));
-  }
-  if (!t->executor.parsing_active && s->global.id) {
-    GPR_ASSERT(grpc_chttp2_stream_map_find(&t->parsing_stream_map,
-                                           s->global.id) == NULL);
+  GPR_ASSERT((s->write_closed && s->read_closed) || s->id == 0);
+  if (s->id != 0) {
+    GPR_ASSERT(grpc_chttp2_stream_map_find(&t->stream_map, s->id) == NULL);
   }
 
-  while (
-      (bs = grpc_chttp2_incoming_frame_queue_pop(&s->global.incoming_frames))) {
-    incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
+  while ((bs = grpc_chttp2_incoming_frame_queue_pop(&s->incoming_frames))) {
+    incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
   }
 
-  grpc_chttp2_list_remove_unannounced_incoming_window_available(&t->global,
-                                                                &s->global);
-  grpc_chttp2_list_remove_stalled_by_transport(&t->global, &s->global);
-  grpc_chttp2_list_remove_check_read_ops(&t->global, &s->global);
+  grpc_chttp2_list_remove_stalled_by_transport(t, s);
 
   for (int i = 0; i < STREAM_LIST_COUNT; i++) {
     if (s->included[i]) {
       gpr_log(GPR_ERROR, "%s stream %d still included in list %d",
-              t->global.is_client ? "client" : "server", s->global.id, i);
+              t->is_client ? "client" : "server", s->id, i);
       abort();
     }
   }
 
-  GPR_ASSERT(s->global.send_initial_metadata_finished == NULL);
-  GPR_ASSERT(s->global.send_message_finished == NULL);
-  GPR_ASSERT(s->global.send_trailing_metadata_finished == NULL);
-  GPR_ASSERT(s->global.recv_initial_metadata_ready == NULL);
-  GPR_ASSERT(s->global.recv_message_ready == NULL);
-  GPR_ASSERT(s->global.recv_trailing_metadata_finished == NULL);
-  grpc_chttp2_data_parser_destroy(exec_ctx, &s->parsing.data_parser);
-  grpc_chttp2_incoming_metadata_buffer_destroy(&s->parsing.metadata_buffer[0]);
-  grpc_chttp2_incoming_metadata_buffer_destroy(&s->parsing.metadata_buffer[1]);
-  grpc_chttp2_incoming_metadata_buffer_destroy(
-      &s->global.received_initial_metadata);
-  grpc_chttp2_incoming_metadata_buffer_destroy(
-      &s->global.received_trailing_metadata);
-  gpr_slice_buffer_destroy(&s->writing.flow_controlled_buffer);
-  GRPC_ERROR_UNREF(s->global.read_closed_error);
-  GRPC_ERROR_UNREF(s->global.write_closed_error);
-
-  UNREF_TRANSPORT(exec_ctx, t, "stream");
+  GPR_ASSERT(s->send_initial_metadata_finished == NULL);
+  GPR_ASSERT(s->fetching_send_message == NULL);
+  GPR_ASSERT(s->send_trailing_metadata_finished == NULL);
+  GPR_ASSERT(s->recv_initial_metadata_ready == NULL);
+  GPR_ASSERT(s->recv_message_ready == NULL);
+  GPR_ASSERT(s->recv_trailing_metadata_finished == NULL);
+  grpc_chttp2_data_parser_destroy(exec_ctx, &s->data_parser);
+  grpc_chttp2_incoming_metadata_buffer_destroy(&s->metadata_buffer[0]);
+  grpc_chttp2_incoming_metadata_buffer_destroy(&s->metadata_buffer[1]);
+  gpr_slice_buffer_destroy(&s->flow_controlled_buffer);
+  GRPC_ERROR_UNREF(s->read_closed_error);
+  GRPC_ERROR_UNREF(s->write_closed_error);
+
+  GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "stream");
 
   GPR_TIMER_END("destroy_stream", 0);
 
-  gpr_free(arg);
+  gpr_free(s->destroy_stream_arg);
 }
 
 static void destroy_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                            grpc_stream *gs, void *and_free_memory) {
+  GPR_TIMER_BEGIN("destroy_stream", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
 
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, destroy_stream_locked,
-                                   and_free_memory, 0);
+  s->destroy_stream_arg = and_free_memory;
+  grpc_closure_init(&s->destroy_stream, destroy_stream_locked, s);
+  grpc_combiner_execute(exec_ctx, t->combiner, &s->destroy_stream,
+                        GRPC_ERROR_NONE, false);
+  GPR_TIMER_END("destroy_stream", 0);
 }
 
-grpc_chttp2_stream_parsing *grpc_chttp2_parsing_lookup_stream(
-    grpc_chttp2_transport_parsing *transport_parsing, uint32_t id) {
-  grpc_chttp2_transport *t = TRANSPORT_FROM_PARSING(transport_parsing);
-  grpc_chttp2_stream *s =
-      grpc_chttp2_stream_map_find(&t->parsing_stream_map, id);
-  return s ? &s->parsing : NULL;
+grpc_chttp2_stream *grpc_chttp2_parsing_lookup_stream(grpc_chttp2_transport *t,
+                                                      uint32_t id) {
+  return grpc_chttp2_stream_map_find(&t->stream_map, id);
 }
 
-grpc_chttp2_stream_parsing *grpc_chttp2_parsing_accept_stream(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    uint32_t id) {
+grpc_chttp2_stream *grpc_chttp2_parsing_accept_stream(grpc_exec_ctx *exec_ctx,
+                                                      grpc_chttp2_transport *t,
+                                                      uint32_t id) {
   grpc_chttp2_stream *accepting;
-  grpc_chttp2_transport *t = TRANSPORT_FROM_PARSING(transport_parsing);
   GPR_ASSERT(t->accepting_stream == NULL);
   t->accepting_stream = &accepting;
   t->channel_callback.accept_stream(exec_ctx,
                                     t->channel_callback.accept_stream_user_data,
                                     &t->base, (void *)(uintptr_t)id);
   t->accepting_stream = NULL;
-  return &accepting->parsing;
+  return accepting;
 }
 
 /*******************************************************************************
- * LOCK MANAGEMENT
+ * OUTPUT PROCESSING
  */
 
-static const char *write_state_name(grpc_chttp2_write_state state) {
-  switch (state) {
-    case GRPC_CHTTP2_WRITING_INACTIVE:
-      return "INACTIVE";
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
-      return "REQUESTED[p=0]";
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-      return "REQUESTED[p=1]";
-    case GRPC_CHTTP2_WRITE_SCHEDULED:
-      return "SCHEDULED";
-    case GRPC_CHTTP2_WRITING:
+static const char *write_state_name(grpc_chttp2_write_state st) {
+  switch (st) {
+    case GRPC_CHTTP2_WRITE_STATE_IDLE:
+      return "IDLE";
+    case GRPC_CHTTP2_WRITE_STATE_WRITING:
       return "WRITING";
-    case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-      return "WRITING[p=1]";
-    case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-      return "WRITING[p=0]";
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE:
+      return "WRITING+MORE";
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
+      return "WRITING+MORE+COVERED";
   }
   GPR_UNREACHABLE_CODE(return "UNKNOWN");
 }
 
 static void set_write_state(grpc_chttp2_transport *t,
-                            grpc_chttp2_write_state state, const char *reason) {
-  if (grpc_http_write_state_trace) {
-    gpr_log(GPR_DEBUG, "W:%p %s -> %s because %s", t,
-            write_state_name(t->executor.write_state), write_state_name(state),
-            reason);
-  }
-  t->executor.write_state = state;
-}
-
-static void finish_global_actions(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t) {
-  grpc_chttp2_executor_action_header *hdr;
-  grpc_chttp2_executor_action_header *next;
-
-  GPR_TIMER_BEGIN("finish_global_actions", 0);
-
-  for (;;) {
-    check_read_ops(exec_ctx, &t->global);
-
-    gpr_mu_lock(&t->executor.mu);
-    if (t->executor.pending_actions_head != NULL) {
-      hdr = t->executor.pending_actions_head;
-      t->executor.pending_actions_head = t->executor.pending_actions_tail =
-          NULL;
-      gpr_mu_unlock(&t->executor.mu);
-      while (hdr != NULL) {
-        GPR_TIMER_BEGIN("chttp2:locked_action", 0);
-        hdr->action(exec_ctx, t, hdr->stream, hdr->arg);
-        GPR_TIMER_END("chttp2:locked_action", 0);
-        next = hdr->next;
-        gpr_free(hdr);
-        UNREF_TRANSPORT(exec_ctx, t, "pending_action");
-        hdr = next;
-      }
-      continue;
-    } else {
-      t->executor.global_active = false;
-      switch (t->executor.write_state) {
-        case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-          set_write_state(t, GRPC_CHTTP2_WRITE_SCHEDULED, "unlocking");
-          REF_TRANSPORT(t, "initiate_writing");
-          gpr_mu_unlock(&t->executor.mu);
-          grpc_exec_ctx_sched(
-              exec_ctx, &t->initiate_writing, GRPC_ERROR_NONE,
-              t->ep != NULL ? grpc_endpoint_get_workqueue(t->ep) : NULL);
-          break;
-        case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
-          start_writing(exec_ctx, t);
-          gpr_mu_unlock(&t->executor.mu);
-          break;
-        case GRPC_CHTTP2_WRITING_INACTIVE:
-        case GRPC_CHTTP2_WRITING:
-        case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-        case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-        case GRPC_CHTTP2_WRITE_SCHEDULED:
-          gpr_mu_unlock(&t->executor.mu);
-          break;
-      }
-    }
-    break;
-  }
-
-  GPR_TIMER_END("finish_global_actions", 0);
+                            grpc_chttp2_write_state st, const char *reason) {
+  GRPC_CHTTP2_IF_TRACING(gpr_log(GPR_DEBUG, "W:%p %s state %s -> %s [%s]", t,
+                                 t->is_client ? "CLIENT" : "SERVER",
+                                 write_state_name(t->write_state),
+                                 write_state_name(st), reason));
+  t->write_state = st;
 }
 
-void grpc_chttp2_run_with_global_lock(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *optional_stream,
-                                      grpc_chttp2_locked_action action,
-                                      void *arg, size_t sizeof_arg) {
-  grpc_chttp2_executor_action_header *hdr;
-
-  GPR_TIMER_BEGIN("grpc_chttp2_run_with_global_lock", 0);
-
-  REF_TRANSPORT(t, "run_global");
-  gpr_mu_lock(&t->executor.mu);
-
-  for (;;) {
-    if (!t->executor.global_active) {
-      t->executor.global_active = 1;
-      gpr_mu_unlock(&t->executor.mu);
-
-      GPR_TIMER_BEGIN("chttp2:locked_action", 0);
-      action(exec_ctx, t, optional_stream, arg);
-      GPR_TIMER_END("chttp2:locked_action", 0);
-
-      finish_global_actions(exec_ctx, t);
-    } else {
-      gpr_mu_unlock(&t->executor.mu);
-
-      hdr = gpr_malloc(sizeof(*hdr) + sizeof_arg);
-      hdr->stream = optional_stream;
-      hdr->action = action;
-      if (sizeof_arg == 0) {
-        hdr->arg = arg;
-      } else {
-        hdr->arg = hdr + 1;
-        memcpy(hdr->arg, arg, sizeof_arg);
-      }
-
-      gpr_mu_lock(&t->executor.mu);
-      if (!t->executor.global_active) {
-        /* global lock was released while allocating memory: release & retry */
-        gpr_free(hdr);
-        continue;
-      }
-      hdr->next = NULL;
-      if (t->executor.pending_actions_head != NULL) {
-        t->executor.pending_actions_tail =
-            t->executor.pending_actions_tail->next = hdr;
-      } else {
-        t->executor.pending_actions_tail = t->executor.pending_actions_head =
-            hdr;
-      }
-      REF_TRANSPORT(t, "pending_action");
-      gpr_mu_unlock(&t->executor.mu);
-    }
-    break;
-  }
-
-  UNREF_TRANSPORT(exec_ctx, t, "run_global");
-
-  GPR_TIMER_END("grpc_chttp2_run_with_global_lock", 0);
-}
-
-/*******************************************************************************
- * OUTPUT PROCESSING
- */
-
 void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport_global *transport_global,
+                                grpc_chttp2_transport *t,
                                 bool covered_by_poller, const char *reason) {
-  /* Perform state checks, and transition to a scheduled state if appropriate.
-     Each time we finish the global lock execution, we check if we need to
-     write. If we do:
-      - (if there is a poller surrounding the write) schedule
-        initiate_writing, which locks and calls initiate_writing_locked to...
-      - call start_writing, which verifies (under the global lock) that there
-        are things that need to be written by calling
-        grpc_chttp2_unlocking_check_writes, and if so schedules writing_action
-        against the current exec_ctx, to be executed OUTSIDE of the global lock
-      - eventually writing_action results in grpc_chttp2_terminate_writing being
-        called, which re-takes the global lock, updates state, checks if we need
-        to do *another* write immediately, and if so loops back to
-        start_writing.
-
-      Current problems:
-       - too much lock entry/exiting
-       - the writing thread can become stuck indefinitely (punt through the
-         workqueue periodically to fix) */
-
-  grpc_chttp2_transport *t = TRANSPORT_FROM_GLOBAL(transport_global);
-  switch (t->executor.write_state) {
-    case GRPC_CHTTP2_WRITING_INACTIVE:
-      set_write_state(t, covered_by_poller
-                             ? GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER
-                             : GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
-                      reason);
+  GPR_TIMER_BEGIN("grpc_chttp2_initiate_write", 0);
+
+  switch (t->write_state) {
+    case GRPC_CHTTP2_WRITE_STATE_IDLE:
+      set_write_state(t, GRPC_CHTTP2_WRITE_STATE_WRITING, reason);
+      GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->combiner,
+                                    &t->write_action_begin_locked,
+                                    GRPC_ERROR_NONE, covered_by_poller);
       break;
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-      /* nothing to do: write already requested */
+    case GRPC_CHTTP2_WRITE_STATE_WRITING:
+      set_write_state(
+          t,
+          covered_by_poller
+              ? GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER
+              : GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE,
+          reason);
       break;
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE:
       if (covered_by_poller) {
-        /* upgrade to note poller is available to cover the write */
-        set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER, reason);
+        set_write_state(
+            t, GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER,
+            reason);
       }
       break;
-    case GRPC_CHTTP2_WRITE_SCHEDULED:
-      /* nothing to do: write already scheduled */
-      break;
-    case GRPC_CHTTP2_WRITING:
-      set_write_state(t,
-                      covered_by_poller ? GRPC_CHTTP2_WRITING_STALE_WITH_POLLER
-                                        : GRPC_CHTTP2_WRITING_STALE_NO_POLLER,
-                      reason);
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
       break;
-    case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-      /* nothing to do: write already requested */
-      break;
-    case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-      if (covered_by_poller) {
-        /* upgrade to note poller is available to cover the write */
-        set_write_state(t, GRPC_CHTTP2_WRITING_STALE_WITH_POLLER, reason);
-      }
-      break;
-  }
-}
-
-static void start_writing(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t) {
-  GPR_ASSERT(t->executor.write_state == GRPC_CHTTP2_WRITE_SCHEDULED ||
-             t->executor.write_state == GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER);
-  if (!t->closed &&
-      grpc_chttp2_unlocking_check_writes(exec_ctx, &t->global, &t->writing)) {
-    set_write_state(t, GRPC_CHTTP2_WRITING, "start_writing");
-    REF_TRANSPORT(t, "writing");
-    prevent_endpoint_shutdown(t);
-    grpc_exec_ctx_sched(exec_ctx, &t->writing_action, GRPC_ERROR_NONE, NULL);
-  } else {
-    if (t->closed) {
-      set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE,
-                      "start_writing:transport_closed");
-    } else {
-      set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE,
-                      "start_writing:nothing_to_write");
-    }
-    end_waiting_for_write(exec_ctx, t, GRPC_ERROR_NONE, "Nothing to write");
-    if (t->ep && !t->endpoint_reading) {
-      destroy_endpoint(exec_ctx, t);
-    }
   }
-}
-
-static void initiate_writing_locked(grpc_exec_ctx *exec_ctx,
-                                    grpc_chttp2_transport *t,
-                                    grpc_chttp2_stream *s_unused,
-                                    void *arg_ignored) {
-  start_writing(exec_ctx, t);
-  UNREF_TRANSPORT(exec_ctx, t, "initiate_writing");
-}
-
-static void initiate_writing(grpc_exec_ctx *exec_ctx, void *arg,
-                             grpc_error *error) {
-  grpc_chttp2_run_with_global_lock(exec_ctx, arg, NULL, initiate_writing_locked,
-                                   NULL, 0);
+  GPR_TIMER_END("grpc_chttp2_initiate_write", 0);
 }
 
 void grpc_chttp2_become_writable(grpc_exec_ctx *exec_ctx,
-                                 grpc_chttp2_transport_global *transport_global,
-                                 grpc_chttp2_stream_global *stream_global,
-                                 bool covered_by_poller, const char *reason) {
-  if (!TRANSPORT_FROM_GLOBAL(transport_global)->closed &&
-      grpc_chttp2_list_add_writable_stream(transport_global, stream_global)) {
-    GRPC_CHTTP2_STREAM_REF(stream_global, "chttp2_writing");
-    grpc_chttp2_initiate_write(exec_ctx, transport_global, covered_by_poller,
-                               reason);
+                                 grpc_chttp2_transport *t,
+                                 grpc_chttp2_stream *s, bool covered_by_poller,
+                                 const char *reason) {
+  if (!t->closed && grpc_chttp2_list_add_writable_stream(t, s)) {
+    GRPC_CHTTP2_STREAM_REF(s, "chttp2_writing:become");
+    grpc_chttp2_initiate_write(exec_ctx, t, covered_by_poller, reason);
   }
 }
 
-static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                         grpc_chttp2_setting_id id, uint32_t value) {
-  const grpc_chttp2_setting_parameters *sp =
-      &grpc_chttp2_settings_parameters[id];
-  uint32_t use_value = GPR_CLAMP(value, sp->min_value, sp->max_value);
-  if (use_value != value) {
-    gpr_log(GPR_INFO, "Requested parameter %s clamped from %d to %d", sp->name,
-            value, use_value);
-  }
-  if (use_value != t->global.settings[GRPC_LOCAL_SETTINGS][id]) {
-    t->global.settings[GRPC_LOCAL_SETTINGS][id] = use_value;
-    t->global.dirtied_local_settings = 1;
-    grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "push_setting");
+static void write_action_begin_locked(grpc_exec_ctx *exec_ctx, void *gt,
+                                      grpc_error *error_ignored) {
+  GPR_TIMER_BEGIN("write_action_begin_locked", 0);
+  grpc_chttp2_transport *t = gt;
+  GPR_ASSERT(t->write_state != GRPC_CHTTP2_WRITE_STATE_IDLE);
+  if (!t->closed && grpc_chttp2_begin_write(exec_ctx, t)) {
+    set_write_state(t, GRPC_CHTTP2_WRITE_STATE_WRITING, "begin writing");
+    grpc_exec_ctx_sched(exec_ctx, &t->write_action, GRPC_ERROR_NONE, NULL);
+  } else {
+    set_write_state(t, GRPC_CHTTP2_WRITE_STATE_IDLE, "begin writing nothing");
+    GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "writing");
   }
+  GPR_TIMER_END("write_action_begin_locked", 0);
 }
 
-/* error may be GRPC_ERROR_NONE if there is no error allocated yet.
-   In that case, use "reason" as the text for a new error. */
-static void end_waiting_for_write(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t, grpc_error *error,
-                                  const char *reason) {
-  grpc_chttp2_stream_global *stream_global;
-  while (grpc_chttp2_list_pop_closed_waiting_for_writing(&t->global,
-                                                         &stream_global)) {
-    if (error == GRPC_ERROR_NONE && reason != NULL) {
-      /* create error object. */
-      error = GRPC_ERROR_CREATE(reason);
-    }
-    fail_pending_writes(exec_ctx, &t->global, stream_global,
-                        GRPC_ERROR_REF(error));
-    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "finish_writes");
-  }
-  GRPC_ERROR_UNREF(error);
+static void write_action(grpc_exec_ctx *exec_ctx, void *gt, grpc_error *error) {
+  grpc_chttp2_transport *t = gt;
+  GPR_TIMER_BEGIN("write_action", 0);
+  grpc_endpoint_write(exec_ctx, t->ep, &t->outbuf, &t->write_action_end);
+  GPR_TIMER_END("write_action", 0);
 }
 
-static void terminate_writing_with_lock(grpc_exec_ctx *exec_ctx,
-                                        grpc_chttp2_transport *t,
-                                        grpc_chttp2_stream *s_ignored,
-                                        void *a) {
-  grpc_error *error = a;
+static void write_action_end(grpc_exec_ctx *exec_ctx, void *gt,
+                             grpc_error *error) {
+  grpc_chttp2_transport *t = gt;
+  GPR_TIMER_BEGIN("write_action_end", 0);
+  grpc_combiner_execute(exec_ctx, t->combiner, &t->write_action_end_locked,
+                        GRPC_ERROR_REF(error), false);
+  GPR_TIMER_END("write_action_end", 0);
+}
 
-  allow_endpoint_shutdown_locked(exec_ctx, t);
+static void write_action_end_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                    grpc_error *error) {
+  GPR_TIMER_BEGIN("terminate_writing_with_lock", 0);
+  grpc_chttp2_transport *t = tp;
 
   if (error != GRPC_ERROR_NONE) {
     drop_connection(exec_ctx, t, GRPC_ERROR_REF(error));
   }
 
-  grpc_chttp2_cleanup_writing(exec_ctx, &t->global, &t->writing);
-
-  end_waiting_for_write(exec_ctx, t, error, NULL);
+  grpc_chttp2_end_write(exec_ctx, t, GRPC_ERROR_REF(error));
 
-  switch (t->executor.write_state) {
-    case GRPC_CHTTP2_WRITING_INACTIVE:
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
-    case GRPC_CHTTP2_WRITE_SCHEDULED:
+  switch (t->write_state) {
+    case GRPC_CHTTP2_WRITE_STATE_IDLE:
       GPR_UNREACHABLE_CODE(break);
-    case GRPC_CHTTP2_WRITING:
-      set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE, "terminate_writing");
+    case GRPC_CHTTP2_WRITE_STATE_WRITING:
+      GPR_TIMER_MARK("state=writing", 0);
+      set_write_state(t, GRPC_CHTTP2_WRITE_STATE_IDLE, "finish writing");
       break;
-    case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-      set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER,
-                      "terminate_writing");
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE:
+      GPR_TIMER_MARK("state=writing_stale_no_poller", 0);
+      set_write_state(t, GRPC_CHTTP2_WRITE_STATE_WRITING,
+                      "continue writing [!covered]");
+      GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->combiner,
+                                    &t->write_action_begin_locked,
+                                    GRPC_ERROR_NONE, false);
       break;
-    case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-      set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
-                      "terminate_writing");
+    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
+      GPR_TIMER_MARK("state=writing_stale_with_poller", 0);
+      set_write_state(t, GRPC_CHTTP2_WRITE_STATE_WRITING,
+                      "continue writing [covered]");
+      GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->combiner,
+                                    &t->write_action_begin_locked,
+                                    GRPC_ERROR_NONE, true);
       break;
   }
 
-  if (t->ep && !t->endpoint_reading) {
-    destroy_endpoint(exec_ctx, t);
-  }
-
-  UNREF_TRANSPORT(exec_ctx, t, "writing");
-}
-
-void grpc_chttp2_terminate_writing(grpc_exec_ctx *exec_ctx,
-                                   void *transport_writing, grpc_error *error) {
-  grpc_chttp2_transport *t = TRANSPORT_FROM_WRITING(transport_writing);
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, t, NULL, terminate_writing_with_lock, GRPC_ERROR_REF(error), 0);
+  GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "writing");
+  GPR_TIMER_END("terminate_writing_with_lock", 0);
 }
 
-static void writing_action(grpc_exec_ctx *exec_ctx, void *gt,
-                           grpc_error *error) {
-  grpc_chttp2_transport *t = gt;
-  GPR_TIMER_BEGIN("writing_action", 0);
-  grpc_chttp2_perform_writes(exec_ctx, &t->writing, t->ep);
-  GPR_TIMER_END("writing_action", 0);
+static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                         grpc_chttp2_setting_id id, uint32_t value) {
+  const grpc_chttp2_setting_parameters *sp =
+      &grpc_chttp2_settings_parameters[id];
+  uint32_t use_value = GPR_CLAMP(value, sp->min_value, sp->max_value);
+  if (use_value != value) {
+    gpr_log(GPR_INFO, "Requested parameter %s clamped from %d to %d", sp->name,
+            value, use_value);
+  }
+  if (use_value != t->settings[GRPC_LOCAL_SETTINGS][id]) {
+    t->settings[GRPC_LOCAL_SETTINGS][id] = use_value;
+    t->dirtied_local_settings = 1;
+    grpc_chttp2_initiate_write(exec_ctx, t, false, "push_setting");
+  }
 }
 
-void grpc_chttp2_add_incoming_goaway(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    uint32_t goaway_error, gpr_slice goaway_text) {
+void grpc_chttp2_add_incoming_goaway(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t,
+                                     uint32_t goaway_error,
+                                     gpr_slice goaway_text) {
   char *msg = gpr_dump_slice(goaway_text, GPR_DUMP_HEX | GPR_DUMP_ASCII);
   GRPC_CHTTP2_IF_TRACING(
       gpr_log(GPR_DEBUG, "got goaway [%d]: %s", goaway_error, msg));
   gpr_slice_unref(goaway_text);
-  transport_global->seen_goaway = 1;
+  t->seen_goaway = 1;
   /* lie: use transient failure from the transport to indicate goaway has been
    * received */
   connectivity_state_set(
-      exec_ctx, transport_global, GRPC_CHANNEL_TRANSIENT_FAILURE,
+      exec_ctx, t, GRPC_CHANNEL_TRANSIENT_FAILURE,
       grpc_error_set_str(
           grpc_error_set_int(GRPC_ERROR_CREATE("GOAWAY received"),
                              GRPC_ERROR_INT_HTTP2_ERROR,
@@ -1036,61 +716,49 @@ void grpc_chttp2_add_incoming_goaway(
   gpr_free(msg);
 }
 
-static void maybe_start_some_streams(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global) {
-  grpc_chttp2_stream_global *stream_global;
+static void maybe_start_some_streams(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t) {
+  grpc_chttp2_stream *s;
   uint32_t stream_incoming_window;
   /* start streams where we have free grpc_chttp2_stream ids and free
    * concurrency */
-  while (transport_global->next_stream_id <= MAX_CLIENT_STREAM_ID &&
-         transport_global->concurrent_stream_count <
-             transport_global
-                 ->settings[GRPC_PEER_SETTINGS]
-                           [GRPC_CHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS] &&
-         grpc_chttp2_list_pop_waiting_for_concurrency(transport_global,
-                                                      &stream_global)) {
+  while (t->next_stream_id <= MAX_CLIENT_STREAM_ID &&
+         grpc_chttp2_stream_map_size(&t->stream_map) <
+             t->settings[GRPC_PEER_SETTINGS]
+                        [GRPC_CHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS] &&
+         grpc_chttp2_list_pop_waiting_for_concurrency(t, &s)) {
     /* safe since we can't (legally) be parsing this stream yet */
-    grpc_chttp2_stream_parsing *stream_parsing =
-        &STREAM_FROM_GLOBAL(stream_global)->parsing;
     GRPC_CHTTP2_IF_TRACING(gpr_log(
         GPR_DEBUG, "HTTP:%s: Allocating new grpc_chttp2_stream %p to id %d",
-        transport_global->is_client ? "CLI" : "SVR", stream_global,
-        transport_global->next_stream_id));
+        t->is_client ? "CLI" : "SVR", s, t->next_stream_id));
 
-    GPR_ASSERT(stream_global->id == 0);
-    stream_global->id = stream_parsing->id = transport_global->next_stream_id;
-    transport_global->next_stream_id += 2;
+    GPR_ASSERT(s->id == 0);
+    s->id = t->next_stream_id;
+    t->next_stream_id += 2;
 
-    if (transport_global->next_stream_id >= MAX_CLIENT_STREAM_ID) {
-      connectivity_state_set(
-          exec_ctx, transport_global, GRPC_CHANNEL_TRANSIENT_FAILURE,
-          GRPC_ERROR_CREATE("Stream IDs exhausted"), "no_more_stream_ids");
+    if (t->next_stream_id >= MAX_CLIENT_STREAM_ID) {
+      connectivity_state_set(exec_ctx, t, GRPC_CHANNEL_TRANSIENT_FAILURE,
+                             GRPC_ERROR_CREATE("Stream IDs exhausted"),
+                             "no_more_stream_ids");
     }
 
-    stream_global->outgoing_window =
-        transport_global->settings[GRPC_PEER_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
-    stream_parsing->incoming_window = stream_incoming_window =
-        transport_global->settings[GRPC_SENT_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
-    stream_global->max_recv_bytes =
-        GPR_MAX(stream_incoming_window, stream_global->max_recv_bytes);
-    grpc_chttp2_stream_map_add(
-        &TRANSPORT_FROM_GLOBAL(transport_global)->new_stream_map,
-        stream_global->id, STREAM_FROM_GLOBAL(stream_global));
-    stream_global->in_stream_map = true;
-    transport_global->concurrent_stream_count++;
-    grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global, true,
-                                "new_stream");
+    s->outgoing_window = t->settings[GRPC_PEER_SETTINGS]
+                                    [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
+    s->incoming_window = stream_incoming_window =
+        t->settings[GRPC_SENT_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
+    s->max_recv_bytes = GPR_MAX(stream_incoming_window, s->max_recv_bytes);
+    grpc_chttp2_stream_map_add(&t->stream_map, s->id, s);
+    grpc_chttp2_become_writable(exec_ctx, t, s, true, "new_stream");
   }
   /* cancel out streams that will never be started */
-  while (transport_global->next_stream_id >= MAX_CLIENT_STREAM_ID &&
-         grpc_chttp2_list_pop_waiting_for_concurrency(transport_global,
-                                                      &stream_global)) {
-    cancel_from_api(exec_ctx, transport_global, stream_global,
-                    grpc_error_set_int(
-                        GRPC_ERROR_CREATE("Stream IDs exhausted"),
-                        GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE));
+  while (t->next_stream_id >= MAX_CLIENT_STREAM_ID &&
+         grpc_chttp2_list_pop_waiting_for_concurrency(t, &s)) {
+    grpc_chttp2_cancel_stream(
+        exec_ctx, t, s,
+        grpc_error_set_int(GRPC_ERROR_CREATE("Stream IDs exhausted"),
+                           GRPC_ERROR_INT_GRPC_STATUS,
+                           GRPC_STATUS_UNAVAILABLE));
   }
 }
 
@@ -1102,104 +770,188 @@ static grpc_closure *add_closure_barrier(grpc_closure *closure) {
   return closure;
 }
 
-void grpc_chttp2_complete_closure_step(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, grpc_closure **pclosure,
-    grpc_error *error) {
+static void null_then_run_closure(grpc_exec_ctx *exec_ctx,
+                                  grpc_closure **closure, grpc_error *error) {
+  grpc_closure *c = *closure;
+  *closure = NULL;
+  grpc_closure_run(exec_ctx, c, error);
+}
+
+void grpc_chttp2_complete_closure_step(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_transport *t,
+                                       grpc_chttp2_stream *s,
+                                       grpc_closure **pclosure,
+                                       grpc_error *error, const char *desc) {
   grpc_closure *closure = *pclosure;
+  *pclosure = NULL;
   if (closure == NULL) {
     GRPC_ERROR_UNREF(error);
     return;
   }
   closure->next_data.scratch -= CLOSURE_BARRIER_FIRST_REF_BIT;
   if (error != GRPC_ERROR_NONE) {
-    if (closure->error == GRPC_ERROR_NONE) {
-      closure->error =
+    if (closure->error_data.error == GRPC_ERROR_NONE) {
+      closure->error_data.error =
           GRPC_ERROR_CREATE("Error in HTTP transport completing operation");
-      closure->error = grpc_error_set_str(
-          closure->error, GRPC_ERROR_STR_TARGET_ADDRESS,
-          TRANSPORT_FROM_GLOBAL(transport_global)->peer_string);
+      closure->error_data.error =
+          grpc_error_set_str(closure->error_data.error,
+                             GRPC_ERROR_STR_TARGET_ADDRESS, t->peer_string);
     }
-    closure->error = grpc_error_add_child(closure->error, error);
+    closure->error_data.error =
+        grpc_error_add_child(closure->error_data.error, error);
   }
   if (closure->next_data.scratch < CLOSURE_BARRIER_FIRST_REF_BIT) {
     if (closure->next_data.scratch & CLOSURE_BARRIER_STATS_BIT) {
-      grpc_transport_move_stats(&stream_global->stats,
-                                stream_global->collecting_stats);
-      stream_global->collecting_stats = NULL;
+      grpc_transport_move_stats(&s->stats, s->collecting_stats);
+      s->collecting_stats = NULL;
     }
-    grpc_exec_ctx_sched(exec_ctx, closure, closure->error, NULL);
+    grpc_closure_run(exec_ctx, closure, closure->error_data.error);
   }
-  *pclosure = NULL;
 }
 
-static int contains_non_ok_status(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_metadata_batch *batch) {
+static bool contains_non_ok_status(grpc_metadata_batch *batch) {
   grpc_linked_mdelem *l;
   for (l = batch->list.head; l; l = l->next) {
     if (l->md->key == GRPC_MDSTR_GRPC_STATUS &&
         l->md != GRPC_MDELEM_GRPC_STATUS_0) {
-      return 1;
+      return true;
     }
   }
-  return 0;
+  return false;
 }
 
-static void do_nothing(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {}
+static void add_fetched_slice_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t,
+                                     grpc_chttp2_stream *s);
+
+static void continue_fetching_send_locked(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s) {
+  if (s->fetching_send_message == NULL) {
+    /* Stream was cancelled before message fetch completed */
+    abort(); /* TODO(ctiller): what cleanup here? */
+    return;
+  }
+  if (s->fetched_send_message_length == s->fetching_send_message->length) {
+    ssize_t notify_offset = s->fetching_slice_end_offset;
+    if (notify_offset <= 0) {
+      grpc_chttp2_complete_closure_step(
+          exec_ctx, t, s, &s->fetching_send_message_finished, GRPC_ERROR_NONE,
+          "fetching_send_message_finished");
+    } else {
+      grpc_chttp2_write_cb *cb = t->write_cb_pool;
+      if (cb == NULL) {
+        cb = gpr_malloc(sizeof(*cb));
+      } else {
+        t->write_cb_pool = cb->next;
+      }
+      cb->call_at_byte = (size_t)notify_offset;
+      cb->closure = s->fetching_send_message_finished;
+      s->fetching_send_message_finished = NULL;
+      cb->next = s->on_write_finished_cbs;
+      s->on_write_finished_cbs = cb;
+    }
+    s->fetching_send_message = NULL;
+  } else if (grpc_byte_stream_next(exec_ctx, s->fetching_send_message,
+                                   &s->fetching_slice, UINT32_MAX,
+                                   &s->complete_fetch)) {
+    add_fetched_slice_locked(exec_ctx, t, s);
+  }
+}
 
-static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
+static void add_fetched_slice_locked(grpc_exec_ctx *exec_ctx,
                                      grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s, void *stream_op) {
+                                     grpc_chttp2_stream *s) {
+  s->fetched_send_message_length +=
+      (uint32_t)GPR_SLICE_LENGTH(s->fetching_slice);
+  gpr_slice_buffer_add(&s->flow_controlled_buffer, s->fetching_slice);
+  if (s->id != 0) {
+    grpc_chttp2_become_writable(exec_ctx, t, s, true, "op.send_message");
+  }
+  continue_fetching_send_locked(exec_ctx, t, s);
+}
+
+static void complete_fetch_locked(grpc_exec_ctx *exec_ctx, void *gs,
+                                  grpc_error *error) {
+  grpc_chttp2_stream *s = gs;
+  grpc_chttp2_transport *t = s->t;
+  if (error == GRPC_ERROR_NONE) {
+    add_fetched_slice_locked(exec_ctx, t, s);
+  } else {
+    /* TODO(ctiller): what to do here */
+    abort();
+  }
+}
+
+static void complete_fetch(grpc_exec_ctx *exec_ctx, void *gs,
+                           grpc_error *error) {
+  grpc_chttp2_stream *s = gs;
+  grpc_chttp2_transport *t = s->t;
+  grpc_combiner_execute(exec_ctx, t->combiner, &s->complete_fetch_locked,
+                        GRPC_ERROR_REF(error),
+                        s->complete_fetch_covered_by_poller);
+}
+
+static void do_nothing(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {}
+
+static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
+                                     grpc_error *error_ignored) {
   GPR_TIMER_BEGIN("perform_stream_op_locked", 0);
 
   grpc_transport_stream_op *op = stream_op;
-  grpc_chttp2_transport_global *transport_global = &t->global;
-  grpc_chttp2_stream_global *stream_global = &s->global;
+  grpc_chttp2_transport *t = op->transport_private.args[0];
+  grpc_chttp2_stream *s = op->transport_private.args[1];
+
+  if (grpc_http_trace) {
+    char *str = grpc_transport_stream_op_string(op);
+    gpr_log(GPR_DEBUG, "perform_stream_op_locked: %s", str);
+    gpr_free(str);
+  }
 
   grpc_closure *on_complete = op->on_complete;
   if (on_complete == NULL) {
     on_complete = grpc_closure_create(do_nothing, NULL);
   }
+
+  if (grpc_http_trace) {
+    gpr_log(GPR_DEBUG, "  on_complete = %p", on_complete);
+  }
+
   /* use final_data as a barrier until enqueue time; the inital counter is
      dropped at the end of this function */
   on_complete->next_data.scratch = CLOSURE_BARRIER_FIRST_REF_BIT;
-  on_complete->error = GRPC_ERROR_NONE;
+  on_complete->error_data.error = GRPC_ERROR_NONE;
 
   if (op->collect_stats != NULL) {
-    GPR_ASSERT(stream_global->collecting_stats == NULL);
-    stream_global->collecting_stats = op->collect_stats;
+    GPR_ASSERT(s->collecting_stats == NULL);
+    s->collecting_stats = op->collect_stats;
     on_complete->next_data.scratch |= CLOSURE_BARRIER_STATS_BIT;
   }
 
   if (op->cancel_error != GRPC_ERROR_NONE) {
-    cancel_from_api(exec_ctx, transport_global, stream_global,
-                    GRPC_ERROR_REF(op->cancel_error));
+    grpc_chttp2_cancel_stream(exec_ctx, t, s, GRPC_ERROR_REF(op->cancel_error));
   }
 
   if (op->close_error != GRPC_ERROR_NONE) {
-    close_from_api(exec_ctx, transport_global, stream_global,
-                   GRPC_ERROR_REF(op->close_error));
+    close_from_api(exec_ctx, t, s, GRPC_ERROR_REF(op->close_error));
   }
 
   if (op->send_initial_metadata != NULL) {
-    GPR_ASSERT(stream_global->send_initial_metadata_finished == NULL);
-    stream_global->send_initial_metadata_finished =
-        add_closure_barrier(on_complete);
-    stream_global->send_initial_metadata = op->send_initial_metadata;
+    GPR_ASSERT(s->send_initial_metadata_finished == NULL);
+    s->send_initial_metadata_finished = add_closure_barrier(on_complete);
+    s->send_initial_metadata = op->send_initial_metadata;
     const size_t metadata_size =
         grpc_metadata_batch_size(op->send_initial_metadata);
     const size_t metadata_peer_limit =
-        transport_global->settings[GRPC_PEER_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
-    if (transport_global->is_client) {
-      stream_global->deadline =
-          gpr_time_min(stream_global->deadline,
-                       stream_global->send_initial_metadata->deadline);
+        t->settings[GRPC_PEER_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
+    if (t->is_client) {
+      s->deadline =
+          gpr_time_min(s->deadline, s->send_initial_metadata->deadline);
     }
     if (metadata_size > metadata_peer_limit) {
-      cancel_from_api(
-          exec_ctx, transport_global, stream_global,
+      grpc_chttp2_cancel_stream(
+          exec_ctx, t, s,
           grpc_error_set_int(
               grpc_error_set_int(
                   grpc_error_set_int(
@@ -1209,63 +961,75 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
                   GRPC_ERROR_INT_LIMIT, (intptr_t)metadata_peer_limit),
               GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
     } else {
-      if (contains_non_ok_status(transport_global, op->send_initial_metadata)) {
-        stream_global->seen_error = true;
-        grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      if (contains_non_ok_status(op->send_initial_metadata)) {
+        s->seen_error = true;
       }
-      if (!stream_global->write_closed) {
-        if (transport_global->is_client) {
-          GPR_ASSERT(stream_global->id == 0);
-          grpc_chttp2_list_add_waiting_for_concurrency(transport_global,
-                                                       stream_global);
-          maybe_start_some_streams(exec_ctx, transport_global);
+      if (!s->write_closed) {
+        if (t->is_client) {
+          GPR_ASSERT(s->id == 0);
+          grpc_chttp2_list_add_waiting_for_concurrency(t, s);
+          maybe_start_some_streams(exec_ctx, t);
         } else {
-          GPR_ASSERT(stream_global->id != 0);
-          grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                      true, "op.send_initial_metadata");
+          GPR_ASSERT(s->id != 0);
+          grpc_chttp2_become_writable(exec_ctx, t, s, true,
+                                      "op.send_initial_metadata");
         }
       } else {
-        stream_global->send_trailing_metadata = NULL;
+        s->send_trailing_metadata = NULL;
         grpc_chttp2_complete_closure_step(
-            exec_ctx, transport_global, stream_global,
-            &stream_global->send_initial_metadata_finished,
+            exec_ctx, t, s, &s->send_initial_metadata_finished,
             GRPC_ERROR_CREATE(
-                "Attempt to send initial metadata after stream was closed"));
+                "Attempt to send initial metadata after stream was closed"),
+            "send_initial_metadata_finished");
       }
     }
   }
 
   if (op->send_message != NULL) {
-    GPR_ASSERT(stream_global->send_message_finished == NULL);
-    GPR_ASSERT(stream_global->send_message == NULL);
-    stream_global->send_message_finished = add_closure_barrier(on_complete);
-    if (stream_global->write_closed) {
+    s->fetching_send_message_finished = add_closure_barrier(op->on_complete);
+    if (s->write_closed) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, transport_global, stream_global,
-          &stream_global->send_message_finished,
-          GRPC_ERROR_CREATE("Attempt to send message after stream was closed"));
+          exec_ctx, t, s, &s->fetching_send_message_finished,
+          GRPC_ERROR_CREATE("Attempt to send message after stream was closed"),
+          "fetching_send_message_finished");
     } else {
-      stream_global->send_message = op->send_message;
-      if (stream_global->id != 0) {
-        grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                    true, "op.send_message");
+      GPR_ASSERT(s->fetching_send_message == NULL);
+      uint8_t *frame_hdr =
+          gpr_slice_buffer_tiny_add(&s->flow_controlled_buffer, 5);
+      uint32_t flags = op->send_message->flags;
+      frame_hdr[0] = (flags & GRPC_WRITE_INTERNAL_COMPRESS) != 0;
+      size_t len = op->send_message->length;
+      frame_hdr[1] = (uint8_t)(len >> 24);
+      frame_hdr[2] = (uint8_t)(len >> 16);
+      frame_hdr[3] = (uint8_t)(len >> 8);
+      frame_hdr[4] = (uint8_t)(len);
+      s->fetching_send_message = op->send_message;
+      s->fetched_send_message_length = 0;
+      s->fetching_slice_end_offset =
+          (ssize_t)s->flow_controlled_buffer.length + (ssize_t)len;
+      s->complete_fetch_covered_by_poller = op->covered_by_poller;
+      if (flags & GRPC_WRITE_BUFFER_HINT) {
+        s->fetching_slice_end_offset -= 65536;
+      }
+      continue_fetching_send_locked(exec_ctx, t, s);
+      if (s->id != 0) {
+        grpc_chttp2_become_writable(exec_ctx, t, s, true, "op.send_message");
       }
     }
   }
 
   if (op->send_trailing_metadata != NULL) {
-    GPR_ASSERT(stream_global->send_trailing_metadata_finished == NULL);
-    stream_global->send_trailing_metadata_finished =
-        add_closure_barrier(on_complete);
-    stream_global->send_trailing_metadata = op->send_trailing_metadata;
+    GPR_ASSERT(s->send_trailing_metadata_finished == NULL);
+    s->send_trailing_metadata_finished = add_closure_barrier(on_complete);
+    s->send_trailing_metadata = op->send_trailing_metadata;
     const size_t metadata_size =
         grpc_metadata_batch_size(op->send_trailing_metadata);
     const size_t metadata_peer_limit =
-        transport_global->settings[GRPC_PEER_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
+        t->settings[GRPC_PEER_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
     if (metadata_size > metadata_peer_limit) {
-      cancel_from_api(
-          exec_ctx, transport_global, stream_global,
+      grpc_chttp2_cancel_stream(
+          exec_ctx, t, s,
           grpc_error_set_int(
               grpc_error_set_int(
                   grpc_error_set_int(
@@ -1275,135 +1039,129 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
                   GRPC_ERROR_INT_LIMIT, (intptr_t)metadata_peer_limit),
               GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
     } else {
-      if (contains_non_ok_status(transport_global,
-                                 op->send_trailing_metadata)) {
-        stream_global->seen_error = true;
-        grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      if (contains_non_ok_status(op->send_trailing_metadata)) {
+        s->seen_error = true;
       }
-      if (stream_global->write_closed) {
-        stream_global->send_trailing_metadata = NULL;
+      if (s->write_closed) {
+        s->send_trailing_metadata = NULL;
         grpc_chttp2_complete_closure_step(
-            exec_ctx, transport_global, stream_global,
-            &stream_global->send_trailing_metadata_finished,
+            exec_ctx, t, s, &s->send_trailing_metadata_finished,
             grpc_metadata_batch_is_empty(op->send_trailing_metadata)
                 ? GRPC_ERROR_NONE
                 : GRPC_ERROR_CREATE("Attempt to send trailing metadata after "
-                                    "stream was closed"));
-      } else if (stream_global->id != 0) {
+                                    "stream was closed"),
+            "send_trailing_metadata_finished");
+      } else if (s->id != 0) {
         /* TODO(ctiller): check if there's flow control for any outstanding
            bytes before going writable */
-        grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                    true, "op.send_trailing_metadata");
+        grpc_chttp2_become_writable(exec_ctx, t, s, true,
+                                    "op.send_trailing_metadata");
       }
     }
   }
 
   if (op->recv_initial_metadata != NULL) {
-    GPR_ASSERT(stream_global->recv_initial_metadata_ready == NULL);
-    stream_global->recv_initial_metadata_ready =
-        op->recv_initial_metadata_ready;
-    stream_global->recv_initial_metadata = op->recv_initial_metadata;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    GPR_ASSERT(s->recv_initial_metadata_ready == NULL);
+    s->recv_initial_metadata_ready = op->recv_initial_metadata_ready;
+    s->recv_initial_metadata = op->recv_initial_metadata;
+    grpc_chttp2_maybe_complete_recv_initial_metadata(exec_ctx, t, s);
   }
 
   if (op->recv_message != NULL) {
-    GPR_ASSERT(stream_global->recv_message_ready == NULL);
-    stream_global->recv_message_ready = op->recv_message_ready;
-    stream_global->recv_message = op->recv_message;
-    if (stream_global->id != 0 &&
-        (stream_global->incoming_frames.head == NULL ||
-         stream_global->incoming_frames.head->is_tail)) {
-      incoming_byte_stream_update_flow_control(
-          exec_ctx, transport_global, stream_global,
-          transport_global->stream_lookahead, 0);
+    GPR_ASSERT(s->recv_message_ready == NULL);
+    s->recv_message_ready = op->recv_message_ready;
+    s->recv_message = op->recv_message;
+    if (s->id != 0 &&
+        (s->incoming_frames.head == NULL || s->incoming_frames.head->is_tail)) {
+      incoming_byte_stream_update_flow_control(exec_ctx, t, s,
+                                               t->stream_lookahead, 0);
     }
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_maybe_complete_recv_message(exec_ctx, t, s);
   }
 
   if (op->recv_trailing_metadata != NULL) {
-    GPR_ASSERT(stream_global->recv_trailing_metadata_finished == NULL);
-    stream_global->recv_trailing_metadata_finished =
-        add_closure_barrier(on_complete);
-    stream_global->recv_trailing_metadata = op->recv_trailing_metadata;
-    stream_global->final_metadata_requested = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    GPR_ASSERT(s->recv_trailing_metadata_finished == NULL);
+    s->recv_trailing_metadata_finished = add_closure_barrier(on_complete);
+    s->recv_trailing_metadata = op->recv_trailing_metadata;
+    s->final_metadata_requested = true;
+    grpc_chttp2_maybe_complete_recv_trailing_metadata(exec_ctx, t, s);
   }
 
-  grpc_chttp2_complete_closure_step(exec_ctx, transport_global, stream_global,
-                                    &on_complete, GRPC_ERROR_NONE);
+  grpc_chttp2_complete_closure_step(exec_ctx, t, s, &on_complete,
+                                    GRPC_ERROR_NONE, "op->on_complete");
 
   GPR_TIMER_END("perform_stream_op_locked", 0);
+  GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "perform_stream_op");
 }
 
 static void perform_stream_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                               grpc_stream *gs, grpc_transport_stream_op *op) {
+  GPR_TIMER_BEGIN("perform_stream_op", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, perform_stream_op_locked, op,
-                                   sizeof(*op));
+
+  if (grpc_http_trace) {
+    char *str = grpc_transport_stream_op_string(op);
+    gpr_log(GPR_DEBUG, "perform_stream_op[s=%p/%d]: %s", s, s->id, str);
+    gpr_free(str);
+  }
+
+  grpc_closure_init(&op->transport_private.closure, perform_stream_op_locked,
+                    op);
+  op->transport_private.args[0] = gt;
+  op->transport_private.args[1] = gs;
+  GRPC_CHTTP2_STREAM_REF(s, "perform_stream_op");
+  grpc_combiner_execute(exec_ctx, t->combiner, &op->transport_private.closure,
+                        GRPC_ERROR_NONE, op->covered_by_poller);
+  GPR_TIMER_END("perform_stream_op", 0);
 }
 
 static void send_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                              grpc_closure *on_recv) {
   grpc_chttp2_outstanding_ping *p = gpr_malloc(sizeof(*p));
-  p->next = &t->global.pings;
+  p->next = &t->pings;
   p->prev = p->next->prev;
   p->prev->next = p->next->prev = p;
-  p->id[0] = (uint8_t)((t->global.ping_counter >> 56) & 0xff);
-  p->id[1] = (uint8_t)((t->global.ping_counter >> 48) & 0xff);
-  p->id[2] = (uint8_t)((t->global.ping_counter >> 40) & 0xff);
-  p->id[3] = (uint8_t)((t->global.ping_counter >> 32) & 0xff);
-  p->id[4] = (uint8_t)((t->global.ping_counter >> 24) & 0xff);
-  p->id[5] = (uint8_t)((t->global.ping_counter >> 16) & 0xff);
-  p->id[6] = (uint8_t)((t->global.ping_counter >> 8) & 0xff);
-  p->id[7] = (uint8_t)(t->global.ping_counter & 0xff);
+  p->id[0] = (uint8_t)((t->ping_counter >> 56) & 0xff);
+  p->id[1] = (uint8_t)((t->ping_counter >> 48) & 0xff);
+  p->id[2] = (uint8_t)((t->ping_counter >> 40) & 0xff);
+  p->id[3] = (uint8_t)((t->ping_counter >> 32) & 0xff);
+  p->id[4] = (uint8_t)((t->ping_counter >> 24) & 0xff);
+  p->id[5] = (uint8_t)((t->ping_counter >> 16) & 0xff);
+  p->id[6] = (uint8_t)((t->ping_counter >> 8) & 0xff);
+  p->id[7] = (uint8_t)(t->ping_counter & 0xff);
+  t->ping_counter++;
   p->on_recv = on_recv;
-  gpr_slice_buffer_add(&t->global.qbuf, grpc_chttp2_ping_create(0, p->id));
-  grpc_chttp2_initiate_write(exec_ctx, &t->global, true, "send_ping");
+  gpr_slice_buffer_add(&t->qbuf, grpc_chttp2_ping_create(0, p->id));
+  grpc_chttp2_initiate_write(exec_ctx, t, true, "send_ping");
 }
 
-static void ack_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                            grpc_chttp2_stream *s, void *opaque_8bytes) {
+void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                          const uint8_t *opaque_8bytes) {
   grpc_chttp2_outstanding_ping *ping;
-  grpc_chttp2_transport_global *transport_global = &t->global;
-  for (ping = transport_global->pings.next; ping != &transport_global->pings;
-       ping = ping->next) {
+  for (ping = t->pings.next; ping != &t->pings; ping = ping->next) {
     if (0 == memcmp(opaque_8bytes, ping->id, 8)) {
       grpc_exec_ctx_sched(exec_ctx, ping->on_recv, GRPC_ERROR_NONE, NULL);
       ping->next->prev = ping->prev;
       ping->prev->next = ping->next;
       gpr_free(ping);
-      break;
+      return;
     }
   }
-}
-
-void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx,
-                          grpc_chttp2_transport_parsing *transport_parsing,
-                          const uint8_t *opaque_8bytes) {
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, TRANSPORT_FROM_PARSING(transport_parsing), NULL,
-      ack_ping_locked, (void *)opaque_8bytes, 8);
+  char *msg = gpr_dump((const char *)opaque_8bytes, 8, GPR_DUMP_HEX);
+  char *from = grpc_endpoint_get_peer(t->ep);
+  gpr_log(GPR_DEBUG, "Unknown ping response from %s: %s", from, msg);
+  gpr_free(from);
+  gpr_free(msg);
 }
 
 static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
-                                        grpc_chttp2_transport *t,
-                                        grpc_chttp2_stream *s_unused,
-                                        void *stream_op) {
+                                        void *stream_op,
+                                        grpc_error *error_ignored) {
   grpc_transport_op *op = stream_op;
+  grpc_chttp2_transport *t = op->transport_private.args[0];
   grpc_error *close_transport = op->disconnect_with_error;
 
-  /* If there's a set_accept_stream ensure that we're not parsing
-     to avoid changing things out from underneath */
-  if (t->executor.parsing_active && op->set_accept_stream) {
-    GPR_ASSERT(t->post_parsing_op == NULL);
-    t->post_parsing_op = gpr_malloc(sizeof(*op));
-    memcpy(t->post_parsing_op, op, sizeof(*op));
-    return;
-  }
-
-  grpc_exec_ctx_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE, NULL);
-
   if (op->on_connectivity_state_change != NULL) {
     grpc_connectivity_state_notify_on_state_change(
         exec_ctx, &t->channel_callback.state_tracker, op->connectivity_state,
@@ -1411,15 +1169,15 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   }
 
   if (op->send_goaway) {
-    t->global.sent_goaway = 1;
+    t->sent_goaway = 1;
     grpc_chttp2_goaway_append(
-        t->global.last_incoming_stream_id,
+        t->last_new_stream_id,
         (uint32_t)grpc_chttp2_grpc_status_to_http2_error(op->goaway_status),
-        gpr_slice_ref(*op->goaway_message), &t->global.qbuf);
-    close_transport = grpc_chttp2_has_streams(t)
-                          ? GRPC_ERROR_NONE
-                          : GRPC_ERROR_CREATE("GOAWAY sent");
-    grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "goaway_sent");
+        gpr_slice_ref(*op->goaway_message), &t->qbuf);
+    close_transport = grpc_chttp2_stream_map_size(&t->stream_map) == 0
+                          ? GRPC_ERROR_CREATE("GOAWAY sent")
+                          : GRPC_ERROR_NONE;
+    grpc_chttp2_initiate_write(exec_ctx, t, false, "goaway_sent");
   }
 
   if (op->set_accept_stream) {
@@ -1429,11 +1187,11 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   }
 
   if (op->bind_pollset) {
-    add_to_pollset_locked(exec_ctx, t, NULL, op->bind_pollset);
+    grpc_endpoint_add_to_pollset(exec_ctx, t->ep, op->bind_pollset);
   }
 
   if (op->bind_pollset_set) {
-    add_to_pollset_set_locked(exec_ctx, t, NULL, op->bind_pollset_set);
+    grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, op->bind_pollset_set);
   }
 
   if (op->send_ping) {
@@ -1443,144 +1201,131 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   if (close_transport != GRPC_ERROR_NONE) {
     close_transport_locked(exec_ctx, t, close_transport);
   }
+
+  grpc_closure_run(exec_ctx, op->on_consumed, GRPC_ERROR_NONE);
+
+  GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "transport_op");
 }
 
 static void perform_transport_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                                  grpc_transport_op *op) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, t, NULL, perform_transport_op_locked, op, sizeof(*op));
+  char *msg = grpc_transport_op_string(op);
+  gpr_free(msg);
+  op->transport_private.args[0] = gt;
+  grpc_closure_init(&op->transport_private.closure, perform_transport_op_locked,
+                    op);
+  GRPC_CHTTP2_REF_TRANSPORT(t, "transport_op");
+  grpc_combiner_execute(exec_ctx, t->combiner, &op->transport_private.closure,
+                        GRPC_ERROR_NONE, false);
 }
 
 /*******************************************************************************
  * INPUT PROCESSING - GENERAL
  */
 
-static void check_read_ops(grpc_exec_ctx *exec_ctx,
-                           grpc_chttp2_transport_global *transport_global) {
-  grpc_chttp2_stream_global *stream_global;
+void grpc_chttp2_maybe_complete_recv_initial_metadata(grpc_exec_ctx *exec_ctx,
+                                                      grpc_chttp2_transport *t,
+                                                      grpc_chttp2_stream *s) {
   grpc_byte_stream *bs;
-  while (
-      grpc_chttp2_list_pop_check_read_ops(transport_global, &stream_global)) {
-    if (stream_global->recv_initial_metadata_ready != NULL &&
-        stream_global->published_initial_metadata) {
-      if (stream_global->seen_error) {
-        while ((bs = grpc_chttp2_incoming_frame_queue_pop(
-                    &stream_global->incoming_frames)) != NULL) {
-          incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
-        }
-        if (stream_global->exceeded_metadata_size) {
-          cancel_from_api(
-              exec_ctx, transport_global, stream_global,
-              grpc_error_set_int(
-                  GRPC_ERROR_CREATE(
-                      "received initial metadata size exceeds limit"),
-                  GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
-        }
+  if (s->recv_initial_metadata_ready != NULL &&
+      s->published_metadata[0] != GRPC_METADATA_NOT_PUBLISHED) {
+    if (s->seen_error) {
+      while ((bs = grpc_chttp2_incoming_frame_queue_pop(&s->incoming_frames)) !=
+             NULL) {
+        gpr_log(GPR_DEBUG, "discard %p", bs);
+        incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
       }
-      grpc_chttp2_incoming_metadata_buffer_publish(
-          &stream_global->received_initial_metadata,
-          stream_global->recv_initial_metadata);
-      grpc_exec_ctx_sched(exec_ctx, stream_global->recv_initial_metadata_ready,
-                          GRPC_ERROR_NONE, NULL);
-      stream_global->recv_initial_metadata_ready = NULL;
     }
-    if (stream_global->recv_message_ready != NULL) {
-      while (stream_global->final_metadata_requested &&
-             stream_global->seen_error &&
-             (bs = grpc_chttp2_incoming_frame_queue_pop(
-                  &stream_global->incoming_frames)) != NULL) {
-        incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
-      }
-      if (stream_global->incoming_frames.head != NULL) {
-        *stream_global->recv_message = grpc_chttp2_incoming_frame_queue_pop(
-            &stream_global->incoming_frames);
-        GPR_ASSERT(*stream_global->recv_message != NULL);
-        grpc_exec_ctx_sched(exec_ctx, stream_global->recv_message_ready,
-                            GRPC_ERROR_NONE, NULL);
-        stream_global->recv_message_ready = NULL;
-      } else if (stream_global->published_trailing_metadata) {
-        *stream_global->recv_message = NULL;
-        grpc_exec_ctx_sched(exec_ctx, stream_global->recv_message_ready,
-                            GRPC_ERROR_NONE, NULL);
-        stream_global->recv_message_ready = NULL;
-      }
+    grpc_chttp2_incoming_metadata_buffer_publish(&s->metadata_buffer[0],
+                                                 s->recv_initial_metadata);
+    null_then_run_closure(exec_ctx, &s->recv_initial_metadata_ready,
+                          GRPC_ERROR_NONE);
+  }
+}
+
+void grpc_chttp2_maybe_complete_recv_message(grpc_exec_ctx *exec_ctx,
+                                             grpc_chttp2_transport *t,
+                                             grpc_chttp2_stream *s) {
+  grpc_byte_stream *bs;
+  if (s->recv_message_ready != NULL) {
+    while (s->final_metadata_requested && s->seen_error &&
+           (bs = grpc_chttp2_incoming_frame_queue_pop(&s->incoming_frames)) !=
+               NULL) {
+      gpr_log(GPR_DEBUG, "discard %p", bs);
+      incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
     }
-    if (stream_global->recv_trailing_metadata_finished != NULL &&
-        stream_global->read_closed && stream_global->write_closed) {
-      if (stream_global->seen_error) {
-        while ((bs = grpc_chttp2_incoming_frame_queue_pop(
-                    &stream_global->incoming_frames)) != NULL) {
-          incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
-        }
-        if (stream_global->exceeded_metadata_size) {
-          cancel_from_api(
-              exec_ctx, transport_global, stream_global,
-              grpc_error_set_int(
-                  GRPC_ERROR_CREATE(
-                      "received trailing metadata size exceeds limit"),
-                  GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
-        }
-      }
-      if (stream_global->all_incoming_byte_streams_finished) {
-        grpc_chttp2_incoming_metadata_buffer_publish(
-            &stream_global->received_trailing_metadata,
-            stream_global->recv_trailing_metadata);
-        grpc_chttp2_complete_closure_step(
-            exec_ctx, transport_global, stream_global,
-            &stream_global->recv_trailing_metadata_finished, GRPC_ERROR_NONE);
+    if (s->incoming_frames.head != NULL) {
+      *s->recv_message =
+          grpc_chttp2_incoming_frame_queue_pop(&s->incoming_frames);
+      GPR_ASSERT(*s->recv_message != NULL);
+      null_then_run_closure(exec_ctx, &s->recv_message_ready, GRPC_ERROR_NONE);
+    } else if (s->published_metadata[1] != GRPC_METADATA_NOT_PUBLISHED) {
+      *s->recv_message = NULL;
+      null_then_run_closure(exec_ctx, &s->recv_message_ready, GRPC_ERROR_NONE);
+    }
+  }
+}
+
+void grpc_chttp2_maybe_complete_recv_trailing_metadata(grpc_exec_ctx *exec_ctx,
+                                                       grpc_chttp2_transport *t,
+                                                       grpc_chttp2_stream *s) {
+  grpc_byte_stream *bs;
+  grpc_chttp2_maybe_complete_recv_message(exec_ctx, t, s);
+  if (s->recv_trailing_metadata_finished != NULL && s->read_closed &&
+      s->write_closed) {
+    if (s->seen_error) {
+      while ((bs = grpc_chttp2_incoming_frame_queue_pop(&s->incoming_frames)) !=
+             NULL) {
+        gpr_log(GPR_DEBUG, "discard %p", bs);
+        incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
       }
     }
+    if (s->all_incoming_byte_streams_finished &&
+        s->recv_trailing_metadata_finished != NULL) {
+      grpc_chttp2_incoming_metadata_buffer_publish(&s->metadata_buffer[1],
+                                                   s->recv_trailing_metadata);
+      grpc_chttp2_complete_closure_step(
+          exec_ctx, t, s, &s->recv_trailing_metadata_finished, GRPC_ERROR_NONE,
+          "recv_trailing_metadata_finished");
+    }
   }
 }
 
-static void decrement_active_streams_locked(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  if ((stream_global->all_incoming_byte_streams_finished =
-           gpr_unref(&stream_global->active_streams))) {
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+static void decrement_active_streams_locked(grpc_exec_ctx *exec_ctx,
+                                            grpc_chttp2_transport *t,
+                                            grpc_chttp2_stream *s) {
+  if ((s->all_incoming_byte_streams_finished = gpr_unref(&s->active_streams))) {
+    grpc_chttp2_maybe_complete_recv_trailing_metadata(exec_ctx, t, s);
   }
 }
 
 static void remove_stream(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                           uint32_t id, grpc_error *error) {
-  size_t new_stream_count;
-  grpc_chttp2_stream *s =
-      grpc_chttp2_stream_map_delete(&t->parsing_stream_map, id);
-  if (!s) {
-    s = grpc_chttp2_stream_map_delete(&t->new_stream_map, id);
-  }
+  grpc_chttp2_stream *s = grpc_chttp2_stream_map_delete(&t->stream_map, id);
   GPR_ASSERT(s);
-  s->global.in_stream_map = false;
-  if (t->parsing.incoming_stream == &s->parsing) {
-    t->parsing.incoming_stream = NULL;
-    grpc_chttp2_parsing_become_skip_parser(exec_ctx, &t->parsing);
+  if (t->incoming_stream == s) {
+    t->incoming_stream = NULL;
+    grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
   }
-  if (s->parsing.data_parser.parsing_frame != NULL) {
+  if (s->data_parser.parsing_frame != NULL) {
     grpc_chttp2_incoming_byte_stream_finished(
-        exec_ctx, s->parsing.data_parser.parsing_frame, GRPC_ERROR_REF(error),
-        0);
-    s->parsing.data_parser.parsing_frame = NULL;
+        exec_ctx, s->data_parser.parsing_frame, GRPC_ERROR_REF(error));
+    s->data_parser.parsing_frame = NULL;
   }
 
-  if (grpc_chttp2_unregister_stream(t, s) && t->global.sent_goaway) {
+  if (grpc_chttp2_stream_map_size(&t->stream_map) == 0 && t->sent_goaway) {
     close_transport_locked(
         exec_ctx, t, GRPC_ERROR_CREATE_REFERENCING(
                          "Last stream closed after sending GOAWAY", &error, 1));
   }
-  if (grpc_chttp2_list_remove_writable_stream(&t->global, &s->global)) {
-    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, &s->global, "chttp2_writing");
+  if (grpc_chttp2_list_remove_writable_stream(t, s)) {
+    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:remove_stream");
   }
 
-  new_stream_count = grpc_chttp2_stream_map_size(&t->parsing_stream_map) +
-                     grpc_chttp2_stream_map_size(&t->new_stream_map);
-  GPR_ASSERT(new_stream_count <= UINT32_MAX);
-  if (new_stream_count != t->global.concurrent_stream_count) {
-    t->global.concurrent_stream_count = (uint32_t)new_stream_count;
-    maybe_start_some_streams(exec_ctx, &t->global);
-  }
   GRPC_ERROR_UNREF(error);
+
+  maybe_start_some_streams(exec_ctx, t);
 }
 
 static void status_codes_from_error(grpc_error *error, gpr_timespec deadline,
@@ -1610,23 +1355,20 @@ static void status_codes_from_error(grpc_error *error, gpr_timespec deadline,
   }
 }
 
-static void cancel_from_api(grpc_exec_ctx *exec_ctx,
-                            grpc_chttp2_transport_global *transport_global,
-                            grpc_chttp2_stream_global *stream_global,
-                            grpc_error *due_to_error) {
-  if (!stream_global->read_closed || !stream_global->write_closed) {
+void grpc_chttp2_cancel_stream(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_transport *t, grpc_chttp2_stream *s,
+                               grpc_error *due_to_error) {
+  if (!s->read_closed || !s->write_closed) {
     grpc_status_code grpc_status;
     grpc_chttp2_error_code http_error;
-    status_codes_from_error(due_to_error, stream_global->deadline, &http_error,
+    status_codes_from_error(due_to_error, s->deadline, &http_error,
                             &grpc_status);
 
-    if (stream_global->id != 0) {
+    if (s->id != 0) {
       gpr_slice_buffer_add(
-          &transport_global->qbuf,
-          grpc_chttp2_rst_stream_create(stream_global->id, (uint32_t)http_error,
-                                        &stream_global->stats.outgoing));
-      grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                                 "rst_stream");
+          &t->qbuf, grpc_chttp2_rst_stream_create(s->id, (uint32_t)http_error,
+                                                  &s->stats.outgoing));
+      grpc_chttp2_initiate_write(exec_ctx, t, false, "rst_stream");
     }
 
     const char *msg =
@@ -1637,25 +1379,20 @@ static void cancel_from_api(grpc_exec_ctx *exec_ctx,
       msg = grpc_error_string(due_to_error);
     }
     gpr_slice msg_slice = gpr_slice_from_copied_string(msg);
-    grpc_chttp2_fake_status(exec_ctx, transport_global, stream_global,
-                            grpc_status, &msg_slice);
+    grpc_chttp2_fake_status(exec_ctx, t, s, grpc_status, &msg_slice);
     if (free_msg) grpc_error_free_string(msg);
   }
-  if (due_to_error != GRPC_ERROR_NONE && !stream_global->seen_error) {
-    stream_global->seen_error = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+  if (due_to_error != GRPC_ERROR_NONE && !s->seen_error) {
+    s->seen_error = true;
   }
-  grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global, 1,
-                                 1, due_to_error);
+  grpc_chttp2_mark_stream_closed(exec_ctx, t, s, 1, 1, due_to_error);
 }
 
-void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
-                             grpc_chttp2_transport_global *transport_global,
-                             grpc_chttp2_stream_global *stream_global,
-                             grpc_status_code status, gpr_slice *slice) {
+void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                             grpc_chttp2_stream *s, grpc_status_code status,
+                             gpr_slice *slice) {
   if (status != GRPC_STATUS_OK) {
-    stream_global->seen_error = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    s->seen_error = true;
   }
   /* stream_global->recv_trailing_metadata_finished gives us a
      last chance replacement: we've received trailing metadata,
@@ -1663,23 +1400,23 @@ void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
      to the upper layers - drop what we've got, and then publish
      what we want - which is safe because we haven't told anyone
      about the metadata yet */
-  if (!stream_global->published_trailing_metadata ||
-      stream_global->recv_trailing_metadata_finished != NULL) {
+  if (s->published_metadata[1] == GRPC_METADATA_NOT_PUBLISHED ||
+      s->recv_trailing_metadata_finished != NULL) {
     char status_string[GPR_LTOA_MIN_BUFSIZE];
     gpr_ltoa(status, status_string);
     grpc_chttp2_incoming_metadata_buffer_add(
-        &stream_global->received_trailing_metadata,
+        &s->metadata_buffer[1],
         grpc_mdelem_from_metadata_strings(
             GRPC_MDSTR_GRPC_STATUS, grpc_mdstr_from_string(status_string)));
     if (slice) {
       grpc_chttp2_incoming_metadata_buffer_add(
-          &stream_global->received_trailing_metadata,
+          &s->metadata_buffer[1],
           grpc_mdelem_from_metadata_strings(
               GRPC_MDSTR_GRPC_MESSAGE,
               grpc_mdstr_from_slice(gpr_slice_ref(*slice))));
     }
-    stream_global->published_trailing_metadata = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    s->published_metadata[1] = GRPC_METADATA_SYNTHESIZED_FROM_FAKE;
+    grpc_chttp2_maybe_complete_recv_trailing_metadata(exec_ctx, t, s);
   }
   if (slice) {
     gpr_slice_unref(*slice);
@@ -1698,11 +1435,11 @@ static void add_error(grpc_error *error, grpc_error **refs, size_t *nrefs) {
 }
 
 static grpc_error *removal_error(grpc_error *extra_error,
-                                 grpc_chttp2_stream_global *stream_global) {
+                                 grpc_chttp2_stream *s) {
   grpc_error *refs[3];
   size_t nrefs = 0;
-  add_error(stream_global->read_closed_error, refs, &nrefs);
-  add_error(stream_global->write_closed_error, refs, &nrefs);
+  add_error(s->read_closed_error, refs, &nrefs);
+  add_error(s->write_closed_error, refs, &nrefs);
   add_error(extra_error, refs, &nrefs);
   grpc_error *error = GRPC_ERROR_NONE;
   if (nrefs > 0) {
@@ -1714,73 +1451,71 @@ static grpc_error *removal_error(grpc_error *extra_error,
 }
 
 static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport_global *transport_global,
-                                grpc_chttp2_stream_global *stream_global,
+                                grpc_chttp2_transport *t, grpc_chttp2_stream *s,
                                 grpc_error *error) {
-  error = removal_error(error, stream_global);
-  stream_global->send_message = NULL;
+  error = removal_error(error, s);
+  s->fetching_send_message = NULL;
+  grpc_chttp2_complete_closure_step(
+      exec_ctx, t, s, &s->send_initial_metadata_finished, GRPC_ERROR_REF(error),
+      "send_initial_metadata_finished");
   grpc_chttp2_complete_closure_step(
-      exec_ctx, transport_global, stream_global,
-      &stream_global->send_initial_metadata_finished, GRPC_ERROR_REF(error));
+      exec_ctx, t, s, &s->send_trailing_metadata_finished,
+      GRPC_ERROR_REF(error), "send_trailing_metadata_finished");
   grpc_chttp2_complete_closure_step(
-      exec_ctx, transport_global, stream_global,
-      &stream_global->send_trailing_metadata_finished, GRPC_ERROR_REF(error));
-  grpc_chttp2_complete_closure_step(exec_ctx, transport_global, stream_global,
-                                    &stream_global->send_message_finished,
-                                    error);
+      exec_ctx, t, s, &s->fetching_send_message_finished, GRPC_ERROR_REF(error),
+      "fetching_send_message_finished");
+  while (s->on_write_finished_cbs) {
+    grpc_chttp2_write_cb *cb = s->on_write_finished_cbs;
+    s->on_write_finished_cbs = cb->next;
+    grpc_chttp2_complete_closure_step(exec_ctx, t, s, &cb->closure,
+                                      GRPC_ERROR_REF(error),
+                                      "on_write_finished_cb");
+    cb->next = t->write_cb_pool;
+    t->write_cb_pool = cb;
+  }
+  GRPC_ERROR_UNREF(error);
 }
 
-void grpc_chttp2_mark_stream_closed(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, int close_reads, int close_writes,
-    grpc_error *error) {
-  if (stream_global->read_closed && stream_global->write_closed) {
+void grpc_chttp2_mark_stream_closed(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_transport *t,
+                                    grpc_chttp2_stream *s, int close_reads,
+                                    int close_writes, grpc_error *error) {
+  if (s->read_closed && s->write_closed) {
     /* already closed */
     GRPC_ERROR_UNREF(error);
     return;
   }
-  grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
-  if (close_reads && !stream_global->read_closed) {
-    stream_global->read_closed_error = GRPC_ERROR_REF(error);
-    stream_global->read_closed = true;
-    stream_global->published_initial_metadata = true;
-    stream_global->published_trailing_metadata = true;
-    decrement_active_streams_locked(exec_ctx, transport_global, stream_global);
-  }
-  if (close_writes && !stream_global->write_closed) {
-    stream_global->write_closed_error = GRPC_ERROR_REF(error);
-    stream_global->write_closed = true;
-    if (TRANSPORT_FROM_GLOBAL(transport_global)->executor.write_state !=
-        GRPC_CHTTP2_WRITING_INACTIVE) {
-      GRPC_CHTTP2_STREAM_REF(stream_global, "finish_writes");
-      grpc_chttp2_list_add_closed_waiting_for_writing(transport_global,
-                                                      stream_global);
-    } else {
-      fail_pending_writes(exec_ctx, transport_global, stream_global,
-                          GRPC_ERROR_REF(error));
-    }
-  }
-  if (stream_global->read_closed && stream_global->write_closed) {
-    if (stream_global->id != 0 &&
-        TRANSPORT_FROM_GLOBAL(transport_global)->executor.parsing_active) {
-      grpc_chttp2_list_add_closed_waiting_for_parsing(transport_global,
-                                                      stream_global);
-    } else {
-      if (stream_global->id != 0) {
-        remove_stream(exec_ctx, TRANSPORT_FROM_GLOBAL(transport_global),
-                      stream_global->id,
-                      removal_error(GRPC_ERROR_REF(error), stream_global));
+  if (close_reads && !s->read_closed) {
+    s->read_closed_error = GRPC_ERROR_REF(error);
+    s->read_closed = true;
+    for (int i = 0; i < 2; i++) {
+      if (s->published_metadata[i] == GRPC_METADATA_NOT_PUBLISHED) {
+        s->published_metadata[i] = GPRC_METADATA_PUBLISHED_AT_CLOSE;
       }
-      GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2");
     }
+    decrement_active_streams_locked(exec_ctx, t, s);
+    grpc_chttp2_maybe_complete_recv_initial_metadata(exec_ctx, t, s);
+    grpc_chttp2_maybe_complete_recv_message(exec_ctx, t, s);
+    grpc_chttp2_maybe_complete_recv_trailing_metadata(exec_ctx, t, s);
+  }
+  if (close_writes && !s->write_closed) {
+    s->write_closed_error = GRPC_ERROR_REF(error);
+    s->write_closed = true;
+    fail_pending_writes(exec_ctx, t, s, GRPC_ERROR_REF(error));
+    grpc_chttp2_maybe_complete_recv_trailing_metadata(exec_ctx, t, s);
+  }
+  if (s->read_closed && s->write_closed) {
+    if (s->id != 0) {
+      remove_stream(exec_ctx, t, s->id,
+                    removal_error(GRPC_ERROR_REF(error), s));
+    }
+    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2");
   }
   GRPC_ERROR_UNREF(error);
 }
 
-static void close_from_api(grpc_exec_ctx *exec_ctx,
-                           grpc_chttp2_transport_global *transport_global,
-                           grpc_chttp2_stream_global *stream_global,
-                           grpc_error *error) {
+static void close_from_api(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                           grpc_chttp2_stream *s, grpc_error *error) {
   gpr_slice hdr;
   gpr_slice status_hdr;
   gpr_slice message_pfx;
@@ -1788,16 +1523,17 @@ static void close_from_api(grpc_exec_ctx *exec_ctx,
   uint32_t len = 0;
   grpc_status_code grpc_status;
   grpc_chttp2_error_code http_error;
-  status_codes_from_error(error, stream_global->deadline, &http_error,
-                          &grpc_status);
+  status_codes_from_error(error, s->deadline, &http_error, &grpc_status);
 
   GPR_ASSERT(grpc_status >= 0 && (int)grpc_status < 100);
 
-  if (stream_global->id != 0 && !transport_global->is_client) {
+  if (s->id != 0 && !t->is_client) {
     /* Hand roll a header block.
-       This is unnecessarily ugly - at some point we should find a more elegant
+       This is unnecessarily ugly - at some point we should find a more
+       elegant
        solution.
-       It's complicated by the fact that our send machinery would be dead by the
+       It's complicated by the fact that our send machinery would be dead by
+       the
        time we got around to sending this, so instead we ignore HPACK
        compression
        and just write the uncompressed bytes onto the wire. */
@@ -1862,23 +1598,22 @@ static void close_from_api(grpc_exec_ctx *exec_ctx,
     *p++ = (uint8_t)(len);
     *p++ = GRPC_CHTTP2_FRAME_HEADER;
     *p++ = GRPC_CHTTP2_DATA_FLAG_END_STREAM | GRPC_CHTTP2_DATA_FLAG_END_HEADERS;
-    *p++ = (uint8_t)(stream_global->id >> 24);
-    *p++ = (uint8_t)(stream_global->id >> 16);
-    *p++ = (uint8_t)(stream_global->id >> 8);
-    *p++ = (uint8_t)(stream_global->id);
+    *p++ = (uint8_t)(s->id >> 24);
+    *p++ = (uint8_t)(s->id >> 16);
+    *p++ = (uint8_t)(s->id >> 8);
+    *p++ = (uint8_t)(s->id);
     GPR_ASSERT(p == GPR_SLICE_END_PTR(hdr));
 
-    gpr_slice_buffer_add(&transport_global->qbuf, hdr);
-    gpr_slice_buffer_add(&transport_global->qbuf, status_hdr);
+    gpr_slice_buffer_add(&t->qbuf, hdr);
+    gpr_slice_buffer_add(&t->qbuf, status_hdr);
     if (optional_message) {
-      gpr_slice_buffer_add(&transport_global->qbuf, message_pfx);
-      gpr_slice_buffer_add(&transport_global->qbuf,
+      gpr_slice_buffer_add(&t->qbuf, message_pfx);
+      gpr_slice_buffer_add(&t->qbuf,
                            gpr_slice_from_copied_string(optional_message));
     }
     gpr_slice_buffer_add(
-        &transport_global->qbuf,
-        grpc_chttp2_rst_stream_create(stream_global->id, GRPC_CHTTP2_NO_ERROR,
-                                      &stream_global->stats.outgoing));
+        &t->qbuf, grpc_chttp2_rst_stream_create(s->id, GRPC_CHTTP2_NO_ERROR,
+                                                &s->stats.outgoing));
   }
 
   const char *msg = grpc_error_get_str(error, GRPC_ERROR_STR_GRPC_MESSAGE);
@@ -1888,38 +1623,39 @@ static void close_from_api(grpc_exec_ctx *exec_ctx,
     msg = grpc_error_string(error);
   }
   gpr_slice msg_slice = gpr_slice_from_copied_string(msg);
-  grpc_chttp2_fake_status(exec_ctx, transport_global, stream_global,
-                          grpc_status, &msg_slice);
+  grpc_chttp2_fake_status(exec_ctx, t, s, grpc_status, &msg_slice);
   if (free_msg) grpc_error_free_string(msg);
 
-  grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global, 1,
-                                 1, error);
-  grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                             "close_from_api");
+  grpc_chttp2_mark_stream_closed(exec_ctx, t, s, 1, 1, error);
+  grpc_chttp2_initiate_write(exec_ctx, t, false, "close_from_api");
 }
 
 typedef struct {
   grpc_exec_ctx *exec_ctx;
   grpc_error *error;
+  grpc_chttp2_transport *t;
 } cancel_stream_cb_args;
 
-static void cancel_stream_cb(grpc_chttp2_transport_global *transport_global,
-                             void *user_data,
-                             grpc_chttp2_stream_global *stream_global) {
+static void cancel_stream_cb(void *user_data, uint32_t key, void *stream) {
   cancel_stream_cb_args *args = user_data;
-  cancel_from_api(args->exec_ctx, transport_global, stream_global,
-                  GRPC_ERROR_REF(args->error));
+  grpc_chttp2_stream *s = stream;
+  grpc_chttp2_cancel_stream(args->exec_ctx, args->t, s,
+                            GRPC_ERROR_REF(args->error));
 }
 
 static void end_all_the_calls(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                               grpc_error *error) {
-  cancel_stream_cb_args args = {exec_ctx, error};
-  grpc_chttp2_for_all_streams(&t->global, &args, cancel_stream_cb);
+  cancel_stream_cb_args args = {exec_ctx, error, t};
+  grpc_chttp2_stream_map_for_each(&t->stream_map, cancel_stream_cb, &args);
   GRPC_ERROR_UNREF(error);
 }
 
 static void drop_connection(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                             grpc_error *error) {
+  if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
+    error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
+                               GRPC_STATUS_UNAVAILABLE);
+  }
   close_transport_locked(exec_ctx, t, GRPC_ERROR_REF(error));
   end_all_the_calls(exec_ctx, t, error);
 }
@@ -1934,20 +1670,23 @@ static void update_global_window(void *args, uint32_t id, void *stream) {
   update_global_window_args *a = args;
   grpc_chttp2_transport *t = a->t;
   grpc_chttp2_stream *s = stream;
-  grpc_chttp2_transport_global *transport_global = &t->global;
-  grpc_chttp2_stream_global *stream_global = &s->global;
   int was_zero;
   int is_zero;
-  int64_t initial_window_update = t->parsing.initial_window_update;
+  int64_t initial_window_update = t->initial_window_update;
 
-  was_zero = stream_global->outgoing_window <= 0;
-  GRPC_CHTTP2_FLOW_CREDIT_STREAM("settings", transport_global, stream_global,
-                                 outgoing_window, initial_window_update);
-  is_zero = stream_global->outgoing_window <= 0;
+  if (initial_window_update > 0) {
+    was_zero = s->outgoing_window <= 0;
+    GRPC_CHTTP2_FLOW_CREDIT_STREAM("settings", t, s, outgoing_window,
+                                   initial_window_update);
+    is_zero = s->outgoing_window <= 0;
 
-  if (was_zero && !is_zero) {
-    grpc_chttp2_become_writable(a->exec_ctx, transport_global, stream_global,
-                                true, "update_global_window");
+    if (was_zero && !is_zero) {
+      grpc_chttp2_become_writable(a->exec_ctx, t, s, true,
+                                  "update_global_window");
+    }
+  } else {
+    GRPC_CHTTP2_FLOW_DEBIT_STREAM("settings", t, s, outgoing_window,
+                                  -initial_window_update);
   }
 }
 
@@ -1955,45 +1694,17 @@ static void update_global_window(void *args, uint32_t id, void *stream) {
  * INPUT PROCESSING - PARSING
  */
 
-static void reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *arg);
-static void parsing_action(grpc_exec_ctx *exec_ctx, void *arg,
-                           grpc_error *error);
-static void post_reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                       grpc_chttp2_transport *t,
-                                       grpc_chttp2_stream *s_unused, void *arg);
-static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                              grpc_chttp2_stream *s_unused, void *arg);
-
-static void reading_action(grpc_exec_ctx *exec_ctx, void *tp,
-                           grpc_error *error) {
+static void read_action_begin(grpc_exec_ctx *exec_ctx, void *tp,
+                              grpc_error *error) {
   /* Control flow:
      reading_action_locked ->
        (parse_unlocked -> post_parse_locked)? ->
        post_reading_action_locked */
-  grpc_chttp2_run_with_global_lock(exec_ctx, tp, NULL, reading_action_locked,
-                                   GRPC_ERROR_REF(error), 0);
-}
-
-static void reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *arg) {
-  grpc_chttp2_transport_global *transport_global = &t->global;
-  grpc_chttp2_transport_parsing *transport_parsing = &t->parsing;
-  grpc_error *error = arg;
-
-  GPR_ASSERT(!t->executor.parsing_active);
-  if (!t->closed) {
-    t->executor.parsing_active = 1;
-    /* merge stream lists */
-    grpc_chttp2_stream_map_move_into(&t->new_stream_map,
-                                     &t->parsing_stream_map);
-    grpc_chttp2_prepare_to_read(transport_global, transport_parsing);
-    grpc_exec_ctx_sched(exec_ctx, &t->parsing_action, error, NULL);
-  } else {
-    post_reading_action_locked(exec_ctx, t, s_unused, arg);
-  }
+  GPR_TIMER_BEGIN("reading_action", 0);
+  grpc_chttp2_transport *t = tp;
+  grpc_combiner_execute(exec_ctx, t->combiner, &t->read_action_locked,
+                        GRPC_ERROR_REF(error), false);
+  GPR_TIMER_END("reading_action", 0);
 }
 
 static grpc_error *try_http_parsing(grpc_exec_ctx *exec_ctx,
@@ -2023,169 +1734,110 @@ static grpc_error *try_http_parsing(grpc_exec_ctx *exec_ctx,
   return error;
 }
 
-static void parsing_action(grpc_exec_ctx *exec_ctx, void *arg,
-                           grpc_error *error) {
-  grpc_chttp2_transport *t = arg;
-  grpc_error *err = GRPC_ERROR_NONE;
-  GPR_TIMER_BEGIN("reading_action.parse", 0);
-  size_t i = 0;
-  grpc_error *errors[3] = {GRPC_ERROR_REF(error), GRPC_ERROR_NONE,
-                           GRPC_ERROR_NONE};
-  for (; i < t->read_buffer.count && errors[1] == GRPC_ERROR_NONE; i++) {
-    errors[1] = grpc_chttp2_perform_read(exec_ctx, &t->parsing,
-                                         t->read_buffer.slices[i]);
-  };
-  if (errors[1] == GRPC_ERROR_NONE) {
-    err = GRPC_ERROR_REF(error);
-  } else {
-    errors[2] = try_http_parsing(exec_ctx, t);
-    err = GRPC_ERROR_CREATE_REFERENCING("Failed parsing HTTP/2", errors,
-                                        GPR_ARRAY_SIZE(errors));
-  }
-  for (i = 0; i < GPR_ARRAY_SIZE(errors); i++) {
-    GRPC_ERROR_UNREF(errors[i]);
-  }
-  GPR_TIMER_END("reading_action.parse", 0);
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, NULL, post_parse_locked, err,
-                                   0);
-}
-
-static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                              grpc_chttp2_stream *s_unused, void *arg) {
-  grpc_chttp2_transport_global *transport_global = &t->global;
-  grpc_chttp2_transport_parsing *transport_parsing = &t->parsing;
-  /* copy parsing qbuf to global qbuf */
-  if (t->parsing.qbuf.count > 0) {
-    gpr_slice_buffer_move_into(&t->parsing.qbuf, &t->global.qbuf);
-    grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                               "parsing_qbuf");
-  }
-  /* merge stream lists */
-  grpc_chttp2_stream_map_move_into(&t->new_stream_map, &t->parsing_stream_map);
-  transport_global->concurrent_stream_count =
-      (uint32_t)grpc_chttp2_stream_map_size(&t->parsing_stream_map);
-  if (transport_parsing->initial_window_update != 0) {
-    update_global_window_args args = {t, exec_ctx};
-    grpc_chttp2_stream_map_for_each(&t->parsing_stream_map,
-                                    update_global_window, &args);
-    transport_parsing->initial_window_update = 0;
-  }
-  /* handle higher level things */
-  grpc_chttp2_publish_reads(exec_ctx, transport_global, transport_parsing);
-  t->executor.parsing_active = 0;
-  /* handle delayed transport ops (if there is one) */
-  if (t->post_parsing_op) {
-    grpc_transport_op *op = t->post_parsing_op;
-    t->post_parsing_op = NULL;
-    perform_transport_op_locked(exec_ctx, t, NULL, op);
-    gpr_free(op);
-  }
-  /* if a stream is in the stream map, and gets cancelled, we need to
-   * ensure we are not parsing before continuing the cancellation to keep
-   * things in a sane state */
-  grpc_chttp2_stream_global *stream_global;
-  while (grpc_chttp2_list_pop_closed_waiting_for_parsing(transport_global,
-                                                         &stream_global)) {
-    GPR_ASSERT(stream_global->in_stream_map);
-    GPR_ASSERT(stream_global->write_closed);
-    GPR_ASSERT(stream_global->read_closed);
-    remove_stream(exec_ctx, t, stream_global->id,
-                  removal_error(GRPC_ERROR_NONE, stream_global));
-    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2");
-  }
-
-  post_reading_action_locked(exec_ctx, t, s_unused, arg);
-}
-
-static void post_reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                       grpc_chttp2_transport *t,
-                                       grpc_chttp2_stream *s_unused,
-                                       void *arg) {
-  grpc_error *error = arg;
+static void read_action_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                               grpc_error *error) {
+  GPR_TIMER_BEGIN("reading_action_locked", 0);
+
+  grpc_chttp2_transport *t = tp;
+
+  GRPC_ERROR_REF(error);
+
+  if (!t->closed) {
+    GPR_TIMER_BEGIN("reading_action.parse", 0);
+    size_t i = 0;
+    grpc_error *errors[3] = {GRPC_ERROR_REF(error), GRPC_ERROR_NONE,
+                             GRPC_ERROR_NONE};
+    for (; i < t->read_buffer.count && errors[1] == GRPC_ERROR_NONE; i++) {
+      errors[1] =
+          grpc_chttp2_perform_read(exec_ctx, t, t->read_buffer.slices[i]);
+    };
+    if (errors[1] != GRPC_ERROR_NONE) {
+      errors[2] = try_http_parsing(exec_ctx, t);
+      GRPC_ERROR_UNREF(error);
+      error = GRPC_ERROR_CREATE_REFERENCING("Failed parsing HTTP/2", errors,
+                                            GPR_ARRAY_SIZE(errors));
+    }
+    for (i = 0; i < GPR_ARRAY_SIZE(errors); i++) {
+      GRPC_ERROR_UNREF(errors[i]);
+    }
+    GPR_TIMER_END("reading_action.parse", 0);
+
+    GPR_TIMER_BEGIN("post_parse_locked", 0);
+    if (t->initial_window_update != 0) {
+      update_global_window_args args = {t, exec_ctx};
+      grpc_chttp2_stream_map_for_each(&t->stream_map, update_global_window,
+                                      &args);
+      t->initial_window_update = 0;
+    }
+    /* handle higher level things */
+    if (t->incoming_window < t->connection_window_target * 3 / 4) {
+      int64_t announce_bytes = t->connection_window_target - t->incoming_window;
+      GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parsed", t, announce_incoming_window,
+                                        announce_bytes);
+      GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parsed", t, incoming_window,
+                                        announce_bytes);
+      grpc_chttp2_initiate_write(exec_ctx, t, false, "global incoming window");
+    }
+
+    GPR_TIMER_END("post_parse_locked", 0);
+  }
+
+  GPR_TIMER_BEGIN("post_reading_action_locked", 0);
   bool keep_reading = false;
   if (error == GRPC_ERROR_NONE && t->closed) {
     error = GRPC_ERROR_CREATE("Transport closed");
   }
   if (error != GRPC_ERROR_NONE) {
-    if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
-      error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
-                                 GRPC_STATUS_UNAVAILABLE);
-    }
     drop_connection(exec_ctx, t, GRPC_ERROR_REF(error));
     t->endpoint_reading = 0;
-    if (grpc_http_write_state_trace) {
-      gpr_log(GPR_DEBUG, "R:%p -> 0 ws=%s", t,
-              write_state_name(t->executor.write_state));
-    }
-    if (t->executor.write_state == GRPC_CHTTP2_WRITING_INACTIVE && t->ep) {
-      destroy_endpoint(exec_ctx, t);
-    }
   } else if (!t->closed) {
     keep_reading = true;
-    REF_TRANSPORT(t, "keep_reading");
-    prevent_endpoint_shutdown(t);
+    GRPC_CHTTP2_REF_TRANSPORT(t, "keep_reading");
   }
   gpr_slice_buffer_reset_and_unref(&t->read_buffer);
-  GRPC_ERROR_UNREF(error);
 
   if (keep_reading) {
-    grpc_endpoint_read(exec_ctx, t->ep, &t->read_buffer, &t->reading_action);
-    allow_endpoint_shutdown_locked(exec_ctx, t);
-    UNREF_TRANSPORT(exec_ctx, t, "keep_reading");
+    grpc_endpoint_read(exec_ctx, t->ep, &t->read_buffer, &t->read_action_begin);
+    GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "keep_reading");
   } else {
-    UNREF_TRANSPORT(exec_ctx, t, "reading_action");
+    GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "reading_action");
   }
+
+  GPR_TIMER_END("post_reading_action_locked", 0);
+
+  GRPC_ERROR_UNREF(error);
+
+  GPR_TIMER_END("reading_action_locked", 0);
 }
 
 /*******************************************************************************
  * CALLBACK LOOP
  */
 
-static void connectivity_state_set(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_connectivity_state state, grpc_error *error, const char *reason) {
+static void connectivity_state_set(grpc_exec_ctx *exec_ctx,
+                                   grpc_chttp2_transport *t,
+                                   grpc_connectivity_state state,
+                                   grpc_error *error, const char *reason) {
   GRPC_CHTTP2_IF_TRACING(
       gpr_log(GPR_DEBUG, "set connectivity_state=%d", state));
-  grpc_connectivity_state_set(
-      exec_ctx,
-      &TRANSPORT_FROM_GLOBAL(transport_global)->channel_callback.state_tracker,
-      state, error, reason);
+  grpc_connectivity_state_set(exec_ctx, &t->channel_callback.state_tracker,
+                              state, error, reason);
 }
 
 /*******************************************************************************
  * POLLSET STUFF
  */
 
-static void add_to_pollset_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *pollset) {
-  if (t->ep) {
-    grpc_endpoint_add_to_pollset(exec_ctx, t->ep, pollset);
-  }
-}
-
-static void add_to_pollset_set_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s_unused,
-                                      void *pollset_set) {
-  if (t->ep) {
-    grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, pollset_set);
-  }
-}
-
 static void set_pollset(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                         grpc_stream *gs, grpc_pollset *pollset) {
-  /* TODO(ctiller): keep pollset alive */
-  grpc_chttp2_run_with_global_lock(exec_ctx, (grpc_chttp2_transport *)gt,
-                                   (grpc_chttp2_stream *)gs,
-                                   add_to_pollset_locked, pollset, 0);
+  grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
+  grpc_endpoint_add_to_pollset(exec_ctx, t->ep, pollset);
 }
 
 static void set_pollset_set(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                             grpc_stream *gs, grpc_pollset_set *pollset_set) {
-  grpc_chttp2_run_with_global_lock(exec_ctx, (grpc_chttp2_transport *)gt,
-                                   (grpc_chttp2_stream *)gs,
-                                   add_to_pollset_set_locked, pollset_set, 0);
+  grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
+  grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, pollset_set);
 }
 
 /*******************************************************************************
@@ -2197,19 +1849,21 @@ static void incoming_byte_stream_unref(grpc_exec_ctx *exec_ctx,
   if (gpr_unref(&bs->refs)) {
     GRPC_ERROR_UNREF(bs->error);
     gpr_slice_buffer_destroy(&bs->slices);
+    gpr_mu_destroy(&bs->slice_mu);
     gpr_free(bs);
   }
 }
 
-static void incoming_byte_stream_update_flow_control(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, size_t max_size_hint,
-    size_t have_already) {
+static void incoming_byte_stream_update_flow_control(grpc_exec_ctx *exec_ctx,
+                                                     grpc_chttp2_transport *t,
+                                                     grpc_chttp2_stream *s,
+                                                     size_t max_size_hint,
+                                                     size_t have_already) {
   uint32_t max_recv_bytes;
 
   /* clamp max recv hint to an allowable size */
-  if (max_size_hint >= UINT32_MAX - transport_global->stream_lookahead) {
-    max_recv_bytes = UINT32_MAX - transport_global->stream_lookahead;
+  if (max_size_hint >= UINT32_MAX - t->stream_lookahead) {
+    max_recv_bytes = UINT32_MAX - t->stream_lookahead;
   } else {
     max_recv_bytes = (uint32_t)max_size_hint;
   }
@@ -2222,58 +1876,50 @@ static void incoming_byte_stream_update_flow_control(
   }
 
   /* add some small lookahead to keep pipelines flowing */
-  GPR_ASSERT(max_recv_bytes <= UINT32_MAX - transport_global->stream_lookahead);
-  max_recv_bytes += transport_global->stream_lookahead;
-  if (stream_global->max_recv_bytes < max_recv_bytes) {
-    uint32_t add_max_recv_bytes =
-        max_recv_bytes - stream_global->max_recv_bytes;
-    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", transport_global, stream_global,
-                                   max_recv_bytes, add_max_recv_bytes);
-    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", transport_global, stream_global,
-                                   unannounced_incoming_window_for_parse,
+  GPR_ASSERT(max_recv_bytes <= UINT32_MAX - t->stream_lookahead);
+  max_recv_bytes += t->stream_lookahead;
+  if (s->max_recv_bytes < max_recv_bytes) {
+    uint32_t add_max_recv_bytes = max_recv_bytes - s->max_recv_bytes;
+    bool new_window_write_is_covered_by_poller =
+        s->max_recv_bytes < have_already;
+    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", t, s, max_recv_bytes,
+                                   add_max_recv_bytes);
+    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", t, s, incoming_window,
                                    add_max_recv_bytes);
-    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", transport_global, stream_global,
-                                   unannounced_incoming_window_for_writing,
+    GRPC_CHTTP2_FLOW_CREDIT_STREAM("op", t, s, announce_window,
                                    add_max_recv_bytes);
-    grpc_chttp2_list_add_unannounced_incoming_window_available(transport_global,
-                                                               stream_global);
-    grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                false, "read_incoming_stream");
+    grpc_chttp2_become_writable(exec_ctx, t, s,
+                                new_window_write_is_covered_by_poller,
+                                "read_incoming_stream");
   }
 }
 
-typedef struct {
-  grpc_chttp2_incoming_byte_stream *byte_stream;
-  gpr_slice *slice;
-  size_t max_size_hint;
-  grpc_closure *on_complete;
-} incoming_byte_stream_next_arg;
-
 static void incoming_byte_stream_next_locked(grpc_exec_ctx *exec_ctx,
-                                             grpc_chttp2_transport *t,
-                                             grpc_chttp2_stream *s,
-                                             void *argp) {
-  incoming_byte_stream_next_arg *arg = argp;
-  grpc_chttp2_incoming_byte_stream *bs =
-      (grpc_chttp2_incoming_byte_stream *)arg->byte_stream;
-  grpc_chttp2_transport_global *transport_global = &bs->transport->global;
-  grpc_chttp2_stream_global *stream_global = &bs->stream->global;
+                                             void *argp,
+                                             grpc_error *error_ignored) {
+  grpc_chttp2_incoming_byte_stream *bs = argp;
+  grpc_chttp2_transport *t = bs->transport;
+  grpc_chttp2_stream *s = bs->stream;
 
   if (bs->is_tail) {
-    incoming_byte_stream_update_flow_control(exec_ctx, transport_global,
-                                             stream_global, arg->max_size_hint,
-                                             bs->slices.length);
+    gpr_mu_lock(&bs->slice_mu);
+    size_t cur_length = bs->slices.length;
+    gpr_mu_unlock(&bs->slice_mu);
+    incoming_byte_stream_update_flow_control(
+        exec_ctx, t, s, bs->next_action.max_size_hint, cur_length);
   }
+  gpr_mu_lock(&bs->slice_mu);
   if (bs->slices.count > 0) {
-    *arg->slice = gpr_slice_buffer_take_first(&bs->slices);
-    grpc_exec_ctx_sched(exec_ctx, arg->on_complete, GRPC_ERROR_NONE, NULL);
+    *bs->next_action.slice = gpr_slice_buffer_take_first(&bs->slices);
+    grpc_closure_run(exec_ctx, bs->next_action.on_complete, GRPC_ERROR_NONE);
   } else if (bs->error != GRPC_ERROR_NONE) {
-    grpc_exec_ctx_sched(exec_ctx, arg->on_complete, GRPC_ERROR_REF(bs->error),
-                        NULL);
+    grpc_closure_run(exec_ctx, bs->next_action.on_complete,
+                     GRPC_ERROR_REF(bs->error));
   } else {
-    bs->on_next = arg->on_complete;
-    bs->next = arg->slice;
+    bs->on_next = bs->next_action.on_complete;
+    bs->next = bs->next_action.slice;
   }
+  gpr_mu_unlock(&bs->slice_mu);
   incoming_byte_stream_unref(exec_ctx, bs);
 }
 
@@ -2281,13 +1927,18 @@ static int incoming_byte_stream_next(grpc_exec_ctx *exec_ctx,
                                      grpc_byte_stream *byte_stream,
                                      gpr_slice *slice, size_t max_size_hint,
                                      grpc_closure *on_complete) {
+  GPR_TIMER_BEGIN("incoming_byte_stream_next", 0);
   grpc_chttp2_incoming_byte_stream *bs =
       (grpc_chttp2_incoming_byte_stream *)byte_stream;
-  incoming_byte_stream_next_arg arg = {bs, slice, max_size_hint, on_complete};
   gpr_ref(&bs->refs);
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_next_locked, &arg,
-                                   sizeof(arg));
+  bs->next_action.slice = slice;
+  bs->next_action.max_size_hint = max_size_hint;
+  bs->next_action.on_complete = on_complete;
+  grpc_closure_init(&bs->next_action.closure, incoming_byte_stream_next_locked,
+                    bs);
+  grpc_combiner_execute(exec_ctx, bs->transport->combiner,
+                        &bs->next_action.closure, GRPC_ERROR_NONE, false);
+  GPR_TIMER_END("incoming_byte_stream_next", 0);
   return 0;
 }
 
@@ -2295,141 +1946,101 @@ static void incoming_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_byte_stream *byte_stream);
 
 static void incoming_byte_stream_destroy_locked(grpc_exec_ctx *exec_ctx,
-                                                grpc_chttp2_transport *t,
-                                                grpc_chttp2_stream *s,
-                                                void *byte_stream) {
+                                                void *byte_stream,
+                                                grpc_error *error_ignored) {
   grpc_chttp2_incoming_byte_stream *bs = byte_stream;
   GPR_ASSERT(bs->base.destroy == incoming_byte_stream_destroy);
-  decrement_active_streams_locked(exec_ctx, &bs->transport->global,
-                                  &bs->stream->global);
+  decrement_active_streams_locked(exec_ctx, bs->transport, bs->stream);
   incoming_byte_stream_unref(exec_ctx, bs);
 }
 
 static void incoming_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_byte_stream *byte_stream) {
+  GPR_TIMER_BEGIN("incoming_byte_stream_destroy", 0);
   grpc_chttp2_incoming_byte_stream *bs =
       (grpc_chttp2_incoming_byte_stream *)byte_stream;
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_destroy_locked, bs, 0);
-}
-
-typedef struct {
-  grpc_chttp2_incoming_byte_stream *byte_stream;
-  gpr_slice slice;
-} incoming_byte_stream_push_arg;
-
-static void incoming_byte_stream_push_locked(grpc_exec_ctx *exec_ctx,
-                                             grpc_chttp2_transport *t,
-                                             grpc_chttp2_stream *s,
-                                             void *argp) {
-  incoming_byte_stream_push_arg *arg = argp;
-  grpc_chttp2_incoming_byte_stream *bs = arg->byte_stream;
-  if (bs->on_next != NULL) {
-    *bs->next = arg->slice;
-    grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_NONE, NULL);
-    bs->on_next = NULL;
-  } else {
-    gpr_slice_buffer_add(&bs->slices, arg->slice);
-  }
-  incoming_byte_stream_unref(exec_ctx, bs);
+  grpc_closure_init(&bs->destroy_action, incoming_byte_stream_destroy_locked,
+                    bs);
+  grpc_combiner_execute(exec_ctx, bs->transport->combiner, &bs->destroy_action,
+                        GRPC_ERROR_NONE, false);
+  GPR_TIMER_END("incoming_byte_stream_destroy", 0);
 }
 
-void grpc_chttp2_incoming_byte_stream_push(grpc_exec_ctx *exec_ctx,
-                                           grpc_chttp2_incoming_byte_stream *bs,
-                                           gpr_slice slice) {
-  incoming_byte_stream_push_arg arg = {bs, slice};
-  gpr_ref(&bs->refs);
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_push_locked, &arg,
-                                   sizeof(arg));
-}
-
-typedef struct {
-  grpc_chttp2_incoming_byte_stream *bs;
-  grpc_error *error;
-} bs_fail_args;
-
-static bs_fail_args *make_bs_fail_args(grpc_chttp2_incoming_byte_stream *bs,
-                                       grpc_error *error) {
-  bs_fail_args *a = gpr_malloc(sizeof(*a));
-  a->bs = bs;
-  a->error = error;
-  return a;
-}
-
-static void incoming_byte_stream_finished_failed_locked(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t, grpc_chttp2_stream *s,
-    void *argp) {
-  bs_fail_args *a = argp;
-  grpc_chttp2_incoming_byte_stream *bs = a->bs;
-  grpc_error *error = a->error;
-  gpr_free(a);
+static void incoming_byte_stream_publish_error(
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_incoming_byte_stream *bs,
+    grpc_error *error) {
+  GPR_ASSERT(error != GRPC_ERROR_NONE);
   grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_REF(error), NULL);
   bs->on_next = NULL;
   GRPC_ERROR_UNREF(bs->error);
   bs->error = error;
-  incoming_byte_stream_unref(exec_ctx, bs);
 }
 
-static void incoming_byte_stream_finished_ok_locked(grpc_exec_ctx *exec_ctx,
-                                                    grpc_chttp2_transport *t,
-                                                    grpc_chttp2_stream *s,
-                                                    void *argp) {
-  grpc_chttp2_incoming_byte_stream *bs = argp;
-  incoming_byte_stream_unref(exec_ctx, bs);
+void grpc_chttp2_incoming_byte_stream_push(grpc_exec_ctx *exec_ctx,
+                                           grpc_chttp2_incoming_byte_stream *bs,
+                                           gpr_slice slice) {
+  gpr_mu_lock(&bs->slice_mu);
+  if (bs->remaining_bytes < GPR_SLICE_LENGTH(slice)) {
+    incoming_byte_stream_publish_error(
+        exec_ctx, bs, GRPC_ERROR_CREATE("Too many bytes in stream"));
+  } else {
+    bs->remaining_bytes -= (uint32_t)GPR_SLICE_LENGTH(slice);
+    if (bs->on_next != NULL) {
+      *bs->next = slice;
+      grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_NONE, NULL);
+      bs->on_next = NULL;
+    } else {
+      gpr_slice_buffer_add(&bs->slices, slice);
+    }
+  }
+  gpr_mu_unlock(&bs->slice_mu);
 }
 
 void grpc_chttp2_incoming_byte_stream_finished(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_incoming_byte_stream *bs,
-    grpc_error *error, int from_parsing_thread) {
-  if (from_parsing_thread) {
-    if (error == GRPC_ERROR_NONE) {
-      grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                       incoming_byte_stream_finished_ok_locked,
-                                       bs, 0);
-    } else {
-      grpc_chttp2_run_with_global_lock(
-          exec_ctx, bs->transport, bs->stream,
-          incoming_byte_stream_finished_failed_locked,
-          make_bs_fail_args(bs, error), 0);
-    }
-  } else {
-    if (error == GRPC_ERROR_NONE) {
-      incoming_byte_stream_finished_ok_locked(exec_ctx, bs->transport,
-                                              bs->stream, bs);
-    } else {
-      incoming_byte_stream_finished_failed_locked(
-          exec_ctx, bs->transport, bs->stream, make_bs_fail_args(bs, error));
+    grpc_error *error) {
+  if (error == GRPC_ERROR_NONE) {
+    gpr_mu_lock(&bs->slice_mu);
+    if (bs->remaining_bytes != 0) {
+      error = GRPC_ERROR_CREATE("Truncated message");
     }
+    gpr_mu_unlock(&bs->slice_mu);
+  }
+  if (error != GRPC_ERROR_NONE) {
+    incoming_byte_stream_publish_error(exec_ctx, bs, error);
   }
+  incoming_byte_stream_unref(exec_ctx, bs);
 }
 
 grpc_chttp2_incoming_byte_stream *grpc_chttp2_incoming_byte_stream_create(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, uint32_t frame_size,
-    uint32_t flags, grpc_chttp2_incoming_frame_queue *add_to_queue) {
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t, grpc_chttp2_stream *s,
+    uint32_t frame_size, uint32_t flags) {
   grpc_chttp2_incoming_byte_stream *incoming_byte_stream =
       gpr_malloc(sizeof(*incoming_byte_stream));
   incoming_byte_stream->base.length = frame_size;
+  incoming_byte_stream->remaining_bytes = frame_size;
   incoming_byte_stream->base.flags = flags;
   incoming_byte_stream->base.next = incoming_byte_stream_next;
   incoming_byte_stream->base.destroy = incoming_byte_stream_destroy;
+  gpr_mu_init(&incoming_byte_stream->slice_mu);
   gpr_ref_init(&incoming_byte_stream->refs, 2);
   incoming_byte_stream->next_message = NULL;
-  incoming_byte_stream->transport = TRANSPORT_FROM_PARSING(transport_parsing);
-  incoming_byte_stream->stream = STREAM_FROM_PARSING(stream_parsing);
-  gpr_ref(&incoming_byte_stream->stream->global.active_streams);
+  incoming_byte_stream->transport = t;
+  incoming_byte_stream->stream = s;
+  gpr_ref(&incoming_byte_stream->stream->active_streams);
   gpr_slice_buffer_init(&incoming_byte_stream->slices);
   incoming_byte_stream->on_next = NULL;
   incoming_byte_stream->is_tail = 1;
   incoming_byte_stream->error = GRPC_ERROR_NONE;
-  if (add_to_queue->head == NULL) {
-    add_to_queue->head = incoming_byte_stream;
+  grpc_chttp2_incoming_frame_queue *q = &s->incoming_frames;
+  if (q->head == NULL) {
+    q->head = incoming_byte_stream;
   } else {
-    add_to_queue->tail->is_tail = 0;
-    add_to_queue->tail->next_message = incoming_byte_stream;
+    q->tail->is_tail = 0;
+    q->tail->next_message = incoming_byte_stream;
   }
-  add_to_queue->tail = incoming_byte_stream;
+  q->tail = incoming_byte_stream;
+  grpc_chttp2_maybe_complete_recv_message(exec_ctx, t, s);
   return incoming_byte_stream;
 }
 
@@ -2438,40 +2049,30 @@ grpc_chttp2_incoming_byte_stream *grpc_chttp2_incoming_byte_stream_create(
  */
 
 static char *format_flowctl_context_var(const char *context, const char *var,
-                                        int64_t val, uint32_t id,
-                                        char **scope) {
-  char *underscore_pos;
-  char *buf;
-  char *result;
+                                        int64_t val, uint32_t id) {
+  char *name;
   if (context == NULL) {
-    *scope = NULL;
-    gpr_asprintf(&buf, "%s(%" PRId64 ")", var, val);
-    result = gpr_leftpad(buf, ' ', 60);
-    gpr_free(buf);
-    return result;
-  }
-  underscore_pos = strchr(context, '_');
-  *scope = gpr_strdup(context);
-  (*scope)[underscore_pos - context] = 0;
-  if (id != 0) {
-    char *tmp = *scope;
-    gpr_asprintf(scope, "%s[%d]", tmp, id);
-    gpr_free(tmp);
-  }
-  gpr_asprintf(&buf, "%s.%s(%" PRId64 ")", underscore_pos + 1, var, val);
-  result = gpr_leftpad(buf, ' ', 60);
-  gpr_free(buf);
-  return result;
-}
-
-static int samestr(char *a, char *b) {
-  if (a == NULL) {
-    return b == NULL;
-  }
-  if (b == NULL) {
-    return 0;
+    name = gpr_strdup(var);
+  } else if (0 == strcmp(context, "t")) {
+    GPR_ASSERT(id == 0);
+    gpr_asprintf(&name, "TRANSPORT:%s", var);
+  } else if (0 == strcmp(context, "s")) {
+    GPR_ASSERT(id != 0);
+    gpr_asprintf(&name, "STREAM[%d]:%s", id, var);
+  } else {
+    gpr_asprintf(&name, "BAD_CONTEXT[%s][%d]:%s", context, id, var);
   }
-  return 0 == strcmp(a, b);
+  char *name_fld = gpr_leftpad(name, ' ', 64);
+  char *value;
+  gpr_asprintf(&value, "%" PRId64, val);
+  char *value_fld = gpr_leftpad(value, ' ', 8);
+  char *result;
+  gpr_asprintf(&result, "%s %s", name_fld, value_fld);
+  gpr_free(name);
+  gpr_free(name_fld);
+  gpr_free(value);
+  gpr_free(value_fld);
+  return result;
 }
 
 void grpc_chttp2_flowctl_trace(const char *file, int line, const char *phase,
@@ -2479,26 +2080,18 @@ void grpc_chttp2_flowctl_trace(const char *file, int line, const char *phase,
                                const char *var1, const char *context2,
                                const char *var2, int is_client,
                                uint32_t stream_id, int64_t val1, int64_t val2) {
-  char *scope1;
-  char *scope2;
   char *tmp_phase;
-  char *tmp_scope1;
-  char *label1 =
-      format_flowctl_context_var(context1, var1, val1, stream_id, &scope1);
-  char *label2 =
-      format_flowctl_context_var(context2, var2, val2, stream_id, &scope2);
+  char *label1 = format_flowctl_context_var(context1, var1, val1, stream_id);
+  char *label2 = format_flowctl_context_var(context2, var2, val2, stream_id);
   char *clisvr = is_client ? "client" : "server";
   char *prefix;
 
   tmp_phase = gpr_leftpad(phase, ' ', 8);
-  tmp_scope1 = gpr_leftpad(scope1, ' ', 11);
-  gpr_asprintf(&prefix, "FLOW %s: %s %s ", tmp_phase, clisvr, scope1);
+  gpr_asprintf(&prefix, "FLOW %s: %s ", tmp_phase, clisvr);
   gpr_free(tmp_phase);
-  gpr_free(tmp_scope1);
 
   switch (op) {
     case GRPC_CHTTP2_FLOWCTL_MOVE:
-      GPR_ASSERT(samestr(scope1, scope2));
       if (val2 != 0) {
         gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
                 "%sMOVE   %s <- %s giving %" PRId64, prefix, label1, label2,
@@ -2523,8 +2116,6 @@ void grpc_chttp2_flowctl_trace(const char *file, int line, const char *phase,
       break;
   }
 
-  gpr_free(scope1);
-  gpr_free(scope2);
   gpr_free(label1);
   gpr_free(label2);
   gpr_free(prefix);
@@ -2561,10 +2152,11 @@ void grpc_chttp2_transport_start_reading(grpc_exec_ctx *exec_ctx,
                                          grpc_transport *transport,
                                          gpr_slice_buffer *read_buffer) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)transport;
-  REF_TRANSPORT(t, "reading_action"); /* matches unref inside reading_action */
+  GRPC_CHTTP2_REF_TRANSPORT(
+      t, "reading_action"); /* matches unref inside reading_action */
   if (read_buffer != NULL) {
     gpr_slice_buffer_move_into(read_buffer, &t->read_buffer);
     gpr_free(read_buffer);
   }
-  reading_action(exec_ctx, t, GRPC_ERROR_NONE);
+  read_action_begin(exec_ctx, t, GRPC_ERROR_NONE);
 }
diff --git a/src/core/ext/transport/chttp2/transport/frame.h b/src/core/ext/transport/chttp2/transport/frame.h
index 507aae4100..1e444a91fd 100644
--- a/src/core/ext/transport/chttp2/transport/frame.h
+++ b/src/core/ext/transport/chttp2/transport/frame.h
@@ -40,8 +40,8 @@
 #include "src/core/lib/iomgr/error.h"
 
 /* defined in internal.h */
-typedef struct grpc_chttp2_stream_parsing grpc_chttp2_stream_parsing;
-typedef struct grpc_chttp2_transport_parsing grpc_chttp2_transport_parsing;
+typedef struct grpc_chttp2_stream grpc_chttp2_stream;
+typedef struct grpc_chttp2_transport grpc_chttp2_transport;
 
 #define GRPC_CHTTP2_FRAME_DATA 0
 #define GRPC_CHTTP2_FRAME_HEADER 1
diff --git a/src/core/ext/transport/chttp2/transport/frame_data.c b/src/core/ext/transport/chttp2/transport/frame_data.c
index 9046fbc453..8668816930 100644
--- a/src/core/ext/transport/chttp2/transport/frame_data.c
+++ b/src/core/ext/transport/chttp2/transport/frame_data.c
@@ -51,16 +51,11 @@ grpc_error *grpc_chttp2_data_parser_init(grpc_chttp2_data_parser *parser) {
 
 void grpc_chttp2_data_parser_destroy(grpc_exec_ctx *exec_ctx,
                                      grpc_chttp2_data_parser *parser) {
-  grpc_byte_stream *bs;
-  if (parser->parsing_frame) {
+  if (parser->parsing_frame != NULL) {
     grpc_chttp2_incoming_byte_stream_finished(
-        exec_ctx, parser->parsing_frame, GRPC_ERROR_CREATE("Parser destroyed"),
-        1);
-  }
-  while (
-      (bs = grpc_chttp2_incoming_frame_queue_pop(&parser->incoming_frames))) {
-    grpc_byte_stream_destroy(exec_ctx, bs);
+        exec_ctx, parser->parsing_frame, GRPC_ERROR_CREATE("Parser destroyed"));
   }
+  GRPC_ERROR_UNREF(parser->error);
 }
 
 grpc_error *grpc_chttp2_data_parser_begin_frame(grpc_chttp2_data_parser *parser,
@@ -145,22 +140,17 @@ void grpc_chttp2_encode_data(uint32_t id, gpr_slice_buffer *inbuf,
   stats->data_bytes += write_bytes;
 }
 
-grpc_error *grpc_chttp2_data_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+static grpc_error *parse_inner(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_data_parser *p,
+                               grpc_chttp2_transport *t, grpc_chttp2_stream *s,
+                               gpr_slice slice) {
   uint8_t *const beg = GPR_SLICE_START_PTR(slice);
   uint8_t *const end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
-  grpc_chttp2_data_parser *p = parser;
   uint32_t message_flags;
   grpc_chttp2_incoming_byte_stream *incoming_byte_stream;
   char *msg;
 
-  if (is_last && p->is_last_frame) {
-    stream_parsing->received_close = 1;
-  }
-
   if (cur == end) {
     return GRPC_ERROR_NONE;
   }
@@ -171,7 +161,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
       return GRPC_ERROR_REF(p->error);
     fh_0:
     case GRPC_CHTTP2_DATA_FH_0:
-      stream_parsing->stats.incoming.framing_bytes++;
+      s->stats.incoming.framing_bytes++;
       p->frame_type = *cur;
       switch (p->frame_type) {
         case 0:
@@ -184,7 +174,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
           gpr_asprintf(&msg, "Bad GRPC frame type 0x%02x", p->frame_type);
           p->error = GRPC_ERROR_CREATE(msg);
           p->error = grpc_error_set_int(p->error, GRPC_ERROR_INT_STREAM_ID,
-                                        (intptr_t)stream_parsing->id);
+                                        (intptr_t)s->id);
           gpr_free(msg);
           msg = gpr_dump_slice(slice, GPR_DUMP_HEX | GPR_DUMP_ASCII);
           p->error =
@@ -201,7 +191,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_1:
-      stream_parsing->stats.incoming.framing_bytes++;
+      s->stats.incoming.framing_bytes++;
       p->frame_size = ((uint32_t)*cur) << 24;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_2;
@@ -209,7 +199,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_2:
-      stream_parsing->stats.incoming.framing_bytes++;
+      s->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur) << 16;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_3;
@@ -217,7 +207,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_3:
-      stream_parsing->stats.incoming.framing_bytes++;
+      s->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur) << 8;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_4;
@@ -225,7 +215,7 @@ grpc_error *grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_4:
-      stream_parsing->stats.incoming.framing_bytes++;
+      s->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur);
       p->state = GRPC_CHTTP2_DATA_FRAME;
       ++cur;
@@ -234,35 +224,32 @@ grpc_error *grpc_chttp2_data_parser_parse(
         message_flags |= GRPC_WRITE_INTERNAL_COMPRESS;
       }
       p->parsing_frame = incoming_byte_stream =
-          grpc_chttp2_incoming_byte_stream_create(
-              exec_ctx, transport_parsing, stream_parsing, p->frame_size,
-              message_flags, &p->incoming_frames);
+          grpc_chttp2_incoming_byte_stream_create(exec_ctx, t, s, p->frame_size,
+                                                  message_flags);
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FRAME:
-      grpc_chttp2_list_add_parsing_seen_stream(transport_parsing,
-                                               stream_parsing);
       if (cur == end) {
         return GRPC_ERROR_NONE;
       }
       uint32_t remaining = (uint32_t)(end - cur);
       if (remaining == p->frame_size) {
-        stream_parsing->stats.incoming.data_bytes += p->frame_size;
+        s->stats.incoming.data_bytes += p->frame_size;
         grpc_chttp2_incoming_byte_stream_push(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg), (size_t)(end - beg)));
         grpc_chttp2_incoming_byte_stream_finished(exec_ctx, p->parsing_frame,
-                                                  GRPC_ERROR_NONE, 1);
+                                                  GRPC_ERROR_NONE);
         p->parsing_frame = NULL;
         p->state = GRPC_CHTTP2_DATA_FH_0;
         return GRPC_ERROR_NONE;
       } else if (remaining > p->frame_size) {
-        stream_parsing->stats.incoming.data_bytes += p->frame_size;
+        s->stats.incoming.data_bytes += p->frame_size;
         grpc_chttp2_incoming_byte_stream_push(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg),
                           (size_t)(cur + p->frame_size - beg)));
         grpc_chttp2_incoming_byte_stream_finished(exec_ctx, p->parsing_frame,
-                                                  GRPC_ERROR_NONE, 1);
+                                                  GRPC_ERROR_NONE);
         p->parsing_frame = NULL;
         cur += p->frame_size;
         goto fh_0; /* loop */
@@ -272,10 +259,25 @@ grpc_error *grpc_chttp2_data_parser_parse(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg), (size_t)(end - beg)));
         p->frame_size -= remaining;
-        stream_parsing->stats.incoming.data_bytes += remaining;
+        s->stats.incoming.data_bytes += remaining;
         return GRPC_ERROR_NONE;
       }
   }
 
   GPR_UNREACHABLE_CODE(return GRPC_ERROR_CREATE("Should never reach here"));
 }
+
+grpc_error *grpc_chttp2_data_parser_parse(grpc_exec_ctx *exec_ctx, void *parser,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s,
+                                          gpr_slice slice, int is_last) {
+  grpc_chttp2_data_parser *p = parser;
+  grpc_error *error = parse_inner(exec_ctx, p, t, s, slice);
+
+  if (is_last && p->is_last_frame) {
+    grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, false,
+                                   GRPC_ERROR_NONE);
+  }
+
+  return error;
+}
diff --git a/src/core/ext/transport/chttp2/transport/frame_data.h b/src/core/ext/transport/chttp2/transport/frame_data.h
index a21a7942b9..eb2d97d898 100644
--- a/src/core/ext/transport/chttp2/transport/frame_data.h
+++ b/src/core/ext/transport/chttp2/transport/frame_data.h
@@ -69,7 +69,6 @@ typedef struct {
   grpc_error *error;
 
   int is_frame_compressed;
-  grpc_chttp2_incoming_frame_queue incoming_frames;
   grpc_chttp2_incoming_byte_stream *parsing_frame;
 } grpc_chttp2_data_parser;
 
@@ -92,10 +91,10 @@ grpc_error *grpc_chttp2_data_parser_begin_frame(grpc_chttp2_data_parser *parser,
 
 /* handle a slice of a data frame - is_last indicates the last slice of a
    frame */
-grpc_error *grpc_chttp2_data_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_data_parser_parse(grpc_exec_ctx *exec_ctx, void *parser,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s,
+                                          gpr_slice slice, int is_last);
 
 void grpc_chttp2_encode_data(uint32_t id, gpr_slice_buffer *inbuf,
                              uint32_t write_bytes, int is_eof,
diff --git a/src/core/ext/transport/chttp2/transport/frame_goaway.c b/src/core/ext/transport/chttp2/transport/frame_goaway.c
index 299e27ad70..33d2269169 100644
--- a/src/core/ext/transport/chttp2/transport/frame_goaway.c
+++ b/src/core/ext/transport/chttp2/transport/frame_goaway.c
@@ -67,10 +67,11 @@ grpc_error *grpc_chttp2_goaway_parser_begin_frame(grpc_chttp2_goaway_parser *p,
   return GRPC_ERROR_NONE;
 }
 
-grpc_error *grpc_chttp2_goaway_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+grpc_error *grpc_chttp2_goaway_parser_parse(grpc_exec_ctx *exec_ctx,
+                                            void *parser,
+                                            grpc_chttp2_transport *t,
+                                            grpc_chttp2_stream *s,
+                                            gpr_slice slice, int is_last) {
   uint8_t *const beg = GPR_SLICE_START_PTR(slice);
   uint8_t *const end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
@@ -148,12 +149,9 @@ grpc_error *grpc_chttp2_goaway_parser_parse(
       p->debug_pos += (uint32_t)(end - cur);
       p->state = GRPC_CHTTP2_GOAWAY_DEBUG;
       if (is_last) {
-        transport_parsing->goaway_received = 1;
-        transport_parsing->goaway_last_stream_index = p->last_stream_id;
-        gpr_slice_unref(transport_parsing->goaway_text);
-        transport_parsing->goaway_error = (grpc_status_code)p->error_code;
-        transport_parsing->goaway_text =
-            gpr_slice_new(p->debug_data, p->debug_length, gpr_free);
+        grpc_chttp2_add_incoming_goaway(
+            exec_ctx, t, (uint32_t)p->error_code,
+            gpr_slice_new(p->debug_data, p->debug_length, gpr_free));
         p->debug_data = NULL;
       }
       return GRPC_ERROR_NONE;
diff --git a/src/core/ext/transport/chttp2/transport/frame_goaway.h b/src/core/ext/transport/chttp2/transport/frame_goaway.h
index eb4303405a..355104a5a7 100644
--- a/src/core/ext/transport/chttp2/transport/frame_goaway.h
+++ b/src/core/ext/transport/chttp2/transport/frame_goaway.h
@@ -65,10 +65,11 @@ void grpc_chttp2_goaway_parser_init(grpc_chttp2_goaway_parser *p);
 void grpc_chttp2_goaway_parser_destroy(grpc_chttp2_goaway_parser *p);
 grpc_error *grpc_chttp2_goaway_parser_begin_frame(
     grpc_chttp2_goaway_parser *parser, uint32_t length, uint8_t flags);
-grpc_error *grpc_chttp2_goaway_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_goaway_parser_parse(grpc_exec_ctx *exec_ctx,
+                                            void *parser,
+                                            grpc_chttp2_transport *t,
+                                            grpc_chttp2_stream *s,
+                                            gpr_slice slice, int is_last);
 
 void grpc_chttp2_goaway_append(uint32_t last_stream_id, uint32_t error_code,
                                gpr_slice debug_data,
diff --git a/src/core/ext/transport/chttp2/transport/frame_ping.c b/src/core/ext/transport/chttp2/transport/frame_ping.c
index 1f814ab1bd..624f42649d 100644
--- a/src/core/ext/transport/chttp2/transport/frame_ping.c
+++ b/src/core/ext/transport/chttp2/transport/frame_ping.c
@@ -73,10 +73,10 @@ grpc_error *grpc_chttp2_ping_parser_begin_frame(grpc_chttp2_ping_parser *parser,
   return GRPC_ERROR_NONE;
 }
 
-grpc_error *grpc_chttp2_ping_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+grpc_error *grpc_chttp2_ping_parser_parse(grpc_exec_ctx *exec_ctx, void *parser,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s,
+                                          gpr_slice slice, int is_last) {
   uint8_t *const beg = GPR_SLICE_START_PTR(slice);
   uint8_t *const end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
@@ -91,10 +91,11 @@ grpc_error *grpc_chttp2_ping_parser_parse(
   if (p->byte == 8) {
     GPR_ASSERT(is_last);
     if (p->is_ack) {
-      grpc_chttp2_ack_ping(exec_ctx, transport_parsing, p->opaque_8bytes);
+      grpc_chttp2_ack_ping(exec_ctx, t, p->opaque_8bytes);
     } else {
-      gpr_slice_buffer_add(&transport_parsing->qbuf,
+      gpr_slice_buffer_add(&t->qbuf,
                            grpc_chttp2_ping_create(1, p->opaque_8bytes));
+      grpc_chttp2_initiate_write(exec_ctx, t, false, "ping response");
     }
   }
 
diff --git a/src/core/ext/transport/chttp2/transport/frame_ping.h b/src/core/ext/transport/chttp2/transport/frame_ping.h
index 5a8723421c..2071f647fb 100644
--- a/src/core/ext/transport/chttp2/transport/frame_ping.h
+++ b/src/core/ext/transport/chttp2/transport/frame_ping.h
@@ -48,9 +48,9 @@ gpr_slice grpc_chttp2_ping_create(uint8_t ack, uint8_t *opaque_8bytes);
 
 grpc_error *grpc_chttp2_ping_parser_begin_frame(grpc_chttp2_ping_parser *parser,
                                                 uint32_t length, uint8_t flags);
-grpc_error *grpc_chttp2_ping_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_ping_parser_parse(grpc_exec_ctx *exec_ctx, void *parser,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s,
+                                          gpr_slice slice, int is_last);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FRAME_PING_H */
diff --git a/src/core/ext/transport/chttp2/transport/frame_rst_stream.c b/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
index e3a3c9e4a7..1bb6ed82b1 100644
--- a/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
+++ b/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
@@ -39,6 +39,8 @@
 #include <grpc/support/string_util.h>
 
 #include "src/core/ext/transport/chttp2/transport/frame.h"
+#include "src/core/ext/transport/chttp2/transport/http2_errors.h"
+#include "src/core/ext/transport/chttp2/transport/status_conversion.h"
 
 gpr_slice grpc_chttp2_rst_stream_create(uint32_t id, uint32_t code,
                                         grpc_transport_one_way_stats *stats) {
@@ -83,10 +85,11 @@ grpc_error *grpc_chttp2_rst_stream_parser_begin_frame(
   return GRPC_ERROR_NONE;
 }
 
-grpc_error *grpc_chttp2_rst_stream_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+grpc_error *grpc_chttp2_rst_stream_parser_parse(grpc_exec_ctx *exec_ctx,
+                                                void *parser,
+                                                grpc_chttp2_transport *t,
+                                                grpc_chttp2_stream *s,
+                                                gpr_slice slice, int is_last) {
   uint8_t *const beg = GPR_SLICE_START_PTR(slice);
   uint8_t *const end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
@@ -97,19 +100,28 @@ grpc_error *grpc_chttp2_rst_stream_parser_parse(
     cur++;
     p->byte++;
   }
-  stream_parsing->stats.incoming.framing_bytes += (uint64_t)(end - cur);
+  s->stats.incoming.framing_bytes += (uint64_t)(end - cur);
 
   if (p->byte == 4) {
     GPR_ASSERT(is_last);
-    stream_parsing->received_close = 1;
-    if (stream_parsing->forced_close_error == GRPC_ERROR_NONE) {
-      stream_parsing->forced_close_error = grpc_error_set_int(
-          GRPC_ERROR_CREATE("RST_STREAM"), GRPC_ERROR_INT_HTTP2_ERROR,
-          (intptr_t)((((uint32_t)p->reason_bytes[0]) << 24) |
-                     (((uint32_t)p->reason_bytes[1]) << 16) |
-                     (((uint32_t)p->reason_bytes[2]) << 8) |
-                     (((uint32_t)p->reason_bytes[3]))));
+    uint32_t reason = (((uint32_t)p->reason_bytes[0]) << 24) |
+                      (((uint32_t)p->reason_bytes[1]) << 16) |
+                      (((uint32_t)p->reason_bytes[2]) << 8) |
+                      (((uint32_t)p->reason_bytes[3]));
+    grpc_error *error = GRPC_ERROR_NONE;
+    if (reason != GRPC_CHTTP2_NO_ERROR) {
+      error = grpc_error_set_int(GRPC_ERROR_CREATE("RST_STREAM"),
+                                 GRPC_ERROR_INT_HTTP2_ERROR, reason);
+      grpc_status_code status_code = grpc_chttp2_http2_error_to_grpc_status(
+          (grpc_chttp2_error_code)reason, s->deadline);
+      char *status_details;
+      gpr_asprintf(&status_details, "Received RST_STREAM with error code %d",
+                   reason);
+      gpr_slice slice_details = gpr_slice_from_copied_string(status_details);
+      gpr_free(status_details);
+      grpc_chttp2_fake_status(exec_ctx, t, s, status_code, &slice_details);
     }
+    grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, true, error);
   }
 
   return GRPC_ERROR_NONE;
diff --git a/src/core/ext/transport/chttp2/transport/frame_rst_stream.h b/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
index 11cf94f3ea..5a1f578a29 100644
--- a/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
+++ b/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
@@ -49,9 +49,10 @@ gpr_slice grpc_chttp2_rst_stream_create(uint32_t stream_id, uint32_t code,
 
 grpc_error *grpc_chttp2_rst_stream_parser_begin_frame(
     grpc_chttp2_rst_stream_parser *parser, uint32_t length, uint8_t flags);
-grpc_error *grpc_chttp2_rst_stream_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_rst_stream_parser_parse(grpc_exec_ctx *exec_ctx,
+                                                void *parser,
+                                                grpc_chttp2_transport *t,
+                                                grpc_chttp2_stream *s,
+                                                gpr_slice slice, int is_last);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FRAME_RST_STREAM_H */
diff --git a/src/core/ext/transport/chttp2/transport/frame_settings.c b/src/core/ext/transport/chttp2/transport/frame_settings.c
index 04b96c4cd9..92022f90c9 100644
--- a/src/core/ext/transport/chttp2/transport/frame_settings.c
+++ b/src/core/ext/transport/chttp2/transport/frame_settings.c
@@ -143,10 +143,10 @@ grpc_error *grpc_chttp2_settings_parser_begin_frame(
   }
 }
 
-grpc_error *grpc_chttp2_settings_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *p,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+grpc_error *grpc_chttp2_settings_parser_parse(grpc_exec_ctx *exec_ctx, void *p,
+                                              grpc_chttp2_transport *t,
+                                              grpc_chttp2_stream *s,
+                                              gpr_slice slice, int is_last) {
   grpc_chttp2_settings_parser *parser = p;
   const uint8_t *cur = GPR_SLICE_START_PTR(slice);
   const uint8_t *end = GPR_SLICE_END_PTR(slice);
@@ -162,11 +162,9 @@ grpc_error *grpc_chttp2_settings_parser_parse(
         if (cur == end) {
           parser->state = GRPC_CHTTP2_SPS_ID0;
           if (is_last) {
-            transport_parsing->settings_updated = 1;
             memcpy(parser->target_settings, parser->incoming_settings,
                    GRPC_CHTTP2_NUM_SETTINGS * sizeof(uint32_t));
-            gpr_slice_buffer_add(&transport_parsing->qbuf,
-                                 grpc_chttp2_settings_ack_create());
+            gpr_slice_buffer_add(&t->qbuf, grpc_chttp2_settings_ack_create());
           }
           return GRPC_ERROR_NONE;
         }
@@ -226,9 +224,9 @@ grpc_error *grpc_chttp2_settings_parser_parse(
                 break;
               case GRPC_CHTTP2_DISCONNECT_ON_INVALID_VALUE:
                 grpc_chttp2_goaway_append(
-                    transport_parsing->last_incoming_stream_id, sp->error_value,
+                    t->last_new_stream_id, sp->error_value,
                     gpr_slice_from_static_string("HTTP2 settings error"),
-                    &transport_parsing->qbuf);
+                    &t->qbuf);
                 gpr_asprintf(&msg, "invalid value %u passed for %s",
                              parser->value, sp->name);
                 grpc_error *err = GRPC_ERROR_CREATE(msg);
@@ -238,18 +236,17 @@ grpc_error *grpc_chttp2_settings_parser_parse(
           }
           if (parser->id == GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE &&
               parser->incoming_settings[parser->id] != parser->value) {
-            transport_parsing->initial_window_update =
+            t->initial_window_update =
                 (int64_t)parser->value - parser->incoming_settings[parser->id];
             if (grpc_http_trace) {
               gpr_log(GPR_DEBUG, "adding %d for initial_window change",
-                      (int)transport_parsing->initial_window_update);
+                      (int)t->initial_window_update);
             }
           }
           parser->incoming_settings[parser->id] = parser->value;
           if (grpc_http_trace) {
             gpr_log(GPR_DEBUG, "CHTTP2:%s: got setting %d = %d",
-                    transport_parsing->is_client ? "CLI" : "SVR", parser->id,
-                    parser->value);
+                    t->is_client ? "CLI" : "SVR", parser->id, parser->value);
           }
         } else if (grpc_http_trace) {
           gpr_log(GPR_ERROR, "CHTTP2: Ignoring unknown setting %d (value %d)",
diff --git a/src/core/ext/transport/chttp2/transport/frame_settings.h b/src/core/ext/transport/chttp2/transport/frame_settings.h
index f654c598c8..4bfa944cf1 100644
--- a/src/core/ext/transport/chttp2/transport/frame_settings.h
+++ b/src/core/ext/transport/chttp2/transport/frame_settings.h
@@ -95,9 +95,10 @@ gpr_slice grpc_chttp2_settings_ack_create(void);
 grpc_error *grpc_chttp2_settings_parser_begin_frame(
     grpc_chttp2_settings_parser *parser, uint32_t length, uint8_t flags,
     uint32_t *settings);
-grpc_error *grpc_chttp2_settings_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_settings_parser_parse(grpc_exec_ctx *exec_ctx,
+                                              void *parser,
+                                              grpc_chttp2_transport *t,
+                                              grpc_chttp2_stream *s,
+                                              gpr_slice slice, int is_last);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FRAME_SETTINGS_H */
diff --git a/src/core/ext/transport/chttp2/transport/frame_window_update.c b/src/core/ext/transport/chttp2/transport/frame_window_update.c
index 3cf848fd5c..418166a6df 100644
--- a/src/core/ext/transport/chttp2/transport/frame_window_update.c
+++ b/src/core/ext/transport/chttp2/transport/frame_window_update.c
@@ -80,9 +80,8 @@ grpc_error *grpc_chttp2_window_update_parser_begin_frame(
 }
 
 grpc_error *grpc_chttp2_window_update_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+    grpc_exec_ctx *exec_ctx, void *parser, grpc_chttp2_transport *t,
+    grpc_chttp2_stream *s, gpr_slice slice, int is_last) {
   uint8_t *const beg = GPR_SLICE_START_PTR(slice);
   uint8_t *const end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
@@ -94,8 +93,8 @@ grpc_error *grpc_chttp2_window_update_parser_parse(
     p->byte++;
   }
 
-  if (stream_parsing != NULL) {
-    stream_parsing->stats.incoming.framing_bytes += (uint32_t)(end - cur);
+  if (s != NULL) {
+    s->stats.incoming.framing_bytes += (uint32_t)(end - cur);
   }
 
   if (p->byte == 4) {
@@ -109,17 +108,26 @@ grpc_error *grpc_chttp2_window_update_parser_parse(
     }
     GPR_ASSERT(is_last);
 
-    if (transport_parsing->incoming_stream_id != 0) {
-      if (stream_parsing != NULL) {
-        GRPC_CHTTP2_FLOW_CREDIT_STREAM("parse", transport_parsing,
-                                       stream_parsing, outgoing_window,
+    if (t->incoming_stream_id != 0) {
+      if (s != NULL) {
+        bool was_zero = s->outgoing_window <= 0;
+        GRPC_CHTTP2_FLOW_CREDIT_STREAM("parse", t, s, outgoing_window,
                                        received_update);
-        grpc_chttp2_list_add_parsing_seen_stream(transport_parsing,
-                                                 stream_parsing);
+        bool is_zero = s->outgoing_window <= 0;
+        if (was_zero && !is_zero) {
+          grpc_chttp2_become_writable(exec_ctx, t, s, false,
+                                      "stream.read_flow_control");
+        }
       }
     } else {
-      GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parse", transport_parsing,
-                                        outgoing_window, received_update);
+      bool was_zero = t->outgoing_window <= 0;
+      GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parse", t, outgoing_window,
+                                        received_update);
+      bool is_zero = t->outgoing_window <= 0;
+      if (was_zero && !is_zero) {
+        grpc_chttp2_initiate_write(exec_ctx, t, false,
+                                   "new_global_flow_control");
+      }
     }
   }
 
diff --git a/src/core/ext/transport/chttp2/transport/frame_window_update.h b/src/core/ext/transport/chttp2/transport/frame_window_update.h
index 1bcbbf9247..6e62f31872 100644
--- a/src/core/ext/transport/chttp2/transport/frame_window_update.h
+++ b/src/core/ext/transport/chttp2/transport/frame_window_update.h
@@ -51,8 +51,7 @@ gpr_slice grpc_chttp2_window_update_create(uint32_t id, uint32_t window_delta,
 grpc_error *grpc_chttp2_window_update_parser_begin_frame(
     grpc_chttp2_window_update_parser *parser, uint32_t length, uint8_t flags);
 grpc_error *grpc_chttp2_window_update_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+    grpc_exec_ctx *exec_ctx, void *parser, grpc_chttp2_transport *t,
+    grpc_chttp2_stream *s, gpr_slice slice, int is_last);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FRAME_WINDOW_UPDATE_H */
diff --git a/src/core/ext/transport/chttp2/transport/hpack_parser.c b/src/core/ext/transport/chttp2/transport/hpack_parser.c
index 522455f7dc..8180f78fc0 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_parser.c
+++ b/src/core/ext/transport/chttp2/transport/hpack_parser.c
@@ -78,69 +78,96 @@ typedef enum {
    a set of indirect jumps, and so not waste stack space. */
 
 /* forward declarations for parsing states */
-static grpc_error *parse_begin(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_begin(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                const uint8_t *end);
-static grpc_error *parse_error(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_error(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                const uint8_t *end, grpc_error *error);
-static grpc_error *still_parse_error(grpc_chttp2_hpack_parser *p,
+static grpc_error *still_parse_error(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_illegal_op(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_illegal_op(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_hpack_parser *p,
                                     const uint8_t *cur, const uint8_t *end);
 
-static grpc_error *parse_string_prefix(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_string_prefix(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_key_string(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_key_string(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_hpack_parser *p,
                                     const uint8_t *cur, const uint8_t *end);
 static grpc_error *parse_value_string_with_indexed_key(
-    grpc_chttp2_hpack_parser *p, const uint8_t *cur, const uint8_t *end);
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+    const uint8_t *end);
 static grpc_error *parse_value_string_with_literal_key(
-    grpc_chttp2_hpack_parser *p, const uint8_t *cur, const uint8_t *end);
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+    const uint8_t *end);
 
-static grpc_error *parse_value0(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value0(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end);
-static grpc_error *parse_value1(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value1(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end);
-static grpc_error *parse_value2(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value2(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end);
-static grpc_error *parse_value3(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value3(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end);
-static grpc_error *parse_value4(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value4(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end);
-static grpc_error *parse_value5up(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_value5up(grpc_exec_ctx *exec_ctx,
+                                  grpc_chttp2_hpack_parser *p,
                                   const uint8_t *cur, const uint8_t *end);
 
-static grpc_error *parse_indexed_field(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_indexed_field(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_indexed_field_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_indexed_field_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_incidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_lithdr_incidx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_incidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_notidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_lithdr_notidx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_notidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_nvridx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_lithdr_nvridx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_lithdr_nvridx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end);
-static grpc_error *parse_max_tbl_size(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_max_tbl_size(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_hpack_parser *p,
                                       const uint8_t *cur, const uint8_t *end);
-static grpc_error *parse_max_tbl_size_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_max_tbl_size_x(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur, const uint8_t *end);
 
 /* we translate the first byte of a hpack field into one of these decoding
@@ -639,8 +666,8 @@ static const uint8_t inverse_base64[256] = {
 };
 
 /* emission helpers */
-static grpc_error *on_hdr(grpc_chttp2_hpack_parser *p, grpc_mdelem *md,
-                          int add_to_table) {
+static grpc_error *on_hdr(grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p,
+                          grpc_mdelem *md, int add_to_table) {
   if (add_to_table) {
     grpc_error *err = grpc_chttp2_hptbl_add(&p->table, md);
     if (err != GRPC_ERROR_NONE) return err;
@@ -649,7 +676,7 @@ static grpc_error *on_hdr(grpc_chttp2_hpack_parser *p, grpc_mdelem *md,
     GRPC_MDELEM_UNREF(md);
     return GRPC_ERROR_CREATE("on_header callback not set");
   }
-  p->on_header(p->on_header_user_data, md);
+  p->on_header(exec_ctx, p->on_header_user_data, md);
   return GRPC_ERROR_NONE;
 }
 
@@ -661,78 +688,86 @@ static grpc_mdstr *take_string(grpc_chttp2_hpack_parser *p,
 }
 
 /* jump to the next state */
-static grpc_error *parse_next(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_next(grpc_exec_ctx *exec_ctx,
+                              grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                               const uint8_t *end) {
   p->state = *p->next_state++;
-  return p->state(p, cur, end);
+  return p->state(exec_ctx, p, cur, end);
 }
 
 /* begin parsing a header: all functionality is encoded into lookup tables
    above */
-static grpc_error *parse_begin(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_begin(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                const uint8_t *end) {
   if (cur == end) {
     p->state = parse_begin;
     return GRPC_ERROR_NONE;
   }
 
-  return first_byte_action[first_byte_lut[*cur]](p, cur, end);
+  return first_byte_action[first_byte_lut[*cur]](exec_ctx, p, cur, end);
 }
 
 /* stream dependency and prioritization data: we just skip it */
-static grpc_error *parse_stream_weight(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_stream_weight(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_stream_weight;
     return GRPC_ERROR_NONE;
   }
 
-  return p->after_prioritization(p, cur + 1, end);
+  return p->after_prioritization(exec_ctx, p, cur + 1, end);
 }
 
-static grpc_error *parse_stream_dep3(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_stream_dep3(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_stream_dep3;
     return GRPC_ERROR_NONE;
   }
 
-  return parse_stream_weight(p, cur + 1, end);
+  return parse_stream_weight(exec_ctx, p, cur + 1, end);
 }
 
-static grpc_error *parse_stream_dep2(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_stream_dep2(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_stream_dep2;
     return GRPC_ERROR_NONE;
   }
 
-  return parse_stream_dep3(p, cur + 1, end);
+  return parse_stream_dep3(exec_ctx, p, cur + 1, end);
 }
 
-static grpc_error *parse_stream_dep1(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_stream_dep1(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_stream_dep1;
     return GRPC_ERROR_NONE;
   }
 
-  return parse_stream_dep2(p, cur + 1, end);
+  return parse_stream_dep2(exec_ctx, p, cur + 1, end);
 }
 
-static grpc_error *parse_stream_dep0(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_stream_dep0(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_stream_dep0;
     return GRPC_ERROR_NONE;
   }
 
-  return parse_stream_dep1(p, cur + 1, end);
+  return parse_stream_dep1(exec_ctx, p, cur + 1, end);
 }
 
 /* emit an indexed field; for now just logs it to console; jumps to
    begin the next field on completion */
-static grpc_error *finish_indexed_field(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_indexed_field(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur,
                                         const uint8_t *end) {
   grpc_mdelem *md = grpc_chttp2_hptbl_lookup(&p->table, p->index);
@@ -743,21 +778,23 @@ static grpc_error *finish_indexed_field(grpc_chttp2_hpack_parser *p,
         GRPC_ERROR_INT_SIZE, (intptr_t)p->table.num_ents);
   }
   GRPC_MDELEM_REF(md);
-  grpc_error *err = on_hdr(p, md, 0);
+  grpc_error *err = on_hdr(exec_ctx, p, md, 0);
   if (err != GRPC_ERROR_NONE) return err;
-  return parse_begin(p, cur, end);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* parse an indexed field with index < 127 */
-static grpc_error *parse_indexed_field(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_indexed_field(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   p->dynamic_table_update_allowed = 0;
   p->index = (*cur) & 0x7f;
-  return finish_indexed_field(p, cur + 1, end);
+  return finish_indexed_field(exec_ctx, p, cur + 1, end);
 }
 
 /* parse an indexed field with index >= 127 */
-static grpc_error *parse_indexed_field_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_indexed_field_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -766,49 +803,53 @@ static grpc_error *parse_indexed_field_x(grpc_chttp2_hpack_parser *p,
   p->next_state = and_then;
   p->index = 0x7f;
   p->parsing.value = &p->index;
-  return parse_value0(p, cur + 1, end);
+  return parse_value0(exec_ctx, p, cur + 1, end);
 }
 
 /* finish a literal header with incremental indexing: just log, and jump to '
    begin */
-static grpc_error *finish_lithdr_incidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_incidx(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur,
                                         const uint8_t *end) {
   grpc_mdelem *md = grpc_chttp2_hptbl_lookup(&p->table, p->index);
   GPR_ASSERT(md != NULL); /* handled in string parsing */
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
-                                                  take_string(p, &p->value)),
-             1);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
+                                                     take_string(p, &p->value)),
+      1);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* finish a literal header with incremental indexing with no index */
-static grpc_error *finish_lithdr_incidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_incidx_v(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_hpack_parser *p,
                                           const uint8_t *cur,
                                           const uint8_t *end) {
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
-                                                  take_string(p, &p->value)),
-             1);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
+                                                     take_string(p, &p->value)),
+      1);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* parse a literal header with incremental indexing; index < 63 */
-static grpc_error *parse_lithdr_incidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
       parse_value_string_with_indexed_key, finish_lithdr_incidx};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
   p->index = (*cur) & 0x3f;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header with incremental indexing; index >= 63 */
-static grpc_error *parse_lithdr_incidx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -818,11 +859,12 @@ static grpc_error *parse_lithdr_incidx_x(grpc_chttp2_hpack_parser *p,
   p->next_state = and_then;
   p->index = 0x3f;
   p->parsing.value = &p->index;
-  return parse_value0(p, cur + 1, end);
+  return parse_value0(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header with incremental indexing; index = 0 */
-static grpc_error *parse_lithdr_incidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_incidx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -830,48 +872,52 @@ static grpc_error *parse_lithdr_incidx_v(grpc_chttp2_hpack_parser *p,
       parse_value_string_with_literal_key, finish_lithdr_incidx_v};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* finish a literal header without incremental indexing */
-static grpc_error *finish_lithdr_notidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_notidx(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur,
                                         const uint8_t *end) {
   grpc_mdelem *md = grpc_chttp2_hptbl_lookup(&p->table, p->index);
   GPR_ASSERT(md != NULL); /* handled in string parsing */
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
-                                                  take_string(p, &p->value)),
-             0);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
+                                                     take_string(p, &p->value)),
+      0);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* finish a literal header without incremental indexing with index = 0 */
-static grpc_error *finish_lithdr_notidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_notidx_v(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_hpack_parser *p,
                                           const uint8_t *cur,
                                           const uint8_t *end) {
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
-                                                  take_string(p, &p->value)),
-             0);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
+                                                     take_string(p, &p->value)),
+      0);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* parse a literal header without incremental indexing; index < 15 */
-static grpc_error *parse_lithdr_notidx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
       parse_value_string_with_indexed_key, finish_lithdr_notidx};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
   p->index = (*cur) & 0xf;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header without incremental indexing; index >= 15 */
-static grpc_error *parse_lithdr_notidx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -881,11 +927,12 @@ static grpc_error *parse_lithdr_notidx_x(grpc_chttp2_hpack_parser *p,
   p->next_state = and_then;
   p->index = 0xf;
   p->parsing.value = &p->index;
-  return parse_value0(p, cur + 1, end);
+  return parse_value0(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header without incremental indexing; index == 0 */
-static grpc_error *parse_lithdr_notidx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_notidx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -893,48 +940,52 @@ static grpc_error *parse_lithdr_notidx_v(grpc_chttp2_hpack_parser *p,
       parse_value_string_with_literal_key, finish_lithdr_notidx_v};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* finish a literal header that is never indexed */
-static grpc_error *finish_lithdr_nvridx(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_nvridx(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur,
                                         const uint8_t *end) {
   grpc_mdelem *md = grpc_chttp2_hptbl_lookup(&p->table, p->index);
   GPR_ASSERT(md != NULL); /* handled in string parsing */
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
-                                                  take_string(p, &p->value)),
-             0);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(GRPC_MDSTR_REF(md->key),
+                                                     take_string(p, &p->value)),
+      0);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* finish a literal header that is never indexed with an extra value */
-static grpc_error *finish_lithdr_nvridx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_lithdr_nvridx_v(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_hpack_parser *p,
                                           const uint8_t *cur,
                                           const uint8_t *end) {
-  grpc_error *err =
-      on_hdr(p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
-                                                  take_string(p, &p->value)),
-             0);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  grpc_error *err = on_hdr(
+      exec_ctx, p, grpc_mdelem_from_metadata_strings(take_string(p, &p->key),
+                                                     take_string(p, &p->value)),
+      0);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* parse a literal header that is never indexed; index < 15 */
-static grpc_error *parse_lithdr_nvridx(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
       parse_value_string_with_indexed_key, finish_lithdr_nvridx};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
   p->index = (*cur) & 0xf;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header that is never indexed; index >= 15 */
-static grpc_error *parse_lithdr_nvridx_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx_x(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -944,11 +995,12 @@ static grpc_error *parse_lithdr_nvridx_x(grpc_chttp2_hpack_parser *p,
   p->next_state = and_then;
   p->index = 0xf;
   p->parsing.value = &p->index;
-  return parse_value0(p, cur + 1, end);
+  return parse_value0(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a literal header that is never indexed; index == 0 */
-static grpc_error *parse_lithdr_nvridx_v(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_lithdr_nvridx_v(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_hpack_parser *p,
                                          const uint8_t *cur,
                                          const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
@@ -956,44 +1008,47 @@ static grpc_error *parse_lithdr_nvridx_v(grpc_chttp2_hpack_parser *p,
       parse_value_string_with_literal_key, finish_lithdr_nvridx_v};
   p->dynamic_table_update_allowed = 0;
   p->next_state = and_then;
-  return parse_string_prefix(p, cur + 1, end);
+  return parse_string_prefix(exec_ctx, p, cur + 1, end);
 }
 
 /* finish parsing a max table size change */
-static grpc_error *finish_max_tbl_size(grpc_chttp2_hpack_parser *p,
+static grpc_error *finish_max_tbl_size(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   if (grpc_http_trace) {
     gpr_log(GPR_INFO, "MAX TABLE SIZE: %d", p->index);
   }
   grpc_error *err =
       grpc_chttp2_hptbl_set_current_table_size(&p->table, p->index);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_begin(p, cur, end);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_begin(exec_ctx, p, cur, end);
 }
 
 /* parse a max table size change, max size < 15 */
-static grpc_error *parse_max_tbl_size(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_max_tbl_size(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_hpack_parser *p,
                                       const uint8_t *cur, const uint8_t *end) {
   if (p->dynamic_table_update_allowed == 0) {
     return parse_error(
-        p, cur, end,
+        exec_ctx, p, cur, end,
         GRPC_ERROR_CREATE(
             "More than two max table size changes in a single frame"));
   }
   p->dynamic_table_update_allowed--;
   p->index = (*cur) & 0x1f;
-  return finish_max_tbl_size(p, cur + 1, end);
+  return finish_max_tbl_size(exec_ctx, p, cur + 1, end);
 }
 
 /* parse a max table size change, max size >= 15 */
-static grpc_error *parse_max_tbl_size_x(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_max_tbl_size_x(grpc_exec_ctx *exec_ctx,
+                                        grpc_chttp2_hpack_parser *p,
                                         const uint8_t *cur,
                                         const uint8_t *end) {
   static const grpc_chttp2_hpack_parser_state and_then[] = {
       finish_max_tbl_size};
   if (p->dynamic_table_update_allowed == 0) {
     return parse_error(
-        p, cur, end,
+        exec_ctx, p, cur, end,
         GRPC_ERROR_CREATE(
             "More than two max table size changes in a single frame"));
   }
@@ -1001,11 +1056,12 @@ static grpc_error *parse_max_tbl_size_x(grpc_chttp2_hpack_parser *p,
   p->next_state = and_then;
   p->index = 0x1f;
   p->parsing.value = &p->index;
-  return parse_value0(p, cur + 1, end);
+  return parse_value0(exec_ctx, p, cur + 1, end);
 }
 
 /* a parse error: jam the parse state into parse_error, and return error */
-static grpc_error *parse_error(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_error(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                const uint8_t *end, grpc_error *err) {
   GPR_ASSERT(err != GRPC_ERROR_NONE);
   if (p->last_error == GRPC_ERROR_NONE) {
@@ -1015,24 +1071,27 @@ static grpc_error *parse_error(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   return err;
 }
 
-static grpc_error *still_parse_error(grpc_chttp2_hpack_parser *p,
+static grpc_error *still_parse_error(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_hpack_parser *p,
                                      const uint8_t *cur, const uint8_t *end) {
   return GRPC_ERROR_REF(p->last_error);
 }
 
-static grpc_error *parse_illegal_op(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_illegal_op(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_hpack_parser *p,
                                     const uint8_t *cur, const uint8_t *end) {
   GPR_ASSERT(cur != end);
   char *msg;
   gpr_asprintf(&msg, "Illegal hpack op code %d", *cur);
   grpc_error *err = GRPC_ERROR_CREATE(msg);
   gpr_free(msg);
-  return parse_error(p, cur, end, err);
+  return parse_error(exec_ctx, p, cur, end, err);
 }
 
 /* parse the 1st byte of a varint into p->parsing.value
    no overflow is possible */
-static grpc_error *parse_value0(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value0(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   if (cur == end) {
     p->state = parse_value0;
@@ -1042,15 +1101,16 @@ static grpc_error *parse_value0(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   *p->parsing.value += (*cur) & 0x7f;
 
   if ((*cur) & 0x80) {
-    return parse_value1(p, cur + 1, end);
+    return parse_value1(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 }
 
 /* parse the 2nd byte of a varint into p->parsing.value
    no overflow is possible */
-static grpc_error *parse_value1(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value1(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   if (cur == end) {
     p->state = parse_value1;
@@ -1060,15 +1120,16 @@ static grpc_error *parse_value1(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   *p->parsing.value += (((uint32_t)*cur) & 0x7f) << 7;
 
   if ((*cur) & 0x80) {
-    return parse_value2(p, cur + 1, end);
+    return parse_value2(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 }
 
 /* parse the 3rd byte of a varint into p->parsing.value
    no overflow is possible */
-static grpc_error *parse_value2(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value2(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   if (cur == end) {
     p->state = parse_value2;
@@ -1078,15 +1139,16 @@ static grpc_error *parse_value2(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   *p->parsing.value += (((uint32_t)*cur) & 0x7f) << 14;
 
   if ((*cur) & 0x80) {
-    return parse_value3(p, cur + 1, end);
+    return parse_value3(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 }
 
 /* parse the 4th byte of a varint into p->parsing.value
    no overflow is possible */
-static grpc_error *parse_value3(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value3(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   if (cur == end) {
     p->state = parse_value3;
@@ -1096,15 +1158,16 @@ static grpc_error *parse_value3(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   *p->parsing.value += (((uint32_t)*cur) & 0x7f) << 21;
 
   if ((*cur) & 0x80) {
-    return parse_value4(p, cur + 1, end);
+    return parse_value4(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 }
 
 /* parse the 5th byte of a varint into p->parsing.value
    depending on the byte, we may overflow, and care must be taken */
-static grpc_error *parse_value4(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_value4(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   uint8_t c;
   uint32_t cur_value;
@@ -1130,9 +1193,9 @@ static grpc_error *parse_value4(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
   *p->parsing.value = cur_value + add_value;
 
   if ((*cur) & 0x80) {
-    return parse_value5up(p, cur + 1, end);
+    return parse_value5up(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 
 error:
@@ -1142,13 +1205,14 @@ error:
                *p->parsing.value, *cur);
   grpc_error *err = GRPC_ERROR_CREATE(msg);
   gpr_free(msg);
-  return parse_error(p, cur, end, err);
+  return parse_error(exec_ctx, p, cur, end, err);
 }
 
 /* parse any trailing bytes in a varint: it's possible to append an arbitrary
    number of 0x80's and not affect the value - a zero will terminate - and
    anything else will overflow */
-static grpc_error *parse_value5up(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_value5up(grpc_exec_ctx *exec_ctx,
+                                  grpc_chttp2_hpack_parser *p,
                                   const uint8_t *cur, const uint8_t *end) {
   while (cur != end && *cur == 0x80) {
     ++cur;
@@ -1160,7 +1224,7 @@ static grpc_error *parse_value5up(grpc_chttp2_hpack_parser *p,
   }
 
   if (*cur == 0) {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 
   char *msg;
@@ -1170,11 +1234,12 @@ static grpc_error *parse_value5up(grpc_chttp2_hpack_parser *p,
                *p->parsing.value, *cur);
   grpc_error *err = GRPC_ERROR_CREATE(msg);
   gpr_free(msg);
-  return parse_error(p, cur, end, err);
+  return parse_error(exec_ctx, p, cur, end, err);
 }
 
 /* parse a string prefix */
-static grpc_error *parse_string_prefix(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_string_prefix(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_hpack_parser *p,
                                        const uint8_t *cur, const uint8_t *end) {
   if (cur == end) {
     p->state = parse_string_prefix;
@@ -1185,9 +1250,9 @@ static grpc_error *parse_string_prefix(grpc_chttp2_hpack_parser *p,
   p->huff = (*cur) >> 7;
   if (p->strlen == 0x7f) {
     p->parsing.value = &p->strlen;
-    return parse_value0(p, cur + 1, end);
+    return parse_value0(exec_ctx, p, cur + 1, end);
   } else {
-    return parse_next(p, cur + 1, end);
+    return parse_next(exec_ctx, p, cur + 1, end);
   }
 }
 
@@ -1205,7 +1270,8 @@ static void append_bytes(grpc_chttp2_hpack_parser_string *str,
   str->length += (uint32_t)length;
 }
 
-static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
+static grpc_error *append_string(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_hpack_parser *p,
                                  const uint8_t *cur, const uint8_t *end) {
   grpc_chttp2_hpack_parser_string *str = p->parsing.str;
   uint32_t bits;
@@ -1223,7 +1289,7 @@ static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
       bits = inverse_base64[*cur];
       ++cur;
       if (bits == 255)
-        return parse_error(p, cur, end,
+        return parse_error(exec_ctx, p, cur, end,
                            GRPC_ERROR_CREATE("Illegal base64 character"));
       else if (bits == 64)
         goto b64_byte0;
@@ -1238,7 +1304,7 @@ static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
       bits = inverse_base64[*cur];
       ++cur;
       if (bits == 255)
-        return parse_error(p, cur, end,
+        return parse_error(exec_ctx, p, cur, end,
                            GRPC_ERROR_CREATE("Illegal base64 character"));
       else if (bits == 64)
         goto b64_byte1;
@@ -1253,7 +1319,7 @@ static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
       bits = inverse_base64[*cur];
       ++cur;
       if (bits == 255)
-        return parse_error(p, cur, end,
+        return parse_error(exec_ctx, p, cur, end,
                            GRPC_ERROR_CREATE("Illegal base64 character"));
       else if (bits == 64)
         goto b64_byte2;
@@ -1268,7 +1334,7 @@ static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
       bits = inverse_base64[*cur];
       ++cur;
       if (bits == 255)
-        return parse_error(p, cur, end,
+        return parse_error(exec_ctx, p, cur, end,
                            GRPC_ERROR_CREATE("Illegal base64 character"));
       else if (bits == 64)
         goto b64_byte3;
@@ -1281,11 +1347,12 @@ static grpc_error *append_string(grpc_chttp2_hpack_parser *p,
       goto b64_byte0;
   }
   GPR_UNREACHABLE_CODE(return parse_error(
-      p, cur, end, GRPC_ERROR_CREATE("Should never reach here")));
+      exec_ctx, p, cur, end, GRPC_ERROR_CREATE("Should never reach here")));
 }
 
 /* append a null terminator to a string */
-static grpc_error *finish_str(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *finish_str(grpc_exec_ctx *exec_ctx,
+                              grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                               const uint8_t *end) {
   uint8_t terminator = 0;
   uint8_t decoded[2];
@@ -1298,7 +1365,7 @@ static grpc_error *finish_str(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
       break;
     case B64_BYTE1:
       return parse_error(
-          p, cur, end,
+          exec_ctx, p, cur, end,
           GRPC_ERROR_CREATE("illegal base64 encoding")); /* illegal encoding */
     case B64_BYTE2:
       bits = p->base64_buffer;
@@ -1308,7 +1375,7 @@ static grpc_error *finish_str(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                      bits & 0xffff);
         grpc_error *err = GRPC_ERROR_CREATE(msg);
         gpr_free(msg);
-        return parse_error(p, cur, end, err);
+        return parse_error(exec_ctx, p, cur, end, err);
       }
       decoded[0] = (uint8_t)(bits >> 16);
       append_bytes(str, decoded, 1);
@@ -1321,7 +1388,7 @@ static grpc_error *finish_str(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                      bits & 0xff);
         grpc_error *err = GRPC_ERROR_CREATE(msg);
         gpr_free(msg);
-        return parse_error(p, cur, end, err);
+        return parse_error(exec_ctx, p, cur, end, err);
       }
       decoded[0] = (uint8_t)(bits >> 16);
       decoded[1] = (uint8_t)(bits >> 8);
@@ -1334,13 +1401,14 @@ static grpc_error *finish_str(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
 }
 
 /* decode a nibble from a huffman encoded stream */
-static grpc_error *huff_nibble(grpc_chttp2_hpack_parser *p, uint8_t nibble) {
+static grpc_error *huff_nibble(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_hpack_parser *p, uint8_t nibble) {
   int16_t emit = emit_sub_tbl[16 * emit_tbl[p->huff_state] + nibble];
   int16_t next = next_sub_tbl[16 * next_tbl[p->huff_state] + nibble];
   if (emit != -1) {
     if (emit >= 0 && emit < 256) {
       uint8_t c = (uint8_t)emit;
-      grpc_error *err = append_string(p, &c, (&c) + 1);
+      grpc_error *err = append_string(exec_ctx, p, &c, (&c) + 1);
       if (err != GRPC_ERROR_NONE) return err;
     } else {
       assert(emit == 256);
@@ -1351,42 +1419,45 @@ static grpc_error *huff_nibble(grpc_chttp2_hpack_parser *p, uint8_t nibble) {
 }
 
 /* decode full bytes from a huffman encoded stream */
-static grpc_error *add_huff_bytes(grpc_chttp2_hpack_parser *p,
+static grpc_error *add_huff_bytes(grpc_exec_ctx *exec_ctx,
+                                  grpc_chttp2_hpack_parser *p,
                                   const uint8_t *cur, const uint8_t *end) {
   for (; cur != end; ++cur) {
-    grpc_error *err = huff_nibble(p, *cur >> 4);
-    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-    err = huff_nibble(p, *cur & 0xf);
-    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
+    grpc_error *err = huff_nibble(exec_ctx, p, *cur >> 4);
+    if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+    err = huff_nibble(exec_ctx, p, *cur & 0xf);
+    if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
   }
   return GRPC_ERROR_NONE;
 }
 
 /* decode some string bytes based on the current decoding mode
    (huffman or not) */
-static grpc_error *add_str_bytes(grpc_chttp2_hpack_parser *p,
+static grpc_error *add_str_bytes(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_hpack_parser *p,
                                  const uint8_t *cur, const uint8_t *end) {
   if (p->huff) {
-    return add_huff_bytes(p, cur, end);
+    return add_huff_bytes(exec_ctx, p, cur, end);
   } else {
-    return append_string(p, cur, end);
+    return append_string(exec_ctx, p, cur, end);
   }
 }
 
 /* parse a string - tries to do large chunks at a time */
-static grpc_error *parse_string(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+static grpc_error *parse_string(grpc_exec_ctx *exec_ctx,
+                                grpc_chttp2_hpack_parser *p, const uint8_t *cur,
                                 const uint8_t *end) {
   size_t remaining = p->strlen - p->strgot;
   size_t given = (size_t)(end - cur);
   if (remaining <= given) {
-    grpc_error *err = add_str_bytes(p, cur, cur + remaining);
-    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-    err = finish_str(p, cur + remaining, end);
-    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-    return parse_next(p, cur + remaining, end);
+    grpc_error *err = add_str_bytes(exec_ctx, p, cur, cur + remaining);
+    if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+    err = finish_str(exec_ctx, p, cur + remaining, end);
+    if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+    return parse_next(exec_ctx, p, cur + remaining, end);
   } else {
-    grpc_error *err = add_str_bytes(p, cur, cur + given);
-    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
+    grpc_error *err = add_str_bytes(exec_ctx, p, cur, cur + given);
+    if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
     GPR_ASSERT(given <= UINT32_MAX - p->strgot);
     p->strgot += (uint32_t)given;
     p->state = parse_string;
@@ -1395,7 +1466,8 @@ static grpc_error *parse_string(grpc_chttp2_hpack_parser *p, const uint8_t *cur,
 }
 
 /* begin parsing a string - performs setup, calls parse_string */
-static grpc_error *begin_parse_string(grpc_chttp2_hpack_parser *p,
+static grpc_error *begin_parse_string(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_hpack_parser *p,
                                       const uint8_t *cur, const uint8_t *end,
                                       uint8_t binary,
                                       grpc_chttp2_hpack_parser_string *str) {
@@ -1404,13 +1476,14 @@ static grpc_error *begin_parse_string(grpc_chttp2_hpack_parser *p,
   p->parsing.str = str;
   p->huff_state = 0;
   p->binary = binary;
-  return parse_string(p, cur, end);
+  return parse_string(exec_ctx, p, cur, end);
 }
 
 /* parse the key string */
-static grpc_error *parse_key_string(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_key_string(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_hpack_parser *p,
                                     const uint8_t *cur, const uint8_t *end) {
-  return begin_parse_string(p, cur, end, NOT_BINARY, &p->key);
+  return begin_parse_string(exec_ctx, p, cur, end, NOT_BINARY, &p->key);
 }
 
 /* check if a key represents a binary header or not */
@@ -1435,24 +1508,27 @@ static grpc_error *is_binary_indexed_header(grpc_chttp2_hpack_parser *p,
 }
 
 /* parse the value string */
-static grpc_error *parse_value_string(grpc_chttp2_hpack_parser *p,
+static grpc_error *parse_value_string(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_hpack_parser *p,
                                       const uint8_t *cur, const uint8_t *end,
                                       bool is_binary) {
-  return begin_parse_string(p, cur, end, is_binary ? B64_BYTE0 : NOT_BINARY,
-                            &p->value);
+  return begin_parse_string(exec_ctx, p, cur, end,
+                            is_binary ? B64_BYTE0 : NOT_BINARY, &p->value);
 }
 
 static grpc_error *parse_value_string_with_indexed_key(
-    grpc_chttp2_hpack_parser *p, const uint8_t *cur, const uint8_t *end) {
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+    const uint8_t *end) {
   bool is_binary = false;
   grpc_error *err = is_binary_indexed_header(p, &is_binary);
-  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
-  return parse_value_string(p, cur, end, is_binary);
+  if (err != GRPC_ERROR_NONE) return parse_error(exec_ctx, p, cur, end, err);
+  return parse_value_string(exec_ctx, p, cur, end, is_binary);
 }
 
 static grpc_error *parse_value_string_with_literal_key(
-    grpc_chttp2_hpack_parser *p, const uint8_t *cur, const uint8_t *end) {
-  return parse_value_string(p, cur, end, is_binary_literal_header(p));
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p, const uint8_t *cur,
+    const uint8_t *end) {
+  return parse_value_string(exec_ctx, p, cur, end, is_binary_literal_header(p));
 }
 
 /* PUBLIC INTERFACE */
@@ -1484,27 +1560,36 @@ void grpc_chttp2_hpack_parser_destroy(grpc_chttp2_hpack_parser *p) {
   gpr_free(p->value.str);
 }
 
-grpc_error *grpc_chttp2_hpack_parser_parse(grpc_chttp2_hpack_parser *p,
+grpc_error *grpc_chttp2_hpack_parser_parse(grpc_exec_ctx *exec_ctx,
+                                           grpc_chttp2_hpack_parser *p,
                                            const uint8_t *beg,
                                            const uint8_t *end) {
   /* TODO(ctiller): limit the distance of end from beg, and perform multiple
      steps in the event of a large chunk of data to limit
      stack space usage when no tail call optimization is
      available */
-  return p->state(p, beg, end);
+  return p->state(exec_ctx, p, beg, end);
 }
 
-grpc_error *grpc_chttp2_header_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *hpack_parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
+typedef void (*maybe_complete_func_type)(grpc_exec_ctx *exec_ctx,
+                                         grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream *s);
+static const maybe_complete_func_type maybe_complete_funcs[] = {
+    grpc_chttp2_maybe_complete_recv_initial_metadata,
+    grpc_chttp2_maybe_complete_recv_trailing_metadata};
+
+grpc_error *grpc_chttp2_header_parser_parse(grpc_exec_ctx *exec_ctx,
+                                            void *hpack_parser,
+                                            grpc_chttp2_transport *t,
+                                            grpc_chttp2_stream *s,
+                                            gpr_slice slice, int is_last) {
   grpc_chttp2_hpack_parser *parser = hpack_parser;
   GPR_TIMER_BEGIN("grpc_chttp2_hpack_parser_parse", 0);
-  if (stream_parsing != NULL) {
-    stream_parsing->stats.incoming.header_bytes += GPR_SLICE_LENGTH(slice);
+  if (s != NULL) {
+    s->stats.incoming.header_bytes += GPR_SLICE_LENGTH(slice);
   }
   grpc_error *error = grpc_chttp2_hpack_parser_parse(
-      parser, GPR_SLICE_START_PTR(slice), GPR_SLICE_END_PTR(slice));
+      exec_ctx, parser, GPR_SLICE_START_PTR(slice), GPR_SLICE_END_PTR(slice));
   if (error != GRPC_ERROR_NONE) {
     GPR_TIMER_END("grpc_chttp2_hpack_parser_parse", 0);
     return error;
@@ -1517,20 +1602,19 @@ grpc_error *grpc_chttp2_header_parser_parse(
     }
     /* need to check for null stream: this can occur if we receive an invalid
        stream id on a header */
-    if (stream_parsing != NULL) {
+    if (s != NULL) {
       if (parser->is_boundary) {
-        if (stream_parsing->header_frames_received ==
-            GPR_ARRAY_SIZE(stream_parsing->got_metadata_on_parse)) {
+        if (s->header_frames_received == GPR_ARRAY_SIZE(s->metadata_buffer)) {
           return GRPC_ERROR_CREATE("Too many trailer frames");
         }
-        stream_parsing
-            ->got_metadata_on_parse[stream_parsing->header_frames_received] = 1;
-        stream_parsing->header_frames_received++;
-        grpc_chttp2_list_add_parsing_seen_stream(transport_parsing,
-                                                 stream_parsing);
+        s->published_metadata[s->header_frames_received] =
+            GRPC_METADATA_PUBLISHED_FROM_WIRE;
+        maybe_complete_funcs[s->header_frames_received](exec_ctx, t, s);
+        s->header_frames_received++;
       }
       if (parser->is_eof) {
-        stream_parsing->received_close = 1;
+        grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, false,
+                                       GRPC_ERROR_NONE);
       }
     }
     parser->on_header = NULL;
diff --git a/src/core/ext/transport/chttp2/transport/hpack_parser.h b/src/core/ext/transport/chttp2/transport/hpack_parser.h
index 78eb38db5e..0290c78d5a 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_parser.h
+++ b/src/core/ext/transport/chttp2/transport/hpack_parser.h
@@ -45,7 +45,8 @@
 typedef struct grpc_chttp2_hpack_parser grpc_chttp2_hpack_parser;
 
 typedef grpc_error *(*grpc_chttp2_hpack_parser_state)(
-    grpc_chttp2_hpack_parser *p, const uint8_t *beg, const uint8_t *end);
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_hpack_parser *p, const uint8_t *beg,
+    const uint8_t *end);
 
 typedef struct {
   char *str;
@@ -55,7 +56,7 @@ typedef struct {
 
 struct grpc_chttp2_hpack_parser {
   /* user specified callback for each header output */
-  void (*on_header)(void *user_data, grpc_mdelem *md);
+  void (*on_header)(grpc_exec_ctx *exec_ctx, void *user_data, grpc_mdelem *md);
   void *on_header_user_data;
 
   grpc_error *last_error;
@@ -104,15 +105,17 @@ void grpc_chttp2_hpack_parser_destroy(grpc_chttp2_hpack_parser *p);
 void grpc_chttp2_hpack_parser_set_has_priority(grpc_chttp2_hpack_parser *p);
 
 /* returns 1 on success, 0 on error */
-grpc_error *grpc_chttp2_hpack_parser_parse(grpc_chttp2_hpack_parser *p,
+grpc_error *grpc_chttp2_hpack_parser_parse(grpc_exec_ctx *exec_ctx,
+                                           grpc_chttp2_hpack_parser *p,
                                            const uint8_t *beg,
                                            const uint8_t *end);
 
 /* wraps grpc_chttp2_hpack_parser_parse to provide a frame level parser for
    the transport */
-grpc_error *grpc_chttp2_header_parser_parse(
-    grpc_exec_ctx *exec_ctx, void *hpack_parser,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);
+grpc_error *grpc_chttp2_header_parser_parse(grpc_exec_ctx *exec_ctx,
+                                            void *hpack_parser,
+                                            grpc_chttp2_transport *t,
+                                            grpc_chttp2_stream *s,
+                                            gpr_slice slice, int is_last);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_PARSER_H */
diff --git a/src/core/ext/transport/chttp2/transport/internal.h b/src/core/ext/transport/chttp2/transport/internal.h
index d67c014e54..3263c99bde 100644
--- a/src/core/ext/transport/chttp2/transport/internal.h
+++ b/src/core/ext/transport/chttp2/transport/internal.h
@@ -48,35 +48,30 @@
 #include "src/core/ext/transport/chttp2/transport/hpack_parser.h"
 #include "src/core/ext/transport/chttp2/transport/incoming_metadata.h"
 #include "src/core/ext/transport/chttp2/transport/stream_map.h"
+#include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/endpoint.h"
 #include "src/core/lib/transport/connectivity_state.h"
 #include "src/core/lib/transport/transport_impl.h"
 
-typedef struct grpc_chttp2_transport grpc_chttp2_transport;
-typedef struct grpc_chttp2_stream grpc_chttp2_stream;
-
 /* streams are kept in various linked lists depending on what things need to
    happen to them... this enum labels each list */
 typedef enum {
-  GRPC_CHTTP2_LIST_ALL_STREAMS,
-  GRPC_CHTTP2_LIST_CHECK_READ_OPS,
-  GRPC_CHTTP2_LIST_UNANNOUNCED_INCOMING_WINDOW_AVAILABLE,
   GRPC_CHTTP2_LIST_WRITABLE,
   GRPC_CHTTP2_LIST_WRITING,
-  GRPC_CHTTP2_LIST_WRITTEN,
-  GRPC_CHTTP2_LIST_PARSING_SEEN,
-  GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING,
-  GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_WRITING,
   GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT,
-  /* streams waiting for the outgoing window in the writing path, they will be
-   * merged to the stalled list or writable list under transport lock. */
-  GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT,
   /** streams that are waiting to start because there are too many concurrent
       streams on the connection */
   GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY,
   STREAM_LIST_COUNT /* must be last */
 } grpc_chttp2_stream_list_id;
 
+typedef enum {
+  GRPC_CHTTP2_WRITE_STATE_IDLE,
+  GRPC_CHTTP2_WRITE_STATE_WRITING,
+  GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE,
+  GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER,
+} grpc_chttp2_write_state;
+
 /* deframer state for the overall http2 stream of bytes */
 typedef enum {
   /* prefix: one entry per http2 connection prefix byte */
@@ -151,6 +146,12 @@ typedef struct grpc_chttp2_outstanding_ping {
   struct grpc_chttp2_outstanding_ping *prev;
 } grpc_chttp2_outstanding_ping;
 
+typedef struct grpc_chttp2_write_cb {
+  size_t call_at_byte;
+  grpc_closure *closure;
+  struct grpc_chttp2_write_cb *next;
+} grpc_chttp2_write_cb;
+
 /* forward declared in frame_data.h */
 struct grpc_chttp2_incoming_byte_stream {
   grpc_byte_stream base;
@@ -160,18 +161,86 @@ struct grpc_chttp2_incoming_byte_stream {
 
   grpc_chttp2_transport *transport;
   grpc_chttp2_stream *stream;
-  int is_tail;
+  bool is_tail;
+
+  gpr_mu slice_mu;  // protects slices, on_next
   gpr_slice_buffer slices;
   grpc_closure *on_next;
   gpr_slice *next;
+  uint32_t remaining_bytes;
+
+  struct {
+    grpc_closure closure;
+    gpr_slice *slice;
+    size_t max_size_hint;
+    grpc_closure *on_complete;
+  } next_action;
+  grpc_closure destroy_action;
+  grpc_closure finished_action;
 };
 
-typedef struct {
+struct grpc_chttp2_transport {
+  grpc_transport base; /* must be first */
+  gpr_refcount refs;
+  grpc_endpoint *ep;
+  char *peer_string;
+
+  grpc_combiner *combiner;
+
+  /** write execution state of the transport */
+  grpc_chttp2_write_state write_state;
+
+  /** is the transport destroying itself? */
+  uint8_t destroying;
+  /** has the upper layer closed the transport? */
+  uint8_t closed;
+
+  /** is there a read request to the endpoint outstanding? */
+  uint8_t endpoint_reading;
+
+  /** various lists of streams */
+  grpc_chttp2_stream_list lists[STREAM_LIST_COUNT];
+
+  /** maps stream id to grpc_chttp2_stream objects */
+  grpc_chttp2_stream_map stream_map;
+
+  grpc_closure write_action_begin_locked;
+  grpc_closure write_action;
+  grpc_closure write_action_end;
+  grpc_closure write_action_end_locked;
+
+  grpc_closure read_action_begin;
+  grpc_closure read_action_locked;
+
+  /** incoming read bytes */
+  gpr_slice_buffer read_buffer;
+
+  /** address to place a newly accepted stream - set and unset by
+      grpc_chttp2_parsing_accept_stream; used by init_stream to
+      publish the accepted server stream */
+  grpc_chttp2_stream **accepting_stream;
+
+  struct {
+    /* accept stream callback */
+    void (*accept_stream)(grpc_exec_ctx *exec_ctx, void *user_data,
+                          grpc_transport *transport, const void *server_data);
+    void *accept_stream_user_data;
+
+    /** connectivity tracking */
+    grpc_connectivity_state_tracker state_tracker;
+  } channel_callback;
+
+  /** data to write now */
+  gpr_slice_buffer outbuf;
+  /** hpack encoding */
+  grpc_chttp2_hpack_compressor hpack_compressor;
+  int64_t outgoing_window;
+  /** is this a client? */
+  uint8_t is_client;
+
   /** data to write next write */
   gpr_slice_buffer qbuf;
 
-  /** window available for us to send to peer */
-  int64_t outgoing_window;
   /** window available to announce to peer */
   int64_t announce_incoming_window;
   /** how much window would we like to have for incoming_window */
@@ -182,8 +251,6 @@ typedef struct {
   /** have we sent a goaway */
   uint8_t sent_goaway;
 
-  /** is this transport a client? */
-  uint8_t is_client;
   /** are the local settings dirty and need to be sent? */
   uint8_t dirtied_local_settings;
   /** have local settings been sent? */
@@ -200,49 +267,14 @@ typedef struct {
   /** how far to lookahead in a stream? */
   uint32_t stream_lookahead;
 
-  /** last received stream id */
-  uint32_t last_incoming_stream_id;
+  /** last new stream id */
+  uint32_t last_new_stream_id;
 
   /** pings awaiting responses */
   grpc_chttp2_outstanding_ping pings;
   /** next payload for an outgoing ping */
   uint64_t ping_counter;
 
-  /** concurrent stream count: updated when not parsing,
-      so this is a strict over-estimation on the client */
-  uint32_t concurrent_stream_count;
-} grpc_chttp2_transport_global;
-
-typedef struct {
-  /** data to write now */
-  gpr_slice_buffer outbuf;
-  /** hpack encoding */
-  grpc_chttp2_hpack_compressor hpack_compressor;
-  int64_t outgoing_window;
-  /** is this a client? */
-  uint8_t is_client;
-  /** callback for when writing is done */
-  grpc_closure done_cb;
-  /** maximum frame size */
-  uint32_t max_frame_size;
-} grpc_chttp2_transport_writing;
-
-struct grpc_chttp2_transport_parsing {
-  /** is this transport a client? (boolean) */
-  uint8_t is_client;
-
-  /** were settings updated? */
-  uint8_t settings_updated;
-  /** was a settings ack received? */
-  uint8_t settings_ack_received;
-  /** was a goaway frame received? */
-  uint8_t goaway_received;
-
-  /** initial window change */
-  int64_t initial_window_update;
-
-  /** data to write later - after parsing */
-  gpr_slice_buffer qbuf;
   /** parser for headers */
   grpc_chttp2_hpack_parser hpack_parser;
   /** simple one shot parsers */
@@ -255,13 +287,12 @@ struct grpc_chttp2_transport_parsing {
   /** parser for goaway frames */
   grpc_chttp2_goaway_parser goaway_parser;
 
+  /** initial window change */
+  int64_t initial_window_update;
+
   /** window available for peer to send to us */
   int64_t incoming_window;
 
-  /** next stream id available at the time of beginning parsing */
-  uint32_t next_stream_id;
-  uint32_t last_incoming_stream_id;
-
   /* deframing */
   grpc_chttp2_deframe_transport_state deframe_state;
   uint8_t incoming_frame_type;
@@ -272,142 +303,38 @@ struct grpc_chttp2_transport_parsing {
   uint32_t incoming_frame_size;
   uint32_t incoming_stream_id;
 
-  /* current max frame size */
-  uint32_t max_frame_size;
-
   /* active parser */
   void *parser_data;
-  grpc_chttp2_stream_parsing *incoming_stream;
+  grpc_chttp2_stream *incoming_stream;
   grpc_error *(*parser)(grpc_exec_ctx *exec_ctx, void *parser_user_data,
-                        grpc_chttp2_transport_parsing *transport_parsing,
-                        grpc_chttp2_stream_parsing *stream_parsing,
+                        grpc_chttp2_transport *t, grpc_chttp2_stream *s,
                         gpr_slice slice, int is_last);
 
-  /* received settings */
-  uint32_t settings[GRPC_CHTTP2_NUM_SETTINGS];
-  /* last settings that were sent */
-  uint32_t last_sent_settings[GRPC_CHTTP2_NUM_SETTINGS];
-
   /* goaway data */
   grpc_status_code goaway_error;
   uint32_t goaway_last_stream_index;
   gpr_slice goaway_text;
 
-  int64_t outgoing_window;
+  grpc_chttp2_write_cb *write_cb_pool;
 };
 
-typedef void (*grpc_chttp2_locked_action)(grpc_exec_ctx *ctx,
-                                          grpc_chttp2_transport *t,
-                                          grpc_chttp2_stream *s, void *arg);
-
-typedef struct grpc_chttp2_executor_action_header {
-  grpc_chttp2_stream *stream;
-  grpc_chttp2_locked_action action;
-  struct grpc_chttp2_executor_action_header *next;
-  void *arg;
-} grpc_chttp2_executor_action_header;
-
 typedef enum {
-  /** no writing activity */
-  GRPC_CHTTP2_WRITING_INACTIVE,
-  /** write has been requested, but not scheduled yet */
-  GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER,
-  GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
-  /** write has been requested and scheduled against the workqueue */
-  GRPC_CHTTP2_WRITE_SCHEDULED,
-  /** write has been initiated after being reaped from the workqueue */
-  GRPC_CHTTP2_WRITING,
-  /** write has been initiated, AND another write needs to be started once it's
-      done */
-  GRPC_CHTTP2_WRITING_STALE_WITH_POLLER,
-  GRPC_CHTTP2_WRITING_STALE_NO_POLLER,
-} grpc_chttp2_write_state;
-
-struct grpc_chttp2_transport {
-  grpc_transport base; /* must be first */
-  gpr_refcount refs;
-  grpc_endpoint *ep;
-  char *peer_string;
-
-  /** when this drops to zero it's safe to shutdown the endpoint */
-  gpr_refcount shutdown_ep_refs;
-
-  struct {
-    gpr_mu mu;
-
-    /** is a thread currently in the global lock */
-    bool global_active;
-    /** is a thread currently parsing */
-    bool parsing_active;
-    /** write execution state of the transport */
-    grpc_chttp2_write_state write_state;
+  GRPC_METADATA_NOT_PUBLISHED,
+  GRPC_METADATA_SYNTHESIZED_FROM_FAKE,
+  GRPC_METADATA_PUBLISHED_FROM_WIRE,
+  GPRC_METADATA_PUBLISHED_AT_CLOSE
+} grpc_published_metadata_method;
 
-    grpc_chttp2_executor_action_header *pending_actions_head;
-    grpc_chttp2_executor_action_header *pending_actions_tail;
-  } executor;
-
-  /** is the transport destroying itself? */
-  uint8_t destroying;
-  /** has the upper layer closed the transport? */
-  uint8_t closed;
-
-  /** is there a read request to the endpoint outstanding? */
-  uint8_t endpoint_reading;
-
-  /** various lists of streams */
-  grpc_chttp2_stream_list lists[STREAM_LIST_COUNT];
-
-  /** global state for reading/writing */
-  grpc_chttp2_transport_global global;
-  /** state only accessible by the chain of execution that
-      set writing_state >= GRPC_WRITING, and only by the writing closure
-      chain. */
-  grpc_chttp2_transport_writing writing;
-  /** state only accessible by the chain of execution that
-      set parsing_active=1 */
-  grpc_chttp2_transport_parsing parsing;
-
-  /** maps stream id to grpc_chttp2_stream objects;
-      owned by the parsing thread when parsing */
-  grpc_chttp2_stream_map parsing_stream_map;
-
-  /** streams created by the client (possibly during parsing);
-      merged with parsing_stream_map during unlock when no
-      parsing is occurring */
-  grpc_chttp2_stream_map new_stream_map;
-
-  /** closure to execute writing */
-  grpc_closure writing_action;
-  /** closure to start reading from the endpoint */
-  grpc_closure reading_action;
-  /** closure to actually do parsing */
-  grpc_closure parsing_action;
-  /** closure to initiate writing */
-  grpc_closure initiate_writing;
-
-  /** incoming read bytes */
-  gpr_slice_buffer read_buffer;
-
-  /** address to place a newly accepted stream - set and unset by
-      grpc_chttp2_parsing_accept_stream; used by init_stream to
-      publish the accepted server stream */
-  grpc_chttp2_stream **accepting_stream;
-
-  struct {
-    /* accept stream callback */
-    void (*accept_stream)(grpc_exec_ctx *exec_ctx, void *user_data,
-                          grpc_transport *transport, const void *server_data);
-    void *accept_stream_user_data;
+struct grpc_chttp2_stream {
+  grpc_chttp2_transport *t;
+  grpc_stream_refcount *refcount;
 
-    /** connectivity tracking */
-    grpc_connectivity_state_tracker state_tracker;
-  } channel_callback;
+  grpc_closure destroy_stream;
+  void *destroy_stream_arg;
 
-  /** Transport op to be applied post-parsing */
-  grpc_transport_op *post_parsing_op;
-};
+  grpc_chttp2_stream_link links[STREAM_LIST_COUNT];
+  uint8_t included[STREAM_LIST_COUNT];
 
-typedef struct {
   /** HTTP2 stream id for this stream, or zero if one has not been assigned */
   uint32_t id;
 
@@ -417,20 +344,21 @@ typedef struct {
       As the upper layer offers more bytes, this value increases.
       As bytes are read, this value decreases. */
   uint32_t max_recv_bytes;
-  /** The number of bytes the upper layer has offered to read but we have
-      not yet announced to HTTP2 flow control.
-      As the upper layers offer to read more bytes, this value increases.
-      As we advertise incoming flow control window, this value decreases. */
-  uint32_t unannounced_incoming_window_for_parse;
-  uint32_t unannounced_incoming_window_for_writing;
   /** things the upper layers would like to send */
   grpc_metadata_batch *send_initial_metadata;
   grpc_closure *send_initial_metadata_finished;
-  grpc_byte_stream *send_message;
-  grpc_closure *send_message_finished;
   grpc_metadata_batch *send_trailing_metadata;
   grpc_closure *send_trailing_metadata_finished;
 
+  grpc_byte_stream *fetching_send_message;
+  uint32_t fetched_send_message_length;
+  gpr_slice fetching_slice;
+  int64_t fetching_slice_end_offset;
+  bool complete_fetch_covered_by_poller;
+  grpc_closure complete_fetch;
+  grpc_closure complete_fetch_locked;
+  grpc_closure *fetching_send_message_finished;
+
   grpc_metadata_batch *recv_initial_metadata;
   grpc_closure *recv_initial_metadata_ready;
   grpc_byte_stream **recv_message;
@@ -450,90 +378,44 @@ typedef struct {
   bool read_closed;
   /** Are all published incoming byte streams closed. */
   bool all_incoming_byte_streams_finished;
-  /** Is this stream in the stream map. */
-  bool in_stream_map;
   /** Has this stream seen an error.
       If true, then pending incoming frames can be thrown away. */
   bool seen_error;
-  bool exceeded_metadata_size;
 
   /** the error that resulted in this stream being read-closed */
   grpc_error *read_closed_error;
   /** the error that resulted in this stream being write-closed */
   grpc_error *write_closed_error;
 
-  bool published_initial_metadata;
-  bool published_trailing_metadata;
+  grpc_published_metadata_method published_metadata[2];
   bool final_metadata_requested;
 
-  grpc_chttp2_incoming_metadata_buffer received_initial_metadata;
-  grpc_chttp2_incoming_metadata_buffer received_trailing_metadata;
+  grpc_chttp2_incoming_metadata_buffer metadata_buffer[2];
 
   grpc_chttp2_incoming_frame_queue incoming_frames;
 
   gpr_timespec deadline;
-} grpc_chttp2_stream_global;
-
-typedef struct {
-  /** HTTP2 stream id for this stream, or zero if one has not been assigned */
-  uint32_t id;
-  uint8_t fetching;
-  bool sent_initial_metadata;
-  uint8_t sent_message;
-  uint8_t sent_trailing_metadata;
-  uint8_t read_closed;
-  /** send this initial metadata */
-  grpc_metadata_batch *send_initial_metadata;
-  grpc_byte_stream *send_message;
-  grpc_metadata_batch *send_trailing_metadata;
-  int64_t outgoing_window;
-  /** how much window should we announce? */
-  uint32_t announce_window;
-  gpr_slice_buffer flow_controlled_buffer;
-  gpr_slice fetching_slice;
-  size_t stream_fetched;
-  grpc_closure finished_fetch;
-  /** stats gathered during the write */
-  grpc_transport_one_way_stats stats;
-} grpc_chttp2_stream_writing;
 
-struct grpc_chttp2_stream_parsing {
   /** saw some stream level error */
   grpc_error *forced_close_error;
-  /** HTTP2 stream id for this stream, or zero if one has not been assigned */
-  uint32_t id;
-  /** has this stream received a close */
-  uint8_t received_close;
   /** how many header frames have we received? */
   uint8_t header_frames_received;
-  /** which metadata did we get (on this parse) */
-  uint8_t got_metadata_on_parse[2];
-  /** should we raise the seen_error flag in transport_global */
-  bool seen_error;
-  bool exceeded_metadata_size;
   /** window available for peer to send to us */
   int64_t incoming_window;
   /** parsing state for data frames */
   grpc_chttp2_data_parser data_parser;
-  /** amount of window given */
-  int64_t outgoing_window;
   /** number of bytes received - reset at end of parse thread execution */
   int64_t received_bytes;
-  /** stats gathered during the parse */
-  grpc_transport_stream_stats stats;
-
-  /** incoming metadata */
-  grpc_chttp2_incoming_metadata_buffer metadata_buffer[2];
-};
 
-struct grpc_chttp2_stream {
-  grpc_stream_refcount *refcount;
-  grpc_chttp2_stream_global global;
-  grpc_chttp2_stream_writing writing;
-  grpc_chttp2_stream_parsing parsing;
+  bool sent_initial_metadata;
+  bool sent_trailing_metadata;
+  /** how much window should we announce? */
+  uint32_t announce_window;
+  gpr_slice_buffer flow_controlled_buffer;
 
-  grpc_chttp2_stream_link links[STREAM_LIST_COUNT];
-  uint8_t included[STREAM_LIST_COUNT];
+  grpc_chttp2_write_cb *on_write_finished_cbs;
+  grpc_chttp2_write_cb *finish_after_write;
+  size_t sending_bytes;
 };
 
 /** Transport writing call flow:
@@ -549,168 +431,71 @@ struct grpc_chttp2_stream {
     The actual call chain is documented in the implementation of this function.
     */
 void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport_global *transport_global,
+                                grpc_chttp2_transport *t,
                                 bool covered_by_poller, const char *reason);
 
 /** Someone is unlocking the transport mutex: check to see if writes
-    are required, and schedule them if so */
-int grpc_chttp2_unlocking_check_writes(grpc_exec_ctx *exec_ctx,
-                                       grpc_chttp2_transport_global *global,
-                                       grpc_chttp2_transport_writing *writing);
-void grpc_chttp2_perform_writes(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_writing *transport_writing,
-    grpc_endpoint *endpoint);
-void grpc_chttp2_terminate_writing(grpc_exec_ctx *exec_ctx,
-                                   void *transport_writing, grpc_error *error);
-void grpc_chttp2_cleanup_writing(grpc_exec_ctx *exec_ctx,
-                                 grpc_chttp2_transport_global *global,
-                                 grpc_chttp2_transport_writing *writing);
-
-void grpc_chttp2_prepare_to_read(grpc_chttp2_transport_global *global,
-                                 grpc_chttp2_transport_parsing *parsing);
+    are required, and frame them if so */
+bool grpc_chttp2_begin_write(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t);
+void grpc_chttp2_end_write(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                           grpc_error *error);
+
 /** Process one slice of incoming data; return 1 if the connection is still
     viable after reading, or 0 if the connection should be torn down */
-grpc_error *grpc_chttp2_perform_read(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    gpr_slice slice);
-void grpc_chttp2_publish_reads(grpc_exec_ctx *exec_ctx,
-                               grpc_chttp2_transport_global *global,
-                               grpc_chttp2_transport_parsing *parsing);
-
-bool grpc_chttp2_list_add_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
+grpc_error *grpc_chttp2_perform_read(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t, gpr_slice slice);
+
+bool grpc_chttp2_list_add_writable_stream(grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s);
 /** Get a writable stream
     returns non-zero if there was a stream available */
-int grpc_chttp2_list_pop_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_writing **stream_writing);
+int grpc_chttp2_list_pop_writable_stream(grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream **s);
 bool grpc_chttp2_list_remove_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) GRPC_MUST_USE_RESULT;
-
-void grpc_chttp2_list_add_writing_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing);
-int grpc_chttp2_list_have_writing_streams(
-    grpc_chttp2_transport_writing *transport_writing);
-int grpc_chttp2_list_pop_writing_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing **stream_writing);
-
-void grpc_chttp2_list_add_written_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing);
-int grpc_chttp2_list_pop_written_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_writing **stream_writing);
-
-void grpc_chttp2_list_add_parsing_seen_stream(
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing);
-int grpc_chttp2_list_pop_parsing_seen_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_parsing **stream_parsing);
-
-void grpc_chttp2_list_add_waiting_for_concurrency(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-int grpc_chttp2_list_pop_waiting_for_concurrency(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
-
-void grpc_chttp2_list_add_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-bool grpc_chttp2_list_remove_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-int grpc_chttp2_list_pop_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
-
-void grpc_chttp2_list_add_writing_stalled_by_transport(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing);
-bool grpc_chttp2_list_flush_writing_stalled_by_transport(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_writing *transport_writing);
-
-void grpc_chttp2_list_add_stalled_by_transport(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing);
-int grpc_chttp2_list_pop_stalled_by_transport(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
-void grpc_chttp2_list_remove_stalled_by_transport(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-
-void grpc_chttp2_list_add_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-void grpc_chttp2_list_remove_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-int grpc_chttp2_list_pop_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_parsing **stream_parsing);
-
-void grpc_chttp2_list_add_closed_waiting_for_parsing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-int grpc_chttp2_list_pop_closed_waiting_for_parsing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
-
-void grpc_chttp2_list_add_closed_waiting_for_writing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global);
-int grpc_chttp2_list_pop_closed_waiting_for_writing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
-
-grpc_chttp2_stream_parsing *grpc_chttp2_parsing_lookup_stream(
-    grpc_chttp2_transport_parsing *transport_parsing, uint32_t id);
-grpc_chttp2_stream_parsing *grpc_chttp2_parsing_accept_stream(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    uint32_t id);
-
-void grpc_chttp2_add_incoming_goaway(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    uint32_t goaway_error, gpr_slice goaway_text);
-
-void grpc_chttp2_register_stream(grpc_chttp2_transport *t,
-                                 grpc_chttp2_stream *s);
-/* returns 1 if this is the last stream, 0 otherwise */
-int grpc_chttp2_unregister_stream(grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s) GRPC_MUST_USE_RESULT;
-int grpc_chttp2_has_streams(grpc_chttp2_transport *t);
-void grpc_chttp2_for_all_streams(
-    grpc_chttp2_transport_global *transport_global, void *user_data,
-    void (*cb)(grpc_chttp2_transport_global *transport_global, void *user_data,
-               grpc_chttp2_stream_global *stream_global));
-
-void grpc_chttp2_parsing_become_skip_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-
-void grpc_chttp2_complete_closure_step(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, grpc_closure **pclosure,
-    grpc_error *error);
-
-void grpc_chttp2_run_with_global_lock(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *transport,
-                                      grpc_chttp2_stream *optional_stream,
-                                      grpc_chttp2_locked_action action,
-                                      void *arg, size_t sizeof_arg);
+    grpc_chttp2_transport *t, grpc_chttp2_stream *s) GRPC_MUST_USE_RESULT;
+
+bool grpc_chttp2_list_add_writing_stream(grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream *s);
+int grpc_chttp2_list_have_writing_streams(grpc_chttp2_transport *t);
+int grpc_chttp2_list_pop_writing_stream(grpc_chttp2_transport *t,
+                                        grpc_chttp2_stream **s);
+
+void grpc_chttp2_list_add_written_stream(grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream *s);
+int grpc_chttp2_list_pop_written_stream(grpc_chttp2_transport *t,
+                                        grpc_chttp2_stream **s);
+
+void grpc_chttp2_list_add_waiting_for_concurrency(grpc_chttp2_transport *t,
+                                                  grpc_chttp2_stream *s);
+int grpc_chttp2_list_pop_waiting_for_concurrency(grpc_chttp2_transport *t,
+                                                 grpc_chttp2_stream **s);
+
+void grpc_chttp2_list_add_stalled_by_transport(grpc_chttp2_transport *t,
+                                               grpc_chttp2_stream *s);
+int grpc_chttp2_list_pop_stalled_by_transport(grpc_chttp2_transport *t,
+                                              grpc_chttp2_stream **s);
+void grpc_chttp2_list_remove_stalled_by_transport(grpc_chttp2_transport *t,
+                                                  grpc_chttp2_stream *s);
+
+grpc_chttp2_stream *grpc_chttp2_parsing_lookup_stream(grpc_chttp2_transport *t,
+                                                      uint32_t id);
+grpc_chttp2_stream *grpc_chttp2_parsing_accept_stream(grpc_exec_ctx *exec_ctx,
+                                                      grpc_chttp2_transport *t,
+                                                      uint32_t id);
+
+void grpc_chttp2_add_incoming_goaway(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t,
+                                     uint32_t goaway_error,
+                                     gpr_slice goaway_text);
+
+void grpc_chttp2_parsing_become_skip_parser(grpc_exec_ctx *exec_ctx,
+                                            grpc_chttp2_transport *t);
+
+void grpc_chttp2_complete_closure_step(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_transport *t,
+                                       grpc_chttp2_stream *s,
+                                       grpc_closure **pclosure,
+                                       grpc_error *error, const char *desc);
 
 #define GRPC_CHTTP2_CLIENT_CONNECT_STRING "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
 #define GRPC_CHTTP2_CLIENT_CONNECT_STRLEN \
@@ -801,57 +586,83 @@ void grpc_chttp2_flowctl_trace(const char *file, int line, const char *phase,
                                const char *var2, int is_client,
                                uint32_t stream_id, int64_t val1, int64_t val2);
 
-void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
-                             grpc_chttp2_transport_global *transport_global,
-                             grpc_chttp2_stream_global *stream,
+void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                             grpc_chttp2_stream *stream,
                              grpc_status_code status, gpr_slice *details);
-void grpc_chttp2_mark_stream_closed(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global, int close_reads, int close_writes,
-    grpc_error *error);
+void grpc_chttp2_mark_stream_closed(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_transport *t,
+                                    grpc_chttp2_stream *s, int close_reads,
+                                    int close_writes, grpc_error *error);
 void grpc_chttp2_start_writing(grpc_exec_ctx *exec_ctx,
-                               grpc_chttp2_transport_global *transport_global);
+                               grpc_chttp2_transport *t);
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
-#define GRPC_CHTTP2_STREAM_REF(stream_global, reason) \
-  grpc_chttp2_stream_ref(stream_global, reason)
-#define GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, reason) \
-  grpc_chttp2_stream_unref(exec_ctx, stream_global, reason)
-void grpc_chttp2_stream_ref(grpc_chttp2_stream_global *stream_global,
-                            const char *reason);
-void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx,
-                              grpc_chttp2_stream_global *stream_global,
+#define GRPC_CHTTP2_STREAM_REF(stream, reason) \
+  grpc_chttp2_stream_ref(stream, reason)
+#define GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream, reason) \
+  grpc_chttp2_stream_unref(exec_ctx, stream, reason)
+void grpc_chttp2_stream_ref(grpc_chttp2_stream *s, const char *reason);
+void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx, grpc_chttp2_stream *s,
                               const char *reason);
 #else
-#define GRPC_CHTTP2_STREAM_REF(stream_global, reason) \
-  grpc_chttp2_stream_ref(stream_global)
-#define GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, reason) \
-  grpc_chttp2_stream_unref(exec_ctx, stream_global)
-void grpc_chttp2_stream_ref(grpc_chttp2_stream_global *stream_global);
-void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx,
-                              grpc_chttp2_stream_global *stream_global);
+#define GRPC_CHTTP2_STREAM_REF(stream, reason) grpc_chttp2_stream_ref(stream)
+#define GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream, reason) \
+  grpc_chttp2_stream_unref(exec_ctx, stream)
+void grpc_chttp2_stream_ref(grpc_chttp2_stream *s);
+void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx, grpc_chttp2_stream *s);
+#endif
+
+//#define GRPC_CHTTP2_REFCOUNTING_DEBUG 1
+#ifdef GRPC_CHTTP2_REFCOUNTING_DEBUG
+#define GRPC_CHTTP2_REF_TRANSPORT(t, r) \
+  grpc_chttp2_ref_transport(t, r, __FILE__, __LINE__)
+#define GRPC_CHTTP2_UNREF_TRANSPORT(cl, t, r) \
+  grpc_chttp2_unref_transport(cl, t, r, __FILE__, __LINE__)
+void grpc_chttp2_unref_transport(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_transport *t, const char *reason,
+                                 const char *file, int line);
+void grpc_chttp2_ref_transport(grpc_chttp2_transport *t, const char *reason,
+                               const char *file, int line);
+#else
+#define GRPC_CHTTP2_REF_TRANSPORT(t, r) grpc_chttp2_ref_transport(t)
+#define GRPC_CHTTP2_UNREF_TRANSPORT(cl, t, r) grpc_chttp2_unref_transport(cl, t)
+void grpc_chttp2_unref_transport(grpc_exec_ctx *exec_ctx,
+                                 grpc_chttp2_transport *t);
+void grpc_chttp2_ref_transport(grpc_chttp2_transport *t);
 #endif
 
 grpc_chttp2_incoming_byte_stream *grpc_chttp2_incoming_byte_stream_create(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing, uint32_t frame_size,
-    uint32_t flags, grpc_chttp2_incoming_frame_queue *add_to_queue);
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t, grpc_chttp2_stream *s,
+    uint32_t frame_size, uint32_t flags);
 void grpc_chttp2_incoming_byte_stream_push(grpc_exec_ctx *exec_ctx,
                                            grpc_chttp2_incoming_byte_stream *bs,
                                            gpr_slice slice);
 void grpc_chttp2_incoming_byte_stream_finished(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_incoming_byte_stream *bs,
-    grpc_error *error, int from_parsing_thread);
+    grpc_error *error);
 
-void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx,
-                          grpc_chttp2_transport_parsing *parsing,
+void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                           const uint8_t *opaque_8bytes);
 
 /** add a ref to the stream and add it to the writable list;
     ref will be dropped in writing.c */
 void grpc_chttp2_become_writable(grpc_exec_ctx *exec_ctx,
-                                 grpc_chttp2_transport_global *transport_global,
-                                 grpc_chttp2_stream_global *stream_global,
-                                 bool covered_by_poller, const char *reason);
+                                 grpc_chttp2_transport *t,
+                                 grpc_chttp2_stream *s, bool covered_by_poller,
+                                 const char *reason);
+
+void grpc_chttp2_cancel_stream(grpc_exec_ctx *exec_ctx,
+                               grpc_chttp2_transport *t, grpc_chttp2_stream *s,
+                               grpc_error *due_to_error);
+
+void grpc_chttp2_maybe_complete_recv_initial_metadata(grpc_exec_ctx *exec_ctx,
+                                                      grpc_chttp2_transport *t,
+                                                      grpc_chttp2_stream *s);
+void grpc_chttp2_maybe_complete_recv_message(grpc_exec_ctx *exec_ctx,
+                                             grpc_chttp2_transport *t,
+                                             grpc_chttp2_stream *s);
+void grpc_chttp2_maybe_complete_recv_trailing_metadata(grpc_exec_ctx *exec_ctx,
+                                                       grpc_chttp2_transport *t,
+                                                       grpc_chttp2_stream *s);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_INTERNAL_H */
diff --git a/src/core/ext/transport/chttp2/transport/parsing.c b/src/core/ext/transport/chttp2/transport/parsing.c
index 482cd55c44..bc12515b0c 100644
--- a/src/core/ext/transport/chttp2/transport/parsing.c
+++ b/src/core/ext/transport/chttp2/transport/parsing.c
@@ -45,223 +45,34 @@
 #include "src/core/lib/transport/static_metadata.h"
 #include "src/core/lib/transport/timeout_encoding.h"
 
-#define TRANSPORT_FROM_PARSING(tp)                                        \
-  ((grpc_chttp2_transport *)((char *)(tp)-offsetof(grpc_chttp2_transport, \
-                                                   parsing)))
-
-static grpc_error *init_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_header_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    int is_continuation);
-static grpc_error *init_data_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_rst_stream_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_settings_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_window_update_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_ping_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_goaway_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
-static grpc_error *init_skip_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    int is_header);
-
-static grpc_error *parse_frame_slice(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    gpr_slice slice, int is_last);
-
-void grpc_chttp2_prepare_to_read(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing) {
-  grpc_chttp2_stream_global *stream_global;
-  grpc_chttp2_stream_parsing *stream_parsing;
-
-  GPR_TIMER_BEGIN("grpc_chttp2_prepare_to_read", 0);
-
-  transport_parsing->next_stream_id = transport_global->next_stream_id;
-  memcpy(transport_parsing->last_sent_settings,
-         transport_global->settings[GRPC_SENT_SETTINGS],
-         sizeof(transport_parsing->last_sent_settings));
-  transport_parsing->max_frame_size =
-      transport_global->settings[GRPC_ACKED_SETTINGS]
-                                [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE];
-
-  /* update the parsing view of incoming window */
-  while (grpc_chttp2_list_pop_unannounced_incoming_window_available(
-      transport_global, transport_parsing, &stream_global, &stream_parsing)) {
-    GRPC_CHTTP2_FLOW_MOVE_STREAM("parse", transport_parsing, stream_parsing,
-                                 incoming_window, stream_global,
-                                 unannounced_incoming_window_for_parse);
-  }
-
-  GPR_TIMER_END("grpc_chttp2_prepare_to_read", 0);
-}
-
-void grpc_chttp2_publish_reads(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing) {
-  grpc_chttp2_stream_global *stream_global;
-  grpc_chttp2_stream_parsing *stream_parsing;
-  int was_zero;
-  int is_zero;
-
-  /* transport_parsing->last_incoming_stream_id is used as
-     last-grpc_chttp2_stream-id when
-     sending GOAWAY frame.
-     https://tools.ietf.org/html/draft-ietf-httpbis-http2-17#section-6.8
-     says that last-grpc_chttp2_stream-id is peer-initiated grpc_chttp2_stream
-     ID.  So,
-     since we don't have server pushed streams, client should send
-     GOAWAY last-grpc_chttp2_stream-id=0 in this case. */
-  if (!transport_parsing->is_client) {
-    transport_global->last_incoming_stream_id =
-        transport_parsing->last_incoming_stream_id;
-  }
-
-  /* update global settings */
-  if (transport_parsing->settings_updated) {
-    memcpy(transport_global->settings[GRPC_PEER_SETTINGS],
-           transport_parsing->settings, sizeof(transport_parsing->settings));
-    transport_parsing->settings_updated = 0;
-  }
-
-  /* update settings based on ack if received */
-  if (transport_parsing->settings_ack_received) {
-    memcpy(transport_global->settings[GRPC_ACKED_SETTINGS],
-           transport_global->settings[GRPC_SENT_SETTINGS],
-           GRPC_CHTTP2_NUM_SETTINGS * sizeof(uint32_t));
-    transport_parsing->settings_ack_received = 0;
-    transport_global->sent_local_settings = 0;
-  }
-
-  /* move goaway to the global state if we received one (it will be
-     published later */
-  if (transport_parsing->goaway_received) {
-    grpc_chttp2_add_incoming_goaway(exec_ctx, transport_global,
-                                    (uint32_t)transport_parsing->goaway_error,
-                                    transport_parsing->goaway_text);
-    transport_parsing->goaway_text = gpr_empty_slice();
-    transport_parsing->goaway_received = 0;
-  }
-
-  /* propagate flow control tokens to global state */
-  was_zero = transport_global->outgoing_window <= 0;
-  GRPC_CHTTP2_FLOW_MOVE_TRANSPORT("parsed", transport_global, outgoing_window,
-                                  transport_parsing, outgoing_window);
-  is_zero = transport_global->outgoing_window <= 0;
-  if (was_zero && !is_zero) {
-    grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                               "new_global_flow_control");
-  }
-
-  if (transport_parsing->incoming_window <
-      transport_global->connection_window_target * 3 / 4) {
-    int64_t announce_bytes = transport_global->connection_window_target -
-                             transport_parsing->incoming_window;
-    GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parsed", transport_global,
-                                      announce_incoming_window, announce_bytes);
-    GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parsed", transport_parsing,
-                                      incoming_window, announce_bytes);
-    grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                               "global incoming window");
-  }
-
-  /* for each stream that saw an update, fixup global state */
-  while (grpc_chttp2_list_pop_parsing_seen_stream(
-      transport_global, transport_parsing, &stream_global, &stream_parsing)) {
-    if (stream_parsing->seen_error) {
-      stream_global->seen_error = true;
-      stream_global->exceeded_metadata_size =
-          stream_parsing->exceeded_metadata_size;
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
-    }
-
-    /* flush stats to global stream state */
-    grpc_transport_move_stats(&stream_parsing->stats, &stream_global->stats);
-
-    /* update outgoing flow control window */
-    was_zero = stream_global->outgoing_window <= 0;
-    GRPC_CHTTP2_FLOW_MOVE_STREAM("parsed", transport_global, stream_global,
-                                 outgoing_window, stream_parsing,
-                                 outgoing_window);
-    is_zero = stream_global->outgoing_window <= 0;
-    if (was_zero && !is_zero) {
-      grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                  false, "stream.read_flow_control");
-    }
-
-    stream_global->max_recv_bytes -= (uint32_t)GPR_MIN(
-        stream_global->max_recv_bytes, stream_parsing->received_bytes);
-    stream_parsing->received_bytes = 0;
-
-    /* publish incoming stream ops */
-    if (stream_global->incoming_frames.tail != NULL) {
-      stream_global->incoming_frames.tail->is_tail = 0;
-    }
-    if (stream_parsing->data_parser.incoming_frames.head != NULL) {
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
-    }
-    grpc_chttp2_incoming_frame_queue_merge(
-        &stream_global->incoming_frames,
-        &stream_parsing->data_parser.incoming_frames);
-    if (stream_global->incoming_frames.tail != NULL) {
-      stream_global->incoming_frames.tail->is_tail = 1;
-    }
-
-    if (!stream_global->published_initial_metadata &&
-        stream_parsing->got_metadata_on_parse[0]) {
-      stream_parsing->got_metadata_on_parse[0] = 0;
-      stream_global->published_initial_metadata = 1;
-      GPR_SWAP(grpc_chttp2_incoming_metadata_buffer,
-               stream_parsing->metadata_buffer[0],
-               stream_global->received_initial_metadata);
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
-    }
-    if (!stream_global->published_trailing_metadata &&
-        stream_parsing->got_metadata_on_parse[1]) {
-      stream_parsing->got_metadata_on_parse[1] = 0;
-      stream_global->published_trailing_metadata = 1;
-      GPR_SWAP(grpc_chttp2_incoming_metadata_buffer,
-               stream_parsing->metadata_buffer[1],
-               stream_global->received_trailing_metadata);
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
-    }
-
-    if (stream_parsing->forced_close_error != GRPC_ERROR_NONE) {
-      intptr_t reason;
-      bool has_reason = grpc_error_get_int(stream_parsing->forced_close_error,
-                                           GRPC_ERROR_INT_HTTP2_ERROR, &reason);
-      if (has_reason && reason != GRPC_CHTTP2_NO_ERROR) {
-        grpc_status_code status_code =
-            has_reason
-                ? grpc_chttp2_http2_error_to_grpc_status(
-                      (grpc_chttp2_error_code)reason, stream_global->deadline)
-                : GRPC_STATUS_INTERNAL;
-        const char *status_details =
-            grpc_error_string(stream_parsing->forced_close_error);
-        gpr_slice slice_details = gpr_slice_from_copied_string(status_details);
-        grpc_error_free_string(status_details);
-        grpc_chttp2_fake_status(exec_ctx, transport_global, stream_global,
-                                status_code, &slice_details);
-      }
-      grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global,
-                                     1, 1, stream_parsing->forced_close_error);
-    }
-
-    if (stream_parsing->received_close) {
-      grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global,
-                                     1, 0, GRPC_ERROR_NONE);
-    }
-  }
-}
-
-grpc_error *grpc_chttp2_perform_read(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    gpr_slice slice) {
+static grpc_error *init_frame_parser(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t);
+static grpc_error *init_header_frame_parser(grpc_exec_ctx *exec_ctx,
+                                            grpc_chttp2_transport *t,
+                                            int is_continuation);
+static grpc_error *init_data_frame_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t);
+static grpc_error *init_rst_stream_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t);
+static grpc_error *init_settings_frame_parser(grpc_exec_ctx *exec_ctx,
+                                              grpc_chttp2_transport *t);
+static grpc_error *init_window_update_frame_parser(grpc_exec_ctx *exec_ctx,
+                                                   grpc_chttp2_transport *t);
+static grpc_error *init_ping_parser(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_transport *t);
+static grpc_error *init_goaway_parser(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_transport *t);
+static grpc_error *init_skip_frame_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t,
+                                          int is_header);
+
+static grpc_error *parse_frame_slice(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t, gpr_slice slice,
+                                     int is_last);
+
+grpc_error *grpc_chttp2_perform_read(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t,
+                                     gpr_slice slice) {
   uint8_t *beg = GPR_SLICE_START_PTR(slice);
   uint8_t *end = GPR_SLICE_END_PTR(slice);
   uint8_t *cur = beg;
@@ -269,7 +80,7 @@ grpc_error *grpc_chttp2_perform_read(
 
   if (cur == end) return GRPC_ERROR_NONE;
 
-  switch (transport_parsing->deframe_state) {
+  switch (t->deframe_state) {
     case GRPC_DTS_CLIENT_PREFIX_0:
     case GRPC_DTS_CLIENT_PREFIX_1:
     case GRPC_DTS_CLIENT_PREFIX_2:
@@ -294,25 +105,22 @@ grpc_error *grpc_chttp2_perform_read(
     case GRPC_DTS_CLIENT_PREFIX_21:
     case GRPC_DTS_CLIENT_PREFIX_22:
     case GRPC_DTS_CLIENT_PREFIX_23:
-      while (cur != end && transport_parsing->deframe_state != GRPC_DTS_FH_0) {
-        if (*cur != GRPC_CHTTP2_CLIENT_CONNECT_STRING[transport_parsing
-                                                          ->deframe_state]) {
+      while (cur != end && t->deframe_state != GRPC_DTS_FH_0) {
+        if (*cur != GRPC_CHTTP2_CLIENT_CONNECT_STRING[t->deframe_state]) {
           char *msg;
           gpr_asprintf(
               &msg,
               "Connect string mismatch: expected '%c' (%d) got '%c' (%d) "
               "at byte %d",
-              GRPC_CHTTP2_CLIENT_CONNECT_STRING[transport_parsing
-                                                    ->deframe_state],
-              (int)(uint8_t)GRPC_CHTTP2_CLIENT_CONNECT_STRING
-                  [transport_parsing->deframe_state],
-              *cur, (int)*cur, transport_parsing->deframe_state);
+              GRPC_CHTTP2_CLIENT_CONNECT_STRING[t->deframe_state],
+              (int)(uint8_t)GRPC_CHTTP2_CLIENT_CONNECT_STRING[t->deframe_state],
+              *cur, (int)*cur, t->deframe_state);
           err = GRPC_ERROR_CREATE(msg);
           gpr_free(msg);
           return err;
         }
         ++cur;
-        ++transport_parsing->deframe_state;
+        ++t->deframe_state;
       }
       if (cur == end) {
         return GRPC_ERROR_NONE;
@@ -321,100 +129,95 @@ grpc_error *grpc_chttp2_perform_read(
     dts_fh_0:
     case GRPC_DTS_FH_0:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_frame_size = ((uint32_t)*cur) << 16;
+      t->incoming_frame_size = ((uint32_t)*cur) << 16;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_1;
+        t->deframe_state = GRPC_DTS_FH_1;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_1:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_frame_size |= ((uint32_t)*cur) << 8;
+      t->incoming_frame_size |= ((uint32_t)*cur) << 8;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_2;
+        t->deframe_state = GRPC_DTS_FH_2;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_2:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_frame_size |= *cur;
+      t->incoming_frame_size |= *cur;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_3;
+        t->deframe_state = GRPC_DTS_FH_3;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_3:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_frame_type = *cur;
+      t->incoming_frame_type = *cur;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_4;
+        t->deframe_state = GRPC_DTS_FH_4;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_4:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_frame_flags = *cur;
+      t->incoming_frame_flags = *cur;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_5;
+        t->deframe_state = GRPC_DTS_FH_5;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_5:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_stream_id = (((uint32_t)*cur) & 0x7f) << 24;
+      t->incoming_stream_id = (((uint32_t)*cur) & 0x7f) << 24;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_6;
+        t->deframe_state = GRPC_DTS_FH_6;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_6:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_stream_id |= ((uint32_t)*cur) << 16;
+      t->incoming_stream_id |= ((uint32_t)*cur) << 16;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_7;
+        t->deframe_state = GRPC_DTS_FH_7;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_7:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_stream_id |= ((uint32_t)*cur) << 8;
+      t->incoming_stream_id |= ((uint32_t)*cur) << 8;
       if (++cur == end) {
-        transport_parsing->deframe_state = GRPC_DTS_FH_8;
+        t->deframe_state = GRPC_DTS_FH_8;
         return GRPC_ERROR_NONE;
       }
     /* fallthrough */
     case GRPC_DTS_FH_8:
       GPR_ASSERT(cur < end);
-      transport_parsing->incoming_stream_id |= ((uint32_t)*cur);
-      transport_parsing->deframe_state = GRPC_DTS_FRAME;
-      err = init_frame_parser(exec_ctx, transport_parsing);
+      t->incoming_stream_id |= ((uint32_t)*cur);
+      t->deframe_state = GRPC_DTS_FRAME;
+      err = init_frame_parser(exec_ctx, t);
       if (err != GRPC_ERROR_NONE) {
         return err;
       }
-      if (transport_parsing->incoming_stream_id != 0 &&
-          transport_parsing->incoming_stream_id >
-              transport_parsing->last_incoming_stream_id) {
-        transport_parsing->last_incoming_stream_id =
-            transport_parsing->incoming_stream_id;
-      }
-      if (transport_parsing->incoming_frame_size == 0) {
-        err = parse_frame_slice(exec_ctx, transport_parsing, gpr_empty_slice(),
-                                1);
+      if (t->incoming_frame_size == 0) {
+        err = parse_frame_slice(exec_ctx, t, gpr_empty_slice(), 1);
         if (err != GRPC_ERROR_NONE) {
           return err;
         }
-        transport_parsing->incoming_stream = NULL;
+        t->incoming_stream = NULL;
         if (++cur == end) {
-          transport_parsing->deframe_state = GRPC_DTS_FH_0;
+          t->deframe_state = GRPC_DTS_FH_0;
           return GRPC_ERROR_NONE;
         }
         goto dts_fh_0; /* loop */
-      } else if (transport_parsing->incoming_frame_size >
-                 transport_parsing->max_frame_size) {
+      } else if (t->incoming_frame_size >
+                 t->settings[GRPC_ACKED_SETTINGS]
+                            [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE]) {
         char *msg;
         gpr_asprintf(&msg, "Frame size %d is larger than max frame size %d",
-                     transport_parsing->incoming_frame_size,
-                     transport_parsing->max_frame_size);
+                     t->incoming_frame_size,
+                     t->settings[GRPC_ACKED_SETTINGS]
+                                [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE]);
         err = GRPC_ERROR_CREATE(msg);
         gpr_free(msg);
         return err;
@@ -425,41 +228,39 @@ grpc_error *grpc_chttp2_perform_read(
     /* fallthrough */
     case GRPC_DTS_FRAME:
       GPR_ASSERT(cur < end);
-      if ((uint32_t)(end - cur) == transport_parsing->incoming_frame_size) {
-        err = parse_frame_slice(exec_ctx, transport_parsing,
+      if ((uint32_t)(end - cur) == t->incoming_frame_size) {
+        err = parse_frame_slice(exec_ctx, t,
                                 gpr_slice_sub_no_ref(slice, (size_t)(cur - beg),
                                                      (size_t)(end - beg)),
                                 1);
         if (err != GRPC_ERROR_NONE) {
           return err;
         }
-        transport_parsing->deframe_state = GRPC_DTS_FH_0;
-        transport_parsing->incoming_stream = NULL;
+        t->deframe_state = GRPC_DTS_FH_0;
+        t->incoming_stream = NULL;
         return GRPC_ERROR_NONE;
-      } else if ((uint32_t)(end - cur) >
-                 transport_parsing->incoming_frame_size) {
+      } else if ((uint32_t)(end - cur) > t->incoming_frame_size) {
         size_t cur_offset = (size_t)(cur - beg);
         err = parse_frame_slice(
-            exec_ctx, transport_parsing,
-            gpr_slice_sub_no_ref(
-                slice, cur_offset,
-                cur_offset + transport_parsing->incoming_frame_size),
+            exec_ctx, t,
+            gpr_slice_sub_no_ref(slice, cur_offset,
+                                 cur_offset + t->incoming_frame_size),
             1);
         if (err != GRPC_ERROR_NONE) {
           return err;
         }
-        cur += transport_parsing->incoming_frame_size;
-        transport_parsing->incoming_stream = NULL;
+        cur += t->incoming_frame_size;
+        t->incoming_stream = NULL;
         goto dts_fh_0; /* loop */
       } else {
-        err = parse_frame_slice(exec_ctx, transport_parsing,
+        err = parse_frame_slice(exec_ctx, t,
                                 gpr_slice_sub_no_ref(slice, (size_t)(cur - beg),
                                                      (size_t)(end - beg)),
                                 0);
         if (err != GRPC_ERROR_NONE) {
           return err;
         }
-        transport_parsing->incoming_frame_size -= (uint32_t)(end - cur);
+        t->incoming_frame_size -= (uint32_t)(end - cur);
         return GRPC_ERROR_NONE;
       }
       GPR_UNREACHABLE_CODE(return 0);
@@ -468,175 +269,164 @@ grpc_error *grpc_chttp2_perform_read(
   GPR_UNREACHABLE_CODE(return 0);
 }
 
-static grpc_error *init_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
-  if (transport_parsing->is_first_frame &&
-      transport_parsing->incoming_frame_type != GRPC_CHTTP2_FRAME_SETTINGS) {
+static grpc_error *init_frame_parser(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t) {
+  if (t->is_first_frame &&
+      t->incoming_frame_type != GRPC_CHTTP2_FRAME_SETTINGS) {
     char *msg;
     gpr_asprintf(
         &msg, "Expected SETTINGS frame as the first frame, got frame type %d",
-        transport_parsing->incoming_frame_type);
+        t->incoming_frame_type);
     grpc_error *err = GRPC_ERROR_CREATE(msg);
     gpr_free(msg);
     return err;
   }
-  transport_parsing->is_first_frame = false;
-  if (transport_parsing->expect_continuation_stream_id != 0) {
-    if (transport_parsing->incoming_frame_type !=
-        GRPC_CHTTP2_FRAME_CONTINUATION) {
+  t->is_first_frame = false;
+  if (t->expect_continuation_stream_id != 0) {
+    if (t->incoming_frame_type != GRPC_CHTTP2_FRAME_CONTINUATION) {
       char *msg;
       gpr_asprintf(&msg, "Expected CONTINUATION frame, got frame type %02x",
-                   transport_parsing->incoming_frame_type);
+                   t->incoming_frame_type);
       grpc_error *err = GRPC_ERROR_CREATE(msg);
       gpr_free(msg);
       return err;
     }
-    if (transport_parsing->expect_continuation_stream_id !=
-        transport_parsing->incoming_stream_id) {
+    if (t->expect_continuation_stream_id != t->incoming_stream_id) {
       char *msg;
       gpr_asprintf(
           &msg,
           "Expected CONTINUATION frame for grpc_chttp2_stream %08x, got "
           "grpc_chttp2_stream %08x",
-          transport_parsing->expect_continuation_stream_id,
-          transport_parsing->incoming_stream_id);
+          t->expect_continuation_stream_id, t->incoming_stream_id);
       grpc_error *err = GRPC_ERROR_CREATE(msg);
       gpr_free(msg);
       return err;
     }
-    return init_header_frame_parser(exec_ctx, transport_parsing, 1);
+    return init_header_frame_parser(exec_ctx, t, 1);
   }
-  switch (transport_parsing->incoming_frame_type) {
+  switch (t->incoming_frame_type) {
     case GRPC_CHTTP2_FRAME_DATA:
-      return init_data_frame_parser(exec_ctx, transport_parsing);
+      return init_data_frame_parser(exec_ctx, t);
     case GRPC_CHTTP2_FRAME_HEADER:
-      return init_header_frame_parser(exec_ctx, transport_parsing, 0);
+      return init_header_frame_parser(exec_ctx, t, 0);
     case GRPC_CHTTP2_FRAME_CONTINUATION:
       return GRPC_ERROR_CREATE("Unexpected CONTINUATION frame");
     case GRPC_CHTTP2_FRAME_RST_STREAM:
-      return init_rst_stream_parser(exec_ctx, transport_parsing);
+      return init_rst_stream_parser(exec_ctx, t);
     case GRPC_CHTTP2_FRAME_SETTINGS:
-      return init_settings_frame_parser(exec_ctx, transport_parsing);
+      return init_settings_frame_parser(exec_ctx, t);
     case GRPC_CHTTP2_FRAME_WINDOW_UPDATE:
-      return init_window_update_frame_parser(exec_ctx, transport_parsing);
+      return init_window_update_frame_parser(exec_ctx, t);
     case GRPC_CHTTP2_FRAME_PING:
-      return init_ping_parser(exec_ctx, transport_parsing);
+      return init_ping_parser(exec_ctx, t);
     case GRPC_CHTTP2_FRAME_GOAWAY:
-      return init_goaway_parser(exec_ctx, transport_parsing);
+      return init_goaway_parser(exec_ctx, t);
     default:
       if (grpc_http_trace) {
-        gpr_log(GPR_ERROR, "Unknown frame type %02x",
-                transport_parsing->incoming_frame_type);
+        gpr_log(GPR_ERROR, "Unknown frame type %02x", t->incoming_frame_type);
       }
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+      return init_skip_frame_parser(exec_ctx, t, 0);
   }
 }
 
 static grpc_error *skip_parser(grpc_exec_ctx *exec_ctx, void *parser,
-                               grpc_chttp2_transport_parsing *transport_parsing,
-                               grpc_chttp2_stream_parsing *stream_parsing,
+                               grpc_chttp2_transport *t, grpc_chttp2_stream *s,
                                gpr_slice slice, int is_last) {
   return GRPC_ERROR_NONE;
 }
 
-static void skip_header(void *tp, grpc_mdelem *md) { GRPC_MDELEM_UNREF(md); }
+static void skip_header(grpc_exec_ctx *exec_ctx, void *tp, grpc_mdelem *md) {
+  GRPC_MDELEM_UNREF(md);
+}
 
-static grpc_error *init_skip_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    int is_header) {
+static grpc_error *init_skip_frame_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t,
+                                          int is_header) {
   if (is_header) {
-    uint8_t is_eoh = transport_parsing->expect_continuation_stream_id != 0;
-    transport_parsing->parser = grpc_chttp2_header_parser_parse;
-    transport_parsing->parser_data = &transport_parsing->hpack_parser;
-    transport_parsing->hpack_parser.on_header = skip_header;
-    transport_parsing->hpack_parser.on_header_user_data = NULL;
-    transport_parsing->hpack_parser.is_boundary = is_eoh;
-    transport_parsing->hpack_parser.is_eof =
-        (uint8_t)(is_eoh ? transport_parsing->header_eof : 0);
+    uint8_t is_eoh = t->expect_continuation_stream_id != 0;
+    t->parser = grpc_chttp2_header_parser_parse;
+    t->parser_data = &t->hpack_parser;
+    t->hpack_parser.on_header = skip_header;
+    t->hpack_parser.on_header_user_data = NULL;
+    t->hpack_parser.is_boundary = is_eoh;
+    t->hpack_parser.is_eof = (uint8_t)(is_eoh ? t->header_eof : 0);
   } else {
-    transport_parsing->parser = skip_parser;
+    t->parser = skip_parser;
   }
   return GRPC_ERROR_NONE;
 }
 
-void grpc_chttp2_parsing_become_skip_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
-  init_skip_frame_parser(
-      exec_ctx, transport_parsing,
-      transport_parsing->parser == grpc_chttp2_header_parser_parse);
+void grpc_chttp2_parsing_become_skip_parser(grpc_exec_ctx *exec_ctx,
+                                            grpc_chttp2_transport *t) {
+  init_skip_frame_parser(exec_ctx, t,
+                         t->parser == grpc_chttp2_header_parser_parse);
 }
 
-static grpc_error *update_incoming_window(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing) {
-  uint32_t incoming_frame_size = transport_parsing->incoming_frame_size;
-  if (incoming_frame_size > transport_parsing->incoming_window) {
+static grpc_error *update_incoming_window(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s) {
+  uint32_t incoming_frame_size = t->incoming_frame_size;
+  if (incoming_frame_size > t->incoming_window) {
     char *msg;
     gpr_asprintf(&msg, "frame of size %d overflows incoming window of %" PRId64,
-                 transport_parsing->incoming_frame_size,
-                 transport_parsing->incoming_window);
+                 t->incoming_frame_size, t->incoming_window);
     grpc_error *err = GRPC_ERROR_CREATE(msg);
     gpr_free(msg);
     return err;
   }
 
-  if (incoming_frame_size > stream_parsing->incoming_window) {
+  if (incoming_frame_size > s->incoming_window) {
     char *msg;
     gpr_asprintf(&msg, "frame of size %d overflows incoming window of %" PRId64,
-                 transport_parsing->incoming_frame_size,
-                 stream_parsing->incoming_window);
+                 t->incoming_frame_size, s->incoming_window);
     grpc_error *err = GRPC_ERROR_CREATE(msg);
     gpr_free(msg);
     return err;
   }
 
-  GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("parse", transport_parsing, incoming_window,
+  GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("parse", t, incoming_window,
                                    incoming_frame_size);
-  GRPC_CHTTP2_FLOW_DEBIT_STREAM("parse", transport_parsing, stream_parsing,
-                                incoming_window, incoming_frame_size);
-  stream_parsing->received_bytes += incoming_frame_size;
-
-  grpc_chttp2_list_add_parsing_seen_stream(transport_parsing, stream_parsing);
+  GRPC_CHTTP2_FLOW_DEBIT_STREAM("parse", t, s, incoming_window,
+                                incoming_frame_size);
+  s->received_bytes += incoming_frame_size;
+  s->max_recv_bytes -=
+      (uint32_t)GPR_MIN(s->max_recv_bytes, incoming_frame_size);
 
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_data_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
-  grpc_chttp2_stream_parsing *stream_parsing =
-      grpc_chttp2_parsing_lookup_stream(transport_parsing,
-                                        transport_parsing->incoming_stream_id);
+static grpc_error *init_data_frame_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t) {
+  grpc_chttp2_stream *s =
+      grpc_chttp2_parsing_lookup_stream(t, t->incoming_stream_id);
   grpc_error *err = GRPC_ERROR_NONE;
-  if (stream_parsing == NULL) {
-    return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+  if (s == NULL) {
+    return init_skip_frame_parser(exec_ctx, t, 0);
   }
-  stream_parsing->stats.incoming.framing_bytes += 9;
-  if (stream_parsing->received_close) {
-    return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+  s->stats.incoming.framing_bytes += 9;
+  if (s->read_closed) {
+    return init_skip_frame_parser(exec_ctx, t, 0);
   }
   if (err == GRPC_ERROR_NONE) {
-    err = update_incoming_window(exec_ctx, transport_parsing, stream_parsing);
+    err = update_incoming_window(exec_ctx, t, s);
   }
   if (err == GRPC_ERROR_NONE) {
-    err = grpc_chttp2_data_parser_begin_frame(
-        &stream_parsing->data_parser, transport_parsing->incoming_frame_flags,
-        stream_parsing->id);
+    err = grpc_chttp2_data_parser_begin_frame(&s->data_parser,
+                                              t->incoming_frame_flags, s->id);
   }
   if (err == GRPC_ERROR_NONE) {
-    transport_parsing->incoming_stream = stream_parsing;
-    transport_parsing->parser = grpc_chttp2_data_parser_parse;
-    transport_parsing->parser_data = &stream_parsing->data_parser;
+    t->incoming_stream = s;
+    t->parser = grpc_chttp2_data_parser_parse;
+    t->parser_data = &s->data_parser;
     return GRPC_ERROR_NONE;
   } else if (grpc_error_get_int(err, GRPC_ERROR_INT_STREAM_ID, NULL)) {
     /* handle stream errors by closing the stream */
-    stream_parsing->received_close = 1;
-    stream_parsing->forced_close_error = err;
+    grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, false, err);
     gpr_slice_buffer_add(
-        &transport_parsing->qbuf,
-        grpc_chttp2_rst_stream_create(transport_parsing->incoming_stream_id,
-                                      GRPC_CHTTP2_PROTOCOL_ERROR,
-                                      &stream_parsing->stats.outgoing));
-    return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+        &t->qbuf, grpc_chttp2_rst_stream_create(t->incoming_stream_id,
+                                                GRPC_CHTTP2_PROTOCOL_ERROR,
+                                                &s->stats.outgoing));
+    return init_skip_frame_parser(exec_ctx, t, 0);
   } else {
     return err;
   }
@@ -644,23 +434,22 @@ static grpc_error *init_data_frame_parser(
 
 static void free_timeout(void *p) { gpr_free(p); }
 
-static void on_initial_header(void *tp, grpc_mdelem *md) {
-  grpc_chttp2_transport_parsing *transport_parsing = tp;
-  grpc_chttp2_stream_parsing *stream_parsing =
-      transport_parsing->incoming_stream;
+static void on_initial_header(grpc_exec_ctx *exec_ctx, void *tp,
+                              grpc_mdelem *md) {
+  grpc_chttp2_transport *t = tp;
+  grpc_chttp2_stream *s = t->incoming_stream;
 
   GPR_TIMER_BEGIN("on_initial_header", 0);
 
-  GPR_ASSERT(stream_parsing);
+  GPR_ASSERT(s != NULL);
 
   GRPC_CHTTP2_IF_TRACING(gpr_log(
-      GPR_INFO, "HTTP:%d:HDR:%s: %s: %s", stream_parsing->id,
-      transport_parsing->is_client ? "CLI" : "SVR",
+      GPR_INFO, "HTTP:%d:HDR:%s: %s: %s", s->id, t->is_client ? "CLI" : "SVR",
       grpc_mdstr_as_c_string(md->key), grpc_mdstr_as_c_string(md->value)));
 
   if (md->key == GRPC_MDSTR_GRPC_STATUS && md != GRPC_MDELEM_GRPC_STATUS_0) {
     /* TODO(ctiller): check for a status like " 0" */
-    stream_parsing->seen_error = true;
+    s->seen_error = true;
   }
 
   if (md->key == GRPC_MDSTR_GRPC_TIMEOUT) {
@@ -677,306 +466,273 @@ static void on_initial_header(void *tp, grpc_mdelem *md) {
       grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
     }
     grpc_chttp2_incoming_metadata_buffer_set_deadline(
-        &stream_parsing->metadata_buffer[0],
+        &s->metadata_buffer[0],
         gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), *cached_timeout));
     GRPC_MDELEM_UNREF(md);
   } else {
-    const size_t new_size =
-        stream_parsing->metadata_buffer[0].size + GRPC_MDELEM_LENGTH(md);
-    grpc_chttp2_transport_global *transport_global =
-        &TRANSPORT_FROM_PARSING(transport_parsing)->global;
+    const size_t new_size = s->metadata_buffer[0].size + GRPC_MDELEM_LENGTH(md);
     const size_t metadata_size_limit =
-        transport_global->settings[GRPC_LOCAL_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
+        t->settings[GRPC_ACKED_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
     if (new_size > metadata_size_limit) {
-      if (!stream_parsing->exceeded_metadata_size) {
-        gpr_log(GPR_DEBUG,
-                "received initial metadata size exceeds limit (%" PRIuPTR
-                " vs. %" PRIuPTR ")",
-                new_size, metadata_size_limit);
-        stream_parsing->seen_error = true;
-        stream_parsing->exceeded_metadata_size = true;
-      }
+      gpr_log(GPR_DEBUG,
+              "received initial metadata size exceeds limit (%" PRIuPTR
+              " vs. %" PRIuPTR ")",
+              new_size, metadata_size_limit);
+      grpc_chttp2_cancel_stream(
+          exec_ctx, t, s,
+          grpc_error_set_int(
+              GRPC_ERROR_CREATE("received initial metadata size exceeds limit"),
+              GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
+      grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
+      s->seen_error = true;
       GRPC_MDELEM_UNREF(md);
     } else {
-      grpc_chttp2_incoming_metadata_buffer_add(
-          &stream_parsing->metadata_buffer[0], md);
+      grpc_chttp2_incoming_metadata_buffer_add(&s->metadata_buffer[0], md);
     }
   }
 
-  grpc_chttp2_list_add_parsing_seen_stream(transport_parsing, stream_parsing);
-
   GPR_TIMER_END("on_initial_header", 0);
 }
 
-static void on_trailing_header(void *tp, grpc_mdelem *md) {
-  grpc_chttp2_transport_parsing *transport_parsing = tp;
-  grpc_chttp2_stream_parsing *stream_parsing =
-      transport_parsing->incoming_stream;
+static void on_trailing_header(grpc_exec_ctx *exec_ctx, void *tp,
+                               grpc_mdelem *md) {
+  grpc_chttp2_transport *t = tp;
+  grpc_chttp2_stream *s = t->incoming_stream;
 
   GPR_TIMER_BEGIN("on_trailing_header", 0);
 
-  GPR_ASSERT(stream_parsing);
+  GPR_ASSERT(s != NULL);
 
   GRPC_CHTTP2_IF_TRACING(gpr_log(
-      GPR_INFO, "HTTP:%d:TRL:%s: %s: %s", stream_parsing->id,
-      transport_parsing->is_client ? "CLI" : "SVR",
+      GPR_INFO, "HTTP:%d:TRL:%s: %s: %s", s->id, t->is_client ? "CLI" : "SVR",
       grpc_mdstr_as_c_string(md->key), grpc_mdstr_as_c_string(md->value)));
 
   if (md->key == GRPC_MDSTR_GRPC_STATUS && md != GRPC_MDELEM_GRPC_STATUS_0) {
     /* TODO(ctiller): check for a status like " 0" */
-    stream_parsing->seen_error = true;
+    s->seen_error = true;
   }
 
-  const size_t new_size =
-      stream_parsing->metadata_buffer[1].size + GRPC_MDELEM_LENGTH(md);
-  grpc_chttp2_transport_global *transport_global =
-      &TRANSPORT_FROM_PARSING(transport_parsing)->global;
+  const size_t new_size = s->metadata_buffer[1].size + GRPC_MDELEM_LENGTH(md);
   const size_t metadata_size_limit =
-      transport_global->settings[GRPC_LOCAL_SETTINGS]
-                                [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
+      t->settings[GRPC_ACKED_SETTINGS]
+                 [GRPC_CHTTP2_SETTINGS_MAX_HEADER_LIST_SIZE];
   if (new_size > metadata_size_limit) {
-    if (!stream_parsing->exceeded_metadata_size) {
-      gpr_log(GPR_DEBUG,
-              "received trailing metadata size exceeds limit (%" PRIuPTR
-              " vs. %" PRIuPTR ")",
-              new_size, metadata_size_limit);
-      stream_parsing->seen_error = true;
-      stream_parsing->exceeded_metadata_size = true;
-    }
+    gpr_log(GPR_DEBUG,
+            "received trailing metadata size exceeds limit (%" PRIuPTR
+            " vs. %" PRIuPTR ")",
+            new_size, metadata_size_limit);
+    grpc_chttp2_cancel_stream(
+        exec_ctx, t, s,
+        grpc_error_set_int(
+            GRPC_ERROR_CREATE("received trailing metadata size exceeds limit"),
+            GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_RESOURCE_EXHAUSTED));
+    grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
+    s->seen_error = true;
     GRPC_MDELEM_UNREF(md);
   } else {
-    grpc_chttp2_incoming_metadata_buffer_add(
-        &stream_parsing->metadata_buffer[1], md);
+    grpc_chttp2_incoming_metadata_buffer_add(&s->metadata_buffer[1], md);
   }
 
-  grpc_chttp2_list_add_parsing_seen_stream(transport_parsing, stream_parsing);
-
   GPR_TIMER_END("on_trailing_header", 0);
 }
 
-static grpc_error *init_header_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    int is_continuation) {
-  uint8_t is_eoh = (transport_parsing->incoming_frame_flags &
-                    GRPC_CHTTP2_DATA_FLAG_END_HEADERS) != 0;
-  int via_accept = 0;
-  grpc_chttp2_stream_parsing *stream_parsing;
+static grpc_error *init_header_frame_parser(grpc_exec_ctx *exec_ctx,
+                                            grpc_chttp2_transport *t,
+                                            int is_continuation) {
+  uint8_t is_eoh =
+      (t->incoming_frame_flags & GRPC_CHTTP2_DATA_FLAG_END_HEADERS) != 0;
+  grpc_chttp2_stream *s;
 
   /* TODO(ctiller): when to increment header_frames_received? */
 
   if (is_eoh) {
-    transport_parsing->expect_continuation_stream_id = 0;
+    t->expect_continuation_stream_id = 0;
   } else {
-    transport_parsing->expect_continuation_stream_id =
-        transport_parsing->incoming_stream_id;
+    t->expect_continuation_stream_id = t->incoming_stream_id;
   }
 
   if (!is_continuation) {
-    transport_parsing->header_eof = (transport_parsing->incoming_frame_flags &
-                                     GRPC_CHTTP2_DATA_FLAG_END_STREAM) != 0;
+    t->header_eof =
+        (t->incoming_frame_flags & GRPC_CHTTP2_DATA_FLAG_END_STREAM) != 0;
   }
 
   /* could be a new grpc_chttp2_stream or an existing grpc_chttp2_stream */
-  stream_parsing = grpc_chttp2_parsing_lookup_stream(
-      transport_parsing, transport_parsing->incoming_stream_id);
-  if (stream_parsing == NULL) {
+  s = grpc_chttp2_parsing_lookup_stream(t, t->incoming_stream_id);
+  if (s == NULL) {
     if (is_continuation) {
-      gpr_log(GPR_ERROR,
-              "grpc_chttp2_stream disbanded before CONTINUATION received");
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
+      GRPC_CHTTP2_IF_TRACING(
+          gpr_log(GPR_ERROR,
+                  "grpc_chttp2_stream disbanded before CONTINUATION received"));
+      return init_skip_frame_parser(exec_ctx, t, 1);
     }
-    if (transport_parsing->is_client) {
-      if ((transport_parsing->incoming_stream_id & 1) &&
-          transport_parsing->incoming_stream_id <
-              transport_parsing->next_stream_id) {
+    if (t->is_client) {
+      if ((t->incoming_stream_id & 1) &&
+          t->incoming_stream_id < t->next_stream_id) {
         /* this is an old (probably cancelled) grpc_chttp2_stream */
       } else {
-        gpr_log(GPR_ERROR,
-                "ignoring new grpc_chttp2_stream creation on client");
+        GRPC_CHTTP2_IF_TRACING(gpr_log(
+            GPR_ERROR, "ignoring new grpc_chttp2_stream creation on client"));
       }
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
-    } else if (transport_parsing->last_incoming_stream_id >
-               transport_parsing->incoming_stream_id) {
-      gpr_log(GPR_ERROR,
-              "ignoring out of order new grpc_chttp2_stream request on server; "
-              "last grpc_chttp2_stream "
-              "id=%d, new grpc_chttp2_stream id=%d",
-              transport_parsing->last_incoming_stream_id,
-              transport_parsing->incoming_stream_id);
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
-    } else if ((transport_parsing->incoming_stream_id & 1) == 0) {
-      gpr_log(GPR_ERROR,
-              "ignoring grpc_chttp2_stream with non-client generated index %d",
-              transport_parsing->incoming_stream_id);
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
+      return init_skip_frame_parser(exec_ctx, t, 1);
+    } else if (t->last_new_stream_id >= t->incoming_stream_id) {
+      GRPC_CHTTP2_IF_TRACING(gpr_log(
+          GPR_ERROR,
+          "ignoring out of order new grpc_chttp2_stream request on server; "
+          "last grpc_chttp2_stream "
+          "id=%d, new grpc_chttp2_stream id=%d",
+          t->last_new_stream_id, t->incoming_stream_id));
+      return init_skip_frame_parser(exec_ctx, t, 1);
+    } else if ((t->incoming_stream_id & 1) == 0) {
+      GRPC_CHTTP2_IF_TRACING(gpr_log(
+          GPR_ERROR,
+          "ignoring grpc_chttp2_stream with non-client generated index %d",
+          t->incoming_stream_id));
+      return init_skip_frame_parser(exec_ctx, t, 1);
     }
-    stream_parsing = transport_parsing->incoming_stream =
-        grpc_chttp2_parsing_accept_stream(
-            exec_ctx, transport_parsing, transport_parsing->incoming_stream_id);
-    if (stream_parsing == NULL) {
-      gpr_log(GPR_ERROR, "grpc_chttp2_stream not accepted");
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
+    t->last_new_stream_id = t->incoming_stream_id;
+    s = t->incoming_stream =
+        grpc_chttp2_parsing_accept_stream(exec_ctx, t, t->incoming_stream_id);
+    if (s == NULL) {
+      GRPC_CHTTP2_IF_TRACING(
+          gpr_log(GPR_ERROR, "grpc_chttp2_stream not accepted"));
+      return init_skip_frame_parser(exec_ctx, t, 1);
     }
-    via_accept = 1;
   } else {
-    transport_parsing->incoming_stream = stream_parsing;
-  }
-  GPR_ASSERT(stream_parsing != NULL && (via_accept == 0 || via_accept == 1));
-  stream_parsing->stats.incoming.framing_bytes += 9;
-  if (stream_parsing->received_close) {
-    gpr_log(GPR_ERROR, "skipping already closed grpc_chttp2_stream header");
-    transport_parsing->incoming_stream = NULL;
-    return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
-  }
-  transport_parsing->parser = grpc_chttp2_header_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->hpack_parser;
-  switch (stream_parsing->header_frames_received) {
+    t->incoming_stream = s;
+  }
+  GPR_ASSERT(s != NULL);
+  s->stats.incoming.framing_bytes += 9;
+  if (s->read_closed) {
+    GRPC_CHTTP2_IF_TRACING(gpr_log(
+        GPR_ERROR, "skipping already closed grpc_chttp2_stream header"));
+    t->incoming_stream = NULL;
+    return init_skip_frame_parser(exec_ctx, t, 1);
+  }
+  t->parser = grpc_chttp2_header_parser_parse;
+  t->parser_data = &t->hpack_parser;
+  switch (s->header_frames_received) {
     case 0:
-      transport_parsing->hpack_parser.on_header = on_initial_header;
+      t->hpack_parser.on_header = on_initial_header;
       break;
     case 1:
-      transport_parsing->hpack_parser.on_header = on_trailing_header;
+      t->hpack_parser.on_header = on_trailing_header;
       break;
     case 2:
       gpr_log(GPR_ERROR, "too many header frames received");
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 1);
+      return init_skip_frame_parser(exec_ctx, t, 1);
   }
-  transport_parsing->hpack_parser.on_header_user_data = transport_parsing;
-  transport_parsing->hpack_parser.is_boundary = is_eoh;
-  transport_parsing->hpack_parser.is_eof =
-      (uint8_t)(is_eoh ? transport_parsing->header_eof : 0);
-  if (!is_continuation && (transport_parsing->incoming_frame_flags &
-                           GRPC_CHTTP2_FLAG_HAS_PRIORITY)) {
-    grpc_chttp2_hpack_parser_set_has_priority(&transport_parsing->hpack_parser);
+  t->hpack_parser.on_header_user_data = t;
+  t->hpack_parser.is_boundary = is_eoh;
+  t->hpack_parser.is_eof = (uint8_t)(is_eoh ? t->header_eof : 0);
+  if (!is_continuation &&
+      (t->incoming_frame_flags & GRPC_CHTTP2_FLAG_HAS_PRIORITY)) {
+    grpc_chttp2_hpack_parser_set_has_priority(&t->hpack_parser);
   }
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_window_update_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
+static grpc_error *init_window_update_frame_parser(grpc_exec_ctx *exec_ctx,
+                                                   grpc_chttp2_transport *t) {
   grpc_error *err = grpc_chttp2_window_update_parser_begin_frame(
-      &transport_parsing->simple.window_update,
-      transport_parsing->incoming_frame_size,
-      transport_parsing->incoming_frame_flags);
+      &t->simple.window_update, t->incoming_frame_size,
+      t->incoming_frame_flags);
   if (err != GRPC_ERROR_NONE) return err;
-  if (transport_parsing->incoming_stream_id != 0) {
-    grpc_chttp2_stream_parsing *stream_parsing =
-        transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
-            transport_parsing, transport_parsing->incoming_stream_id);
-    if (stream_parsing == NULL) {
-      return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+  if (t->incoming_stream_id != 0) {
+    grpc_chttp2_stream *s = t->incoming_stream =
+        grpc_chttp2_parsing_lookup_stream(t, t->incoming_stream_id);
+    if (s == NULL) {
+      return init_skip_frame_parser(exec_ctx, t, 0);
     }
-    stream_parsing->stats.incoming.framing_bytes += 9;
+    s->stats.incoming.framing_bytes += 9;
   }
-  transport_parsing->parser = grpc_chttp2_window_update_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->simple.window_update;
+  t->parser = grpc_chttp2_window_update_parser_parse;
+  t->parser_data = &t->simple.window_update;
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_ping_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
+static grpc_error *init_ping_parser(grpc_exec_ctx *exec_ctx,
+                                    grpc_chttp2_transport *t) {
   grpc_error *err = grpc_chttp2_ping_parser_begin_frame(
-      &transport_parsing->simple.ping, transport_parsing->incoming_frame_size,
-      transport_parsing->incoming_frame_flags);
+      &t->simple.ping, t->incoming_frame_size, t->incoming_frame_flags);
   if (err != GRPC_ERROR_NONE) return err;
-  transport_parsing->parser = grpc_chttp2_ping_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->simple.ping;
+  t->parser = grpc_chttp2_ping_parser_parse;
+  t->parser_data = &t->simple.ping;
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_rst_stream_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
+static grpc_error *init_rst_stream_parser(grpc_exec_ctx *exec_ctx,
+                                          grpc_chttp2_transport *t) {
   grpc_error *err = grpc_chttp2_rst_stream_parser_begin_frame(
-      &transport_parsing->simple.rst_stream,
-      transport_parsing->incoming_frame_size,
-      transport_parsing->incoming_frame_flags);
+      &t->simple.rst_stream, t->incoming_frame_size, t->incoming_frame_flags);
   if (err != GRPC_ERROR_NONE) return err;
-  grpc_chttp2_stream_parsing *stream_parsing =
-      transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
-          transport_parsing, transport_parsing->incoming_stream_id);
-  if (!transport_parsing->incoming_stream) {
-    return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
-  }
-  stream_parsing->stats.incoming.framing_bytes += 9;
-  transport_parsing->parser = grpc_chttp2_rst_stream_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->simple.rst_stream;
+  grpc_chttp2_stream *s = t->incoming_stream =
+      grpc_chttp2_parsing_lookup_stream(t, t->incoming_stream_id);
+  if (!t->incoming_stream) {
+    return init_skip_frame_parser(exec_ctx, t, 0);
+  }
+  s->stats.incoming.framing_bytes += 9;
+  t->parser = grpc_chttp2_rst_stream_parser_parse;
+  t->parser_data = &t->simple.rst_stream;
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_goaway_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
+static grpc_error *init_goaway_parser(grpc_exec_ctx *exec_ctx,
+                                      grpc_chttp2_transport *t) {
   grpc_error *err = grpc_chttp2_goaway_parser_begin_frame(
-      &transport_parsing->goaway_parser, transport_parsing->incoming_frame_size,
-      transport_parsing->incoming_frame_flags);
+      &t->goaway_parser, t->incoming_frame_size, t->incoming_frame_flags);
   if (err != GRPC_ERROR_NONE) return err;
-  transport_parsing->parser = grpc_chttp2_goaway_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->goaway_parser;
+  t->parser = grpc_chttp2_goaway_parser_parse;
+  t->parser_data = &t->goaway_parser;
   return GRPC_ERROR_NONE;
 }
 
-static grpc_error *init_settings_frame_parser(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing) {
-  if (transport_parsing->incoming_stream_id != 0) {
+static grpc_error *init_settings_frame_parser(grpc_exec_ctx *exec_ctx,
+                                              grpc_chttp2_transport *t) {
+  if (t->incoming_stream_id != 0) {
     return GRPC_ERROR_CREATE("Settings frame received for grpc_chttp2_stream");
   }
 
   grpc_error *err = grpc_chttp2_settings_parser_begin_frame(
-      &transport_parsing->simple.settings,
-      transport_parsing->incoming_frame_size,
-      transport_parsing->incoming_frame_flags, transport_parsing->settings);
+      &t->simple.settings, t->incoming_frame_size, t->incoming_frame_flags,
+      t->settings[GRPC_PEER_SETTINGS]);
   if (err != GRPC_ERROR_NONE) {
     return err;
   }
-  if (transport_parsing->incoming_frame_flags & GRPC_CHTTP2_FLAG_ACK) {
-    transport_parsing->settings_ack_received = 1;
+  if (t->incoming_frame_flags & GRPC_CHTTP2_FLAG_ACK) {
+    memcpy(t->settings[GRPC_ACKED_SETTINGS], t->settings[GRPC_SENT_SETTINGS],
+           GRPC_CHTTP2_NUM_SETTINGS * sizeof(uint32_t));
     grpc_chttp2_hptbl_set_max_bytes(
-        &transport_parsing->hpack_parser.table,
-        transport_parsing
-            ->last_sent_settings[GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
-    transport_parsing->max_frame_size =
-        transport_parsing
-            ->last_sent_settings[GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE];
+        &t->hpack_parser.table,
+        t->settings[GRPC_ACKED_SETTINGS]
+                   [GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
+    t->sent_local_settings = 0;
   }
-  transport_parsing->parser = grpc_chttp2_settings_parser_parse;
-  transport_parsing->parser_data = &transport_parsing->simple.settings;
+  t->parser = grpc_chttp2_settings_parser_parse;
+  t->parser_data = &t->simple.settings;
   return GRPC_ERROR_NONE;
 }
 
-/*
-static int is_window_update_legal(int64_t window_update, int64_t window) {
-  return window + window_update < MAX_WINDOW;
-}
-*/
-
-static grpc_error *parse_frame_slice(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing,
-    gpr_slice slice, int is_last) {
-  grpc_chttp2_stream_parsing *stream_parsing =
-      transport_parsing->incoming_stream;
-  grpc_error *err = transport_parsing->parser(
-      exec_ctx, transport_parsing->parser_data, transport_parsing,
-      stream_parsing, slice, is_last);
+static grpc_error *parse_frame_slice(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t, gpr_slice slice,
+                                     int is_last) {
+  grpc_chttp2_stream *s = t->incoming_stream;
+  grpc_error *err = t->parser(exec_ctx, t->parser_data, t, s, slice, is_last);
   if (err == GRPC_ERROR_NONE) {
-    if (stream_parsing) {
-      grpc_chttp2_list_add_parsing_seen_stream(transport_parsing,
-                                               stream_parsing);
-    }
-    return GRPC_ERROR_NONE;
+    return err;
   } else if (grpc_error_get_int(err, GRPC_ERROR_INT_STREAM_ID, NULL)) {
     if (grpc_http_trace) {
       const char *msg = grpc_error_string(err);
       gpr_log(GPR_ERROR, "%s", msg);
       grpc_error_free_string(msg);
     }
-    grpc_chttp2_parsing_become_skip_parser(exec_ctx, transport_parsing);
-    if (stream_parsing) {
-      stream_parsing->forced_close_error = err;
+    grpc_chttp2_parsing_become_skip_parser(exec_ctx, t);
+    if (s) {
+      s->forced_close_error = err;
       gpr_slice_buffer_add(
-          &transport_parsing->qbuf,
-          grpc_chttp2_rst_stream_create(transport_parsing->incoming_stream_id,
-                                        GRPC_CHTTP2_PROTOCOL_ERROR,
-                                        &stream_parsing->stats.outgoing));
+          &t->qbuf, grpc_chttp2_rst_stream_create(t->incoming_stream_id,
+                                                  GRPC_CHTTP2_PROTOCOL_ERROR,
+                                                  &s->stats.outgoing));
     } else {
       GRPC_ERROR_UNREF(err);
     }
diff --git a/src/core/ext/transport/chttp2/transport/stream_lists.c b/src/core/ext/transport/chttp2/transport/stream_lists.c
index 2eb5f5f632..6d25b3ae57 100644
--- a/src/core/ext/transport/chttp2/transport/stream_lists.c
+++ b/src/core/ext/transport/chttp2/transport/stream_lists.c
@@ -35,27 +35,6 @@
 
 #include <grpc/support/log.h>
 
-#define TRANSPORT_FROM_GLOBAL(tg)                                         \
-  ((grpc_chttp2_transport *)((char *)(tg)-offsetof(grpc_chttp2_transport, \
-                                                   global)))
-
-#define STREAM_FROM_GLOBAL(sg) \
-  ((grpc_chttp2_stream *)((char *)(sg)-offsetof(grpc_chttp2_stream, global)))
-
-#define TRANSPORT_FROM_WRITING(tw)                                        \
-  ((grpc_chttp2_transport *)((char *)(tw)-offsetof(grpc_chttp2_transport, \
-                                                   writing)))
-
-#define STREAM_FROM_WRITING(sw) \
-  ((grpc_chttp2_stream *)((char *)(sw)-offsetof(grpc_chttp2_stream, writing)))
-
-#define TRANSPORT_FROM_PARSING(tp)                                        \
-  ((grpc_chttp2_transport *)((char *)(tp)-offsetof(grpc_chttp2_transport, \
-                                                   parsing)))
-
-#define STREAM_FROM_PARSING(sp) \
-  ((grpc_chttp2_stream *)((char *)(sp)-offsetof(grpc_chttp2_stream, parsing)))
-
 /* core list management */
 
 static int stream_list_empty(grpc_chttp2_transport *t,
@@ -139,314 +118,57 @@ static bool stream_list_add(grpc_chttp2_transport *t, grpc_chttp2_stream *s,
 
 /* wrappers for specializations */
 
-bool grpc_chttp2_list_add_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  GPR_ASSERT(stream_global->id != 0);
-  return stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                         STREAM_FROM_GLOBAL(stream_global),
-                         GRPC_CHTTP2_LIST_WRITABLE);
-}
-
-int grpc_chttp2_list_pop_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_writing **stream_writing) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_WRITABLE);
-  if (r != 0) {
-    *stream_global = &stream->global;
-    *stream_writing = &stream->writing;
-  }
-  return r;
-}
-
-bool grpc_chttp2_list_remove_writable_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  return stream_list_maybe_remove(TRANSPORT_FROM_GLOBAL(transport_global),
-                                  STREAM_FROM_GLOBAL(stream_global),
-                                  GRPC_CHTTP2_LIST_WRITABLE);
-}
-
-void grpc_chttp2_list_add_writing_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing) {
-  GPR_ASSERT(stream_list_add(TRANSPORT_FROM_WRITING(transport_writing),
-                             STREAM_FROM_WRITING(stream_writing),
-                             GRPC_CHTTP2_LIST_WRITING));
-}
-
-int grpc_chttp2_list_have_writing_streams(
-    grpc_chttp2_transport_writing *transport_writing) {
-  return !stream_list_empty(TRANSPORT_FROM_WRITING(transport_writing),
-                            GRPC_CHTTP2_LIST_WRITING);
+bool grpc_chttp2_list_add_writable_stream(grpc_chttp2_transport *t,
+                                          grpc_chttp2_stream *s) {
+  GPR_ASSERT(s->id != 0);
+  return stream_list_add(t, s, GRPC_CHTTP2_LIST_WRITABLE);
 }
 
-int grpc_chttp2_list_pop_writing_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing **stream_writing) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_WRITING(transport_writing), &stream,
-                          GRPC_CHTTP2_LIST_WRITING);
-  if (r != 0) {
-    *stream_writing = &stream->writing;
-  }
-  return r;
-}
-
-void grpc_chttp2_list_add_written_stream(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing) {
-  stream_list_add(TRANSPORT_FROM_WRITING(transport_writing),
-                  STREAM_FROM_WRITING(stream_writing),
-                  GRPC_CHTTP2_LIST_WRITTEN);
+int grpc_chttp2_list_pop_writable_stream(grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream **s) {
+  return stream_list_pop(t, s, GRPC_CHTTP2_LIST_WRITABLE);
 }
 
-int grpc_chttp2_list_pop_written_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_writing **stream_writing) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_WRITING(transport_writing), &stream,
-                          GRPC_CHTTP2_LIST_WRITTEN);
-  if (r != 0) {
-    *stream_global = &stream->global;
-    *stream_writing = &stream->writing;
-  }
-  return r;
+bool grpc_chttp2_list_remove_writable_stream(grpc_chttp2_transport *t,
+                                             grpc_chttp2_stream *s) {
+  return stream_list_maybe_remove(t, s, GRPC_CHTTP2_LIST_WRITABLE);
 }
 
-void grpc_chttp2_list_add_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  GPR_ASSERT(stream_global->id != 0);
-  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                  STREAM_FROM_GLOBAL(stream_global),
-                  GRPC_CHTTP2_LIST_UNANNOUNCED_INCOMING_WINDOW_AVAILABLE);
+bool grpc_chttp2_list_add_writing_stream(grpc_chttp2_transport *t,
+                                         grpc_chttp2_stream *s) {
+  return stream_list_add(t, s, GRPC_CHTTP2_LIST_WRITING);
 }
 
-void grpc_chttp2_list_remove_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_maybe_remove(
-      TRANSPORT_FROM_GLOBAL(transport_global),
-      STREAM_FROM_GLOBAL(stream_global),
-      GRPC_CHTTP2_LIST_UNANNOUNCED_INCOMING_WINDOW_AVAILABLE);
+int grpc_chttp2_list_have_writing_streams(grpc_chttp2_transport *t) {
+  return !stream_list_empty(t, GRPC_CHTTP2_LIST_WRITING);
 }
 
-int grpc_chttp2_list_pop_unannounced_incoming_window_available(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_parsing **stream_parsing) {
-  grpc_chttp2_stream *stream;
-  int r =
-      stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                      GRPC_CHTTP2_LIST_UNANNOUNCED_INCOMING_WINDOW_AVAILABLE);
-  if (r != 0) {
-    *stream_global = &stream->global;
-    *stream_parsing = &stream->parsing;
-  }
-  return r;
+int grpc_chttp2_list_pop_writing_stream(grpc_chttp2_transport *t,
+                                        grpc_chttp2_stream **s) {
+  return stream_list_pop(t, s, GRPC_CHTTP2_LIST_WRITING);
 }
 
-void grpc_chttp2_list_add_parsing_seen_stream(
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_parsing *stream_parsing) {
-  stream_list_add(TRANSPORT_FROM_PARSING(transport_parsing),
-                  STREAM_FROM_PARSING(stream_parsing),
-                  GRPC_CHTTP2_LIST_PARSING_SEEN);
+void grpc_chttp2_list_add_waiting_for_concurrency(grpc_chttp2_transport *t,
+                                                  grpc_chttp2_stream *s) {
+  stream_list_add(t, s, GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY);
 }
 
-int grpc_chttp2_list_pop_parsing_seen_stream(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_parsing *transport_parsing,
-    grpc_chttp2_stream_global **stream_global,
-    grpc_chttp2_stream_parsing **stream_parsing) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_PARSING(transport_parsing), &stream,
-                          GRPC_CHTTP2_LIST_PARSING_SEEN);
-  if (r != 0) {
-    *stream_global = &stream->global;
-    *stream_parsing = &stream->parsing;
-  }
-  return r;
+int grpc_chttp2_list_pop_waiting_for_concurrency(grpc_chttp2_transport *t,
+                                                 grpc_chttp2_stream **s) {
+  return stream_list_pop(t, s, GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY);
 }
 
-void grpc_chttp2_list_add_waiting_for_concurrency(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                  STREAM_FROM_GLOBAL(stream_global),
-                  GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY);
+void grpc_chttp2_list_add_stalled_by_transport(grpc_chttp2_transport *t,
+                                               grpc_chttp2_stream *s) {
+  stream_list_add(t, s, GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
 }
 
-int grpc_chttp2_list_pop_waiting_for_concurrency(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY);
-  if (r != 0) {
-    *stream_global = &stream->global;
-  }
-  return r;
+int grpc_chttp2_list_pop_stalled_by_transport(grpc_chttp2_transport *t,
+                                              grpc_chttp2_stream **s) {
+  return stream_list_pop(t, s, GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
 }
 
-void grpc_chttp2_list_add_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                  STREAM_FROM_GLOBAL(stream_global),
-                  GRPC_CHTTP2_LIST_CHECK_READ_OPS);
-}
-
-bool grpc_chttp2_list_remove_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  return stream_list_maybe_remove(TRANSPORT_FROM_GLOBAL(transport_global),
-                                  STREAM_FROM_GLOBAL(stream_global),
-                                  GRPC_CHTTP2_LIST_CHECK_READ_OPS);
-}
-
-int grpc_chttp2_list_pop_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_CHECK_READ_OPS);
-  if (r != 0) {
-    *stream_global = &stream->global;
-  }
-  return r;
-}
-
-void grpc_chttp2_list_add_writing_stalled_by_transport(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing) {
-  grpc_chttp2_stream *stream = STREAM_FROM_WRITING(stream_writing);
-  gpr_log(GPR_DEBUG, "writing stalled %d", stream->global.id);
-  if (!stream->included[GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT]) {
-    GRPC_CHTTP2_STREAM_REF(&stream->global, "chttp2_writing_stalled");
-  }
-  stream_list_add(TRANSPORT_FROM_WRITING(transport_writing), stream,
-                  GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT);
-}
-
-bool grpc_chttp2_list_flush_writing_stalled_by_transport(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_writing *transport_writing) {
-  grpc_chttp2_stream *stream;
-  bool out = false;
-  grpc_chttp2_transport *transport = TRANSPORT_FROM_WRITING(transport_writing);
-  while (stream_list_pop(transport, &stream,
-                         GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT)) {
-    gpr_log(GPR_DEBUG, "move %d from writing stalled to just stalled",
-            stream->global.id);
-    grpc_chttp2_list_add_stalled_by_transport(transport_writing,
-                                              &stream->writing);
-    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, &stream->global,
-                             "chttp2_writing_stalled");
-    out = true;
-  }
-  return out;
-}
-
-void grpc_chttp2_list_add_stalled_by_transport(
-    grpc_chttp2_transport_writing *transport_writing,
-    grpc_chttp2_stream_writing *stream_writing) {
-  gpr_log(GPR_DEBUG, "stalled %d", stream_writing->id);
-  stream_list_add(TRANSPORT_FROM_WRITING(transport_writing),
-                  STREAM_FROM_WRITING(stream_writing),
-                  GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
-}
-
-int grpc_chttp2_list_pop_stalled_by_transport(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
-  if (r != 0) {
-    *stream_global = &stream->global;
-  }
-  return r;
-}
-
-void grpc_chttp2_list_remove_stalled_by_transport(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_maybe_remove(TRANSPORT_FROM_GLOBAL(transport_global),
-                           STREAM_FROM_GLOBAL(stream_global),
-                           GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
-}
-
-void grpc_chttp2_list_add_closed_waiting_for_parsing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                  STREAM_FROM_GLOBAL(stream_global),
-                  GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING);
-}
-
-int grpc_chttp2_list_pop_closed_waiting_for_parsing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING);
-  if (r != 0) {
-    *stream_global = &stream->global;
-  }
-  return r;
-}
-
-void grpc_chttp2_list_add_closed_waiting_for_writing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global *stream_global) {
-  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
-                  STREAM_FROM_GLOBAL(stream_global),
-                  GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_WRITING);
-}
-
-int grpc_chttp2_list_pop_closed_waiting_for_writing(
-    grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
-  grpc_chttp2_stream *stream;
-  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
-                          GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_WRITING);
-  if (r != 0) {
-    *stream_global = &stream->global;
-  }
-  return r;
-}
-
-void grpc_chttp2_register_stream(grpc_chttp2_transport *t,
-                                 grpc_chttp2_stream *s) {
-  stream_list_add_tail(t, s, GRPC_CHTTP2_LIST_ALL_STREAMS);
-}
-
-int grpc_chttp2_unregister_stream(grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s) {
-  stream_list_maybe_remove(t, s, GRPC_CHTTP2_LIST_ALL_STREAMS);
-  return stream_list_empty(t, GRPC_CHTTP2_LIST_ALL_STREAMS);
-}
-
-int grpc_chttp2_has_streams(grpc_chttp2_transport *t) {
-  return !stream_list_empty(t, GRPC_CHTTP2_LIST_ALL_STREAMS);
-}
-
-void grpc_chttp2_for_all_streams(
-    grpc_chttp2_transport_global *transport_global, void *user_data,
-    void (*cb)(grpc_chttp2_transport_global *transport_global, void *user_data,
-               grpc_chttp2_stream_global *stream_global)) {
-  grpc_chttp2_stream *s;
-  grpc_chttp2_transport *t = TRANSPORT_FROM_GLOBAL(transport_global);
-  for (s = t->lists[GRPC_CHTTP2_LIST_ALL_STREAMS].head; s != NULL;
-       s = s->links[GRPC_CHTTP2_LIST_ALL_STREAMS].next) {
-    cb(transport_global, user_data, &s->global);
-  }
+void grpc_chttp2_list_remove_stalled_by_transport(grpc_chttp2_transport *t,
+                                                  grpc_chttp2_stream *s) {
+  stream_list_maybe_remove(t, s, GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
 }
diff --git a/src/core/ext/transport/chttp2/transport/stream_map.c b/src/core/ext/transport/chttp2/transport/stream_map.c
index f70791c422..59b3a14e0a 100644
--- a/src/core/ext/transport/chttp2/transport/stream_map.c
+++ b/src/core/ext/transport/chttp2/transport/stream_map.c
@@ -77,6 +77,7 @@ void grpc_chttp2_stream_map_add(grpc_chttp2_stream_map *map, uint32_t key,
 
   GPR_ASSERT(count == 0 || keys[count - 1] < key);
   GPR_ASSERT(value);
+  GPR_ASSERT(grpc_chttp2_stream_map_find(map, key) == NULL);
 
   if (count == capacity) {
     if (map->free > capacity / 4) {
@@ -96,40 +97,6 @@ void grpc_chttp2_stream_map_add(grpc_chttp2_stream_map *map, uint32_t key,
   map->count = count + 1;
 }
 
-void grpc_chttp2_stream_map_move_into(grpc_chttp2_stream_map *src,
-                                      grpc_chttp2_stream_map *dst) {
-  /* if src is empty we dont need to do anything */
-  if (src->count == src->free) {
-    return;
-  }
-  /* if dst is empty we simply need to swap */
-  if (dst->count == dst->free) {
-    GPR_SWAP(grpc_chttp2_stream_map, *src, *dst);
-    return;
-  }
-  /* the first element of src must be greater than the last of dst...
-   * however the maps may need compacting for this property to hold */
-  if (src->keys[0] <= dst->keys[dst->count - 1]) {
-    src->count = compact(src->keys, src->values, src->count);
-    src->free = 0;
-    dst->count = compact(dst->keys, dst->values, dst->count);
-    dst->free = 0;
-  }
-  GPR_ASSERT(src->keys[0] > dst->keys[dst->count - 1]);
-  /* if dst doesn't have capacity, resize */
-  if (dst->count + src->count > dst->capacity) {
-    dst->capacity = GPR_MAX(dst->capacity * 3 / 2, dst->count + src->count);
-    dst->keys = gpr_realloc(dst->keys, dst->capacity * sizeof(uint32_t));
-    dst->values = gpr_realloc(dst->values, dst->capacity * sizeof(void *));
-  }
-  memcpy(dst->keys + dst->count, src->keys, src->count * sizeof(uint32_t));
-  memcpy(dst->values + dst->count, src->values, src->count * sizeof(void *));
-  dst->count += src->count;
-  dst->free += src->free;
-  src->count = 0;
-  src->free = 0;
-}
-
 static void **find(grpc_chttp2_stream_map *map, uint32_t key) {
   size_t min_idx = 0;
   size_t max_idx = map->count;
@@ -170,6 +137,7 @@ void *grpc_chttp2_stream_map_delete(grpc_chttp2_stream_map *map, uint32_t key) {
     if (map->free == map->count) {
       map->free = map->count = 0;
     }
+    GPR_ASSERT(grpc_chttp2_stream_map_find(map, key) == NULL);
   }
   return out;
 }
diff --git a/src/core/ext/transport/chttp2/transport/stream_map.h b/src/core/ext/transport/chttp2/transport/stream_map.h
index b1d59ca6a3..e76312dd1a 100644
--- a/src/core/ext/transport/chttp2/transport/stream_map.h
+++ b/src/core/ext/transport/chttp2/transport/stream_map.h
@@ -65,10 +65,6 @@ void grpc_chttp2_stream_map_add(grpc_chttp2_stream_map *map, uint32_t key,
    or NULL otherwise */
 void *grpc_chttp2_stream_map_delete(grpc_chttp2_stream_map *map, uint32_t key);
 
-/* Move all elements of src into dst */
-void grpc_chttp2_stream_map_move_into(grpc_chttp2_stream_map *src,
-                                      grpc_chttp2_stream_map *dst);
-
 /* Return an existing key, or NULL if it does not exist */
 void *grpc_chttp2_stream_map_find(grpc_chttp2_stream_map *map, uint32_t key);
 
diff --git a/src/core/ext/transport/chttp2/transport/writing.c b/src/core/ext/transport/chttp2/transport/writing.c
index 311b26e354..bc490569b7 100644
--- a/src/core/ext/transport/chttp2/transport/writing.c
+++ b/src/core/ext/transport/chttp2/transport/writing.c
@@ -40,346 +40,215 @@
 #include "src/core/ext/transport/chttp2/transport/http2_errors.h"
 #include "src/core/lib/profiling/timers.h"
 
-static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
-                            grpc_chttp2_transport_writing *transport_writing);
+static void add_to_write_list(grpc_chttp2_write_cb **list,
+                              grpc_chttp2_write_cb *cb) {
+  cb->next = *list;
+  *list = cb;
+}
 
-int grpc_chttp2_unlocking_check_writes(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing) {
-  grpc_chttp2_stream_global *stream_global;
-  grpc_chttp2_stream_writing *stream_writing;
+static void finish_write_cb(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                            grpc_chttp2_stream *s, grpc_chttp2_write_cb *cb,
+                            grpc_error *error) {
+  grpc_chttp2_complete_closure_step(exec_ctx, t, s, &cb->closure, error,
+                                    "finish_write_cb");
+  cb->next = t->write_cb_pool;
+  t->write_cb_pool = cb;
+}
 
-  GPR_TIMER_BEGIN("grpc_chttp2_unlocking_check_writes", 0);
+static void update_list(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                        grpc_chttp2_stream *s, size_t send_bytes,
+                        grpc_chttp2_write_cb **list, grpc_error *error) {
+  grpc_chttp2_write_cb *cb = *list;
+  *list = NULL;
+  while (cb) {
+    grpc_chttp2_write_cb *next = cb->next;
+    if (cb->call_at_byte <= send_bytes) {
+      finish_write_cb(exec_ctx, t, s, cb, GRPC_ERROR_REF(error));
+    } else {
+      cb->call_at_byte -= send_bytes;
+      add_to_write_list(list, cb);
+    }
+    cb = next;
+  }
+}
 
-  transport_writing->max_frame_size =
-      transport_global->settings[GRPC_ACKED_SETTINGS]
-                                [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE];
+bool grpc_chttp2_begin_write(grpc_exec_ctx *exec_ctx,
+                             grpc_chttp2_transport *t) {
+  grpc_chttp2_stream *s;
 
-  /* simple writes are queued to qbuf, and flushed here */
-  gpr_slice_buffer_swap(&transport_global->qbuf, &transport_writing->outbuf);
-  GPR_ASSERT(transport_global->qbuf.count == 0);
+  GPR_TIMER_BEGIN("grpc_chttp2_begin_write", 0);
 
-  grpc_chttp2_hpack_compressor_set_max_table_size(
-      &transport_writing->hpack_compressor,
-      transport_global->settings[GRPC_PEER_SETTINGS]
-                                [GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
-
-  if (transport_global->dirtied_local_settings &&
-      !transport_global->sent_local_settings) {
+  if (t->dirtied_local_settings && !t->sent_local_settings) {
     gpr_slice_buffer_add(
-        &transport_writing->outbuf,
+        &t->outbuf,
         grpc_chttp2_settings_create(
-            transport_global->settings[GRPC_SENT_SETTINGS],
-            transport_global->settings[GRPC_LOCAL_SETTINGS],
-            transport_global->force_send_settings, GRPC_CHTTP2_NUM_SETTINGS));
-    transport_global->force_send_settings = 0;
-    transport_global->dirtied_local_settings = 0;
-    transport_global->sent_local_settings = 1;
+            t->settings[GRPC_SENT_SETTINGS], t->settings[GRPC_LOCAL_SETTINGS],
+            t->force_send_settings, GRPC_CHTTP2_NUM_SETTINGS));
+    t->force_send_settings = 0;
+    t->dirtied_local_settings = 0;
+    t->sent_local_settings = 1;
   }
 
-  GRPC_CHTTP2_FLOW_MOVE_TRANSPORT("write", transport_writing, outgoing_window,
-                                  transport_global, outgoing_window);
-  if (transport_writing->outgoing_window > 0) {
-    while (grpc_chttp2_list_pop_stalled_by_transport(transport_global,
-                                                     &stream_global)) {
-      grpc_chttp2_become_writable(exec_ctx, transport_global, stream_global,
-                                  false, "transport.read_flow_control");
+  /* simple writes are queued to qbuf, and flushed here */
+  gpr_slice_buffer_move_into(&t->qbuf, &t->outbuf);
+  GPR_ASSERT(t->qbuf.count == 0);
+
+  grpc_chttp2_hpack_compressor_set_max_table_size(
+      &t->hpack_compressor,
+      t->settings[GRPC_PEER_SETTINGS][GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
+
+  if (t->outgoing_window > 0) {
+    while (grpc_chttp2_list_pop_stalled_by_transport(t, &s)) {
+      grpc_chttp2_become_writable(exec_ctx, t, s, false,
+                                  "transport.read_flow_control");
     }
   }
 
   /* for each grpc_chttp2_stream that's become writable, frame it's data
      (according to available window sizes) and add to the output buffer */
-  while (grpc_chttp2_list_pop_writable_stream(
-      transport_global, transport_writing, &stream_global, &stream_writing)) {
-    bool sent_initial_metadata = stream_writing->sent_initial_metadata;
-    bool become_writable = false;
-
-    stream_writing->id = stream_global->id;
-    stream_writing->read_closed = stream_global->read_closed;
+  while (grpc_chttp2_list_pop_writable_stream(t, &s)) {
+    bool sent_initial_metadata = s->sent_initial_metadata;
+    bool now_writing = false;
 
-    GRPC_CHTTP2_FLOW_MOVE_STREAM("write", transport_writing, stream_writing,
-                                 outgoing_window, stream_global,
-                                 outgoing_window);
+    GRPC_CHTTP2_IF_TRACING(gpr_log(
+        GPR_DEBUG, "W:%p %s[%d] im-(sent,send)=(%d,%d) announce=%d", t,
+        t->is_client ? "CLIENT" : "SERVER", s->id, sent_initial_metadata,
+        s->send_initial_metadata != NULL, s->announce_window));
 
-    if (!sent_initial_metadata && stream_global->send_initial_metadata) {
-      stream_writing->send_initial_metadata =
-          stream_global->send_initial_metadata;
-      stream_global->send_initial_metadata = NULL;
-      become_writable = true;
+    /* send initial metadata if it's available */
+    if (!sent_initial_metadata && s->send_initial_metadata) {
+      grpc_chttp2_encode_header(
+          &t->hpack_compressor, s->id, s->send_initial_metadata, 0,
+          t->settings[GRPC_ACKED_SETTINGS][GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
+          &s->stats.outgoing, &t->outbuf);
+      s->send_initial_metadata = NULL;
+      s->sent_initial_metadata = true;
       sent_initial_metadata = true;
+      now_writing = true;
+    }
+    /* send any window updates */
+    if (s->announce_window > 0) {
+      uint32_t announce = s->announce_window;
+      gpr_slice_buffer_add(&t->outbuf,
+                           grpc_chttp2_window_update_create(
+                               s->id, s->announce_window, &s->stats.outgoing));
+      GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", t, s, announce_window, announce);
     }
     if (sent_initial_metadata) {
-      if (stream_global->send_message != NULL) {
-        gpr_slice hdr = gpr_slice_malloc(5);
-        uint8_t *p = GPR_SLICE_START_PTR(hdr);
-        uint32_t len = stream_global->send_message->length;
-        GPR_ASSERT(stream_writing->send_message == NULL);
-        p[0] = (stream_global->send_message->flags &
-                GRPC_WRITE_INTERNAL_COMPRESS) != 0;
-        p[1] = (uint8_t)(len >> 24);
-        p[2] = (uint8_t)(len >> 16);
-        p[3] = (uint8_t)(len >> 8);
-        p[4] = (uint8_t)(len);
-        gpr_slice_buffer_add(&stream_writing->flow_controlled_buffer, hdr);
-        if (stream_global->send_message->length > 0) {
-          stream_writing->send_message = stream_global->send_message;
-        } else {
-          stream_writing->send_message = NULL;
+      /* send any body bytes, if allowed by flow control */
+      if (s->flow_controlled_buffer.length > 0) {
+        uint32_t max_outgoing =
+            (uint32_t)GPR_MIN(t->settings[GRPC_ACKED_SETTINGS]
+                                         [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
+                              GPR_MIN(s->outgoing_window, t->outgoing_window));
+        if (max_outgoing > 0) {
+          uint32_t send_bytes =
+              (uint32_t)GPR_MIN(max_outgoing, s->flow_controlled_buffer.length);
+          bool is_last_data_frame =
+              s->fetching_send_message == NULL &&
+              send_bytes == s->flow_controlled_buffer.length;
+          bool is_last_frame =
+              is_last_data_frame && s->send_trailing_metadata != NULL &&
+              grpc_metadata_batch_is_empty(s->send_trailing_metadata);
+          grpc_chttp2_encode_data(s->id, &s->flow_controlled_buffer, send_bytes,
+                                  is_last_frame, &s->stats.outgoing,
+                                  &t->outbuf);
+          GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", t, s, outgoing_window,
+                                        send_bytes);
+          GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("write", t, outgoing_window,
+                                           send_bytes);
+          if (is_last_frame) {
+            s->send_trailing_metadata = NULL;
+            s->sent_trailing_metadata = true;
+            if (!t->is_client && !s->read_closed) {
+              gpr_slice_buffer_add(&t->outbuf, grpc_chttp2_rst_stream_create(
+                                                   s->id, GRPC_CHTTP2_NO_ERROR,
+                                                   &s->stats.outgoing));
+            }
+          }
+          s->sending_bytes += send_bytes;
+          now_writing = true;
+          if (s->flow_controlled_buffer.length > 0) {
+            GRPC_CHTTP2_STREAM_REF(s, "chttp2_writing:fork");
+            grpc_chttp2_list_add_writable_stream(t, s);
+          }
+        } else if (t->outgoing_window == 0) {
+          grpc_chttp2_list_add_stalled_by_transport(t, s);
+          now_writing = true;
         }
-        stream_writing->stream_fetched = 0;
-        stream_global->send_message = NULL;
       }
-      if ((stream_writing->send_message != NULL ||
-           stream_writing->flow_controlled_buffer.length > 0) &&
-          stream_writing->outgoing_window > 0) {
-        if (transport_writing->outgoing_window > 0) {
-          become_writable = true;
-        } else {
-          grpc_chttp2_list_add_stalled_by_transport(transport_writing,
-                                                    stream_writing);
+      if (s->send_trailing_metadata != NULL &&
+          s->fetching_send_message == NULL &&
+          s->flow_controlled_buffer.length == 0) {
+        grpc_chttp2_encode_header(
+            &t->hpack_compressor, s->id, s->send_trailing_metadata, true,
+            t->settings[GRPC_ACKED_SETTINGS]
+                       [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
+            &s->stats.outgoing, &t->outbuf);
+        s->send_trailing_metadata = NULL;
+        s->sent_trailing_metadata = true;
+        if (!t->is_client && !s->read_closed) {
+          gpr_slice_buffer_add(
+              &t->outbuf, grpc_chttp2_rst_stream_create(
+                              s->id, GRPC_CHTTP2_NO_ERROR, &s->stats.outgoing));
         }
+        now_writing = true;
       }
-      if (stream_global->send_trailing_metadata) {
-        stream_writing->send_trailing_metadata =
-            stream_global->send_trailing_metadata;
-        stream_global->send_trailing_metadata = NULL;
-        become_writable = true;
-      }
-    }
-
-    if (!stream_global->read_closed &&
-        stream_global->unannounced_incoming_window_for_writing > 1024) {
-      GRPC_CHTTP2_FLOW_MOVE_STREAM("write", transport_global, stream_writing,
-                                   announce_window, stream_global,
-                                   unannounced_incoming_window_for_writing);
-      become_writable = true;
     }
 
-    if (become_writable) {
-      grpc_chttp2_list_add_writing_stream(transport_writing, stream_writing);
+    if (now_writing) {
+      if (!grpc_chttp2_list_add_writing_stream(t, s)) {
+        /* already in writing list: drop ref */
+        GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:already_writing");
+      }
     } else {
-      GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2_writing");
+      GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:no_write");
     }
   }
 
   /* if the grpc_chttp2_transport is ready to send a window update, do so here
      also; 3/4 is a magic number that will likely get tuned soon */
-  if (transport_global->announce_incoming_window > 0) {
-    uint32_t announced = (uint32_t)GPR_MIN(
-        transport_global->announce_incoming_window, UINT32_MAX);
-    GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("write", transport_global,
-                                     announce_incoming_window, announced);
+  if (t->announce_incoming_window > 0) {
+    uint32_t announced =
+        (uint32_t)GPR_MIN(t->announce_incoming_window, UINT32_MAX);
+    GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("write", t, announce_incoming_window,
+                                     announced);
     grpc_transport_one_way_stats throwaway_stats;
-    gpr_slice_buffer_add(
-        &transport_writing->outbuf,
-        grpc_chttp2_window_update_create(0, announced, &throwaway_stats));
-  }
-
-  GPR_TIMER_END("grpc_chttp2_unlocking_check_writes", 0);
-
-  return transport_writing->outbuf.count > 0 ||
-         grpc_chttp2_list_have_writing_streams(transport_writing);
-}
-
-void grpc_chttp2_perform_writes(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_writing *transport_writing,
-    grpc_endpoint *endpoint) {
-  GPR_ASSERT(transport_writing->outbuf.count > 0 ||
-             grpc_chttp2_list_have_writing_streams(transport_writing));
-
-  finalize_outbuf(exec_ctx, transport_writing);
-
-  GPR_ASSERT(endpoint);
-
-  if (transport_writing->outbuf.count > 0) {
-    grpc_endpoint_write(exec_ctx, endpoint, &transport_writing->outbuf,
-                        &transport_writing->done_cb);
-  } else {
-    grpc_exec_ctx_sched(exec_ctx, &transport_writing->done_cb, GRPC_ERROR_NONE,
-                        NULL);
+    gpr_slice_buffer_add(&t->outbuf, grpc_chttp2_window_update_create(
+                                         0, announced, &throwaway_stats));
   }
-}
-
-static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
-                            grpc_chttp2_transport_writing *transport_writing) {
-  grpc_chttp2_stream_writing *stream_writing;
 
-  GPR_TIMER_BEGIN("finalize_outbuf", 0);
-
-  bool is_first_data_frame = true;
-  while (
-      grpc_chttp2_list_pop_writing_stream(transport_writing, &stream_writing)) {
-    uint32_t max_outgoing =
-        (uint32_t)GPR_MIN(transport_writing->max_frame_size,
-                          GPR_MIN(stream_writing->outgoing_window,
-                                  transport_writing->outgoing_window));
-    /* send initial metadata if it's available */
-    if (stream_writing->send_initial_metadata != NULL) {
-      grpc_chttp2_encode_header(
-          &transport_writing->hpack_compressor, stream_writing->id,
-          stream_writing->send_initial_metadata, 0,
-          transport_writing->max_frame_size, &stream_writing->stats,
-          &transport_writing->outbuf);
-      stream_writing->send_initial_metadata = NULL;
-      stream_writing->sent_initial_metadata = 1;
-    }
-    /* send any window updates */
-    if (stream_writing->announce_window > 0 &&
-        stream_writing->send_initial_metadata == NULL) {
-      uint32_t announce = stream_writing->announce_window;
-      gpr_slice_buffer_add(
-          &transport_writing->outbuf,
-          grpc_chttp2_window_update_create(stream_writing->id,
-                                           stream_writing->announce_window,
-                                           &stream_writing->stats));
-      GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", transport_writing, stream_writing,
-                                    announce_window, announce);
-      stream_writing->announce_window = 0;
-    }
-    /* fetch any body bytes */
-    while (!stream_writing->fetching && stream_writing->send_message &&
-           stream_writing->flow_controlled_buffer.length < max_outgoing &&
-           stream_writing->stream_fetched <
-               stream_writing->send_message->length) {
-      if (grpc_byte_stream_next(exec_ctx, stream_writing->send_message,
-                                &stream_writing->fetching_slice, max_outgoing,
-                                &stream_writing->finished_fetch)) {
-        stream_writing->stream_fetched +=
-            GPR_SLICE_LENGTH(stream_writing->fetching_slice);
-        if (stream_writing->stream_fetched ==
-            stream_writing->send_message->length) {
-          stream_writing->send_message = NULL;
-        }
-        gpr_slice_buffer_add(&stream_writing->flow_controlled_buffer,
-                             stream_writing->fetching_slice);
-      } else {
-        stream_writing->fetching = 1;
-      }
-    }
-    /* send any body bytes */
-    if (stream_writing->flow_controlled_buffer.length > 0) {
-      if (max_outgoing > 0) {
-        uint32_t send_bytes = (uint32_t)GPR_MIN(
-            max_outgoing, stream_writing->flow_controlled_buffer.length);
-        int is_last_data_frame =
-            stream_writing->send_message == NULL &&
-            send_bytes == stream_writing->flow_controlled_buffer.length;
-        int is_last_frame = is_last_data_frame &&
-                            stream_writing->send_trailing_metadata != NULL &&
-                            grpc_metadata_batch_is_empty(
-                                stream_writing->send_trailing_metadata);
-        grpc_chttp2_encode_data(
-            stream_writing->id, &stream_writing->flow_controlled_buffer,
-            send_bytes, is_last_frame, &stream_writing->stats,
-            &transport_writing->outbuf);
-        if (is_first_data_frame) {
-          /* TODO(dgq): this is a hack. It'll be fix in a future refactoring */
-          stream_writing->stats.data_bytes -= 5; /* discount grpc framing */
-          is_first_data_frame = false;
-        }
-        GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", transport_writing,
-                                      stream_writing, outgoing_window,
-                                      send_bytes);
-        GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("write", transport_writing,
-                                         outgoing_window, send_bytes);
-        if (is_last_frame) {
-          stream_writing->send_trailing_metadata = NULL;
-          stream_writing->sent_trailing_metadata = 1;
-        }
-        if (is_last_data_frame) {
-          GPR_ASSERT(stream_writing->send_message == NULL);
-          stream_writing->sent_message = 1;
-        }
-      } else if (transport_writing->outgoing_window == 0) {
-        grpc_chttp2_list_add_writing_stalled_by_transport(transport_writing,
-                                                          stream_writing);
-        grpc_chttp2_list_add_written_stream(transport_writing, stream_writing);
-      }
-    }
-    /* send trailing metadata if it's available and we're ready for it */
-    if (stream_writing->send_message == NULL &&
-        stream_writing->flow_controlled_buffer.length == 0 &&
-        stream_writing->send_trailing_metadata != NULL) {
-      if (grpc_metadata_batch_is_empty(
-              stream_writing->send_trailing_metadata)) {
-        grpc_chttp2_encode_data(
-            stream_writing->id, &stream_writing->flow_controlled_buffer, 0, 1,
-            &stream_writing->stats, &transport_writing->outbuf);
-      } else {
-        grpc_chttp2_encode_header(
-            &transport_writing->hpack_compressor, stream_writing->id,
-            stream_writing->send_trailing_metadata, 1,
-            transport_writing->max_frame_size, &stream_writing->stats,
-            &transport_writing->outbuf);
-      }
-      if (!transport_writing->is_client && !stream_writing->read_closed) {
-        gpr_slice_buffer_add(&transport_writing->outbuf,
-                             grpc_chttp2_rst_stream_create(
-                                 stream_writing->id, GRPC_CHTTP2_NO_ERROR,
-                                 &stream_writing->stats));
-      }
-      stream_writing->send_trailing_metadata = NULL;
-      stream_writing->sent_trailing_metadata = 1;
-    }
-    /* if there's more to write, then loop, otherwise prepare to finish the
-     * write */
-    if ((stream_writing->flow_controlled_buffer.length > 0 ||
-         (stream_writing->send_message && !stream_writing->fetching)) &&
-        stream_writing->outgoing_window > 0) {
-      if (transport_writing->outgoing_window > 0) {
-        grpc_chttp2_list_add_writing_stream(transport_writing, stream_writing);
-      } else {
-        grpc_chttp2_list_add_writing_stalled_by_transport(transport_writing,
-                                                          stream_writing);
-        grpc_chttp2_list_add_written_stream(transport_writing, stream_writing);
-      }
-    } else {
-      grpc_chttp2_list_add_written_stream(transport_writing, stream_writing);
-    }
-  }
+  GPR_TIMER_END("grpc_chttp2_begin_write", 0);
 
-  GPR_TIMER_END("finalize_outbuf", 0);
+  return t->outbuf.count > 0;
 }
 
-void grpc_chttp2_cleanup_writing(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_transport_writing *transport_writing) {
-  grpc_chttp2_stream_writing *stream_writing;
-  grpc_chttp2_stream_global *stream_global;
+void grpc_chttp2_end_write(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
+                           grpc_error *error) {
+  GPR_TIMER_BEGIN("grpc_chttp2_end_write", 0);
+  grpc_chttp2_stream *s;
 
-  if (grpc_chttp2_list_flush_writing_stalled_by_transport(exec_ctx,
-                                                          transport_writing)) {
-    grpc_chttp2_initiate_write(exec_ctx, transport_global, false,
-                               "resume_stalled_stream");
-  }
-
-  while (grpc_chttp2_list_pop_written_stream(
-      transport_global, transport_writing, &stream_global, &stream_writing)) {
-    if (stream_writing->sent_initial_metadata) {
+  while (grpc_chttp2_list_pop_writing_stream(t, &s)) {
+    if (s->sent_initial_metadata) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, transport_global, stream_global,
-          &stream_global->send_initial_metadata_finished, GRPC_ERROR_NONE);
+          exec_ctx, t, s, &s->send_initial_metadata_finished,
+          GRPC_ERROR_REF(error), "send_initial_metadata_finished");
     }
-    grpc_transport_move_one_way_stats(&stream_writing->stats,
-                                      &stream_global->stats.outgoing);
-    if (stream_writing->sent_message) {
-      GPR_ASSERT(stream_writing->send_message == NULL);
-      grpc_chttp2_complete_closure_step(
-          exec_ctx, transport_global, stream_global,
-          &stream_global->send_message_finished, GRPC_ERROR_NONE);
-      stream_writing->sent_message = 0;
+    if (s->sending_bytes != 0) {
+      update_list(exec_ctx, t, s, s->sending_bytes, &s->on_write_finished_cbs,
+                  GRPC_ERROR_REF(error));
+      s->sending_bytes = 0;
     }
-    if (stream_writing->sent_trailing_metadata) {
+    if (s->sent_trailing_metadata) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, transport_global, stream_global,
-          &stream_global->send_trailing_metadata_finished, GRPC_ERROR_NONE);
-    }
-    if (stream_writing->sent_trailing_metadata) {
-      grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global,
-                                     !transport_global->is_client, 1,
-                                     GRPC_ERROR_NONE);
+          exec_ctx, t, s, &s->send_trailing_metadata_finished,
+          GRPC_ERROR_REF(error), "send_trailing_metadata_finished");
+      grpc_chttp2_mark_stream_closed(exec_ctx, t, s, !t->is_client, 1,
+                                     GRPC_ERROR_REF(error));
     }
-    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2_writing");
+    GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:end");
   }
-  gpr_slice_buffer_reset_and_unref(&transport_writing->outbuf);
+  gpr_slice_buffer_reset_and_unref(&t->outbuf);
+  GRPC_ERROR_UNREF(error);
+  GPR_TIMER_END("grpc_chttp2_end_write", 0);
 }
diff --git a/src/core/lib/channel/channel_args.c b/src/core/lib/channel/channel_args.c
index 79ceeb66b3..3a56b1ff20 100644
--- a/src/core/lib/channel/channel_args.c
+++ b/src/core/lib/channel/channel_args.c
@@ -271,3 +271,21 @@ int grpc_channel_args_compare(const grpc_channel_args *a,
   }
   return 0;
 }
+
+int grpc_channel_arg_get_integer(grpc_arg *arg, grpc_integer_options options) {
+  if (arg->type != GRPC_ARG_INTEGER) {
+    gpr_log(GPR_ERROR, "%s ignored: it must be an integer", arg->key);
+    return options.default_value;
+  }
+  if (arg->value.integer < options.min_value) {
+    gpr_log(GPR_ERROR, "%s ignored: it must be >= %d", arg->key,
+            options.min_value);
+    return options.default_value;
+  }
+  if (arg->value.integer > options.max_value) {
+    gpr_log(GPR_ERROR, "%s ignored: it must be <= %d", arg->key,
+            options.max_value);
+    return options.default_value;
+  }
+  return arg->value.integer;
+}
diff --git a/src/core/lib/channel/channel_args.h b/src/core/lib/channel/channel_args.h
index aec61ee7c6..586a296d1f 100644
--- a/src/core/lib/channel/channel_args.h
+++ b/src/core/lib/channel/channel_args.h
@@ -89,4 +89,12 @@ uint32_t grpc_channel_args_compression_algorithm_get_states(
 int grpc_channel_args_compare(const grpc_channel_args *a,
                               const grpc_channel_args *b);
 
+typedef struct grpc_integer_options {
+  int default_value;  // Return this if value is outside of expected bounds.
+  int min_value;
+  int max_value;
+} grpc_integer_options;
+/** Returns the value of \a arg, subject to the contraints in \a options. */
+int grpc_channel_arg_get_integer(grpc_arg *arg, grpc_integer_options options);
+
 #endif /* GRPC_CORE_LIB_CHANNEL_CHANNEL_ARGS_H */
diff --git a/src/core/lib/channel/channel_stack.c b/src/core/lib/channel/channel_stack.c
index 98f304f2da..0655b9353f 100644
--- a/src/core/lib/channel/channel_stack.c
+++ b/src/core/lib/channel/channel_stack.c
@@ -32,6 +32,7 @@
  */
 
 #include "src/core/lib/channel/channel_stack.h"
+#include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 
 #include <stdlib.h>
@@ -270,21 +271,27 @@ grpc_call_stack *grpc_call_stack_from_top_element(grpc_call_element *elem) {
       sizeof(grpc_call_stack)));
 }
 
+static void destroy_op(grpc_exec_ctx *exec_ctx, void *op, grpc_error *error) {
+  gpr_free(op);
+}
+
 void grpc_call_element_send_cancel(grpc_exec_ctx *exec_ctx,
                                    grpc_call_element *cur_elem) {
-  grpc_transport_stream_op op;
-  memset(&op, 0, sizeof(op));
-  op.cancel_error = GRPC_ERROR_CANCELLED;
-  grpc_call_next_op(exec_ctx, cur_elem, &op);
+  grpc_transport_stream_op *op = gpr_malloc(sizeof(*op));
+  memset(op, 0, sizeof(*op));
+  op->cancel_error = GRPC_ERROR_CANCELLED;
+  op->on_complete = grpc_closure_create(destroy_op, op);
+  grpc_call_next_op(exec_ctx, cur_elem, op);
 }
 
 void grpc_call_element_send_cancel_with_message(grpc_exec_ctx *exec_ctx,
                                                 grpc_call_element *cur_elem,
                                                 grpc_status_code status,
                                                 gpr_slice *optional_message) {
-  grpc_transport_stream_op op;
-  memset(&op, 0, sizeof(op));
-  grpc_transport_stream_op_add_cancellation_with_message(&op, status,
+  grpc_transport_stream_op *op = gpr_malloc(sizeof(*op));
+  memset(op, 0, sizeof(*op));
+  op->on_complete = grpc_closure_create(destroy_op, op);
+  grpc_transport_stream_op_add_cancellation_with_message(op, status,
                                                          optional_message);
-  grpc_call_next_op(exec_ctx, cur_elem, &op);
+  grpc_call_next_op(exec_ctx, cur_elem, op);
 }
diff --git a/src/core/lib/channel/compress_filter.c b/src/core/lib/channel/compress_filter.c
index 134180e619..0981d59f63 100644
--- a/src/core/lib/channel/compress_filter.c
+++ b/src/core/lib/channel/compress_filter.c
@@ -60,7 +60,7 @@ typedef struct call_data {
   /** If true, contents of \a compression_algorithm are authoritative */
   int has_compression_algorithm;
 
-  grpc_transport_stream_op send_op;
+  grpc_transport_stream_op *send_op;
   uint32_t send_length;
   uint32_t send_flags;
   gpr_slice incoming_slice;
@@ -199,11 +199,11 @@ static void finish_send_message(grpc_exec_ctx *exec_ctx,
 
   grpc_slice_buffer_stream_init(&calld->replacement_stream, &calld->slices,
                                 calld->send_flags);
-  calld->send_op.send_message = &calld->replacement_stream.base;
-  calld->post_send = calld->send_op.on_complete;
-  calld->send_op.on_complete = &calld->send_done;
+  calld->send_op->send_message = &calld->replacement_stream.base;
+  calld->post_send = calld->send_op->on_complete;
+  calld->send_op->on_complete = &calld->send_done;
 
-  grpc_call_next_op(exec_ctx, elem, &calld->send_op);
+  grpc_call_next_op(exec_ctx, elem, calld->send_op);
 }
 
 static void got_slice(grpc_exec_ctx *exec_ctx, void *elemp, grpc_error *error) {
@@ -220,7 +220,7 @@ static void got_slice(grpc_exec_ctx *exec_ctx, void *elemp, grpc_error *error) {
 static void continue_send_message(grpc_exec_ctx *exec_ctx,
                                   grpc_call_element *elem) {
   call_data *calld = elem->call_data;
-  while (grpc_byte_stream_next(exec_ctx, calld->send_op.send_message,
+  while (grpc_byte_stream_next(exec_ctx, calld->send_op->send_message,
                                &calld->incoming_slice, ~(size_t)0,
                                &calld->got_slice)) {
     gpr_slice_buffer_add(&calld->slices, calld->incoming_slice);
@@ -243,7 +243,7 @@ static void compress_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
   }
   if (op->send_message != NULL && !skip_compression(elem) &&
       0 == (op->send_message->flags & GRPC_WRITE_NO_COMPRESS)) {
-    calld->send_op = *op;
+    calld->send_op = op;
     calld->send_length = op->send_message->length;
     calld->send_flags = op->send_message->flags;
     continue_send_message(exec_ctx, elem);
diff --git a/src/core/lib/channel/message_size_filter.c b/src/core/lib/channel/message_size_filter.c
new file mode 100644
index 0000000000..6613785dea
--- /dev/null
+++ b/src/core/lib/channel/message_size_filter.c
@@ -0,0 +1,165 @@
+//
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+#include "src/core/lib/channel/message_size_filter.h"
+
+#include <limits.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/channel/channel_args.h"
+
+// The protobuf library will (by default) start warning at 100 megs.
+#define DEFAULT_MAX_MESSAGE_LENGTH (4 * 1024 * 1024)
+
+typedef struct call_data {
+  // Receive closures are chained: we inject this closure as the
+  // recv_message_ready up-call on transport_stream_op, and remember to
+  // call our next_recv_message_ready member after handling it.
+  grpc_closure recv_message_ready;
+  // Used by recv_message_ready.
+  grpc_byte_stream** recv_message;
+  // Original recv_message_ready callback, invoked after our own.
+  grpc_closure* next_recv_message_ready;
+} call_data;
+
+typedef struct channel_data {
+  size_t max_send_size;
+  size_t max_recv_size;
+} channel_data;
+
+// Callback invoked when we receive a message.  Here we check the max
+// receive message size.
+static void recv_message_ready(grpc_exec_ctx* exec_ctx, void* user_data,
+                               grpc_error* error) {
+  grpc_call_element* elem = user_data;
+  call_data* calld = elem->call_data;
+  channel_data* chand = elem->channel_data;
+  if (*calld->recv_message != NULL &&
+      (*calld->recv_message)->length > chand->max_recv_size) {
+    char* message_string;
+    gpr_asprintf(
+        &message_string, "Received message larger than max (%u vs. %lu)",
+        (*calld->recv_message)->length, (unsigned long)chand->max_recv_size);
+    gpr_slice message = gpr_slice_from_copied_string(message_string);
+    gpr_free(message_string);
+    grpc_call_element_send_cancel_with_message(
+        exec_ctx, elem, GRPC_STATUS_INVALID_ARGUMENT, &message);
+  }
+  // Invoke the next callback.
+  grpc_exec_ctx_sched(exec_ctx, calld->next_recv_message_ready, error, NULL);
+}
+
+// Start transport op.
+static void start_transport_stream_op(grpc_exec_ctx* exec_ctx,
+                                      grpc_call_element* elem,
+                                      grpc_transport_stream_op* op) {
+  call_data* calld = elem->call_data;
+  channel_data* chand = elem->channel_data;
+  // Check max send message size.
+  if (op->send_message != NULL &&
+      op->send_message->length > chand->max_send_size) {
+    char* message_string;
+    gpr_asprintf(&message_string, "Sent message larger than max (%u vs. %lu)",
+                 op->send_message->length, (unsigned long)chand->max_send_size);
+    gpr_slice message = gpr_slice_from_copied_string(message_string);
+    gpr_free(message_string);
+    grpc_call_element_send_cancel_with_message(
+        exec_ctx, elem, GRPC_STATUS_INVALID_ARGUMENT, &message);
+  }
+  // Inject callback for receiving a message.
+  if (op->recv_message_ready != NULL) {
+    calld->next_recv_message_ready = op->recv_message_ready;
+    calld->recv_message = op->recv_message;
+    op->recv_message_ready = &calld->recv_message_ready;
+  }
+  // Chain to the next filter.
+  grpc_call_next_op(exec_ctx, elem, op);
+}
+
+// Constructor for call_data.
+static grpc_error* init_call_elem(grpc_exec_ctx* exec_ctx,
+                                  grpc_call_element* elem,
+                                  grpc_call_element_args* args) {
+  call_data* calld = elem->call_data;
+  calld->next_recv_message_ready = NULL;
+  grpc_closure_init(&calld->recv_message_ready, recv_message_ready, elem);
+  return GRPC_ERROR_NONE;
+}
+
+// Destructor for call_data.
+static void destroy_call_elem(grpc_exec_ctx* exec_ctx, grpc_call_element* elem,
+                              const grpc_call_final_info* final_info,
+                              void* ignored) {}
+
+// Constructor for channel_data.
+static void init_channel_elem(grpc_exec_ctx* exec_ctx,
+                              grpc_channel_element* elem,
+                              grpc_channel_element_args* args) {
+  GPR_ASSERT(!args->is_last);
+  channel_data* chand = elem->channel_data;
+  memset(chand, 0, sizeof(*chand));
+  chand->max_send_size = DEFAULT_MAX_MESSAGE_LENGTH;
+  chand->max_recv_size = DEFAULT_MAX_MESSAGE_LENGTH;
+  const grpc_integer_options options = {DEFAULT_MAX_MESSAGE_LENGTH, 0, INT_MAX};
+  for (size_t i = 0; i < args->channel_args->num_args; ++i) {
+    if (strcmp(args->channel_args->args[i].key,
+               GRPC_ARG_MAX_SEND_MESSAGE_LENGTH) == 0) {
+      chand->max_send_size = (size_t)grpc_channel_arg_get_integer(
+          &args->channel_args->args[i], options);
+    }
+    if (strcmp(args->channel_args->args[i].key,
+               GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH) == 0) {
+      chand->max_recv_size = (size_t)grpc_channel_arg_get_integer(
+          &args->channel_args->args[i], options);
+    }
+  }
+}
+
+// Destructor for channel_data.
+static void destroy_channel_elem(grpc_exec_ctx* exec_ctx,
+                                 grpc_channel_element* elem) {}
+
+const grpc_channel_filter grpc_message_size_filter = {
+    start_transport_stream_op,
+    grpc_channel_next_op,
+    sizeof(call_data),
+    init_call_elem,
+    grpc_call_stack_ignore_set_pollset_or_pollset_set,
+    destroy_call_elem,
+    sizeof(channel_data),
+    init_channel_elem,
+    destroy_channel_elem,
+    grpc_call_next_get_peer,
+    "message_size"};
diff --git a/src/core/lib/channel/message_size_filter.h b/src/core/lib/channel/message_size_filter.h
new file mode 100644
index 0000000000..a88ff7f81a
--- /dev/null
+++ b/src/core/lib/channel/message_size_filter.h
@@ -0,0 +1,39 @@
+//
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+#ifndef GRPC_CORE_LIB_CHANNEL_MESSAGE_SIZE_FILTER_H
+#define GRPC_CORE_LIB_CHANNEL_MESSAGE_SIZE_FILTER_H
+
+#include "src/core/lib/channel/channel_stack.h"
+
+extern const grpc_channel_filter grpc_message_size_filter;
+
+#endif /* GRPC_CORE_LIB_CHANNEL_MESSAGE_SIZE_FILTER_H */
diff --git a/src/core/lib/iomgr/closure.c b/src/core/lib/iomgr/closure.c
index 0b6c3b2539..2c84e82aca 100644
--- a/src/core/lib/iomgr/closure.c
+++ b/src/core/lib/iomgr/closure.c
@@ -35,19 +35,25 @@
 
 #include <grpc/support/alloc.h>
 
+#include "src/core/lib/profiling/timers.h"
+
 void grpc_closure_init(grpc_closure *closure, grpc_iomgr_cb_func cb,
                        void *cb_arg) {
   closure->cb = cb;
   closure->cb_arg = cb_arg;
 }
 
+void grpc_closure_list_init(grpc_closure_list *closure_list) {
+  closure_list->head = closure_list->tail = NULL;
+}
+
 void grpc_closure_list_append(grpc_closure_list *closure_list,
                               grpc_closure *closure, grpc_error *error) {
   if (closure == NULL) {
     GRPC_ERROR_UNREF(error);
     return;
   }
-  closure->error = error;
+  closure->error_data.error = error;
   closure->next_data.next = NULL;
   if (closure_list->head == NULL) {
     closure_list->head = closure;
@@ -60,8 +66,8 @@ void grpc_closure_list_append(grpc_closure_list *closure_list,
 void grpc_closure_list_fail_all(grpc_closure_list *list,
                                 grpc_error *forced_failure) {
   for (grpc_closure *c = list->head; c != NULL; c = c->next_data.next) {
-    if (c->error == GRPC_ERROR_NONE) {
-      c->error = GRPC_ERROR_REF(forced_failure);
+    if (c->error_data.error == GRPC_ERROR_NONE) {
+      c->error_data.error = GRPC_ERROR_REF(forced_failure);
     }
   }
   GRPC_ERROR_UNREF(forced_failure);
@@ -106,3 +112,11 @@ grpc_closure *grpc_closure_create(grpc_iomgr_cb_func cb, void *cb_arg) {
   grpc_closure_init(&wc->wrapper, closure_wrapper, wc);
   return &wc->wrapper;
 }
+
+void grpc_closure_run(grpc_exec_ctx *exec_ctx, grpc_closure *c,
+                      grpc_error *error) {
+  GPR_TIMER_BEGIN("grpc_closure_run", 0);
+  c->cb(exec_ctx, c->cb_arg, error);
+  GRPC_ERROR_UNREF(error);
+  GPR_TIMER_END("grpc_closure_run", 0);
+}
diff --git a/src/core/lib/iomgr/closure.h b/src/core/lib/iomgr/closure.h
index 08e59a168e..2b4b271eaa 100644
--- a/src/core/lib/iomgr/closure.h
+++ b/src/core/lib/iomgr/closure.h
@@ -37,6 +37,7 @@
 #include <grpc/support/port_platform.h>
 #include <stdbool.h>
 #include "src/core/lib/iomgr/error.h"
+#include "src/core/lib/support/mpscq.h"
 
 struct grpc_closure;
 typedef struct grpc_closure grpc_closure;
@@ -60,6 +61,14 @@ typedef void (*grpc_iomgr_cb_func)(grpc_exec_ctx *exec_ctx, void *arg,
 
 /** A closure over a grpc_iomgr_cb_func. */
 struct grpc_closure {
+  /** Once queued, next indicates the next queued closure; before then, scratch
+   *  space */
+  union {
+    grpc_closure *next;
+    gpr_mpscq_node atm_next;
+    uintptr_t scratch;
+  } next_data;
+
   /** Bound callback. */
   grpc_iomgr_cb_func cb;
 
@@ -67,14 +76,10 @@ struct grpc_closure {
   void *cb_arg;
 
   /** Once queued, the result of the closure. Before then: scratch space */
-  grpc_error *error;
-
-  /** Once queued, next indicates the next queued closure; before then, scratch
-   *  space */
   union {
-    grpc_closure *next;
+    grpc_error *error;
     uintptr_t scratch;
-  } next_data;
+  } error_data;
 };
 
 /** Initializes \a closure with \a cb and \a cb_arg. */
@@ -87,6 +92,8 @@ grpc_closure *grpc_closure_create(grpc_iomgr_cb_func cb, void *cb_arg);
 #define GRPC_CLOSURE_LIST_INIT \
   { NULL, NULL }
 
+void grpc_closure_list_init(grpc_closure_list *list);
+
 /** add \a closure to the end of \a list
     and set \a closure's result to \a error */
 void grpc_closure_list_append(grpc_closure_list *list, grpc_closure *closure,
@@ -102,4 +109,10 @@ void grpc_closure_list_move(grpc_closure_list *src, grpc_closure_list *dst);
 /** return whether \a list is empty. */
 bool grpc_closure_list_empty(grpc_closure_list list);
 
+/** Run a closure directly. Caller ensures that no locks are being held above.
+ *  Note that calling this at the end of a closure callback function itself is
+ *  by definition safe. */
+void grpc_closure_run(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                      grpc_error *error);
+
 #endif /* GRPC_CORE_LIB_IOMGR_CLOSURE_H */
diff --git a/src/core/lib/iomgr/combiner.c b/src/core/lib/iomgr/combiner.c
new file mode 100644
index 0000000000..48806abc38
--- /dev/null
+++ b/src/core/lib/iomgr/combiner.c
@@ -0,0 +1,324 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/combiner.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/workqueue.h"
+#include "src/core/lib/profiling/timers.h"
+
+int grpc_combiner_trace = 0;
+
+#define GRPC_COMBINER_TRACE(fn) \
+  do {                          \
+    if (grpc_combiner_trace) {  \
+      fn;                       \
+    }                           \
+  } while (0)
+
+struct grpc_combiner {
+  grpc_combiner *next_combiner_on_this_exec_ctx;
+  grpc_workqueue *optional_workqueue;
+  gpr_mpscq queue;
+  // state is:
+  // lower bit - zero if orphaned
+  // other bits - number of items queued on the lock
+  gpr_atm state;
+  // number of elements in the list that are covered by a poller: if >0, we can
+  // offload safely
+  gpr_atm covered_by_poller;
+  bool time_to_execute_final_list;
+  bool final_list_covered_by_poller;
+  grpc_closure_list final_list;
+  grpc_closure offload;
+};
+
+static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
+
+typedef struct {
+  grpc_error *error;
+  bool covered_by_poller;
+} error_data;
+
+static uintptr_t pack_error_data(error_data d) {
+  return ((uintptr_t)d.error) | (d.covered_by_poller ? 1 : 0);
+}
+
+static error_data unpack_error_data(uintptr_t p) {
+  return (error_data){(grpc_error *)(p & ~(uintptr_t)1), p & 1};
+}
+
+static bool is_covered_by_poller(grpc_combiner *lock) {
+  return lock->final_list_covered_by_poller ||
+         gpr_atm_acq_load(&lock->covered_by_poller) > 0;
+}
+
+grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue) {
+  grpc_combiner *lock = gpr_malloc(sizeof(*lock));
+  lock->next_combiner_on_this_exec_ctx = NULL;
+  lock->time_to_execute_final_list = false;
+  lock->optional_workqueue = optional_workqueue;
+  lock->final_list_covered_by_poller = false;
+  gpr_atm_no_barrier_store(&lock->state, 1);
+  gpr_atm_no_barrier_store(&lock->covered_by_poller, 0);
+  gpr_mpscq_init(&lock->queue);
+  grpc_closure_list_init(&lock->final_list);
+  grpc_closure_init(&lock->offload, offload, lock);
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p create", lock));
+  return lock;
+}
+
+static void really_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p really_destroy", lock));
+  GPR_ASSERT(gpr_atm_no_barrier_load(&lock->state) == 0);
+  gpr_mpscq_destroy(&lock->queue);
+  GRPC_WORKQUEUE_UNREF(exec_ctx, lock->optional_workqueue, "combiner");
+  gpr_free(lock);
+}
+
+void grpc_combiner_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
+  gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -1);
+  GRPC_COMBINER_TRACE(gpr_log(
+      GPR_DEBUG, "C:%p really_destroy old_state=%" PRIdPTR, lock, old_state));
+  if (old_state == 1) {
+    really_destroy(exec_ctx, lock);
+  }
+}
+
+static void push_last_on_exec_ctx(grpc_exec_ctx *exec_ctx,
+                                  grpc_combiner *lock) {
+  lock->next_combiner_on_this_exec_ctx = NULL;
+  if (exec_ctx->active_combiner == NULL) {
+    exec_ctx->active_combiner = exec_ctx->last_combiner = lock;
+  } else {
+    exec_ctx->last_combiner->next_combiner_on_this_exec_ctx = lock;
+    exec_ctx->last_combiner = lock;
+  }
+}
+
+static void push_first_on_exec_ctx(grpc_exec_ctx *exec_ctx,
+                                   grpc_combiner *lock) {
+  lock->next_combiner_on_this_exec_ctx = exec_ctx->active_combiner;
+  exec_ctx->active_combiner = lock;
+  if (lock->next_combiner_on_this_exec_ctx == NULL) {
+    exec_ctx->last_combiner = lock;
+  }
+}
+
+void grpc_combiner_execute(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
+                           grpc_closure *cl, grpc_error *error,
+                           bool covered_by_poller) {
+  GPR_TIMER_BEGIN("combiner.execute", 0);
+  gpr_atm last = gpr_atm_full_fetch_add(&lock->state, 2);
+  GRPC_COMBINER_TRACE(gpr_log(
+      GPR_DEBUG, "C:%p grpc_combiner_execute c=%p cov=%d last=%" PRIdPTR, lock,
+      cl, covered_by_poller, last));
+  GPR_ASSERT(last & 1);  // ensure lock has not been destroyed
+  cl->error_data.scratch =
+      pack_error_data((error_data){error, covered_by_poller});
+  if (covered_by_poller) {
+    gpr_atm_no_barrier_fetch_add(&lock->covered_by_poller, 1);
+  }
+  gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next);
+  if (last == 1) {
+    // code will be written when the exec_ctx calls
+    // grpc_combiner_continue_exec_ctx
+    push_last_on_exec_ctx(exec_ctx, lock);
+  }
+  GPR_TIMER_END("combiner.execute", 0);
+}
+
+static void move_next(grpc_exec_ctx *exec_ctx) {
+  exec_ctx->active_combiner =
+      exec_ctx->active_combiner->next_combiner_on_this_exec_ctx;
+  if (exec_ctx->active_combiner == NULL) {
+    exec_ctx->last_combiner = NULL;
+  }
+}
+
+static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
+  grpc_combiner *lock = arg;
+  push_last_on_exec_ctx(exec_ctx, lock);
+}
+
+static void queue_offload(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
+  move_next(exec_ctx);
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p queue_offload --> %p", lock,
+                              lock->optional_workqueue));
+  grpc_workqueue_enqueue(exec_ctx, lock->optional_workqueue, &lock->offload,
+                         GRPC_ERROR_NONE);
+}
+
+bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_TIMER_BEGIN("combiner.continue_exec_ctx", 0);
+  grpc_combiner *lock = exec_ctx->active_combiner;
+  if (lock == NULL) {
+    GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+    return false;
+  }
+
+  GRPC_COMBINER_TRACE(
+      gpr_log(GPR_DEBUG,
+              "C:%p grpc_combiner_continue_exec_ctx workqueue=%p "
+              "is_covered_by_poller=%d exec_ctx_ready_to_finish=%d "
+              "time_to_execute_final_list=%d",
+              lock, lock->optional_workqueue, is_covered_by_poller(lock),
+              grpc_exec_ctx_ready_to_finish(exec_ctx),
+              lock->time_to_execute_final_list));
+
+  if (lock->optional_workqueue != NULL && is_covered_by_poller(lock) &&
+      grpc_exec_ctx_ready_to_finish(exec_ctx)) {
+    GPR_TIMER_MARK("offload_from_finished_exec_ctx", 0);
+    // this execution context wants to move on, and we have a workqueue (and
+    // so can help the execution context out): schedule remaining work to be
+    // picked up on the workqueue
+    queue_offload(exec_ctx, lock);
+    GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+    return true;
+  }
+
+  if (!lock->time_to_execute_final_list ||
+      // peek to see if something new has shown up, and execute that with
+      // priority
+      (gpr_atm_acq_load(&lock->state) >> 1) > 1) {
+    gpr_mpscq_node *n = gpr_mpscq_pop(&lock->queue);
+    GRPC_COMBINER_TRACE(
+        gpr_log(GPR_DEBUG, "C:%p maybe_finish_one n=%p", lock, n));
+    if (n == NULL) {
+      // queue is in an inconsistant state: use this as a cue that we should
+      // go off and do something else for a while (and come back later)
+      GPR_TIMER_MARK("delay_busy", 0);
+      if (lock->optional_workqueue != NULL && is_covered_by_poller(lock)) {
+        queue_offload(exec_ctx, lock);
+      }
+      GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+      return true;
+    }
+    GPR_TIMER_BEGIN("combiner.exec1", 0);
+    grpc_closure *cl = (grpc_closure *)n;
+    error_data err = unpack_error_data(cl->error_data.scratch);
+    cl->cb(exec_ctx, cl->cb_arg, err.error);
+    if (err.covered_by_poller) {
+      gpr_atm_no_barrier_fetch_add(&lock->covered_by_poller, -1);
+    }
+    GRPC_ERROR_UNREF(err.error);
+    GPR_TIMER_END("combiner.exec1", 0);
+  } else {
+    grpc_closure *c = lock->final_list.head;
+    GPR_ASSERT(c != NULL);
+    grpc_closure_list_init(&lock->final_list);
+    lock->final_list_covered_by_poller = false;
+    int loops = 0;
+    while (c != NULL) {
+      GPR_TIMER_BEGIN("combiner.exec_1final", 0);
+      GRPC_COMBINER_TRACE(
+          gpr_log(GPR_DEBUG, "C:%p execute_final[%d] c=%p", lock, loops, c));
+      grpc_closure *next = c->next_data.next;
+      grpc_error *error = c->error_data.error;
+      c->cb(exec_ctx, c->cb_arg, error);
+      GRPC_ERROR_UNREF(error);
+      c = next;
+      GPR_TIMER_END("combiner.exec_1final", 0);
+    }
+  }
+
+  GPR_TIMER_MARK("unref", 0);
+  move_next(exec_ctx);
+  lock->time_to_execute_final_list = false;
+  gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -2);
+  GRPC_COMBINER_TRACE(
+      gpr_log(GPR_DEBUG, "C:%p finish old_state=%" PRIdPTR, lock, old_state));
+  switch (old_state) {
+    default:
+      // we have multiple queued work items: just continue executing them
+      break;
+    case 5:  // we're down to one queued item: if it's the final list we
+    case 4:  // should do that
+      if (!grpc_closure_list_empty(lock->final_list)) {
+        lock->time_to_execute_final_list = true;
+      }
+      break;
+    case 3:  // had one count, one unorphaned --> unlocked unorphaned
+      GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+      return true;
+    case 2:  // and one count, one orphaned --> unlocked and orphaned
+      really_destroy(exec_ctx, lock);
+      GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+      return true;
+    case 1:
+    case 0:
+      // these values are illegal - representing an already unlocked or
+      // deleted lock
+      GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+      GPR_UNREACHABLE_CODE(return true);
+  }
+  push_first_on_exec_ctx(exec_ctx, lock);
+  GPR_TIMER_END("combiner.continue_exec_ctx", 0);
+  return true;
+}
+
+static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure,
+                            grpc_error *error) {
+  grpc_combiner_execute_finally(exec_ctx, exec_ctx->active_combiner, closure,
+                                GRPC_ERROR_REF(error), false);
+}
+
+void grpc_combiner_execute_finally(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
+                                   grpc_closure *closure, grpc_error *error,
+                                   bool covered_by_poller) {
+  GRPC_COMBINER_TRACE(gpr_log(
+      GPR_DEBUG, "C:%p grpc_combiner_execute_finally c=%p; ac=%p; cov=%d", lock,
+      closure, exec_ctx->active_combiner, covered_by_poller));
+  GPR_TIMER_BEGIN("combiner.execute_finally", 0);
+  if (exec_ctx->active_combiner != lock) {
+    GPR_TIMER_MARK("slowpath", 0);
+    grpc_combiner_execute(exec_ctx, lock,
+                          grpc_closure_create(enqueue_finally, closure), error,
+                          false);
+    GPR_TIMER_END("combiner.execute_finally", 0);
+    return;
+  }
+
+  if (grpc_closure_list_empty(lock->final_list)) {
+    gpr_atm_full_fetch_add(&lock->state, 2);
+  }
+  if (covered_by_poller) {
+    lock->final_list_covered_by_poller = true;
+  }
+  grpc_closure_list_append(&lock->final_list, closure, error);
+  GPR_TIMER_END("combiner.execute_finally", 0);
+}
diff --git a/src/core/lib/iomgr/combiner.h b/src/core/lib/iomgr/combiner.h
new file mode 100644
index 0000000000..d04eeed83a
--- /dev/null
+++ b/src/core/lib/iomgr/combiner.h
@@ -0,0 +1,66 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_COMBINER_H
+#define GRPC_CORE_LIB_IOMGR_COMBINER_H
+
+#include <stddef.h>
+
+#include <grpc/support/atm.h>
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/support/mpscq.h"
+
+// Provides serialized access to some resource.
+// Each action queued on a combiner is executed serially in a borrowed thread.
+// The actual thread executing actions may change over time (but there will only
+// every be one at a time).
+
+// Initialize the lock, with an optional workqueue to shift load to when
+// necessary
+grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue);
+// Destroy the lock
+void grpc_combiner_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock);
+// Execute \a action within the lock.
+void grpc_combiner_execute(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
+                           grpc_closure *closure, grpc_error *error,
+                           bool covered_by_poller);
+// Execute \a action within the lock just prior to unlocking.
+void grpc_combiner_execute_finally(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
+                                   grpc_closure *closure, grpc_error *error,
+                                   bool covered_by_poller);
+
+bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx);
+
+extern int grpc_combiner_trace;
+
+#endif /* GRPC_CORE_LIB_IOMGR_COMBINER_H */
diff --git a/src/core/lib/iomgr/error.c b/src/core/lib/iomgr/error.c
index 149c55663c..45ef75e04d 100644
--- a/src/core/lib/iomgr/error.c
+++ b/src/core/lib/iomgr/error.c
@@ -265,7 +265,7 @@ static grpc_error *copy_error_and_unref(grpc_error *in) {
   } else {
     out = gpr_malloc(sizeof(*out));
 #ifdef GRPC_ERROR_REFCOUNT_DEBUG
-    gpr_log(GPR_DEBUG, "%p create copying", out);
+    gpr_log(GPR_DEBUG, "%p create copying %p", out, in);
 #endif
     out->ints = gpr_avl_ref(in->ints);
     out->strs = gpr_avl_ref(in->strs);
@@ -332,7 +332,7 @@ grpc_error *grpc_error_add_child(grpc_error *src, grpc_error *child) {
   return new;
 }
 
-static const char *no_error_string = "null";
+static const char *no_error_string = "\"No Error\"";
 static const char *oom_error_string = "\"Out of memory\"";
 static const char *cancelled_error_string = "\"Cancelled\"";
 
diff --git a/src/core/lib/iomgr/error.h b/src/core/lib/iomgr/error.h
index 6c769accdb..2ab3ef9f40 100644
--- a/src/core/lib/iomgr/error.h
+++ b/src/core/lib/iomgr/error.h
@@ -123,9 +123,13 @@ typedef enum {
   GRPC_ERROR_TIME_CREATED,
 } grpc_error_times;
 
+/// The following "special" errors can be propagated without allocating memory.
+/// They are always even so that other code (particularly combiner locks) can
+/// safely use the lower bit for themselves.
+
 #define GRPC_ERROR_NONE ((grpc_error *)NULL)
-#define GRPC_ERROR_OOM ((grpc_error *)1)
-#define GRPC_ERROR_CANCELLED ((grpc_error *)2)
+#define GRPC_ERROR_OOM ((grpc_error *)2)
+#define GRPC_ERROR_CANCELLED ((grpc_error *)4)
 
 const char *grpc_error_string(grpc_error *error);
 void grpc_error_free_string(const char *str);
diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index eba347125e..42c0ae2dcd 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -152,14 +152,13 @@ static void fd_global_shutdown(void);
  * Polling island Declarations
  */
 
-//#define GRPC_PI_REF_COUNT_DEBUG
-#ifdef GRPC_PI_REF_COUNT_DEBUG
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
 
 #define PI_ADD_REF(p, r) pi_add_ref_dbg((p), (r), __FILE__, __LINE__)
 #define PI_UNREF(exec_ctx, p, r) \
   pi_unref_dbg((exec_ctx), (p), (r), __FILE__, __LINE__)
 
-#else /* defined(GRPC_PI_REF_COUNT_DEBUG) */
+#else /* defined(GRPC_WORKQUEUE_REFCOUNT_DEBUG) */
 
 #define PI_ADD_REF(p, r) pi_add_ref((p))
 #define PI_UNREF(exec_ctx, p, r) pi_unref((exec_ctx), (p))
@@ -185,8 +184,11 @@ typedef struct polling_island {
    * (except mu and ref_count) are invalid and must be ignored. */
   gpr_atm merged_to;
 
-  /* The workqueue associated with this polling island */
-  grpc_workqueue *workqueue;
+  gpr_atm poller_count;
+  gpr_mu workqueue_read_mu;
+  gpr_mpscq workqueue_items;
+  gpr_atm workqueue_item_count;
+  grpc_wakeup_fd workqueue_wakeup_fd;
 
   /* The fd of the underlying epoll set */
   int epoll_fd;
@@ -275,6 +277,8 @@ static bool append_error(grpc_error **composite, grpc_error *error,
    threads that woke up MUST NOT call grpc_wakeup_fd_consume_wakeup() */
 static grpc_wakeup_fd polling_island_wakeup_fd;
 
+static __thread polling_island *g_current_thread_polling_island;
+
 /* Forward declaration */
 static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi);
 
@@ -289,12 +293,12 @@ static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi);
 gpr_atm g_epoll_sync;
 #endif /* defined(GRPC_TSAN) */
 
-#ifdef GRPC_PI_REF_COUNT_DEBUG
 static void pi_add_ref(polling_island *pi);
 static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi);
 
-static void pi_add_ref_dbg(polling_island *pi, char *reason, char *file,
-                           int line) {
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+static void pi_add_ref_dbg(polling_island *pi, const char *reason,
+                           const char *file, int line) {
   long old_cnt = gpr_atm_acq_load(&pi->ref_count);
   pi_add_ref(pi);
   gpr_log(GPR_DEBUG, "Add ref pi: %p, old: %ld -> new:%ld (%s) - (%s, %d)",
@@ -302,12 +306,42 @@ static void pi_add_ref_dbg(polling_island *pi, char *reason, char *file,
 }
 
 static void pi_unref_dbg(grpc_exec_ctx *exec_ctx, polling_island *pi,
-                         char *reason, char *file, int line) {
+                         const char *reason, const char *file, int line) {
   long old_cnt = gpr_atm_acq_load(&pi->ref_count);
   pi_unref(exec_ctx, pi);
   gpr_log(GPR_DEBUG, "Unref pi: %p, old:%ld -> new:%ld (%s) - (%s, %d)",
           (void *)pi, old_cnt, (old_cnt - 1), reason, file, line);
 }
+
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
+                                     const char *file, int line,
+                                     const char *reason) {
+  if (workqueue != NULL) {
+    pi_add_ref_dbg((polling_island *)workqueue, reason, file, line);
+  }
+  return workqueue;
+}
+
+static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                            const char *file, int line, const char *reason) {
+  if (workqueue != NULL) {
+    pi_unref_dbg(exec_ctx, (polling_island *)workqueue, reason, file, line);
+  }
+}
+#else
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
+  if (workqueue != NULL) {
+    pi_add_ref((polling_island *)workqueue);
+  }
+  return workqueue;
+}
+
+static void workqueue_unref(grpc_exec_ctx *exec_ctx,
+                            grpc_workqueue *workqueue) {
+  if (workqueue != NULL) {
+    pi_unref(exec_ctx, (polling_island *)workqueue);
+  }
+}
 #endif
 
 static void pi_add_ref(polling_island *pi) {
@@ -315,10 +349,7 @@ static void pi_add_ref(polling_island *pi) {
 }
 
 static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi) {
-  /* If ref count went to one, we're back to just the workqueue owning a ref.
-     Unref the workqueue to break the loop.
-
-     If ref count went to zero, delete the polling island.
+  /* If ref count went to zero, delete the polling island.
      Note that this deletion not be done under a lock. Once the ref count goes
      to zero, we are guaranteed that no one else holds a reference to the
      polling island (and that there is no racing pi_add_ref() call either).
@@ -326,20 +357,12 @@ static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi) {
      Also, if we are deleting the polling island and the merged_to field is
      non-empty, we should remove a ref to the merged_to polling island
    */
-  switch (gpr_atm_full_fetch_add(&pi->ref_count, -1)) {
-    case 2: /* last external ref: the only one now owned is by the workqueue */
-      GRPC_WORKQUEUE_UNREF(exec_ctx, pi->workqueue, "polling_island");
-      break;
-    case 1: {
-      polling_island *next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-      polling_island_delete(exec_ctx, pi);
-      if (next != NULL) {
-        PI_UNREF(exec_ctx, next, "pi_delete"); /* Recursive call */
-      }
-      break;
+  if (1 == gpr_atm_full_fetch_add(&pi->ref_count, -1)) {
+    polling_island *next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
+    polling_island_delete(exec_ctx, pi);
+    if (next != NULL) {
+      PI_UNREF(exec_ctx, next, "pi_delete"); /* Recursive call */
     }
-    case 0:
-      GPR_UNREACHABLE_CODE(return );
   }
 }
 
@@ -488,11 +511,20 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
   pi->fd_capacity = 0;
   pi->fds = NULL;
   pi->epoll_fd = -1;
-  pi->workqueue = NULL;
+
+  gpr_mu_init(&pi->workqueue_read_mu);
+  gpr_mpscq_init(&pi->workqueue_items);
+  gpr_atm_rel_store(&pi->workqueue_item_count, 0);
 
   gpr_atm_rel_store(&pi->ref_count, 0);
+  gpr_atm_rel_store(&pi->poller_count, 0);
   gpr_atm_rel_store(&pi->merged_to, (gpr_atm)NULL);
 
+  if (!append_error(error, grpc_wakeup_fd_init(&pi->workqueue_wakeup_fd),
+                    err_desc)) {
+    goto done;
+  }
+
   pi->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
 
   if (pi->epoll_fd < 0) {
@@ -501,26 +533,14 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
   }
 
   polling_island_add_wakeup_fd_locked(pi, &grpc_global_wakeup_fd, error);
+  polling_island_add_wakeup_fd_locked(pi, &pi->workqueue_wakeup_fd, error);
 
   if (initial_fd != NULL) {
     polling_island_add_fds_locked(pi, &initial_fd, 1, true, error);
   }
 
-  if (append_error(error, grpc_workqueue_create(exec_ctx, &pi->workqueue),
-                   err_desc) &&
-      *error == GRPC_ERROR_NONE) {
-    polling_island_add_fds_locked(pi, &pi->workqueue->wakeup_read_fd, 1, true,
-                                  error);
-    GPR_ASSERT(pi->workqueue->wakeup_read_fd->polling_island == NULL);
-    pi->workqueue->wakeup_read_fd->polling_island = pi;
-    PI_ADD_REF(pi, "fd");
-  }
-
 done:
   if (*error != GRPC_ERROR_NONE) {
-    if (pi->workqueue != NULL) {
-      GRPC_WORKQUEUE_UNREF(exec_ctx, pi->workqueue, "polling_island");
-    }
     polling_island_delete(exec_ctx, pi);
     pi = NULL;
   }
@@ -533,7 +553,11 @@ static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi) {
   if (pi->epoll_fd >= 0) {
     close(pi->epoll_fd);
   }
+  GPR_ASSERT(gpr_atm_no_barrier_load(&pi->workqueue_item_count) == 0);
+  gpr_mu_destroy(&pi->workqueue_read_mu);
+  gpr_mpscq_destroy(&pi->workqueue_items);
   gpr_mu_destroy(&pi->mu);
+  grpc_wakeup_fd_destroy(&pi->workqueue_wakeup_fd);
   gpr_free(pi->fds);
   gpr_free(pi);
 }
@@ -678,6 +702,40 @@ static void polling_island_unlock_pair(polling_island *p, polling_island *q) {
   }
 }
 
+static void workqueue_maybe_wakeup(polling_island *pi) {
+  bool force_wakeup = false;
+  bool is_current_poller = (g_current_thread_polling_island == pi);
+  gpr_atm min_current_pollers_for_wakeup = is_current_poller ? 1 : 0;
+  gpr_atm current_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
+  if (force_wakeup || current_pollers > min_current_pollers_for_wakeup) {
+    GRPC_LOG_IF_ERROR("workqueue_wakeup_fd",
+                      grpc_wakeup_fd_wakeup(&pi->workqueue_wakeup_fd));
+  }
+}
+
+static void workqueue_move_items_to_parent(polling_island *q) {
+  polling_island *p = (polling_island *)gpr_atm_no_barrier_load(&q->merged_to);
+  if (p == NULL) {
+    return;
+  }
+  gpr_mu_lock(&q->workqueue_read_mu);
+  int num_added = 0;
+  while (gpr_atm_no_barrier_load(&q->workqueue_item_count) > 0) {
+    gpr_mpscq_node *n = gpr_mpscq_pop(&q->workqueue_items);
+    if (n != NULL) {
+      gpr_atm_no_barrier_fetch_add(&q->workqueue_item_count, -1);
+      gpr_atm_no_barrier_fetch_add(&p->workqueue_item_count, 1);
+      gpr_mpscq_push(&p->workqueue_items, n);
+      num_added++;
+    }
+  }
+  gpr_mu_unlock(&q->workqueue_read_mu);
+  if (num_added > 0) {
+    workqueue_maybe_wakeup(p);
+  }
+  workqueue_move_items_to_parent(p);
+}
+
 static polling_island *polling_island_merge(polling_island *p,
                                             polling_island *q,
                                             grpc_error **error) {
@@ -702,6 +760,8 @@ static polling_island *polling_island_merge(polling_island *p,
     /* Add the 'merged_to' link from p --> q */
     gpr_atm_rel_store(&p->merged_to, (gpr_atm)q);
     PI_ADD_REF(q, "pi_merge"); /* To account for the new incoming ref from p */
+
+    workqueue_move_items_to_parent(q);
   }
   /* else if p == q, nothing needs to be done */
 
@@ -712,6 +772,26 @@ static polling_island *polling_island_merge(polling_island *p,
   return q;
 }
 
+static void workqueue_enqueue(grpc_exec_ctx *exec_ctx,
+                              grpc_workqueue *workqueue, grpc_closure *closure,
+                              grpc_error *error) {
+  GPR_TIMER_BEGIN("workqueue.enqueue", 0);
+  /* take a ref to the workqueue: otherwise it can happen that whatever events
+   * this kicks off ends up destroying the workqueue before this function
+   * completes */
+  GRPC_WORKQUEUE_REF(workqueue, "enqueue");
+  polling_island *pi = (polling_island *)workqueue;
+  gpr_atm last = gpr_atm_no_barrier_fetch_add(&pi->workqueue_item_count, 1);
+  closure->error_data.error = error;
+  gpr_mpscq_push(&pi->workqueue_items, &closure->next_data.atm_next);
+  if (last == 0) {
+    workqueue_maybe_wakeup(pi);
+  }
+  workqueue_move_items_to_parent(pi);
+  GRPC_WORKQUEUE_UNREF(exec_ctx, workqueue, "enqueue");
+  GPR_TIMER_END("workqueue.enqueue", 0);
+}
+
 static grpc_error *polling_island_global_init() {
   grpc_error *error = GRPC_ERROR_NONE;
 
@@ -1042,11 +1122,8 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
 
 static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
   gpr_mu_lock(&fd->mu);
-  grpc_workqueue *workqueue = NULL;
-  if (fd->polling_island != NULL) {
-    workqueue =
-        GRPC_WORKQUEUE_REF(fd->polling_island->workqueue, "get_workqueue");
-  }
+  grpc_workqueue *workqueue = GRPC_WORKQUEUE_REF(
+      (grpc_workqueue *)fd->polling_island, "fd_get_workqueue");
   gpr_mu_unlock(&fd->mu);
   return workqueue;
 }
@@ -1299,7 +1376,26 @@ static void pollset_reset(grpc_pollset *pollset) {
   GPR_ASSERT(pollset->polling_island == NULL);
 }
 
-#define GRPC_EPOLL_MAX_EVENTS 1000
+static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx,
+                                    polling_island *pi) {
+  if (gpr_mu_trylock(&pi->workqueue_read_mu)) {
+    gpr_mpscq_node *n = gpr_mpscq_pop(&pi->workqueue_items);
+    gpr_mu_unlock(&pi->workqueue_read_mu);
+    if (n != NULL) {
+      if (gpr_atm_full_fetch_add(&pi->workqueue_item_count, -1) > 1) {
+        workqueue_maybe_wakeup(pi);
+      }
+      grpc_closure *c = (grpc_closure *)n;
+      grpc_closure_run(exec_ctx, c, c->error_data.error);
+      return true;
+    } else if (gpr_atm_no_barrier_load(&pi->workqueue_item_count) > 0) {
+      workqueue_maybe_wakeup(pi);
+    }
+  }
+  return false;
+}
+
+#define GRPC_EPOLL_MAX_EVENTS 100
 /* Note: sig_mask contains the signal mask to use *during* epoll_wait() */
 static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
                                     grpc_pollset *pollset,
@@ -1354,7 +1450,10 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
   PI_ADD_REF(pi, "ps_work");
   gpr_mu_unlock(&pollset->mu);
 
-  do {
+  if (!maybe_do_workqueue_work(exec_ctx, pi)) {
+    gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1);
+    g_current_thread_polling_island = pi;
+
     GRPC_SCHEDULING_START_BLOCKING_REGION;
     ep_rv = epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms,
                         sig_mask);
@@ -1386,6 +1485,11 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
         append_error(error,
                      grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd),
                      err_desc);
+      } else if (data_ptr == &pi->workqueue_wakeup_fd) {
+        append_error(error,
+                     grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd),
+                     err_desc);
+        maybe_do_workqueue_work(exec_ctx, pi);
       } else if (data_ptr == &polling_island_wakeup_fd) {
         GRPC_POLLING_TRACE(
             "pollset_work: pollset: %p, worker: %p polling island (epoll_fd: "
@@ -1408,7 +1512,10 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
         }
       }
     }
-  } while (ep_rv == GRPC_EPOLL_MAX_EVENTS);
+
+    g_current_thread_polling_island = NULL;
+    gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1);
+  }
 
   GPR_ASSERT(pi != NULL);
 
@@ -1531,6 +1638,8 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
 
 static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                            grpc_fd *fd) {
+  GPR_TIMER_BEGIN("pollset_add_fd", 0);
+
   grpc_error *error = GRPC_ERROR_NONE;
 
   gpr_mu_lock(&pollset->mu);
@@ -1643,6 +1752,8 @@ retry:
   gpr_mu_unlock(&pollset->mu);
 
   GRPC_LOG_IF_ERROR("pollset_add_fd", error);
+
+  GPR_TIMER_END("pollset_add_fd", 0);
 }
 
 /*******************************************************************************
@@ -1864,6 +1975,10 @@ static const grpc_event_engine_vtable vtable = {
 
     .kick_poller = kick_poller,
 
+    .workqueue_ref = workqueue_ref,
+    .workqueue_unref = workqueue_unref,
+    .workqueue_enqueue = workqueue_enqueue,
+
     .shutdown_engine = shutdown_engine,
 };
 
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
index c2107e5e39..1829440a6e 100644
--- a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
@@ -1989,6 +1989,32 @@ static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
 }
 
 /*******************************************************************************
+ * workqueue stubs
+ */
+
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
+                                     const char *file, int line,
+                                     const char *reason) {
+  return workqueue;
+}
+static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                            const char *file, int line, const char *reason) {}
+#else
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
+  return workqueue;
+}
+static void workqueue_unref(grpc_exec_ctx *exec_ctx,
+                            grpc_workqueue *workqueue) {}
+#endif
+
+static void workqueue_enqueue(grpc_exec_ctx *exec_ctx,
+                              grpc_workqueue *workqueue, grpc_closure *closure,
+                              grpc_error *error) {
+  grpc_exec_ctx_sched(exec_ctx, closure, error, NULL);
+}
+
+/*******************************************************************************
  * event engine binding
  */
 
@@ -2029,6 +2055,10 @@ static const grpc_event_engine_vtable vtable = {
 
     .kick_poller = kick_poller,
 
+    .workqueue_ref = workqueue_ref,
+    .workqueue_unref = workqueue_unref,
+    .workqueue_enqueue = workqueue_enqueue,
+
     .shutdown_engine = shutdown_engine,
 };
 
diff --git a/src/core/lib/iomgr/ev_poll_posix.c b/src/core/lib/iomgr/ev_poll_posix.c
index 16a5e3083e..b84a56018f 100644
--- a/src/core/lib/iomgr/ev_poll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_posix.c
@@ -1236,6 +1236,32 @@ static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
 }
 
 /*******************************************************************************
+ * workqueue stubs
+ */
+
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
+                                     const char *file, int line,
+                                     const char *reason) {
+  return workqueue;
+}
+static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                            const char *file, int line, const char *reason) {}
+#else
+static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
+  return workqueue;
+}
+static void workqueue_unref(grpc_exec_ctx *exec_ctx,
+                            grpc_workqueue *workqueue) {}
+#endif
+
+static void workqueue_enqueue(grpc_exec_ctx *exec_ctx,
+                              grpc_workqueue *workqueue, grpc_closure *closure,
+                              grpc_error *error) {
+  grpc_exec_ctx_sched(exec_ctx, closure, error, NULL);
+}
+
+/*******************************************************************************
  * event engine binding
  */
 
@@ -1273,6 +1299,10 @@ static const grpc_event_engine_vtable vtable = {
 
     .kick_poller = kick_poller,
 
+    .workqueue_ref = workqueue_ref,
+    .workqueue_unref = workqueue_unref,
+    .workqueue_enqueue = workqueue_enqueue,
+
     .shutdown_engine = shutdown_engine,
 };
 
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index 6536672685..26618f8d55 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -258,4 +258,27 @@ void grpc_pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
 
 grpc_error *grpc_kick_poller(void) { return g_event_engine->kick_poller(); }
 
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
+                                   int line, const char *reason) {
+  return g_event_engine->workqueue_ref(workqueue, file, line, reason);
+}
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                          const char *file, int line, const char *reason) {
+  g_event_engine->workqueue_unref(exec_ctx, workqueue, file, line, reason);
+}
+#else
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue) {
+  return g_event_engine->workqueue_ref(workqueue);
+}
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
+  g_event_engine->workqueue_unref(exec_ctx, workqueue);
+}
+#endif
+
+void grpc_workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                            grpc_closure *closure, grpc_error *error) {
+  g_event_engine->workqueue_enqueue(exec_ctx, workqueue, closure, error);
+}
+
 #endif  // GPR_POSIX_SOCKET
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
index c2aa1756ea..2fdef06838 100644
--- a/src/core/lib/iomgr/ev_posix.h
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -40,6 +40,7 @@
 #include "src/core/lib/iomgr/pollset.h"
 #include "src/core/lib/iomgr/pollset_set.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
+#include "src/core/lib/iomgr/workqueue.h"
 
 typedef struct grpc_fd grpc_fd;
 
@@ -95,6 +96,18 @@ typedef struct grpc_event_engine_vtable {
   grpc_error *(*kick_poller)(void);
 
   void (*shutdown_engine)(void);
+
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+  grpc_workqueue *(*workqueue_ref)(grpc_workqueue *workqueue, const char *file,
+                                   int line, const char *reason);
+  void (*workqueue_unref)(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                          const char *file, int line, const char *reason);
+#else
+  grpc_workqueue *(*workqueue_ref)(grpc_workqueue *workqueue);
+  void (*workqueue_unref)(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
+#endif
+  void (*workqueue_enqueue)(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                            grpc_closure *closure, grpc_error *error);
 } grpc_event_engine_vtable;
 
 void grpc_event_engine_init(void);
diff --git a/src/core/lib/iomgr/exec_ctx.c b/src/core/lib/iomgr/exec_ctx.c
index ac7785ec13..a3c40e8092 100644
--- a/src/core/lib/iomgr/exec_ctx.c
+++ b/src/core/lib/iomgr/exec_ctx.c
@@ -37,6 +37,7 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/thd.h>
 
+#include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 
@@ -60,18 +61,47 @@ bool grpc_always_ready_to_finish(grpc_exec_ctx *exec_ctx, void *arg_ignored) {
 bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
   bool did_something = 0;
   GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
-  while (!grpc_closure_list_empty(exec_ctx->closure_list)) {
-    grpc_closure *c = exec_ctx->closure_list.head;
-    exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
-    while (c != NULL) {
-      grpc_closure *next = c->next_data.next;
-      grpc_error *error = c->error;
-      did_something = true;
-      GPR_TIMER_BEGIN("grpc_exec_ctx_flush.cb", 0);
+  for (;;) {
+    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
+      grpc_closure *c = exec_ctx->closure_list.head;
+      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
+      while (c != NULL) {
+        grpc_closure *next = c->next_data.next;
+        did_something = true;
+        grpc_closure_run(exec_ctx, c, c->error_data.error);
+        c = next;
+      }
+      continue;
+    }
+    if (grpc_combiner_continue_exec_ctx(exec_ctx)) {
+      continue;
+    }
+    break;
+  }
+  GPR_ASSERT(exec_ctx->active_combiner == NULL);
+  if (exec_ctx->stealing_from_workqueue != NULL) {
+    if (grpc_exec_ctx_ready_to_finish(exec_ctx)) {
+      grpc_workqueue_enqueue(exec_ctx, exec_ctx->stealing_from_workqueue,
+                             exec_ctx->stolen_closure,
+                             exec_ctx->stolen_closure->error_data.error);
+      GRPC_WORKQUEUE_UNREF(exec_ctx, exec_ctx->stealing_from_workqueue,
+                           "exec_ctx_sched");
+      exec_ctx->stealing_from_workqueue = NULL;
+      exec_ctx->stolen_closure = NULL;
+    } else {
+      grpc_closure *c = exec_ctx->stolen_closure;
+      GRPC_WORKQUEUE_UNREF(exec_ctx, exec_ctx->stealing_from_workqueue,
+                           "exec_ctx_sched");
+      exec_ctx->stealing_from_workqueue = NULL;
+      exec_ctx->stolen_closure = NULL;
+      grpc_error *error = c->error_data.error;
+      GPR_TIMER_BEGIN("grpc_exec_ctx_flush.stolen_cb", 0);
       c->cb(exec_ctx, c->cb_arg, error);
       GRPC_ERROR_UNREF(error);
-      GPR_TIMER_END("grpc_exec_ctx_flush.cb", 0);
-      c = next;
+      GPR_TIMER_END("grpc_exec_ctx_flush.stolen_cb", 0);
+      grpc_exec_ctx_flush(exec_ctx);
+      GPR_TIMER_END("grpc_exec_ctx_flush", 0);
+      return true;
     }
   }
   GPR_TIMER_END("grpc_exec_ctx_flush", 0);
@@ -86,12 +116,25 @@ void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {
 void grpc_exec_ctx_sched(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
                          grpc_error *error,
                          grpc_workqueue *offload_target_or_null) {
+  GPR_TIMER_BEGIN("grpc_exec_ctx_sched", 0);
   if (offload_target_or_null == NULL) {
     grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
-  } else {
+  } else if (exec_ctx->stealing_from_workqueue == NULL) {
+    exec_ctx->stealing_from_workqueue = offload_target_or_null;
+    closure->error_data.error = error;
+    exec_ctx->stolen_closure = closure;
+  } else if (exec_ctx->stealing_from_workqueue != offload_target_or_null) {
     grpc_workqueue_enqueue(exec_ctx, offload_target_or_null, closure, error);
     GRPC_WORKQUEUE_UNREF(exec_ctx, offload_target_or_null, "exec_ctx_sched");
+  } else { /* stealing_from_workqueue == offload_target_or_null */
+    grpc_workqueue_enqueue(exec_ctx, offload_target_or_null,
+                           exec_ctx->stolen_closure,
+                           exec_ctx->stolen_closure->error_data.error);
+    closure->error_data.error = error;
+    exec_ctx->stolen_closure = closure;
+    GRPC_WORKQUEUE_UNREF(exec_ctx, offload_target_or_null, "exec_ctx_sched");
   }
+  GPR_TIMER_END("grpc_exec_ctx_sched", 0);
 }
 
 void grpc_exec_ctx_enqueue_list(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/iomgr/exec_ctx.h b/src/core/lib/iomgr/exec_ctx.h
index 917f332f03..91029f5fba 100644
--- a/src/core/lib/iomgr/exec_ctx.h
+++ b/src/core/lib/iomgr/exec_ctx.h
@@ -40,8 +40,8 @@
 
 /** A workqueue represents a list of work to be executed asynchronously.
     Forward declared here to avoid a circular dependency with workqueue.h. */
-struct grpc_workqueue;
 typedef struct grpc_workqueue grpc_workqueue;
+typedef struct grpc_combiner grpc_combiner;
 
 #ifndef GRPC_EXECUTION_CONTEXT_SANITIZER
 /** Execution context.
@@ -66,13 +66,23 @@ typedef struct grpc_workqueue grpc_workqueue;
  */
 struct grpc_exec_ctx {
   grpc_closure_list closure_list;
+  grpc_workqueue *stealing_from_workqueue;
+  grpc_closure *stolen_closure;
+  /** currently active combiner: updated only via combiner.c */
+  grpc_combiner *active_combiner;
+  grpc_combiner *last_combiner;
   bool cached_ready_to_finish;
   void *check_ready_to_finish_arg;
   bool (*check_ready_to_finish)(grpc_exec_ctx *exec_ctx, void *arg);
 };
 
+/* initializer for grpc_exec_ctx:
+   prefer to use GRPC_EXEC_CTX_INIT whenever possible */
 #define GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(finish_check, finish_check_arg) \
-  { GRPC_CLOSURE_LIST_INIT, false, finish_check_arg, finish_check }
+  {                                                                          \
+    GRPC_CLOSURE_LIST_INIT, NULL, NULL, NULL, NULL, false, finish_check_arg, \
+        finish_check                                                         \
+  }
 #else
 struct grpc_exec_ctx {
   bool cached_ready_to_finish;
@@ -83,8 +93,10 @@ struct grpc_exec_ctx {
   { false, finish_check_arg, finish_check }
 #endif
 
+/* initialize an execution context at the top level of an API call into grpc
+   (this is safe to use elsewhere, though possibly not as efficient) */
 #define GRPC_EXEC_CTX_INIT \
-  GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(grpc_never_ready_to_finish, NULL)
+  GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(grpc_always_ready_to_finish, NULL)
 
 /** Flush any work that has been enqueued onto this grpc_exec_ctx.
  *  Caller must guarantee that no interfering locks are held.
diff --git a/src/core/lib/iomgr/iomgr.c b/src/core/lib/iomgr/iomgr.c
index d67d388b8c..4fd83e0b22 100644
--- a/src/core/lib/iomgr/iomgr.c
+++ b/src/core/lib/iomgr/iomgr.c
@@ -112,6 +112,14 @@ void grpc_iomgr_shutdown(void) {
       continue;
     }
     if (g_root_object.next != &g_root_object) {
+      if (grpc_iomgr_abort_on_leaks()) {
+        gpr_log(GPR_DEBUG, "Failed to free %" PRIuPTR
+                           " iomgr objects before shutdown deadline: "
+                           "memory leaks are likely",
+                count_objects());
+        dump_objects("LEAKED");
+        abort();
+      }
       gpr_timespec short_deadline = gpr_time_add(
           gpr_now(GPR_CLOCK_REALTIME), gpr_time_from_millis(100, GPR_TIMESPAN));
       if (gpr_cv_wait(&g_rcv, &g_mu, short_deadline)) {
@@ -122,9 +130,6 @@ void grpc_iomgr_shutdown(void) {
                                "memory leaks are likely",
                     count_objects());
             dump_objects("LEAKED");
-            if (grpc_iomgr_abort_on_leaks()) {
-              abort();
-            }
           }
           break;
         }
diff --git a/src/core/lib/iomgr/tcp_posix.c b/src/core/lib/iomgr/tcp_posix.c
index 974d5ae479..00fd77679a 100644
--- a/src/core/lib/iomgr/tcp_posix.c
+++ b/src/core/lib/iomgr/tcp_posix.c
@@ -177,7 +177,7 @@ static void call_read_cb(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp,
 
   tcp->read_cb = NULL;
   tcp->incoming_buffer = NULL;
-  grpc_exec_ctx_sched(exec_ctx, cb, error, NULL);
+  grpc_closure_run(exec_ctx, cb, error);
 }
 
 #define MAX_READ_IOVEC 4
@@ -209,11 +209,11 @@ static void tcp_continue_read(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
   msg.msg_controllen = 0;
   msg.msg_flags = 0;
 
-  GPR_TIMER_BEGIN("recvmsg", 1);
+  GPR_TIMER_BEGIN("recvmsg", 0);
   do {
     read_bytes = recvmsg(tcp->fd, &msg, 0);
   } while (read_bytes < 0 && errno == EINTR);
-  GPR_TIMER_END("recvmsg", 0);
+  GPR_TIMER_END("recvmsg", read_bytes >= 0);
 
   if (read_bytes < 0) {
     /* NB: After calling call_read_cb a parallel call of the read handler may
@@ -379,15 +379,21 @@ static void tcp_handle_write(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
   }
 
   if (!tcp_flush(tcp, &error)) {
+    if (grpc_tcp_trace) {
+      gpr_log(GPR_DEBUG, "write: delayed");
+    }
     grpc_fd_notify_on_write(exec_ctx, tcp->em_fd, &tcp->write_closure);
   } else {
     cb = tcp->write_cb;
     tcp->write_cb = NULL;
-    GPR_TIMER_BEGIN("tcp_handle_write.cb", 0);
-    cb->cb(exec_ctx, cb->cb_arg, error);
-    GPR_TIMER_END("tcp_handle_write.cb", 0);
+    if (grpc_tcp_trace) {
+      const char *str = grpc_error_string(error);
+      gpr_log(GPR_DEBUG, "write: %s", str);
+      grpc_error_free_string(str);
+    }
+
+    grpc_closure_run(exec_ctx, cb, error);
     TCP_UNREF(exec_ctx, tcp, "write");
-    GRPC_ERROR_UNREF(error);
   }
 }
 
@@ -425,8 +431,16 @@ static void tcp_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
   if (!tcp_flush(tcp, &error)) {
     TCP_REF(tcp, "write");
     tcp->write_cb = cb;
+    if (grpc_tcp_trace) {
+      gpr_log(GPR_DEBUG, "write: delayed");
+    }
     grpc_fd_notify_on_write(exec_ctx, tcp->em_fd, &tcp->write_closure);
   } else {
+    if (grpc_tcp_trace) {
+      const char *str = grpc_error_string(error);
+      gpr_log(GPR_DEBUG, "write: %s", str);
+      grpc_error_free_string(str);
+    }
     grpc_exec_ctx_sched(exec_ctx, cb, error, NULL);
   }
 
diff --git a/src/core/lib/iomgr/workqueue.h b/src/core/lib/iomgr/workqueue.h
index 7156e490d7..5b96d1d851 100644
--- a/src/core/lib/iomgr/workqueue.h
+++ b/src/core/lib/iomgr/workqueue.h
@@ -40,20 +40,12 @@
 #include "src/core/lib/iomgr/pollset.h"
 #include "src/core/lib/iomgr/pollset_set.h"
 
-#ifdef GPR_POSIX_SOCKET
-#include "src/core/lib/iomgr/workqueue_posix.h"
-#endif
-
 #ifdef GPR_WINDOWS
 #include "src/core/lib/iomgr/workqueue_windows.h"
 #endif
 
 /* grpc_workqueue is forward declared in exec_ctx.h */
 
-/* Deprecated: do not use.
-   This has *already* been removed in a future commit. */
-void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
-
 /* Reference counting functions. Use the macro's always
    (GRPC_WORKQUEUE_{REF,UNREF}).
 
@@ -62,20 +54,20 @@ void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
    string will be printed alongside the refcount. When it is not defined, the
    string will be discarded at compilation time. */
 
-//#define GRPC_WORKQUEUE_REFCOUNT_DEBUG
+/*#define GRPC_WORKQUEUE_REFCOUNT_DEBUG*/
 #ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
 #define GRPC_WORKQUEUE_REF(p, r) \
-  (grpc_workqueue_ref((p), __FILE__, __LINE__, (r)), (p))
+  grpc_workqueue_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_WORKQUEUE_UNREF(exec_ctx, p, r) \
   grpc_workqueue_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
-void grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file, int line,
-                        const char *reason);
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
+                                   int line, const char *reason);
 void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
                           const char *file, int line, const char *reason);
 #else
-#define GRPC_WORKQUEUE_REF(p, r) (grpc_workqueue_ref((p)), (p))
+#define GRPC_WORKQUEUE_REF(p, r) grpc_workqueue_ref((p))
 #define GRPC_WORKQUEUE_UNREF(cl, p, r) grpc_workqueue_unref((cl), (p))
-void grpc_workqueue_ref(grpc_workqueue *workqueue);
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue);
 void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
 #endif
 
diff --git a/src/core/lib/iomgr/workqueue_posix.c b/src/core/lib/iomgr/workqueue_posix.c
deleted file mode 100644
index e0d6dac230..0000000000
--- a/src/core/lib/iomgr/workqueue_posix.c
+++ /dev/null
@@ -1,151 +0,0 @@
-/*
- *
- * Copyright 2015, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-#include <grpc/support/port_platform.h>
-
-#ifdef GPR_POSIX_SOCKET
-
-#include "src/core/lib/iomgr/workqueue.h"
-
-#include <stdio.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/lib/iomgr/ev_posix.h"
-
-static void on_readable(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
-
-grpc_error *grpc_workqueue_create(grpc_exec_ctx *exec_ctx,
-                                  grpc_workqueue **workqueue) {
-  char name[32];
-  *workqueue = gpr_malloc(sizeof(grpc_workqueue));
-  gpr_ref_init(&(*workqueue)->refs, 1);
-  gpr_mu_init(&(*workqueue)->mu);
-  (*workqueue)->closure_list.head = (*workqueue)->closure_list.tail = NULL;
-  grpc_error *err = grpc_wakeup_fd_init(&(*workqueue)->wakeup_fd);
-  if (err != GRPC_ERROR_NONE) {
-    gpr_free(*workqueue);
-    return err;
-  }
-  sprintf(name, "workqueue:%p", (void *)(*workqueue));
-  (*workqueue)->wakeup_read_fd = grpc_fd_create(
-      GRPC_WAKEUP_FD_GET_READ_FD(&(*workqueue)->wakeup_fd), name);
-  grpc_closure_init(&(*workqueue)->read_closure, on_readable, *workqueue);
-  grpc_fd_notify_on_read(exec_ctx, (*workqueue)->wakeup_read_fd,
-                         &(*workqueue)->read_closure);
-  return GRPC_ERROR_NONE;
-}
-
-static void workqueue_destroy(grpc_exec_ctx *exec_ctx,
-                              grpc_workqueue *workqueue) {
-  grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
-  grpc_fd_shutdown(exec_ctx, workqueue->wakeup_read_fd);
-}
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-void grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file, int line,
-                        const char *reason) {
-  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "WORKQUEUE:%p   ref %d -> %d %s",
-          workqueue, (int)workqueue->refs.count, (int)workqueue->refs.count + 1,
-          reason);
-#else
-void grpc_workqueue_ref(grpc_workqueue *workqueue) {
-#endif
-  gpr_ref(&workqueue->refs);
-}
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason) {
-  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "WORKQUEUE:%p unref %d -> %d %s",
-          workqueue, (int)workqueue->refs.count, (int)workqueue->refs.count - 1,
-          reason);
-#else
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
-#endif
-  if (gpr_unref(&workqueue->refs)) {
-    workqueue_destroy(exec_ctx, workqueue);
-  }
-}
-
-void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
-  gpr_mu_lock(&workqueue->mu);
-  grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
-  gpr_mu_unlock(&workqueue->mu);
-}
-
-static void on_readable(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  grpc_workqueue *workqueue = arg;
-
-  if (error != GRPC_ERROR_NONE) {
-    gpr_mu_destroy(&workqueue->mu);
-    /* HACK: let wakeup_fd code know that we stole the fd */
-    workqueue->wakeup_fd.read_fd = 0;
-    grpc_wakeup_fd_destroy(&workqueue->wakeup_fd);
-    grpc_fd_orphan(exec_ctx, workqueue->wakeup_read_fd, NULL, NULL, "destroy");
-    gpr_free(workqueue);
-  } else {
-    gpr_mu_lock(&workqueue->mu);
-    grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
-    error = grpc_wakeup_fd_consume_wakeup(&workqueue->wakeup_fd);
-    gpr_mu_unlock(&workqueue->mu);
-    if (error == GRPC_ERROR_NONE) {
-      grpc_fd_notify_on_read(exec_ctx, workqueue->wakeup_read_fd,
-                             &workqueue->read_closure);
-    } else {
-      /* recurse to get error handling */
-      on_readable(exec_ctx, arg, error);
-    }
-  }
-}
-
-void grpc_workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            grpc_closure *closure, grpc_error *error) {
-  grpc_error *push_error = GRPC_ERROR_NONE;
-  gpr_mu_lock(&workqueue->mu);
-  if (grpc_closure_list_empty(workqueue->closure_list)) {
-    push_error = grpc_wakeup_fd_wakeup(&workqueue->wakeup_fd);
-  }
-  grpc_closure_list_append(&workqueue->closure_list, closure, error);
-  if (push_error != GRPC_ERROR_NONE) {
-    const char *msg = grpc_error_string(push_error);
-    gpr_log(GPR_ERROR, "Failed to push to workqueue: %s", msg);
-    grpc_error_free_string(msg);
-    grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
-  }
-  gpr_mu_unlock(&workqueue->mu);
-}
-
-#endif /* GPR_POSIX_SOCKET */
diff --git a/src/core/lib/iomgr/workqueue_windows.c b/src/core/lib/iomgr/workqueue_windows.c
index 23e2dea185..5c93d3c59e 100644
--- a/src/core/lib/iomgr/workqueue_windows.c
+++ b/src/core/lib/iomgr/workqueue_windows.c
@@ -42,15 +42,17 @@
 // context, which is at least correct, if not performant or in the spirit of
 // workqueues.
 
-void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {}
-
 #ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-void grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file, int line,
-                        const char *reason) {}
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
+                                   int line, const char *reason) {
+  return workqueue;
+}
 void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
                           const char *file, int line, const char *reason) {}
 #else
-void grpc_workqueue_ref(grpc_workqueue *workqueue) {}
+grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue) {
+  return workqueue;
+}
 void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {}
 #endif
 
diff --git a/src/core/lib/profiling/basic_timers.c b/src/core/lib/profiling/basic_timers.c
index 51813d0461..bdf9af2339 100644
--- a/src/core/lib/profiling/basic_timers.c
+++ b/src/core/lib/profiling/basic_timers.c
@@ -83,6 +83,7 @@ static int g_shutdown;
 static gpr_thd_id g_writing_thread;
 static __thread int g_thread_id;
 static int g_next_thread_id;
+static int g_writing_enabled = 1;
 
 static int timer_log_push_back(gpr_timer_log_list *list, gpr_timer_log *log) {
   if (list->head == NULL) {
@@ -177,7 +178,7 @@ static void flush_logs(gpr_timer_log_list *list) {
   }
 }
 
-static void finish_writing() {
+static void finish_writing(void) {
   pthread_mutex_lock(&g_mu);
   g_shutdown = 1;
   pthread_cond_signal(&g_cv);
@@ -230,6 +231,10 @@ static void gpr_timers_log_add(const char *tagstr, marker_type type,
                                int important, const char *file, int line) {
   gpr_timer_entry *entry;
 
+  if (!g_writing_enabled) {
+    return;
+  }
+
   if (g_thread_log == NULL || g_thread_log->num_entries == MAX_COUNT) {
     rotate_log();
   }
@@ -261,6 +266,8 @@ void gpr_timer_end(const char *tagstr, int important, const char *file,
   gpr_timers_log_add(tagstr, END, important, file, line);
 }
 
+void gpr_timer_set_enabled(int enabled) { g_writing_enabled = enabled; }
+
 /* Basic profiler specific API functions. */
 void gpr_timers_global_init(void) {}
 
@@ -272,4 +279,6 @@ void gpr_timers_global_init(void) {}
 void gpr_timers_global_destroy(void) {}
 
 void gpr_timers_set_log_filename(const char *filename) {}
+
+void gpr_timer_set_enabled(int enabled) {}
 #endif /* GRPC_BASIC_PROFILER */
diff --git a/src/core/lib/profiling/timers.h b/src/core/lib/profiling/timers.h
index c8567e8137..621cdbf656 100644
--- a/src/core/lib/profiling/timers.h
+++ b/src/core/lib/profiling/timers.h
@@ -50,6 +50,8 @@ void gpr_timer_end(const char *tagstr, int important, const char *file,
 
 void gpr_timers_set_log_filename(const char *filename);
 
+void gpr_timer_set_enabled(int enabled);
+
 #if !(defined(GRPC_STAP_PROFILER) + defined(GRPC_BASIC_PROFILER))
 /* No profiling. No-op all the things. */
 #define GPR_TIMER_MARK(tag, important) \
diff --git a/src/core/lib/security/credentials/plugin/plugin_credentials.c b/src/core/lib/security/credentials/plugin/plugin_credentials.c
index 824ff081dc..905de3723e 100644
--- a/src/core/lib/security/credentials/plugin/plugin_credentials.c
+++ b/src/core/lib/security/credentials/plugin/plugin_credentials.c
@@ -37,6 +37,7 @@
 
 #include "src/core/lib/surface/api_trace.h"
 
+#include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
@@ -71,17 +72,33 @@ static void plugin_md_request_metadata_ready(void *request,
           error_details);
   } else {
     size_t i;
+    bool seen_illegal_header = false;
     grpc_credentials_md *md_array = NULL;
-    if (num_md > 0) {
+    for (i = 0; i < num_md; i++) {
+      if (!grpc_header_key_is_legal(md[i].key, strlen(md[i].key))) {
+        gpr_log(GPR_ERROR, "Plugin added invalid metadata key: %s", md[i].key);
+        seen_illegal_header = true;
+        break;
+      } else if (!grpc_is_binary_header(md[i].key, strlen(md[i].key)) &&
+                 !grpc_header_nonbin_value_is_legal(md[i].value,
+                                                    md[i].value_length)) {
+        gpr_log(GPR_ERROR, "Plugin added invalid metadata value.");
+        seen_illegal_header = true;
+        break;
+      }
+    }
+    if (seen_illegal_header) {
+      r->cb(&exec_ctx, r->user_data, NULL, 0, GRPC_CREDENTIALS_ERROR,
+            "Illegal metadata");
+    } else if (num_md > 0) {
       md_array = gpr_malloc(num_md * sizeof(grpc_credentials_md));
       for (i = 0; i < num_md; i++) {
         md_array[i].key = gpr_slice_from_copied_string(md[i].key);
         md_array[i].value =
             gpr_slice_from_copied_buffer(md[i].value, md[i].value_length);
       }
-    }
-    r->cb(&exec_ctx, r->user_data, md_array, num_md, GRPC_CREDENTIALS_OK, NULL);
-    if (md_array != NULL) {
+      r->cb(&exec_ctx, r->user_data, md_array, num_md, GRPC_CREDENTIALS_OK,
+            NULL);
       for (i = 0; i < num_md; i++) {
         gpr_slice_unref(md_array[i].key);
         gpr_slice_unref(md_array[i].value);
diff --git a/src/core/lib/security/transport/client_auth_filter.c b/src/core/lib/security/transport/client_auth_filter.c
index 2a1bf4d4e3..b366d1410f 100644
--- a/src/core/lib/security/transport/client_auth_filter.c
+++ b/src/core/lib/security/transport/client_auth_filter.c
@@ -40,6 +40,7 @@
 #include <grpc/support/string_util.h>
 
 #include "src/core/lib/channel/channel_stack.h"
+#include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/security/context/security_context.h"
 #include "src/core/lib/security/credentials/credentials.h"
 #include "src/core/lib/security/transport/security_connector.h"
@@ -218,6 +219,8 @@ static void on_host_checked(grpc_exec_ctx *exec_ctx, void *user_data,
 static void auth_start_transport_op(grpc_exec_ctx *exec_ctx,
                                     grpc_call_element *elem,
                                     grpc_transport_stream_op *op) {
+  GPR_TIMER_BEGIN("auth_start_transport_op", 0);
+
   /* grab pointers to our data from the call element */
   call_data *calld = elem->call_data;
   channel_data *chand = elem->channel_data;
@@ -258,12 +261,14 @@ static void auth_start_transport_op(grpc_exec_ctx *exec_ctx,
       grpc_channel_security_connector_check_call_host(
           exec_ctx, chand->security_connector, call_host, chand->auth_context,
           on_host_checked, elem);
+      GPR_TIMER_END("auth_start_transport_op", 0);
       return; /* early exit */
     }
   }
 
   /* pass control down the stack */
   grpc_call_next_op(exec_ctx, elem, op);
+  GPR_TIMER_END("auth_start_transport_op", 0);
 }
 
 /* Constructor for call_data */
diff --git a/src/core/lib/security/transport/secure_endpoint.c b/src/core/lib/security/transport/secure_endpoint.c
index 0169ccd9ef..acb0113ea8 100644
--- a/src/core/lib/security/transport/secure_endpoint.c
+++ b/src/core/lib/security/transport/secure_endpoint.c
@@ -38,6 +38,7 @@
 #include <grpc/support/slice_buffer.h>
 #include <grpc/support/sync.h>
 #include "src/core/lib/debug/trace.h"
+#include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/security/transport/tsi_error.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/tsi/transport_security_interface.h"
@@ -248,6 +249,8 @@ static void flush_write_staging_buffer(secure_endpoint *ep, uint8_t **cur,
 
 static void endpoint_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *secure_ep,
                            gpr_slice_buffer *slices, grpc_closure *cb) {
+  GPR_TIMER_BEGIN("secure_endpoint.endpoint_write", 0);
+
   unsigned i;
   tsi_result result = TSI_OK;
   secure_endpoint *ep = (secure_endpoint *)secure_ep;
@@ -323,10 +326,12 @@ static void endpoint_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *secure_ep,
         exec_ctx, cb,
         grpc_set_tsi_error_result(GRPC_ERROR_CREATE("Wrap failed"), result),
         NULL);
+    GPR_TIMER_END("secure_endpoint.endpoint_write", 0);
     return;
   }
 
   grpc_endpoint_write(exec_ctx, ep->wrapped_ep, &ep->output_buffer, cb);
+  GPR_TIMER_END("secure_endpoint.endpoint_write", 0);
 }
 
 static void endpoint_shutdown(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/security/transport/server_auth_filter.c b/src/core/lib/security/transport/server_auth_filter.c
index def16c8229..b2c6815af8 100644
--- a/src/core/lib/security/transport/server_auth_filter.c
+++ b/src/core/lib/security/transport/server_auth_filter.c
@@ -48,7 +48,7 @@ typedef struct call_data {
      up-call on transport_op, and remember to call our on_done_recv member after
      handling it. */
   grpc_closure auth_on_recv;
-  grpc_transport_stream_op transport_op;
+  grpc_transport_stream_op *transport_op;
   grpc_metadata_array md;
   const grpc_metadata *consumed_md;
   size_t num_consumed_md;
@@ -106,6 +106,10 @@ static grpc_mdelem *remove_consumed_md(void *user_data, grpc_mdelem *md) {
   return md;
 }
 
+static void destroy_op(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
+  gpr_free(arg);
+}
+
 /* called from application code */
 static void on_md_processing_done(
     void *user_data, const grpc_metadata *consumed_md, size_t num_consumed_md,
@@ -131,21 +135,22 @@ static void on_md_processing_done(
     grpc_exec_ctx_sched(&exec_ctx, calld->on_done_recv, GRPC_ERROR_NONE, NULL);
   } else {
     gpr_slice message;
-    grpc_transport_stream_op close_op;
-    memset(&close_op, 0, sizeof(close_op));
+    grpc_transport_stream_op *close_op = gpr_malloc(sizeof(*close_op));
+    memset(close_op, 0, sizeof(*close_op));
     grpc_metadata_array_destroy(&calld->md);
     error_details = error_details != NULL
                         ? error_details
                         : "Authentication metadata processing failed.";
     message = gpr_slice_from_copied_string(error_details);
-    calld->transport_op.send_initial_metadata = NULL;
-    if (calld->transport_op.send_message != NULL) {
-      grpc_byte_stream_destroy(&exec_ctx, calld->transport_op.send_message);
-      calld->transport_op.send_message = NULL;
+    calld->transport_op->send_initial_metadata = NULL;
+    if (calld->transport_op->send_message != NULL) {
+      grpc_byte_stream_destroy(&exec_ctx, calld->transport_op->send_message);
+      calld->transport_op->send_message = NULL;
     }
-    calld->transport_op.send_trailing_metadata = NULL;
-    grpc_transport_stream_op_add_close(&close_op, status, &message);
-    grpc_call_next_op(&exec_ctx, elem, &close_op);
+    calld->transport_op->send_trailing_metadata = NULL;
+    close_op->on_complete = grpc_closure_create(destroy_op, close_op);
+    grpc_transport_stream_op_add_close(close_op, status, &message);
+    grpc_call_next_op(&exec_ctx, elem, close_op);
     grpc_exec_ctx_sched(&exec_ctx, calld->on_done_recv,
                         grpc_error_set_int(GRPC_ERROR_CREATE(error_details),
                                            GRPC_ERROR_INT_GRPC_STATUS, status),
@@ -182,7 +187,7 @@ static void set_recv_ops_md_callbacks(grpc_call_element *elem,
     calld->recv_initial_metadata = op->recv_initial_metadata;
     calld->on_done_recv = op->recv_initial_metadata_ready;
     op->recv_initial_metadata_ready = &calld->auth_on_recv;
-    calld->transport_op = *op;
+    calld->transport_op = op;
   }
 }
 
diff --git a/src/core/lib/support/log.c b/src/core/lib/support/log.c
index 899f1218b6..af1651dae5 100644
--- a/src/core/lib/support/log.c
+++ b/src/core/lib/support/log.c
@@ -60,8 +60,9 @@ const char *gpr_log_severity_string(gpr_log_severity severity) {
 
 void gpr_log_message(const char *file, int line, gpr_log_severity severity,
                      const char *message) {
-  if ((gpr_atm)severity < gpr_atm_no_barrier_load(&g_min_severity_to_print))
+  if ((gpr_atm)severity < gpr_atm_no_barrier_load(&g_min_severity_to_print)) {
     return;
+  }
 
   gpr_log_func_args lfargs;
   memset(&lfargs, 0, sizeof(lfargs));
@@ -82,11 +83,11 @@ void gpr_log_verbosity_init() {
 
   gpr_atm min_severity_to_print = GPR_LOG_SEVERITY_ERROR;
   if (verbosity != NULL) {
-    if (strcmp(verbosity, "DEBUG") == 0) {
+    if (gpr_stricmp(verbosity, "DEBUG") == 0) {
       min_severity_to_print = (gpr_atm)GPR_LOG_SEVERITY_DEBUG;
-    } else if (strcmp(verbosity, "INFO") == 0) {
+    } else if (gpr_stricmp(verbosity, "INFO") == 0) {
       min_severity_to_print = (gpr_atm)GPR_LOG_SEVERITY_INFO;
-    } else if (strcmp(verbosity, "ERROR") == 0) {
+    } else if (gpr_stricmp(verbosity, "ERROR") == 0) {
       min_severity_to_print = (gpr_atm)GPR_LOG_SEVERITY_ERROR;
     }
     gpr_free(verbosity);
diff --git a/src/core/lib/support/mpscq.c b/src/core/lib/support/mpscq.c
new file mode 100644
index 0000000000..5b9323275a
--- /dev/null
+++ b/src/core/lib/support/mpscq.c
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/support/mpscq.h"
+
+#include <grpc/support/log.h>
+
+void gpr_mpscq_init(gpr_mpscq *q) {
+  gpr_atm_no_barrier_store(&q->head, (gpr_atm)&q->stub);
+  q->tail = &q->stub;
+  gpr_atm_no_barrier_store(&q->stub.next, (gpr_atm)NULL);
+}
+
+void gpr_mpscq_destroy(gpr_mpscq *q) {
+  GPR_ASSERT(gpr_atm_no_barrier_load(&q->head) == (gpr_atm)&q->stub);
+  GPR_ASSERT(q->tail == &q->stub);
+}
+
+void gpr_mpscq_push(gpr_mpscq *q, gpr_mpscq_node *n) {
+  gpr_atm_no_barrier_store(&n->next, (gpr_atm)NULL);
+  gpr_mpscq_node *prev =
+      (gpr_mpscq_node *)gpr_atm_full_xchg(&q->head, (gpr_atm)n);
+  gpr_atm_rel_store(&prev->next, (gpr_atm)n);
+}
+
+gpr_mpscq_node *gpr_mpscq_pop(gpr_mpscq *q) {
+  gpr_mpscq_node *tail = q->tail;
+  gpr_mpscq_node *next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next);
+  if (tail == &q->stub) {
+    // indicates the list is actually (ephemerally) empty
+    if (next == NULL) return NULL;
+    q->tail = next;
+    tail = next;
+    next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next);
+  }
+  if (next != NULL) {
+    q->tail = next;
+    return tail;
+  }
+  gpr_mpscq_node *head = (gpr_mpscq_node *)gpr_atm_acq_load(&q->head);
+  if (tail != head) {
+    // indicates a retry is in order: we're still adding
+    return NULL;
+  }
+  gpr_mpscq_push(q, &q->stub);
+  next = (gpr_mpscq_node *)gpr_atm_acq_load(&tail->next);
+  if (next != NULL) {
+    q->tail = next;
+    return tail;
+  }
+  // indicates a retry is in order: we're still adding
+  return NULL;
+}
diff --git a/src/core/lib/iomgr/workqueue_posix.h b/src/core/lib/support/mpscq.h
index 0f26ba58e2..977a117952 100644
--- a/src/core/lib/iomgr/workqueue_posix.h
+++ b/src/core/lib/support/mpscq.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,28 +31,35 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H
-#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H
+#ifndef GRPC_CORE_LIB_SUPPORT_MPSCQ_H
+#define GRPC_CORE_LIB_SUPPORT_MPSCQ_H
 
-#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+#include <grpc/support/atm.h>
+#include <stddef.h>
 
-struct grpc_fd;
+// Multiple-producer single-consumer lock free queue, based upon the
+// implementation from Dmitry Vyukov here:
+// http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue
 
-struct grpc_workqueue {
-  gpr_refcount refs;
+// List node (include this in a data structure at the top, and add application
+// fields after it - to simulate inheritance)
+typedef struct gpr_mpscq_node { gpr_atm next; } gpr_mpscq_node;
 
-  gpr_mu mu;
-  grpc_closure_list closure_list;
+// Actual queue type
+typedef struct gpr_mpscq {
+  gpr_atm head;
+  // make sure head & tail don't share a cacheline
+  char padding[GPR_CACHELINE_SIZE];
+  gpr_mpscq_node *tail;
+  gpr_mpscq_node stub;
+} gpr_mpscq;
 
-  grpc_wakeup_fd wakeup_fd;
-  struct grpc_fd *wakeup_read_fd;
+void gpr_mpscq_init(gpr_mpscq *q);
+void gpr_mpscq_destroy(gpr_mpscq *q);
+// Push a node
+void gpr_mpscq_push(gpr_mpscq *q, gpr_mpscq_node *n);
+// Pop a node (returns NULL if no node is ready - which doesn't indicate that
+// the queue is empty!!)
+gpr_mpscq_node *gpr_mpscq_pop(gpr_mpscq *q);
 
-  grpc_closure read_closure;
-};
-
-/** Create a work queue. Returns an error if creation fails. If creation
-    succeeds, sets *workqueue to point to it. */
-grpc_error *grpc_workqueue_create(grpc_exec_ctx *exec_ctx,
-                                  grpc_workqueue **workqueue);
-
-#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H */
+#endif /* GRPC_CORE_LIB_SUPPORT_MPSCQ_H */
diff --git a/src/core/lib/support/string.c b/src/core/lib/support/string.c
index 30c1e67647..d17fb9da4b 100644
--- a/src/core/lib/support/string.c
+++ b/src/core/lib/support/string.c
@@ -304,3 +304,14 @@ void gpr_strvec_add(gpr_strvec *sv, char *str) {
 char *gpr_strvec_flatten(gpr_strvec *sv, size_t *final_length) {
   return gpr_strjoin((const char **)sv->strs, sv->count, final_length);
 }
+
+int gpr_stricmp(const char *a, const char *b) {
+  int ca, cb;
+  do {
+    ca = tolower(*a);
+    cb = tolower(*b);
+    ++a;
+    ++b;
+  } while (ca == cb && ca && cb);
+  return ca - cb;
+}
diff --git a/src/core/lib/support/string.h b/src/core/lib/support/string.h
index 2b6bb3eec6..9a94e9471c 100644
--- a/src/core/lib/support/string.h
+++ b/src/core/lib/support/string.h
@@ -118,6 +118,10 @@ void gpr_strvec_add(gpr_strvec *strs, char *add);
    total_length as per gpr_strjoin */
 char *gpr_strvec_flatten(gpr_strvec *strs, size_t *total_length);
 
+/** Case insensitive string comparison... return <0 if lower(a)<lower(b), ==0 if
+    lower(a)==lower(b), >0 if lower(a)>lower(b) */
+int gpr_stricmp(const char *a, const char *b);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 772681109a..6b2badf71b 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -109,6 +109,10 @@ typedef struct batch_control {
   uint8_t recv_message;
   uint8_t recv_final_op;
   uint8_t is_notify_tag_closure;
+
+  /* TODO(ctiller): now that this is inlined, figure out how much of the above
+                    state can be eliminated */
+  grpc_transport_stream_op op;
 } batch_control;
 
 struct grpc_call {
@@ -226,33 +230,33 @@ static void destroy_call(grpc_exec_ctx *exec_ctx, void *call_stack,
 static void receiving_slice_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
                                   grpc_error *error);
 
-grpc_call *grpc_call_create(
-    grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
-    grpc_completion_queue *cq, grpc_pollset_set *pollset_set_alternative,
-    const void *server_transport_data, grpc_mdelem **add_initial_metadata,
-    size_t add_initial_metadata_count, gpr_timespec send_deadline) {
+grpc_error *grpc_call_create(const grpc_call_create_args *args,
+                             grpc_call **out_call) {
   size_t i, j;
-  grpc_channel_stack *channel_stack = grpc_channel_get_channel_stack(channel);
+  grpc_channel_stack *channel_stack =
+      grpc_channel_get_channel_stack(args->channel);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_call *call;
   GPR_TIMER_BEGIN("grpc_call_create", 0);
   call = gpr_malloc(sizeof(grpc_call) + channel_stack->call_stack_size);
+  *out_call = call;
   memset(call, 0, sizeof(grpc_call));
   gpr_mu_init(&call->mu);
-  call->channel = channel;
-  call->cq = cq;
-  call->parent = parent_call;
+  call->channel = args->channel;
+  call->cq = args->cq;
+  call->parent = args->parent_call;
   /* Always support no compression */
   GPR_BITSET(&call->encodings_accepted_by_peer, GRPC_COMPRESS_NONE);
-  call->is_client = server_transport_data == NULL;
+  call->is_client = args->server_transport_data == NULL;
   if (call->is_client) {
-    GPR_ASSERT(add_initial_metadata_count < MAX_SEND_EXTRA_METADATA_COUNT);
-    for (i = 0; i < add_initial_metadata_count; i++) {
-      call->send_extra_metadata[i].md = add_initial_metadata[i];
+    GPR_ASSERT(args->add_initial_metadata_count <
+               MAX_SEND_EXTRA_METADATA_COUNT);
+    for (i = 0; i < args->add_initial_metadata_count; i++) {
+      call->send_extra_metadata[i].md = args->add_initial_metadata[i];
     }
-    call->send_extra_metadata_count = (int)add_initial_metadata_count;
+    call->send_extra_metadata_count = (int)args->add_initial_metadata_count;
   } else {
-    GPR_ASSERT(add_initial_metadata_count == 0);
+    GPR_ASSERT(args->add_initial_metadata_count == 0);
     call->send_extra_metadata_count = 0;
   }
   for (i = 0; i < 2; i++) {
@@ -261,78 +265,79 @@ grpc_call *grpc_call_create(
     }
   }
   call->send_deadline =
-      gpr_convert_clock_type(send_deadline, GPR_CLOCK_MONOTONIC);
-  GRPC_CHANNEL_INTERNAL_REF(channel, "call");
+      gpr_convert_clock_type(args->send_deadline, GPR_CLOCK_MONOTONIC);
+  GRPC_CHANNEL_INTERNAL_REF(args->channel, "call");
   /* initial refcount dropped by grpc_call_destroy */
   grpc_error *error = grpc_call_stack_init(
       &exec_ctx, channel_stack, 1, destroy_call, call, call->context,
-      server_transport_data, CALL_STACK_FROM_CALL(call));
+      args->server_transport_data, CALL_STACK_FROM_CALL(call));
   if (error != GRPC_ERROR_NONE) {
     intptr_t status;
-    if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, &status))
+    if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, &status)) {
       status = GRPC_STATUS_UNKNOWN;
+    }
     const char *error_str =
         grpc_error_get_str(error, GRPC_ERROR_STR_DESCRIPTION);
     close_with_status(&exec_ctx, call, (grpc_status_code)status,
                       error_str == NULL ? "unknown error" : error_str);
-    GRPC_ERROR_UNREF(error);
   }
-  if (cq != NULL) {
+  if (args->cq != NULL) {
     GPR_ASSERT(
-        pollset_set_alternative == NULL &&
+        args->pollset_set_alternative == NULL &&
         "Only one of 'cq' and 'pollset_set_alternative' should be non-NULL.");
-    GRPC_CQ_INTERNAL_REF(cq, "bind");
+    GRPC_CQ_INTERNAL_REF(args->cq, "bind");
     call->pollent =
-        grpc_polling_entity_create_from_pollset(grpc_cq_pollset(cq));
+        grpc_polling_entity_create_from_pollset(grpc_cq_pollset(args->cq));
   }
-  if (pollset_set_alternative != NULL) {
-    call->pollent =
-        grpc_polling_entity_create_from_pollset_set(pollset_set_alternative);
+  if (args->pollset_set_alternative != NULL) {
+    call->pollent = grpc_polling_entity_create_from_pollset_set(
+        args->pollset_set_alternative);
   }
   if (!grpc_polling_entity_is_empty(&call->pollent)) {
     grpc_call_stack_set_pollset_or_pollset_set(
         &exec_ctx, CALL_STACK_FROM_CALL(call), &call->pollent);
   }
-  if (parent_call != NULL) {
-    GRPC_CALL_INTERNAL_REF(parent_call, "child");
+  gpr_timespec send_deadline = args->send_deadline;
+  if (args->parent_call != NULL) {
+    GRPC_CALL_INTERNAL_REF(args->parent_call, "child");
     GPR_ASSERT(call->is_client);
-    GPR_ASSERT(!parent_call->is_client);
+    GPR_ASSERT(!args->parent_call->is_client);
 
-    gpr_mu_lock(&parent_call->mu);
+    gpr_mu_lock(&args->parent_call->mu);
 
-    if (propagation_mask & GRPC_PROPAGATE_DEADLINE) {
+    if (args->propagation_mask & GRPC_PROPAGATE_DEADLINE) {
       send_deadline = gpr_time_min(
           gpr_convert_clock_type(send_deadline,
-                                 parent_call->send_deadline.clock_type),
-          parent_call->send_deadline);
+                                 args->parent_call->send_deadline.clock_type),
+          args->parent_call->send_deadline);
     }
     /* for now GRPC_PROPAGATE_TRACING_CONTEXT *MUST* be passed with
      * GRPC_PROPAGATE_STATS_CONTEXT */
     /* TODO(ctiller): This should change to use the appropriate census start_op
      * call. */
-    if (propagation_mask & GRPC_PROPAGATE_CENSUS_TRACING_CONTEXT) {
-      GPR_ASSERT(propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
-      grpc_call_context_set(call, GRPC_CONTEXT_TRACING,
-                            parent_call->context[GRPC_CONTEXT_TRACING].value,
-                            NULL);
+    if (args->propagation_mask & GRPC_PROPAGATE_CENSUS_TRACING_CONTEXT) {
+      GPR_ASSERT(args->propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
+      grpc_call_context_set(
+          call, GRPC_CONTEXT_TRACING,
+          args->parent_call->context[GRPC_CONTEXT_TRACING].value, NULL);
     } else {
-      GPR_ASSERT(propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
+      GPR_ASSERT(args->propagation_mask & GRPC_PROPAGATE_CENSUS_STATS_CONTEXT);
     }
-    if (propagation_mask & GRPC_PROPAGATE_CANCELLATION) {
+    if (args->propagation_mask & GRPC_PROPAGATE_CANCELLATION) {
       call->cancellation_is_inherited = 1;
     }
 
-    if (parent_call->first_child == NULL) {
-      parent_call->first_child = call;
+    if (args->parent_call->first_child == NULL) {
+      args->parent_call->first_child = call;
       call->sibling_next = call->sibling_prev = call;
     } else {
-      call->sibling_next = parent_call->first_child;
-      call->sibling_prev = parent_call->first_child->sibling_prev;
+      call->sibling_next = args->parent_call->first_child;
+      call->sibling_prev = args->parent_call->first_child->sibling_prev;
       call->sibling_next->sibling_prev = call->sibling_prev->sibling_next =
           call;
     }
 
-    gpr_mu_unlock(&parent_call->mu);
+    gpr_mu_unlock(&args->parent_call->mu);
   }
   if (gpr_time_cmp(send_deadline, gpr_inf_future(send_deadline.clock_type)) !=
       0) {
@@ -340,7 +345,7 @@ grpc_call *grpc_call_create(
   }
   grpc_exec_ctx_finish(&exec_ctx);
   GPR_TIMER_END("grpc_call_create", 0);
-  return call;
+  return error;
 }
 
 void grpc_call_set_completion_queue(grpc_exec_ctx *exec_ctx, grpc_call *call,
@@ -778,6 +783,7 @@ typedef struct termination_closure {
   grpc_error *error;
   grpc_closure *op_closure;
   enum { TC_CANCEL, TC_CLOSE } type;
+  grpc_transport_stream_op op;
 } termination_closure;
 
 static void done_termination(grpc_exec_ctx *exec_ctx, void *tcp,
@@ -797,26 +803,24 @@ static void done_termination(grpc_exec_ctx *exec_ctx, void *tcp,
 }
 
 static void send_cancel(grpc_exec_ctx *exec_ctx, void *tcp, grpc_error *error) {
-  grpc_transport_stream_op op;
   termination_closure *tc = tcp;
-  memset(&op, 0, sizeof(op));
-  op.cancel_error = tc->error;
+  memset(&tc->op, 0, sizeof(tc->op));
+  tc->op.cancel_error = tc->error;
   /* reuse closure to catch completion */
   grpc_closure_init(&tc->closure, done_termination, tc);
-  op.on_complete = &tc->closure;
-  execute_op(exec_ctx, tc->call, &op);
+  tc->op.on_complete = &tc->closure;
+  execute_op(exec_ctx, tc->call, &tc->op);
 }
 
 static void send_close(grpc_exec_ctx *exec_ctx, void *tcp, grpc_error *error) {
-  grpc_transport_stream_op op;
   termination_closure *tc = tcp;
-  memset(&op, 0, sizeof(op));
-  op.close_error = tc->error;
+  memset(&tc->op, 0, sizeof(tc->op));
+  tc->op.close_error = tc->error;
   /* reuse closure to catch completion */
   grpc_closure_init(&tc->closure, done_termination, tc);
-  tc->op_closure = op.on_complete;
-  op.on_complete = &tc->closure;
-  execute_op(exec_ctx, tc->call, &op);
+  tc->op_closure = tc->op.on_complete;
+  tc->op.on_complete = &tc->closure;
+  execute_op(exec_ctx, tc->call, &tc->op);
 }
 
 static grpc_call_error terminate_with_status(grpc_exec_ctx *exec_ctx,
@@ -1086,9 +1090,14 @@ static void finish_batch_completion(grpc_exec_ctx *exec_ctx, void *user_data,
 static void post_batch_completion(grpc_exec_ctx *exec_ctx,
                                   batch_control *bctl) {
   grpc_call *call = bctl->call;
+  grpc_error *error = bctl->error;
+  if (bctl->recv_final_op) {
+    GRPC_ERROR_UNREF(error);
+    error = GRPC_ERROR_NONE;
+  }
   if (bctl->is_notify_tag_closure) {
     /* unrefs bctl->error */
-    grpc_exec_ctx_sched(exec_ctx, bctl->notify_tag, bctl->error, NULL);
+    grpc_closure_run(exec_ctx, bctl->notify_tag, error);
     gpr_mu_lock(&call->mu);
     bctl->call->used_batches =
         (uint8_t)(bctl->call->used_batches &
@@ -1097,7 +1106,7 @@ static void post_batch_completion(grpc_exec_ctx *exec_ctx,
     GRPC_CALL_INTERNAL_UNREF(exec_ctx, call, "completion");
   } else {
     /* unrefs bctl->error */
-    grpc_cq_end_op(exec_ctx, bctl->call->cq, bctl->notify_tag, bctl->error,
+    grpc_cq_end_op(exec_ctx, bctl->call->cq, bctl->notify_tag, error,
                    finish_batch_completion, bctl, &bctl->cq_completion);
   }
 }
@@ -1160,17 +1169,6 @@ static void process_data_after_md(grpc_exec_ctx *exec_ctx, batch_control *bctl,
     if (gpr_unref(&bctl->steps_to_complete)) {
       post_batch_completion(exec_ctx, bctl);
     }
-  } else if (call->receiving_stream->length >
-             grpc_channel_get_max_message_length(call->channel)) {
-    cancel_with_status(exec_ctx, call, GRPC_STATUS_INTERNAL,
-                       "Max message size exceeded");
-    grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
-    call->receiving_stream = NULL;
-    *call->receiving_buffer = NULL;
-    call->receiving_message = 0;
-    if (gpr_unref(&bctl->steps_to_complete)) {
-      post_batch_completion(exec_ctx, bctl);
-    }
   } else {
     call->test_only_last_message_flags = call->receiving_stream->flags;
     if ((call->receiving_stream->flags & GRPC_WRITE_INTERNAL_COMPRESS) &&
@@ -1254,6 +1252,14 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
   }
 }
 
+static void add_batch_error(batch_control *bctl, grpc_error *error) {
+  if (error == GRPC_ERROR_NONE) return;
+  if (bctl->error == GRPC_ERROR_NONE) {
+    bctl->error = GRPC_ERROR_CREATE("Call batch operation failed");
+  }
+  bctl->error = grpc_error_add_child(bctl->error, error);
+}
+
 static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
                                              void *bctlp, grpc_error *error) {
   batch_control *bctl = bctlp;
@@ -1261,9 +1267,8 @@ static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
 
   gpr_mu_lock(&call->mu);
 
-  if (error != GRPC_ERROR_NONE) {
-    bctl->error = GRPC_ERROR_REF(error);
-  } else {
+  add_batch_error(bctl, GRPC_ERROR_REF(error));
+  if (error == GRPC_ERROR_NONE) {
     grpc_metadata_batch *md =
         &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
     grpc_metadata_batch_filter(md, recv_initial_filter, call);
@@ -1356,8 +1361,7 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp,
     GRPC_ERROR_UNREF(error);
     error = GRPC_ERROR_NONE;
   }
-  GRPC_ERROR_UNREF(bctl->error);
-  bctl->error = GRPC_ERROR_REF(error);
+  add_batch_error(bctl, GRPC_ERROR_REF(error));
   gpr_mu_unlock(&call->mu);
   if (gpr_unref(&bctl->steps_to_complete)) {
     post_batch_completion(exec_ctx, bctl);
@@ -1370,7 +1374,6 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
                                         grpc_call *call, const grpc_op *ops,
                                         size_t nops, void *notify_tag,
                                         int is_notify_tag_closure) {
-  grpc_transport_stream_op stream_op;
   size_t i;
   const grpc_op *op;
   batch_control *bctl;
@@ -1384,8 +1387,6 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
 
   GRPC_CALL_LOG_BATCH(GPR_INFO, call, ops, nops, notify_tag);
 
-  memset(&stream_op, 0, sizeof(stream_op));
-
   /* TODO(ctiller): this feels like it could be made lock-free */
   gpr_mu_lock(&call->mu);
   bctl = allocate_batch_control(call);
@@ -1394,6 +1395,10 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
   bctl->notify_tag = notify_tag;
   bctl->is_notify_tag_closure = (uint8_t)(is_notify_tag_closure != 0);
 
+  grpc_transport_stream_op *stream_op = &bctl->op;
+  memset(stream_op, 0, sizeof(*stream_op));
+  stream_op->covered_by_poller = true;
+
   if (nops == 0) {
     GRPC_CALL_INTERNAL_REF(call, "completion");
     bctl->error = GRPC_ERROR_NONE;
@@ -1471,9 +1476,9 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         }
         /* TODO(ctiller): just make these the same variable? */
         call->metadata_batch[0][0].deadline = call->send_deadline;
-        stream_op.send_initial_metadata =
+        stream_op->send_initial_metadata =
             &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */];
-        stream_op.send_initial_metadata_flags = op->flags;
+        stream_op->send_initial_metadata_flags = op->flags;
         break;
       case GRPC_OP_SEND_MESSAGE:
         if (!are_write_flags_valid(op->flags)) {
@@ -1493,7 +1498,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         grpc_slice_buffer_stream_init(
             &call->sending_stream,
             &op->data.send_message->data.raw.slice_buffer, op->flags);
-        stream_op.send_message = &call->sending_stream.base;
+        stream_op->send_message = &call->sending_stream.base;
         break;
       case GRPC_OP_SEND_CLOSE_FROM_CLIENT:
         /* Flag validation: currently allow no flags */
@@ -1511,7 +1516,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         }
         bctl->send_final_op = 1;
         call->sent_final_op = 1;
-        stream_op.send_trailing_metadata =
+        stream_op->send_trailing_metadata =
             &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
         break;
       case GRPC_OP_SEND_STATUS_FROM_SERVER:
@@ -1558,7 +1563,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
           error = GRPC_CALL_ERROR_INVALID_METADATA;
           goto done_with_error;
         }
-        stream_op.send_trailing_metadata =
+        stream_op->send_trailing_metadata =
             &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
         break;
       case GRPC_OP_RECV_INITIAL_METADATA:
@@ -1576,9 +1581,9 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         grpc_closure_init(&call->receiving_initial_metadata_ready,
                           receiving_initial_metadata_ready, bctl);
         bctl->recv_initial_metadata = 1;
-        stream_op.recv_initial_metadata =
+        stream_op->recv_initial_metadata =
             &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
-        stream_op.recv_initial_metadata_ready =
+        stream_op->recv_initial_metadata_ready =
             &call->receiving_initial_metadata_ready;
         num_completion_callbacks_needed++;
         break;
@@ -1595,10 +1600,10 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->receiving_message = 1;
         bctl->recv_message = 1;
         call->receiving_buffer = op->data.recv_message;
-        stream_op.recv_message = &call->receiving_stream;
+        stream_op->recv_message = &call->receiving_stream;
         grpc_closure_init(&call->receiving_stream_ready, receiving_stream_ready,
                           bctl);
-        stream_op.recv_message_ready = &call->receiving_stream_ready;
+        stream_op->recv_message_ready = &call->receiving_stream_ready;
         num_completion_callbacks_needed++;
         break;
       case GRPC_OP_RECV_STATUS_ON_CLIENT:
@@ -1624,9 +1629,9 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->final_op.client.status_details_capacity =
             op->data.recv_status_on_client.status_details_capacity;
         bctl->recv_final_op = 1;
-        stream_op.recv_trailing_metadata =
+        stream_op->recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-        stream_op.collect_stats =
+        stream_op->collect_stats =
             &call->final_info.stats.transport_stream_stats;
         break;
       case GRPC_OP_RECV_CLOSE_ON_SERVER:
@@ -1647,9 +1652,9 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->final_op.server.cancelled =
             op->data.recv_close_on_server.cancelled;
         bctl->recv_final_op = 1;
-        stream_op.recv_trailing_metadata =
+        stream_op->recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-        stream_op.collect_stats =
+        stream_op->collect_stats =
             &call->final_info.stats.transport_stream_stats;
         break;
     }
@@ -1661,12 +1666,12 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
   }
   gpr_ref_init(&bctl->steps_to_complete, num_completion_callbacks_needed);
 
-  stream_op.context = call->context;
+  stream_op->context = call->context;
   grpc_closure_init(&bctl->finish_batch, finish_batch, bctl);
-  stream_op.on_complete = &bctl->finish_batch;
+  stream_op->on_complete = &bctl->finish_batch;
   gpr_mu_unlock(&call->mu);
 
-  execute_op(exec_ctx, call, &stream_op);
+  execute_op(exec_ctx, call, stream_op);
 
 done:
   GPR_TIMER_END("grpc_call_start_batch", 0);
diff --git a/src/core/lib/surface/call.h b/src/core/lib/surface/call.h
index 3a78fe3aa3..18af41b7fb 100644
--- a/src/core/lib/surface/call.h
+++ b/src/core/lib/surface/call.h
@@ -49,15 +49,29 @@ typedef void (*grpc_ioreq_completion_func)(grpc_exec_ctx *exec_ctx,
                                            grpc_call *call, int success,
                                            void *user_data);
 
-grpc_call *grpc_call_create(grpc_channel *channel, grpc_call *parent_call,
-                            uint32_t propagation_mask,
-                            grpc_completion_queue *cq,
-                            /* if not NULL, it'll be used in lieu of \a cq */
-                            grpc_pollset_set *pollset_set_alternative,
-                            const void *server_transport_data,
-                            grpc_mdelem **add_initial_metadata,
-                            size_t add_initial_metadata_count,
-                            gpr_timespec send_deadline);
+typedef struct grpc_call_create_args {
+  grpc_channel *channel;
+
+  grpc_call *parent_call;
+  uint32_t propagation_mask;
+
+  grpc_completion_queue *cq;
+  /* if not NULL, it'll be used in lieu of cq */
+  grpc_pollset_set *pollset_set_alternative;
+
+  const void *server_transport_data;
+
+  grpc_mdelem **add_initial_metadata;
+  size_t add_initial_metadata_count;
+
+  gpr_timespec send_deadline;
+} grpc_call_create_args;
+
+/* Create a new call based on \a args.
+   Regardless of success or failure, always returns a valid new call into *call
+   */
+grpc_error *grpc_call_create(const grpc_call_create_args *args,
+                             grpc_call **call);
 
 void grpc_call_set_completion_queue(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                     grpc_completion_queue *cq);
diff --git a/src/core/lib/surface/channel.c b/src/core/lib/surface/channel.c
index 6d2b1c4935..92d783b78d 100644
--- a/src/core/lib/surface/channel.c
+++ b/src/core/lib/surface/channel.c
@@ -64,7 +64,6 @@ typedef struct registered_call {
 
 struct grpc_channel {
   int is_client;
-  uint32_t max_message_length;
   grpc_compression_options compression_options;
   grpc_mdelem *default_authority;
 
@@ -80,9 +79,6 @@ struct grpc_channel {
 #define CHANNEL_FROM_TOP_ELEM(top_elem) \
   CHANNEL_FROM_CHANNEL_STACK(grpc_channel_stack_from_top_element(top_elem))
 
-/* the protobuf library will (by default) start warning at 100megs */
-#define DEFAULT_MAX_MESSAGE_LENGTH (4 * 1024 * 1024)
-
 static void destroy_channel(grpc_exec_ctx *exec_ctx, void *arg,
                             grpc_error *error);
 
@@ -114,21 +110,10 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
   gpr_mu_init(&channel->registered_call_mu);
   channel->registered_calls = NULL;
 
-  channel->max_message_length = DEFAULT_MAX_MESSAGE_LENGTH;
   grpc_compression_options_init(&channel->compression_options);
   if (args) {
     for (size_t i = 0; i < args->num_args; i++) {
-      if (0 == strcmp(args->args[i].key, GRPC_ARG_MAX_MESSAGE_LENGTH)) {
-        if (args->args[i].type != GRPC_ARG_INTEGER) {
-          gpr_log(GPR_ERROR, "%s ignored: it must be an integer",
-                  GRPC_ARG_MAX_MESSAGE_LENGTH);
-        } else if (args->args[i].value.integer < 0) {
-          gpr_log(GPR_ERROR, "%s ignored: it must be >= 0",
-                  GRPC_ARG_MAX_MESSAGE_LENGTH);
-        } else {
-          channel->max_message_length = (uint32_t)args->args[i].value.integer;
-        }
-      } else if (0 == strcmp(args->args[i].key, GRPC_ARG_DEFAULT_AUTHORITY)) {
+      if (0 == strcmp(args->args[i].key, GRPC_ARG_DEFAULT_AUTHORITY)) {
         if (args->args[i].type != GRPC_ARG_STRING) {
           gpr_log(GPR_ERROR, "%s ignored: it must be a string",
                   GRPC_ARG_DEFAULT_AUTHORITY);
@@ -208,9 +193,21 @@ static grpc_call *grpc_channel_create_call_internal(
     send_metadata[num_metadata++] = GRPC_MDELEM_REF(channel->default_authority);
   }
 
-  return grpc_call_create(channel, parent_call, propagation_mask, cq,
-                          pollset_set_alternative, NULL, send_metadata,
-                          num_metadata, deadline);
+  grpc_call_create_args args;
+  memset(&args, 0, sizeof(args));
+  args.channel = channel;
+  args.parent_call = parent_call;
+  args.propagation_mask = propagation_mask;
+  args.cq = cq;
+  args.pollset_set_alternative = pollset_set_alternative;
+  args.server_transport_data = NULL;
+  args.add_initial_metadata = send_metadata;
+  args.add_initial_metadata_count = num_metadata;
+  args.send_deadline = deadline;
+
+  grpc_call *call;
+  GRPC_LOG_IF_ERROR("call_create", grpc_call_create(&args, &call));
+  return call;
 }
 
 grpc_call *grpc_channel_create_call(grpc_channel *channel,
@@ -334,14 +331,13 @@ static void destroy_channel(grpc_exec_ctx *exec_ctx, void *arg,
 }
 
 void grpc_channel_destroy(grpc_channel *channel) {
-  grpc_transport_op op;
+  grpc_transport_op *op = grpc_make_transport_op(NULL);
   grpc_channel_element *elem;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   GRPC_API_TRACE("grpc_channel_destroy(channel=%p)", 1, (channel));
-  memset(&op, 0, sizeof(op));
-  op.disconnect_with_error = GRPC_ERROR_CREATE("Channel Destroyed");
+  op->disconnect_with_error = GRPC_ERROR_CREATE("Channel Destroyed");
   elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CHANNEL(channel), 0);
-  elem->filter->start_transport_op(&exec_ctx, elem, &op);
+  elem->filter->start_transport_op(&exec_ctx, elem, op);
 
   GRPC_CHANNEL_INTERNAL_UNREF(&exec_ctx, channel, "channel");
 
@@ -371,7 +367,3 @@ grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_channel *channel, int i) {
   return grpc_mdelem_from_metadata_strings(GRPC_MDSTR_GRPC_STATUS,
                                            grpc_mdstr_from_string(tmp));
 }
-
-uint32_t grpc_channel_get_max_message_length(grpc_channel *channel) {
-  return channel->max_message_length;
-}
diff --git a/src/core/lib/surface/channel.h b/src/core/lib/surface/channel.h
index 4c62974346..23cc8656ca 100644
--- a/src/core/lib/surface/channel.h
+++ b/src/core/lib/surface/channel.h
@@ -64,7 +64,6 @@ grpc_channel_stack *grpc_channel_get_channel_stack(grpc_channel *channel);
     The returned elem is owned by the caller. */
 grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_channel *channel,
                                                  int status_code);
-uint32_t grpc_channel_get_max_message_length(grpc_channel *channel);
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
 void grpc_channel_internal_ref(grpc_channel *channel, const char *reason);
diff --git a/src/core/lib/surface/channel_ping.c b/src/core/lib/surface/channel_ping.c
index 9818f9d2f2..0d2f01a649 100644
--- a/src/core/lib/surface/channel_ping.c
+++ b/src/core/lib/surface/channel_ping.c
@@ -61,19 +61,20 @@ static void ping_done(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
 
 void grpc_channel_ping(grpc_channel *channel, grpc_completion_queue *cq,
                        void *tag, void *reserved) {
-  grpc_transport_op op;
+  GRPC_API_TRACE("grpc_channel_ping(channel=%p, cq=%p, tag=%p, reserved=%p)", 4,
+                 (channel, cq, tag, reserved));
+  grpc_transport_op *op = grpc_make_transport_op(NULL);
   ping_result *pr = gpr_malloc(sizeof(*pr));
   grpc_channel_element *top_elem =
       grpc_channel_stack_element(grpc_channel_get_channel_stack(channel), 0);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   GPR_ASSERT(reserved == NULL);
-  memset(&op, 0, sizeof(op));
   pr->tag = tag;
   pr->cq = cq;
   grpc_closure_init(&pr->closure, ping_done, pr);
-  op.send_ping = &pr->closure;
-  op.bind_pollset = grpc_cq_pollset(cq);
+  op->send_ping = &pr->closure;
+  op->bind_pollset = grpc_cq_pollset(cq);
   grpc_cq_begin_op(cq, tag);
-  top_elem->filter->start_transport_op(&exec_ctx, top_elem, &op);
+  top_elem->filter->start_transport_op(&exec_ctx, top_elem, op);
   grpc_exec_ctx_finish(&exec_ctx);
 }
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index 5978884db8..4e0feb56ac 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -39,6 +39,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/atm.h>
 #include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 #include <grpc/support/time.h>
 
 #include "src/core/lib/iomgr/pollset.h"
@@ -50,6 +51,9 @@
 #include "src/core/lib/surface/event_string.h"
 
 int grpc_trace_operation_failures;
+#ifndef NDEBUG
+int grpc_trace_pending_tags;
+#endif
 
 typedef struct {
   grpc_pollset_worker **worker;
@@ -67,6 +71,9 @@ struct grpc_completion_queue {
   gpr_refcount pending_events;
   /** Once owning_refs drops to zero, we will destroy the cq */
   gpr_refcount owning_refs;
+  /** counter of how many things have ever been queued on this completion queue
+      useful for avoiding locks to check the queue */
+  gpr_atm things_queued_ever;
   /** 0 initially, 1 once we've begun shutting down */
   int shutdown;
   int shutdown_called;
@@ -121,15 +128,6 @@ void grpc_cq_global_shutdown(void) {
   }
 }
 
-struct grpc_cq_alarm {
-  grpc_timer alarm;
-  grpc_cq_completion completion;
-  /** completion queue where events about this alarm will be posted */
-  grpc_completion_queue *cq;
-  /** user supplied tag */
-  void *tag;
-};
-
 grpc_completion_queue *grpc_completion_queue_create(void *reserved) {
   grpc_completion_queue *cc;
   GPR_ASSERT(!reserved);
@@ -166,6 +164,7 @@ grpc_completion_queue *grpc_completion_queue_create(void *reserved) {
   cc->is_server_cq = 0;
   cc->is_non_listening_server_cq = 0;
   cc->num_pluckers = 0;
+  gpr_atm_no_barrier_store(&cc->things_queued_ever, 0);
 #ifndef NDEBUG
   cc->outstanding_tag_count = 0;
 #endif
@@ -276,6 +275,7 @@ void grpc_cq_end_op(grpc_exec_ctx *exec_ctx, grpc_completion_queue *cc,
   GPR_ASSERT(found);
 #endif
   shutdown = gpr_unref(&cc->pending_events);
+  gpr_atm_no_barrier_fetch_add(&cc->things_queued_ever, 1);
   if (!shutdown) {
     cc->completed_tail->next =
         ((uintptr_t)storage) | (1u & (uintptr_t)cc->completed_tail->next);
@@ -313,13 +313,66 @@ void grpc_cq_end_op(grpc_exec_ctx *exec_ctx, grpc_completion_queue *cc,
   GRPC_ERROR_UNREF(error);
 }
 
+typedef struct {
+  gpr_atm last_seen_things_queued_ever;
+  grpc_completion_queue *cq;
+  gpr_timespec deadline;
+  grpc_cq_completion *stolen_completion;
+  void *tag; /* for pluck */
+  bool first_loop;
+} cq_is_finished_arg;
+
+static bool cq_is_next_finished(grpc_exec_ctx *exec_ctx, void *arg) {
+  cq_is_finished_arg *a = arg;
+  grpc_completion_queue *cq = a->cq;
+  GPR_ASSERT(a->stolen_completion == NULL);
+  gpr_atm current_last_seen_things_queued_ever =
+      gpr_atm_no_barrier_load(&cq->things_queued_ever);
+  if (current_last_seen_things_queued_ever != a->last_seen_things_queued_ever) {
+    gpr_mu_lock(cq->mu);
+    a->last_seen_things_queued_ever =
+        gpr_atm_no_barrier_load(&cq->things_queued_ever);
+    if (cq->completed_tail != &cq->completed_head) {
+      a->stolen_completion = (grpc_cq_completion *)cq->completed_head.next;
+      cq->completed_head.next = a->stolen_completion->next & ~(uintptr_t)1;
+      if (a->stolen_completion == cq->completed_tail) {
+        cq->completed_tail = &cq->completed_head;
+      }
+      gpr_mu_unlock(cq->mu);
+      return true;
+    }
+    gpr_mu_unlock(cq->mu);
+  }
+  return !a->first_loop &&
+         gpr_time_cmp(a->deadline, gpr_now(a->deadline.clock_type)) < 0;
+}
+
+#ifndef NDEBUG
+static void dump_pending_tags(grpc_completion_queue *cc) {
+  if (!grpc_trace_pending_tags) return;
+
+  gpr_strvec v;
+  gpr_strvec_init(&v);
+  gpr_strvec_add(&v, gpr_strdup("PENDING TAGS:"));
+  for (size_t i = 0; i < cc->outstanding_tag_count; i++) {
+    char *s;
+    gpr_asprintf(&s, " %p", cc->outstanding_tags[i]);
+    gpr_strvec_add(&v, s);
+  }
+  char *out = gpr_strvec_flatten(&v, NULL);
+  gpr_strvec_destroy(&v);
+  gpr_log(GPR_DEBUG, "%s", out);
+  gpr_free(out);
+}
+#else
+static void dump_pending_tags(grpc_completion_queue *cc) {}
+#endif
+
 grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
                                       gpr_timespec deadline, void *reserved) {
   grpc_event ret;
   grpc_pollset_worker *worker = NULL;
-  int first_loop = 1;
   gpr_timespec now;
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
   GPR_TIMER_BEGIN("grpc_completion_queue_next", 0);
 
@@ -333,11 +386,33 @@ grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
           reserved));
   GPR_ASSERT(!reserved);
 
+  dump_pending_tags(cc);
+
   deadline = gpr_convert_clock_type(deadline, GPR_CLOCK_MONOTONIC);
 
   GRPC_CQ_INTERNAL_REF(cc, "next");
   gpr_mu_lock(cc->mu);
+  cq_is_finished_arg is_finished_arg = {
+      .last_seen_things_queued_ever =
+          gpr_atm_no_barrier_load(&cc->things_queued_ever),
+      .cq = cc,
+      .deadline = deadline,
+      .stolen_completion = NULL,
+      .tag = NULL,
+      .first_loop = true};
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(
+      cq_is_next_finished, &is_finished_arg);
   for (;;) {
+    if (is_finished_arg.stolen_completion != NULL) {
+      gpr_mu_unlock(cc->mu);
+      grpc_cq_completion *c = is_finished_arg.stolen_completion;
+      is_finished_arg.stolen_completion = NULL;
+      ret.type = GRPC_OP_COMPLETE;
+      ret.success = c->next & 1u;
+      ret.tag = c->tag;
+      c->done(&exec_ctx, c->done_arg, c);
+      break;
+    }
     if (cc->completed_tail != &cc->completed_head) {
       grpc_cq_completion *c = (grpc_cq_completion *)cc->completed_head.next;
       cc->completed_head.next = c->next & ~(uintptr_t)1;
@@ -358,13 +433,13 @@ grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
       break;
     }
     now = gpr_now(GPR_CLOCK_MONOTONIC);
-    if (!first_loop && gpr_time_cmp(now, deadline) >= 0) {
+    if (!is_finished_arg.first_loop && gpr_time_cmp(now, deadline) >= 0) {
       gpr_mu_unlock(cc->mu);
       memset(&ret, 0, sizeof(ret));
       ret.type = GRPC_QUEUE_TIMEOUT;
+      dump_pending_tags(cc);
       break;
     }
-    first_loop = 0;
     /* Check alarms - these are a global resource so we just ping
        each time through on every pollset.
        May update deadline to ensure timely wakeups.
@@ -387,13 +462,16 @@ grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
         GRPC_ERROR_UNREF(err);
         memset(&ret, 0, sizeof(ret));
         ret.type = GRPC_QUEUE_TIMEOUT;
+        dump_pending_tags(cc);
         break;
       }
     }
+    is_finished_arg.first_loop = false;
   }
   GRPC_SURFACE_TRACE_RETURNED_EVENT(cc, &ret);
   GRPC_CQ_INTERNAL_UNREF(cc, "next");
   grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(is_finished_arg.stolen_completion == NULL);
 
   GPR_TIMER_END("grpc_completion_queue_next", 0);
 
@@ -424,6 +502,37 @@ static void del_plucker(grpc_completion_queue *cc, void *tag,
   GPR_UNREACHABLE_CODE(return );
 }
 
+static bool cq_is_pluck_finished(grpc_exec_ctx *exec_ctx, void *arg) {
+  cq_is_finished_arg *a = arg;
+  grpc_completion_queue *cq = a->cq;
+  GPR_ASSERT(a->stolen_completion == NULL);
+  gpr_atm current_last_seen_things_queued_ever =
+      gpr_atm_no_barrier_load(&cq->things_queued_ever);
+  if (current_last_seen_things_queued_ever != a->last_seen_things_queued_ever) {
+    gpr_mu_lock(cq->mu);
+    a->last_seen_things_queued_ever =
+        gpr_atm_no_barrier_load(&cq->things_queued_ever);
+    grpc_cq_completion *c;
+    grpc_cq_completion *prev = &cq->completed_head;
+    while ((c = (grpc_cq_completion *)(prev->next & ~(uintptr_t)1)) !=
+           &cq->completed_head) {
+      if (c->tag == a->tag) {
+        prev->next = (prev->next & (uintptr_t)1) | (c->next & ~(uintptr_t)1);
+        if (c == cq->completed_tail) {
+          cq->completed_tail = prev;
+        }
+        gpr_mu_unlock(cq->mu);
+        a->stolen_completion = c;
+        return true;
+      }
+      prev = c;
+    }
+    gpr_mu_unlock(cq->mu);
+  }
+  return !a->first_loop &&
+         gpr_time_cmp(a->deadline, gpr_now(a->deadline.clock_type)) < 0;
+}
+
 grpc_event grpc_completion_queue_pluck(grpc_completion_queue *cc, void *tag,
                                        gpr_timespec deadline, void *reserved) {
   grpc_event ret;
@@ -431,8 +540,6 @@ grpc_event grpc_completion_queue_pluck(grpc_completion_queue *cc, void *tag,
   grpc_cq_completion *prev;
   grpc_pollset_worker *worker = NULL;
   gpr_timespec now;
-  int first_loop = 1;
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
   GPR_TIMER_BEGIN("grpc_completion_queue_pluck", 0);
 
@@ -448,11 +555,33 @@ grpc_event grpc_completion_queue_pluck(grpc_completion_queue *cc, void *tag,
   }
   GPR_ASSERT(!reserved);
 
+  dump_pending_tags(cc);
+
   deadline = gpr_convert_clock_type(deadline, GPR_CLOCK_MONOTONIC);
 
   GRPC_CQ_INTERNAL_REF(cc, "pluck");
   gpr_mu_lock(cc->mu);
+  cq_is_finished_arg is_finished_arg = {
+      .last_seen_things_queued_ever =
+          gpr_atm_no_barrier_load(&cc->things_queued_ever),
+      .cq = cc,
+      .deadline = deadline,
+      .stolen_completion = NULL,
+      .tag = tag,
+      .first_loop = true};
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(
+      cq_is_pluck_finished, &is_finished_arg);
   for (;;) {
+    if (is_finished_arg.stolen_completion != NULL) {
+      gpr_mu_unlock(cc->mu);
+      c = is_finished_arg.stolen_completion;
+      is_finished_arg.stolen_completion = NULL;
+      ret.type = GRPC_OP_COMPLETE;
+      ret.success = c->next & 1u;
+      ret.tag = c->tag;
+      c->done(&exec_ctx, c->done_arg, c);
+      break;
+    }
     prev = &cc->completed_head;
     while ((c = (grpc_cq_completion *)(prev->next & ~(uintptr_t)1)) !=
            &cc->completed_head) {
@@ -485,17 +614,18 @@ grpc_event grpc_completion_queue_pluck(grpc_completion_queue *cc, void *tag,
       memset(&ret, 0, sizeof(ret));
       /* TODO(ctiller): should we use a different result here */
       ret.type = GRPC_QUEUE_TIMEOUT;
+      dump_pending_tags(cc);
       break;
     }
     now = gpr_now(GPR_CLOCK_MONOTONIC);
-    if (!first_loop && gpr_time_cmp(now, deadline) >= 0) {
+    if (!is_finished_arg.first_loop && gpr_time_cmp(now, deadline) >= 0) {
       del_plucker(cc, tag, &worker);
       gpr_mu_unlock(cc->mu);
       memset(&ret, 0, sizeof(ret));
       ret.type = GRPC_QUEUE_TIMEOUT;
+      dump_pending_tags(cc);
       break;
     }
-    first_loop = 0;
     /* Check alarms - these are a global resource so we just ping
        each time through on every pollset.
        May update deadline to ensure timely wakeups.
@@ -518,15 +648,18 @@ grpc_event grpc_completion_queue_pluck(grpc_completion_queue *cc, void *tag,
         GRPC_ERROR_UNREF(err);
         memset(&ret, 0, sizeof(ret));
         ret.type = GRPC_QUEUE_TIMEOUT;
+        dump_pending_tags(cc);
         break;
       }
     }
+    is_finished_arg.first_loop = false;
     del_plucker(cc, tag, &worker);
   }
 done:
   GRPC_SURFACE_TRACE_RETURNED_EVENT(cc, &ret);
   GRPC_CQ_INTERNAL_UNREF(cc, "pluck");
   grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(is_finished_arg.stolen_completion == NULL);
 
   GPR_TIMER_END("grpc_completion_queue_pluck", 0);
 
diff --git a/src/core/lib/surface/completion_queue.h b/src/core/lib/surface/completion_queue.h
index 3049284f68..e9d840df77 100644
--- a/src/core/lib/surface/completion_queue.h
+++ b/src/core/lib/surface/completion_queue.h
@@ -44,6 +44,9 @@
 extern int grpc_cq_pluck_trace;
 extern int grpc_cq_event_timeout_trace;
 extern int grpc_trace_operation_failures;
+#ifndef NDEBUG
+extern int grpc_trace_pending_tags;
+#endif
 
 typedef struct grpc_cq_completion {
   /** user supplied tag */
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index 5397913a21..3cbbaa7b0c 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -45,8 +45,10 @@
 #include "src/core/lib/channel/connected_channel.h"
 #include "src/core/lib/channel/http_client_filter.h"
 #include "src/core/lib/channel/http_server_filter.h"
+#include "src/core/lib/channel/message_size_filter.h"
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/http/parser.h"
+#include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/profiling/timers.h"
@@ -98,6 +100,15 @@ static bool maybe_add_http_filter(grpc_channel_stack_builder *builder,
 
 static void register_builtin_channel_init() {
   grpc_channel_init_register_stage(
+      GRPC_CLIENT_SUBCHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY,
+      prepend_filter, (void *)&grpc_message_size_filter);
+  grpc_channel_init_register_stage(
+      GRPC_CLIENT_DIRECT_CHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY,
+      prepend_filter, (void *)&grpc_message_size_filter);
+  grpc_channel_init_register_stage(
+      GRPC_SERVER_CHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY, prepend_filter,
+      (void *)&grpc_message_size_filter);
+  grpc_channel_init_register_stage(
       GRPC_CLIENT_CHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY, prepend_filter,
       (void *)&grpc_compress_filter);
   grpc_channel_init_register_stage(
@@ -165,12 +176,17 @@ void grpc_init(void) {
     grpc_register_tracer("http1", &grpc_http1_trace);
     grpc_register_tracer("compression", &grpc_compression_trace);
     grpc_register_tracer("queue_pluck", &grpc_cq_pluck_trace);
+    grpc_register_tracer("combiner", &grpc_combiner_trace);
+    grpc_register_tracer("server_channel", &grpc_server_channel_trace);
     // Default pluck trace to 1
     grpc_cq_pluck_trace = 1;
     grpc_register_tracer("queue_timeout", &grpc_cq_event_timeout_trace);
     // Default timeout trace to 1
     grpc_cq_event_timeout_trace = 1;
     grpc_register_tracer("op_failure", &grpc_trace_operation_failures);
+#ifndef NDEBUG
+    grpc_register_tracer("pending_tags", &grpc_trace_pending_tags);
+#endif
     grpc_security_pre_init();
     grpc_iomgr_init();
     grpc_executor_init();
diff --git a/src/core/lib/surface/lame_client.c b/src/core/lib/surface/lame_client.c
index 19b78369dd..d32c884e8e 100644
--- a/src/core/lib/surface/lame_client.c
+++ b/src/core/lib/surface/lame_client.c
@@ -97,14 +97,14 @@ static void lame_start_transport_op(grpc_exec_ctx *exec_ctx,
     grpc_exec_ctx_sched(exec_ctx, op->on_connectivity_state_change,
                         GRPC_ERROR_NONE, NULL);
   }
-  if (op->on_consumed != NULL) {
-    grpc_exec_ctx_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE, NULL);
-  }
   if (op->send_ping != NULL) {
     grpc_exec_ctx_sched(exec_ctx, op->send_ping,
                         GRPC_ERROR_CREATE("lame client channel"), NULL);
   }
   GRPC_ERROR_UNREF(op->disconnect_with_error);
+  if (op->on_consumed != NULL) {
+    grpc_exec_ctx_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE, NULL);
+  }
 }
 
 static grpc_error *init_call_elem(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 55e6d99057..cec3e3ce97 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -71,6 +71,8 @@ typedef struct registered_method registered_method;
 
 typedef enum { BATCH_CALL, REGISTERED_CALL } requested_call_type;
 
+int grpc_server_channel_trace = 0;
+
 typedef struct requested_call {
   requested_call_type type;
   size_t cq_idx;
@@ -273,23 +275,21 @@ static void shutdown_cleanup(grpc_exec_ctx *exec_ctx, void *arg,
 }
 
 static void send_shutdown(grpc_exec_ctx *exec_ctx, grpc_channel *channel,
-                          bool send_goaway, grpc_error *send_disconnect) {
-  grpc_transport_op op;
-  struct shutdown_cleanup_args *sc;
+                          int send_goaway, grpc_error *send_disconnect) {
+  struct shutdown_cleanup_args *sc = gpr_malloc(sizeof(*sc));
+  grpc_closure_init(&sc->closure, shutdown_cleanup, sc);
+  grpc_transport_op *op = grpc_make_transport_op(&sc->closure);
   grpc_channel_element *elem;
 
-  memset(&op, 0, sizeof(op));
-  op.send_goaway = send_goaway;
-  sc = gpr_malloc(sizeof(*sc));
+  op->send_goaway = send_goaway;
+  op->set_accept_stream = true;
   sc->slice = gpr_slice_from_copied_string("Server shutdown");
-  op.goaway_message = &sc->slice;
-  op.goaway_status = GRPC_STATUS_OK;
-  op.disconnect_with_error = send_disconnect;
-  grpc_closure_init(&sc->closure, shutdown_cleanup, sc);
-  op.on_consumed = &sc->closure;
+  op->goaway_message = &sc->slice;
+  op->goaway_status = GRPC_STATUS_OK;
+  op->disconnect_with_error = send_disconnect;
 
   elem = grpc_channel_stack_element(grpc_channel_get_channel_stack(channel), 0);
-  elem->filter->start_transport_op(exec_ctx, elem, &op);
+  elem->filter->start_transport_op(exec_ctx, elem, op);
 }
 
 static void channel_broadcaster_shutdown(grpc_exec_ctx *exec_ctx,
@@ -432,7 +432,8 @@ static void finish_destroy_channel(grpc_exec_ctx *exec_ctx, void *cd,
   server_unref(exec_ctx, server);
 }
 
-static void destroy_channel(grpc_exec_ctx *exec_ctx, channel_data *chand) {
+static void destroy_channel(grpc_exec_ctx *exec_ctx, channel_data *chand,
+                            grpc_error *error) {
   if (is_channel_orphaned(chand)) return;
   GPR_ASSERT(chand->server != NULL);
   orphan_channel(chand);
@@ -441,14 +442,20 @@ static void destroy_channel(grpc_exec_ctx *exec_ctx, channel_data *chand) {
   chand->finish_destroy_channel_closure.cb = finish_destroy_channel;
   chand->finish_destroy_channel_closure.cb_arg = chand;
 
-  grpc_transport_op op;
-  memset(&op, 0, sizeof(op));
-  op.set_accept_stream = true;
-  op.on_consumed = &chand->finish_destroy_channel_closure;
+  if (grpc_server_channel_trace && error != GRPC_ERROR_NONE) {
+    const char *msg = grpc_error_string(error);
+    gpr_log(GPR_INFO, "Disconnected client: %s", msg);
+    grpc_error_free_string(msg);
+  }
+  GRPC_ERROR_UNREF(error);
+
+  grpc_transport_op *op =
+      grpc_make_transport_op(&chand->finish_destroy_channel_closure);
+  op->set_accept_stream = true;
   grpc_channel_next_op(exec_ctx,
                        grpc_channel_stack_element(
                            grpc_channel_get_channel_stack(chand->channel), 0),
-                       &op);
+                       op);
 }
 
 static void cpstr(char **dest, size_t *capacity, grpc_mdstr *value) {
@@ -769,8 +776,7 @@ static void server_on_recv_initial_metadata(grpc_exec_ctx *exec_ctx, void *ptr,
         GRPC_ERROR_CREATE_REFERENCING("Missing :authority or :path", &error, 1);
   }
 
-  grpc_exec_ctx_sched(exec_ctx, calld->on_done_recv_initial_metadata, error,
-                      NULL);
+  grpc_closure_run(exec_ctx, calld->on_done_recv_initial_metadata, error);
 }
 
 static void server_mutate_op(grpc_call_element *elem,
@@ -825,11 +831,20 @@ static void accept_stream(grpc_exec_ctx *exec_ctx, void *cd,
                           const void *transport_server_data) {
   channel_data *chand = cd;
   /* create a call */
-  grpc_call *call = grpc_call_create(chand->channel, NULL, 0, NULL, NULL,
-                                     transport_server_data, NULL, 0,
-                                     gpr_inf_future(GPR_CLOCK_MONOTONIC));
+  grpc_call_create_args args;
+  memset(&args, 0, sizeof(args));
+  args.channel = chand->channel;
+  args.server_transport_data = transport_server_data;
+  args.send_deadline = gpr_inf_future(GPR_CLOCK_MONOTONIC);
+  grpc_call *call;
+  grpc_error *error = grpc_call_create(&args, &call);
   grpc_call_element *elem =
       grpc_call_stack_element(grpc_call_get_call_stack(call), 0);
+  if (error != GRPC_ERROR_NONE) {
+    got_initial_metadata(exec_ctx, elem, error);
+    GRPC_ERROR_UNREF(error);
+    return;
+  }
   call_data *calld = elem->call_data;
   grpc_op op;
   memset(&op, 0, sizeof(op));
@@ -845,17 +860,16 @@ static void channel_connectivity_changed(grpc_exec_ctx *exec_ctx, void *cd,
   channel_data *chand = cd;
   grpc_server *server = chand->server;
   if (chand->connectivity_state != GRPC_CHANNEL_SHUTDOWN) {
-    grpc_transport_op op;
-    memset(&op, 0, sizeof(op));
-    op.on_connectivity_state_change = &chand->channel_connectivity_changed,
-    op.connectivity_state = &chand->connectivity_state;
+    grpc_transport_op *op = grpc_make_transport_op(NULL);
+    op->on_connectivity_state_change = &chand->channel_connectivity_changed,
+    op->connectivity_state = &chand->connectivity_state;
     grpc_channel_next_op(exec_ctx,
                          grpc_channel_stack_element(
                              grpc_channel_get_channel_stack(chand->channel), 0),
-                         &op);
+                         op);
   } else {
     gpr_mu_lock(&server->mu_global);
-    destroy_channel(exec_ctx, chand);
+    destroy_channel(exec_ctx, chand, GRPC_ERROR_REF(error));
     gpr_mu_unlock(&server->mu_global);
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, chand->channel, "connectivity");
   }
@@ -1119,7 +1133,7 @@ void grpc_server_setup_transport(grpc_exec_ctx *exec_ctx, grpc_server *s,
   size_t slots;
   uint32_t probes;
   uint32_t max_probes = 0;
-  grpc_transport_op op;
+  grpc_transport_op *op = NULL;
 
   channel =
       grpc_channel_create(exec_ctx, NULL, args, GRPC_SERVER_CHANNEL, transport);
@@ -1179,16 +1193,16 @@ void grpc_server_setup_transport(grpc_exec_ctx *exec_ctx, grpc_server *s,
   gpr_mu_unlock(&s->mu_global);
 
   GRPC_CHANNEL_INTERNAL_REF(channel, "connectivity");
-  memset(&op, 0, sizeof(op));
-  op.set_accept_stream = true;
-  op.set_accept_stream_fn = accept_stream;
-  op.set_accept_stream_user_data = chand;
-  op.on_connectivity_state_change = &chand->channel_connectivity_changed;
-  op.connectivity_state = &chand->connectivity_state;
+  op = grpc_make_transport_op(NULL);
+  op->set_accept_stream = true;
+  op->set_accept_stream_fn = accept_stream;
+  op->set_accept_stream_user_data = chand;
+  op->on_connectivity_state_change = &chand->channel_connectivity_changed;
+  op->connectivity_state = &chand->connectivity_state;
   if (gpr_atm_acq_load(&s->shutdown_flag) != 0) {
-    op.disconnect_with_error = GRPC_ERROR_CREATE("Server shutdown");
+    op->disconnect_with_error = GRPC_ERROR_CREATE("Server shutdown");
   }
-  grpc_transport_perform_op(exec_ctx, transport, &op);
+  grpc_transport_perform_op(exec_ctx, transport, op);
 }
 
 void done_published_shutdown(grpc_exec_ctx *exec_ctx, void *done_arg,
diff --git a/src/core/lib/surface/server.h b/src/core/lib/surface/server.h
index fb6e4d60c5..2a4e65c7ce 100644
--- a/src/core/lib/surface/server.h
+++ b/src/core/lib/surface/server.h
@@ -40,6 +40,9 @@
 
 extern const grpc_channel_filter grpc_server_top_filter;
 
+/** Lightweight tracing of server channel state */
+extern int grpc_server_channel_trace;
+
 /* Add a listener to the server: when the server starts, it will call start,
    and when it shuts down, it will call destroy */
 void grpc_server_add_listener(
diff --git a/src/core/lib/transport/connectivity_state.c b/src/core/lib/transport/connectivity_state.c
index 68d05e3a85..fdb5307814 100644
--- a/src/core/lib/transport/connectivity_state.c
+++ b/src/core/lib/transport/connectivity_state.c
@@ -180,7 +180,8 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
     *w->current = tracker->current_state;
     tracker->watchers = w->next;
     if (grpc_connectivity_state_trace) {
-      gpr_log(GPR_DEBUG, "NOTIFY: %p", w->notify);
+      gpr_log(GPR_DEBUG, "NOTIFY: %p %s: %p", tracker, tracker->name,
+              w->notify);
     }
     grpc_exec_ctx_sched(exec_ctx, w->notify,
                         GRPC_ERROR_REF(tracker->current_error), NULL);
diff --git a/src/core/lib/transport/metadata.c b/src/core/lib/transport/metadata.c
index 0677f29766..4b40c275ad 100644
--- a/src/core/lib/transport/metadata.c
+++ b/src/core/lib/transport/metadata.c
@@ -278,7 +278,7 @@ static void ref_md_locked(mdtab_shard *shard,
                           internal_metadata *md DEBUG_ARGS) {
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
-          "ELM   REF:%p:%d->%d: '%s' = '%s'", md,
+          "ELM   REF:%p:%zu->%zu: '%s' = '%s'", (void *)md,
           gpr_atm_no_barrier_load(&md->refcnt),
           gpr_atm_no_barrier_load(&md->refcnt) + 1,
           grpc_mdstr_as_c_string((grpc_mdstr *)md->key),
@@ -566,7 +566,7 @@ grpc_mdelem *grpc_mdelem_from_metadata_strings(grpc_mdstr *mkey,
   shard->elems[idx] = md;
   gpr_mu_init(&md->mu_user_data);
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
-  gpr_log(GPR_DEBUG, "ELM   NEW:%p:%d: '%s' = '%s'", md,
+  gpr_log(GPR_DEBUG, "ELM   NEW:%p:%zu: '%s' = '%s'", (void *)md,
           gpr_atm_no_barrier_load(&md->refcnt),
           grpc_mdstr_as_c_string((grpc_mdstr *)md->key),
           grpc_mdstr_as_c_string((grpc_mdstr *)md->value));
@@ -639,7 +639,7 @@ grpc_mdelem *grpc_mdelem_ref(grpc_mdelem *gmd DEBUG_ARGS) {
   if (is_mdelem_static(gmd)) return gmd;
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
-          "ELM   REF:%p:%d->%d: '%s' = '%s'", md,
+          "ELM   REF:%p:%zu->%zu: '%s' = '%s'", (void *)md,
           gpr_atm_no_barrier_load(&md->refcnt),
           gpr_atm_no_barrier_load(&md->refcnt) + 1,
           grpc_mdstr_as_c_string((grpc_mdstr *)md->key),
@@ -649,7 +649,7 @@ grpc_mdelem *grpc_mdelem_ref(grpc_mdelem *gmd DEBUG_ARGS) {
      this function - meaning that no adjustment to mdtab_free is necessary,
      simplifying the logic here to be just an atomic increment */
   /* use C assert to have this removed in opt builds */
-  assert(gpr_atm_no_barrier_load(&md->refcnt) >= 1);
+  GPR_ASSERT(gpr_atm_no_barrier_load(&md->refcnt) >= 1);
   gpr_atm_no_barrier_fetch_add(&md->refcnt, 1);
   return gmd;
 }
@@ -660,14 +660,16 @@ void grpc_mdelem_unref(grpc_mdelem *gmd DEBUG_ARGS) {
   if (is_mdelem_static(gmd)) return;
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
-          "ELM UNREF:%p:%d->%d: '%s' = '%s'", md,
+          "ELM UNREF:%p:%zu->%zu: '%s' = '%s'", (void *)md,
           gpr_atm_no_barrier_load(&md->refcnt),
           gpr_atm_no_barrier_load(&md->refcnt) - 1,
           grpc_mdstr_as_c_string((grpc_mdstr *)md->key),
           grpc_mdstr_as_c_string((grpc_mdstr *)md->value));
 #endif
   uint32_t hash = GRPC_MDSTR_KV_HASH(md->key->hash, md->value->hash);
-  if (1 == gpr_atm_full_fetch_add(&md->refcnt, -1)) {
+  const gpr_atm prev_refcount = gpr_atm_full_fetch_add(&md->refcnt, -1);
+  GPR_ASSERT(prev_refcount >= 1);
+  if (1 == prev_refcount) {
     /* once the refcount hits zero, some other thread can come along and
        free md at any time: it's unsafe from this point on to access it */
     mdtab_shard *shard =
@@ -676,10 +678,12 @@ void grpc_mdelem_unref(grpc_mdelem *gmd DEBUG_ARGS) {
   }
 }
 
-const char *grpc_mdstr_as_c_string(grpc_mdstr *s) {
+const char *grpc_mdstr_as_c_string(const grpc_mdstr *s) {
   return (const char *)GPR_SLICE_START_PTR(s->slice);
 }
 
+size_t grpc_mdstr_length(const grpc_mdstr *s) { return GRPC_MDSTR_LENGTH(s); }
+
 grpc_mdstr *grpc_mdstr_ref(grpc_mdstr *gs DEBUG_ARGS) {
   internal_string *s = (internal_string *)gs;
   if (is_mdstr_static(gs)) return gs;
diff --git a/src/core/lib/transport/metadata.h b/src/core/lib/transport/metadata.h
index 2b0921c8d7..71eff0acf2 100644
--- a/src/core/lib/transport/metadata.h
+++ b/src/core/lib/transport/metadata.h
@@ -147,7 +147,7 @@ void grpc_mdelem_unref(grpc_mdelem *md);
 
 /* Recover a char* from a grpc_mdstr. The returned string is null terminated.
    Does not promise that the returned string has no embedded nulls however. */
-const char *grpc_mdstr_as_c_string(grpc_mdstr *s);
+const char *grpc_mdstr_as_c_string(const grpc_mdstr *s);
 
 #define GRPC_MDSTR_LENGTH(s) (GPR_SLICE_LENGTH(s->slice))
 
diff --git a/src/core/lib/transport/transport.c b/src/core/lib/transport/transport.c
index 857c3909d2..b951218130 100644
--- a/src/core/lib/transport/transport.c
+++ b/src/core/lib/transport/transport.c
@@ -32,18 +32,23 @@
  */
 
 #include "src/core/lib/transport/transport.h"
+
+#include <string.h>
+
 #include <grpc/support/alloc.h>
 #include <grpc/support/atm.h>
 #include <grpc/support/log.h>
 #include <grpc/support/sync.h>
+
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/transport/transport_impl.h"
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
 void grpc_stream_ref(grpc_stream_refcount *refcount, const char *reason) {
   gpr_atm val = gpr_atm_no_barrier_load(&refcount->refs.count);
-  gpr_log(GPR_DEBUG, "%s %p:%p   REF %d->%d %s", refcount->object_type,
-          refcount, refcount->destroy.cb_arg, val, val + 1, reason);
+  gpr_log(GPR_DEBUG, "%s %p:%p   REF %" PRIdPTR "->%" PRIdPTR " %s",
+          refcount->object_type, refcount, refcount->destroy.cb_arg, val,
+          val + 1, reason);
 #else
 void grpc_stream_ref(grpc_stream_refcount *refcount) {
 #endif
@@ -54,8 +59,9 @@ void grpc_stream_ref(grpc_stream_refcount *refcount) {
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx, grpc_stream_refcount *refcount,
                        const char *reason) {
   gpr_atm val = gpr_atm_no_barrier_load(&refcount->refs.count);
-  gpr_log(GPR_DEBUG, "%s %p:%p UNREF %d->%d %s", refcount->object_type,
-          refcount, refcount->destroy.cb_arg, val, val - 1, reason);
+  gpr_log(GPR_DEBUG, "%s %p:%p UNREF %" PRIdPTR "->%" PRIdPTR " %s",
+          refcount->object_type, refcount, refcount->destroy.cb_arg, val,
+          val - 1, reason);
 #else
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx,
                        grpc_stream_refcount *refcount) {
@@ -247,3 +253,51 @@ void grpc_transport_stream_op_add_close(grpc_transport_stream_op *op,
   error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS, status);
   add_error(op, &op->close_error, error);
 }
+
+typedef struct {
+  grpc_closure outer_on_complete;
+  grpc_closure *inner_on_complete;
+  grpc_transport_op op;
+} made_transport_op;
+
+static void destroy_made_transport_op(grpc_exec_ctx *exec_ctx, void *arg,
+                                      grpc_error *error) {
+  made_transport_op *op = arg;
+  grpc_exec_ctx_sched(exec_ctx, op->inner_on_complete, GRPC_ERROR_REF(error),
+                      NULL);
+  gpr_free(op);
+}
+
+grpc_transport_op *grpc_make_transport_op(grpc_closure *on_complete) {
+  made_transport_op *op = gpr_malloc(sizeof(*op));
+  grpc_closure_init(&op->outer_on_complete, destroy_made_transport_op, op);
+  op->inner_on_complete = on_complete;
+  memset(&op->op, 0, sizeof(op->op));
+  op->op.on_consumed = &op->outer_on_complete;
+  return &op->op;
+}
+
+typedef struct {
+  grpc_closure outer_on_complete;
+  grpc_closure *inner_on_complete;
+  grpc_transport_stream_op op;
+} made_transport_stream_op;
+
+static void destroy_made_transport_stream_op(grpc_exec_ctx *exec_ctx, void *arg,
+                                             grpc_error *error) {
+  made_transport_stream_op *op = arg;
+  grpc_exec_ctx_sched(exec_ctx, op->inner_on_complete, GRPC_ERROR_REF(error),
+                      NULL);
+  gpr_free(op);
+}
+
+grpc_transport_stream_op *grpc_make_transport_stream_op(
+    grpc_closure *on_complete) {
+  made_transport_stream_op *op = gpr_malloc(sizeof(*op));
+  grpc_closure_init(&op->outer_on_complete, destroy_made_transport_stream_op,
+                    op);
+  op->inner_on_complete = on_complete;
+  memset(&op->op, 0, sizeof(op->op));
+  op->op.on_complete = &op->outer_on_complete;
+  return &op->op;
+}
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 26ed6cb839..50253ebad1 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -100,6 +100,11 @@ void grpc_transport_move_one_way_stats(grpc_transport_one_way_stats *from,
 void grpc_transport_move_stats(grpc_transport_stream_stats *from,
                                grpc_transport_stream_stats *to);
 
+typedef struct {
+  grpc_closure closure;
+  void *args[2];
+} grpc_transport_private_op_data;
+
 /* Transport stream op: a set of operations to perform on a transport
    against a single stream */
 typedef struct grpc_transport_stream_op {
@@ -108,6 +113,10 @@ typedef struct grpc_transport_stream_op {
       have been completed. */
   grpc_closure *on_complete;
 
+  /** Is the completion of this op covered by a poller (if false: the op should
+      complete independently of some pollset being polled) */
+  bool covered_by_poller;
+
   /** Send initial metadata to the peer, from the provided metadata batch.
       idempotent_request MUST be set if this is non-null */
   grpc_metadata_batch *send_initial_metadata;
@@ -149,6 +158,12 @@ typedef struct grpc_transport_stream_op {
 
   /* Indexes correspond to grpc_context_index enum values */
   grpc_call_context_element *context;
+
+  /***************************************************************************
+   * remaining fields are initialized and used at the discretion of the
+   * transport implementation */
+
+  grpc_transport_private_op_data transport_private;
 } grpc_transport_stream_op;
 
 /** Transport op: a set of operations to perform on a transport as a whole */
@@ -182,6 +197,12 @@ typedef struct grpc_transport_op {
   grpc_pollset_set *bind_pollset_set;
   /** send a ping, call this back if not NULL */
   grpc_closure *send_ping;
+
+  /***************************************************************************
+   * remaining fields are initialized and used at the discretion of the
+   * transport implementation */
+
+  grpc_transport_private_op_data transport_private;
 } grpc_transport_op;
 
 /* Returns the amount of memory required to store a grpc_stream for this
@@ -235,6 +256,7 @@ void grpc_transport_stream_op_add_close(grpc_transport_stream_op *op,
                                         gpr_slice *optional_message);
 
 char *grpc_transport_stream_op_string(grpc_transport_stream_op *op);
+char *grpc_transport_op_string(grpc_transport_op *op);
 
 /* Send a batch of operations on a transport
 
@@ -273,6 +295,14 @@ void grpc_transport_destroy(grpc_exec_ctx *exec_ctx, grpc_transport *transport);
 char *grpc_transport_get_peer(grpc_exec_ctx *exec_ctx,
                               grpc_transport *transport);
 
+/* Allocate a grpc_transport_op, and preconfigure the on_consumed closure to
+   \a on_consumed and then delete the returned transport op */
+grpc_transport_op *grpc_make_transport_op(grpc_closure *on_consumed);
+/* Allocate a grpc_transport_stream_op, and preconfigure the on_consumed closure
+   to \a on_consumed and then delete the returned transport op */
+grpc_transport_stream_op *grpc_make_transport_stream_op(
+    grpc_closure *on_consumed);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/core/lib/transport/transport_op_string.c b/src/core/lib/transport/transport_op_string.c
index 138591db2a..f350e55b34 100644
--- a/src/core/lib/transport/transport_op_string.c
+++ b/src/core/lib/transport/transport_op_string.c
@@ -41,6 +41,7 @@
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
 #include "src/core/lib/support/string.h"
+#include "src/core/lib/transport/connectivity_state.h"
 
 /* These routines are here to facilitate debugging - they produce string
    representations of various transport data structures */
@@ -72,14 +73,14 @@ static void put_metadata_list(gpr_strvec *b, grpc_metadata_batch md) {
 char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
   char *tmp;
   char *out;
-  int first = 1;
+  bool first = true;
 
   gpr_strvec b;
   gpr_strvec_init(&b);
 
   if (op->send_initial_metadata != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_strvec_add(&b, gpr_strdup("SEND_INITIAL_METADATA{"));
     put_metadata_list(&b, *op->send_initial_metadata);
     gpr_strvec_add(&b, gpr_strdup("}"));
@@ -87,7 +88,7 @@ char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
 
   if (op->send_message != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_asprintf(&tmp, "SEND_MESSAGE:flags=0x%08x:len=%d",
                  op->send_message->flags, op->send_message->length);
     gpr_strvec_add(&b, tmp);
@@ -95,7 +96,7 @@ char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
 
   if (op->send_trailing_metadata != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_strvec_add(&b, gpr_strdup("SEND_TRAILING_METADATA{"));
     put_metadata_list(&b, *op->send_trailing_metadata);
     gpr_strvec_add(&b, gpr_strdup("}"));
@@ -103,25 +104,25 @@ char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
 
   if (op->recv_initial_metadata != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_strvec_add(&b, gpr_strdup("RECV_INITIAL_METADATA"));
   }
 
   if (op->recv_message != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_strvec_add(&b, gpr_strdup("RECV_MESSAGE"));
   }
 
   if (op->recv_trailing_metadata != NULL) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     gpr_strvec_add(&b, gpr_strdup("RECV_TRAILING_METADATA"));
   }
 
   if (op->cancel_error != GRPC_ERROR_NONE) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     const char *msg = grpc_error_string(op->cancel_error);
     gpr_asprintf(&tmp, "CANCEL:%s", msg);
     grpc_error_free_string(msg);
@@ -130,7 +131,7 @@ char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
 
   if (op->close_error != GRPC_ERROR_NONE) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
-    first = 0;
+    first = false;
     const char *msg = grpc_error_string(op->close_error);
     gpr_asprintf(&tmp, "CLOSE:%s", msg);
     grpc_error_free_string(msg);
@@ -143,6 +144,82 @@ char *grpc_transport_stream_op_string(grpc_transport_stream_op *op) {
   return out;
 }
 
+char *grpc_transport_op_string(grpc_transport_op *op) {
+  char *tmp;
+  char *out;
+  bool first = true;
+
+  gpr_strvec b;
+  gpr_strvec_init(&b);
+
+  if (op->on_connectivity_state_change != NULL) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    if (op->connectivity_state != NULL) {
+      gpr_asprintf(&tmp, "ON_CONNECTIVITY_STATE_CHANGE:p=%p:from=%s",
+                   op->on_connectivity_state_change,
+                   grpc_connectivity_state_name(*op->connectivity_state));
+      gpr_strvec_add(&b, tmp);
+    } else {
+      gpr_asprintf(&tmp, "ON_CONNECTIVITY_STATE_CHANGE:p=%p:unsubscribe",
+                   op->on_connectivity_state_change);
+      gpr_strvec_add(&b, tmp);
+    }
+  }
+
+  if (op->disconnect_with_error != GRPC_ERROR_NONE) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    const char *err = grpc_error_string(op->disconnect_with_error);
+    gpr_asprintf(&tmp, "DISCONNECT:%s", err);
+    gpr_strvec_add(&b, tmp);
+    grpc_error_free_string(err);
+  }
+
+  if (op->send_goaway) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    char *msg = op->goaway_message == NULL
+                    ? "null"
+                    : gpr_dump_slice(*op->goaway_message,
+                                     GPR_DUMP_ASCII | GPR_DUMP_HEX);
+    gpr_asprintf(&tmp, "SEND_GOAWAY:status=%d:msg=%s", op->goaway_status, msg);
+    if (op->goaway_message != NULL) gpr_free(msg);
+    gpr_strvec_add(&b, tmp);
+  }
+
+  if (op->set_accept_stream) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    gpr_asprintf(&tmp, "SET_ACCEPT_STREAM:%p(%p,...)", op->set_accept_stream_fn,
+                 op->set_accept_stream_user_data);
+    gpr_strvec_add(&b, tmp);
+  }
+
+  if (op->bind_pollset != NULL) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    gpr_strvec_add(&b, gpr_strdup("BIND_POLLSET"));
+  }
+
+  if (op->bind_pollset_set != NULL) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    gpr_strvec_add(&b, gpr_strdup("BIND_POLLSET_SET"));
+  }
+
+  if (op->send_ping != NULL) {
+    if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
+    first = false;
+    gpr_strvec_add(&b, gpr_strdup("SEND_PING"));
+  }
+
+  out = gpr_strvec_flatten(&b, NULL);
+  gpr_strvec_destroy(&b);
+
+  return out;
+}
+
 void grpc_call_log_op(char *file, int line, gpr_log_severity severity,
                       grpc_call_element *elem, grpc_transport_stream_op *op) {
   char *str = grpc_transport_stream_op_string(op);
diff --git a/src/cpp/server/server_builder.cc b/src/cpp/server/server_builder.cc
index 1a014da3b8..2980b16c56 100644
--- a/src/cpp/server/server_builder.cc
+++ b/src/cpp/server/server_builder.cc
@@ -52,7 +52,9 @@ static void do_plugin_list_init(void) {
 }
 
 ServerBuilder::ServerBuilder()
-    : max_message_size_(-1), generic_service_(nullptr) {
+    : max_receive_message_size_(-1),
+      max_send_message_size_(-1),
+      generic_service_(nullptr) {
   gpr_once_init(&once_init_plugin_list, do_plugin_list_init);
   for (auto it = g_plugin_factory_list->begin();
        it != g_plugin_factory_list->end(); it++) {
@@ -160,8 +162,11 @@ std::unique_ptr<Server> ServerBuilder::BuildAndStart() {
     }
     (*plugin)->UpdateChannelArguments(&args);
   }
-  if (max_message_size_ > 0) {
-    args.SetInt(GRPC_ARG_MAX_MESSAGE_LENGTH, max_message_size_);
+  if (max_receive_message_size_ >= 0) {
+    args.SetInt(GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH, max_receive_message_size_);
+  }
+  if (max_send_message_size_ >= 0) {
+    args.SetInt(GRPC_ARG_MAX_SEND_MESSAGE_LENGTH, max_send_message_size_);
   }
   args.SetInt(GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET,
               enabled_compression_algorithms_bitset_);
@@ -173,8 +178,8 @@ std::unique_ptr<Server> ServerBuilder::BuildAndStart() {
     args.SetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM,
                 maybe_default_compression_algorithm_.algorithm);
   }
-  std::unique_ptr<Server> server(
-      new Server(thread_pool.release(), true, max_message_size_, &args));
+  std::unique_ptr<Server> server(new Server(thread_pool.release(), true,
+                                            max_receive_message_size_, &args));
   ServerInitializer* initializer = server->initializer();
 
   // If the server has atleast one sync methods, we know that this is a Sync
diff --git a/src/cpp/server/server_cc.cc b/src/cpp/server/server_cc.cc
index af04fd4ca6..a693ce9b8e 100644
--- a/src/cpp/server/server_cc.cc
+++ b/src/cpp/server/server_cc.cc
@@ -220,7 +220,7 @@ class Server::SyncRequest GRPC_FINAL : public CompletionQueueTag {
    public:
     explicit CallData(Server* server, SyncRequest* mrd)
         : cq_(mrd->cq_),
-          call_(mrd->call_, server, &cq_, server->max_message_size_),
+          call_(mrd->call_, server, &cq_, server->max_receive_message_size_),
           ctx_(mrd->deadline_, mrd->request_metadata_.metadata,
                mrd->request_metadata_.count),
           has_request_payload_(mrd->has_request_payload_),
@@ -243,7 +243,7 @@ class Server::SyncRequest GRPC_FINAL : public CompletionQueueTag {
       ctx_.BeginCompletionOp(&call_);
       global_callbacks->PreSynchronousRequest(&ctx_);
       method_->handler()->RunHandler(MethodHandler::HandlerParameter(
-          &call_, &ctx_, request_payload_, call_.max_message_size()));
+          &call_, &ctx_, request_payload_, call_.max_receive_message_size()));
       global_callbacks->PostSynchronousRequest(&ctx_);
       request_payload_ = nullptr;
       void* ignored_tag;
@@ -277,8 +277,8 @@ class Server::SyncRequest GRPC_FINAL : public CompletionQueueTag {
 
 static internal::GrpcLibraryInitializer g_gli_initializer;
 Server::Server(ThreadPoolInterface* thread_pool, bool thread_pool_owned,
-               int max_message_size, ChannelArguments* args)
-    : max_message_size_(max_message_size),
+               int max_receive_message_size, ChannelArguments* args)
+    : max_receive_message_size_(max_receive_message_size),
       started_(false),
       shutdown_(false),
       shutdown_notified_(false),
@@ -514,7 +514,7 @@ bool ServerInterface::BaseAsyncRequest::FinalizeResult(void** tag,
   grpc_metadata_array_destroy(&initial_metadata_array_);
   context_->set_call(call_);
   context_->cq_ = call_cq_;
-  Call call(call_, server_, call_cq_, server_->max_message_size());
+  Call call(call_, server_, call_cq_, server_->max_receive_message_size());
   if (*status && call_) {
     context_->BeginCompletionOp(&call);
   }
diff --git a/src/csharp/Grpc.Core.Tests/Internal/AsyncCallServerTest.cs b/src/csharp/Grpc.Core.Tests/Internal/AsyncCallServerTest.cs
index c35aaf680f..09790120d1 100644
--- a/src/csharp/Grpc.Core.Tests/Internal/AsyncCallServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/Internal/AsyncCallServerTest.cs
@@ -33,6 +33,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 
@@ -149,8 +150,7 @@ namespace Grpc.Core.Internal.Tests
 
             var writeTask = responseStream.WriteAsync("request1");
             fakeCall.SendCompletionHandler(false);
-            // TODO(jtattermusch): should we throw a different exception type instead?
-            Assert.ThrowsAsync(typeof(InvalidOperationException), async () => await writeTask);
+            Assert.ThrowsAsync(typeof(IOException), async () => await writeTask);
 
             fakeCall.ReceivedCloseOnServerHandler(true, cancelled: true);
             AssertFinished(asyncCallServer, fakeCall, finishedTask);
diff --git a/src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs b/src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs
index 98e27a17a1..616bc06d76 100644
--- a/src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs
+++ b/src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs
@@ -180,21 +180,74 @@ namespace Grpc.Core.Internal.Tests
         }
 
         [Test]
-        public void ClientStreaming_WriteCompletionFailure()
+        public void ClientStreaming_WriteFailureThrowsRpcException()
         {
             var resultTask = asyncCall.ClientStreamingCallAsync();
             var requestStream = new ClientRequestStream<string, string>(asyncCall);
 
             var writeTask = requestStream.WriteAsync("request1");
             fakeCall.SendCompletionHandler(false);
-            // TODO: maybe IOException or waiting for RPCException is more appropriate here.
-            Assert.ThrowsAsync(typeof(InvalidOperationException), async () => await writeTask);
+
+            // The write will wait for call to finish to receive the status code.
+            Assert.IsFalse(writeTask.IsCompleted);
 
             fakeCall.UnaryResponseClientHandler(true,
                 CreateClientSideStatus(StatusCode.Internal),
                 null,
                 new Metadata());
 
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
+            Assert.AreEqual(StatusCode.Internal, ex.Status.StatusCode);
+
+            AssertUnaryResponseError(asyncCall, fakeCall, resultTask, StatusCode.Internal);
+        }
+
+        [Test]
+        public void ClientStreaming_WriteFailureThrowsRpcException2()
+        {
+            var resultTask = asyncCall.ClientStreamingCallAsync();
+            var requestStream = new ClientRequestStream<string, string>(asyncCall);
+
+            var writeTask = requestStream.WriteAsync("request1");
+
+            fakeCall.UnaryResponseClientHandler(true,
+                CreateClientSideStatus(StatusCode.Internal),
+                null,
+                new Metadata());
+
+            fakeCall.SendCompletionHandler(false);
+
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
+            Assert.AreEqual(StatusCode.Internal, ex.Status.StatusCode);
+
+            AssertUnaryResponseError(asyncCall, fakeCall, resultTask, StatusCode.Internal);
+        }
+
+        [Test]
+        public void ClientStreaming_WriteFailureThrowsRpcException3()
+        {
+            var resultTask = asyncCall.ClientStreamingCallAsync();
+            var requestStream = new ClientRequestStream<string, string>(asyncCall);
+
+            var writeTask = requestStream.WriteAsync("request1");
+            fakeCall.SendCompletionHandler(false);
+
+            // Until the delayed write completion has been triggered,
+            // we still act as if there was an active write.
+            Assert.Throws(typeof(InvalidOperationException), () => requestStream.WriteAsync("request2"));
+
+            fakeCall.UnaryResponseClientHandler(true,
+                CreateClientSideStatus(StatusCode.Internal),
+                null,
+                new Metadata());
+
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
+            Assert.AreEqual(StatusCode.Internal, ex.Status.StatusCode);
+
+            // Following attempts to write keep delivering the same status
+            var ex2 = Assert.ThrowsAsync<RpcException>(async () => await requestStream.WriteAsync("after call has finished"));
+            Assert.AreEqual(StatusCode.Internal, ex2.Status.StatusCode);
+
             AssertUnaryResponseError(asyncCall, fakeCall, resultTask, StatusCode.Internal);
         }
 
@@ -416,6 +469,49 @@ namespace Grpc.Core.Internal.Tests
         }
 
         [Test]
+        public void DuplexStreaming_WriteFailureThrowsRpcException()
+        {
+            asyncCall.StartDuplexStreamingCall();
+            var requestStream = new ClientRequestStream<string, string>(asyncCall);
+            var responseStream = new ClientResponseStream<string, string>(asyncCall);
+
+            var writeTask = requestStream.WriteAsync("request1");
+            fakeCall.SendCompletionHandler(false);
+
+            // The write will wait for call to finish to receive the status code.
+            Assert.IsFalse(writeTask.IsCompleted);
+
+            var readTask = responseStream.MoveNext();
+            fakeCall.ReceivedMessageHandler(true, null);
+            fakeCall.ReceivedStatusOnClientHandler(true, CreateClientSideStatus(StatusCode.PermissionDenied));
+
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
+            Assert.AreEqual(StatusCode.PermissionDenied, ex.Status.StatusCode);
+
+            AssertStreamingResponseError(asyncCall, fakeCall, readTask, StatusCode.PermissionDenied);
+        }
+
+        [Test]
+        public void DuplexStreaming_WriteFailureThrowsRpcException2()
+        {
+            asyncCall.StartDuplexStreamingCall();
+            var requestStream = new ClientRequestStream<string, string>(asyncCall);
+            var responseStream = new ClientResponseStream<string, string>(asyncCall);
+
+            var writeTask = requestStream.WriteAsync("request1");
+
+            var readTask = responseStream.MoveNext();
+            fakeCall.ReceivedMessageHandler(true, null);
+            fakeCall.ReceivedStatusOnClientHandler(true, CreateClientSideStatus(StatusCode.PermissionDenied));
+            fakeCall.SendCompletionHandler(false);
+
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await writeTask);
+            Assert.AreEqual(StatusCode.PermissionDenied, ex.Status.StatusCode);
+
+            AssertStreamingResponseError(asyncCall, fakeCall, readTask, StatusCode.PermissionDenied);
+        }
+
+        [Test]
         public void DuplexStreaming_WriteAfterCancellationRequestThrowsTaskCanceledException()
         {
             asyncCall.StartDuplexStreamingCall();
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index f549c52876..9abaf1120f 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -341,6 +341,11 @@ namespace Grpc.Core.Internal
             get { return true; }
         }
 
+        protected override Exception GetRpcExceptionClientOnly()
+        {
+            return new RpcException(finishedStatus.Value.Status);
+        }
+
         protected override Task CheckSendAllowedOrEarlyResult()
         {
             var earlyResult = CheckSendPreconditionsClientSide();
@@ -452,6 +457,7 @@ namespace Grpc.Core.Internal
 
             using (Profilers.ForCurrentThread().NewScope("AsyncCall.HandleUnaryResponse"))
             {
+                TaskCompletionSource<object> delayedStreamingWriteTcs = null;
                 TResponse msg = default(TResponse);
                 var deserializeException = TryDeserialize(receivedMessage, out msg);
 
@@ -465,13 +471,23 @@ namespace Grpc.Core.Internal
                     }
                     finishedStatus = receivedStatus;
 
+                    if (isStreamingWriteCompletionDelayed)
+                    {
+                        delayedStreamingWriteTcs = streamingWriteTcs;
+                        streamingWriteTcs = null;
+                    }
+
                     ReleaseResourcesIfPossible();
                 }
 
                 responseHeadersTcs.SetResult(responseHeaders);
 
-                var status = receivedStatus.Status;
+                if (delayedStreamingWriteTcs != null)
+                {
+                    delayedStreamingWriteTcs.SetException(GetRpcExceptionClientOnly());
+                }
 
+                var status = receivedStatus.Status;
                 if (status.StatusCode != StatusCode.OK)
                 {
                     unaryResponseTcs.SetException(new RpcException(status));
@@ -490,16 +506,27 @@ namespace Grpc.Core.Internal
             // NOTE: because this event is a result of batch containing GRPC_OP_RECV_STATUS_ON_CLIENT,
             // success will be always set to true.
 
+            TaskCompletionSource<object> delayedStreamingWriteTcs = null;
+
             lock (myLock)
             {
                 finished = true;
                 finishedStatus = receivedStatus;
+                if (isStreamingWriteCompletionDelayed)
+                {
+                    delayedStreamingWriteTcs = streamingWriteTcs;
+                    streamingWriteTcs = null;
+                }
 
                 ReleaseResourcesIfPossible();
             }
 
-            var status = receivedStatus.Status;
+            if (delayedStreamingWriteTcs != null)
+            {
+                delayedStreamingWriteTcs.SetException(GetRpcExceptionClientOnly());
+            }
 
+            var status = receivedStatus.Status;
             if (status.StatusCode != StatusCode.OK)
             {
                 streamingCallFinishedTcs.SetException(new RpcException(status));
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
index eb9c3ea62d..9f9d260e7e 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
@@ -69,6 +69,7 @@ namespace Grpc.Core.Internal
         protected TaskCompletionSource<TRead> streamingReadTcs;  // Completion of a pending streaming read if not null.
         protected TaskCompletionSource<object> streamingWriteTcs;  // Completion of a pending streaming write or send close from client if not null.
         protected TaskCompletionSource<object> sendStatusFromServerTcs;
+        protected bool isStreamingWriteCompletionDelayed;  // Only used for the client side.
 
         protected bool readingDone;  // True if last read (i.e. read with null payload) was already received.
         protected bool halfcloseRequested;  // True if send close have been initiated.
@@ -200,6 +201,12 @@ namespace Grpc.Core.Internal
             get;
         }
 
+        /// <summary>
+        /// Returns an exception to throw for a failed send operation.
+        /// It is only allowed to call this method for a call that has already finished.
+        /// </summary>
+        protected abstract Exception GetRpcExceptionClientOnly();
+
         private void ReleaseResources()
         {
             if (call != null)
@@ -252,18 +259,43 @@ namespace Grpc.Core.Internal
         /// </summary>
         protected void HandleSendFinished(bool success)
         {
+            bool delayCompletion = false;
             TaskCompletionSource<object> origTcs = null;
             lock (myLock)
             {
-                origTcs = streamingWriteTcs;
-                streamingWriteTcs = null;
+                if (!success && !finished && IsClient) {
+                    // We should be setting this only once per call, following writes will be short circuited
+                    // because they cannot start until the entire call finishes.
+                    GrpcPreconditions.CheckState(!isStreamingWriteCompletionDelayed);
+
+                    // leave streamingWriteTcs set, it will be completed once call finished.
+                    isStreamingWriteCompletionDelayed = true;
+                    delayCompletion = true;
+                }
+                else
+                {
+                    origTcs = streamingWriteTcs;
+                    streamingWriteTcs = null;    
+                }
 
                 ReleaseResourcesIfPossible();
             }
 
             if (!success)
             {
-                origTcs.SetException(new InvalidOperationException("Send failed"));
+                if (!delayCompletion)
+                {
+                    if (IsClient)
+                    {
+                        GrpcPreconditions.CheckState(finished);  // implied by !success && !delayCompletion && IsClient
+                        origTcs.SetException(GetRpcExceptionClientOnly());
+                    }
+                    else
+                    {
+                        origTcs.SetException (new IOException("Error sending from server."));
+                    }
+                }
+                // if delayCompletion == true, postpone SetException until call finishes.
             }
             else
             {
@@ -283,7 +315,7 @@ namespace Grpc.Core.Internal
 
             if (!success)
             {
-                sendStatusFromServerTcs.SetException(new InvalidOperationException("Error sending status from server."));
+                sendStatusFromServerTcs.SetException(new IOException("Error sending status from server."));
             }
             else
             {
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index 56c23ba3ef..50fdfa9006 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -33,6 +33,7 @@
 
 using System;
 using System.Diagnostics;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -193,6 +194,11 @@ namespace Grpc.Core.Internal
             get { return false; }
         }
 
+        protected override Exception GetRpcExceptionClientOnly()
+        {
+            throw new InvalidOperationException("Call be only called for client calls");
+        }
+
         protected override void OnAfterReleaseResources()
         {
             server.RemoveCallReference(this);
diff --git a/src/csharp/Grpc.Tools.nuspec b/src/csharp/Grpc.Tools.nuspec
index 31d1bed647..0c937ab9cb 100644
--- a/src/csharp/Grpc.Tools.nuspec
+++ b/src/csharp/Grpc.Tools.nuspec
@@ -16,17 +16,18 @@
     <tags>gRPC RPC Protocol HTTP/2</tags>
   </metadata>
   <files>
-    <file src="protoc_plugins\windows_x86\protoc.exe" target="tools\windows_x86\protoc.exe" />
-    <file src="protoc_plugins\windows_x86\grpc_csharp_plugin.exe" target="tools\windows_x86\grpc_csharp_plugin.exe" />
-    <file src="protoc_plugins\windows_x64\protoc.exe" target="tools\windows_x64\protoc.exe" />
-    <file src="protoc_plugins\windows_x64\grpc_csharp_plugin.exe" target="tools\windows_x64\grpc_csharp_plugin.exe" />
-    <file src="protoc_plugins\linux_x86\protoc" target="tools\linux_x86\protoc" />
-    <file src="protoc_plugins\linux_x86\grpc_csharp_plugin" target="tools\linux_x86\grpc_csharp_plugin" />
-    <file src="protoc_plugins\linux_x64\protoc" target="tools\linux_x64\protoc" />
-    <file src="protoc_plugins\linux_x64\grpc_csharp_plugin" target="tools\linux_x64\grpc_csharp_plugin" />
-    <file src="protoc_plugins\macosx_x86\protoc" target="tools\macosx_x86\protoc" />
-    <file src="protoc_plugins\macosx_x86\grpc_csharp_plugin" target="tools\macosx_x86\grpc_csharp_plugin" />
-    <file src="protoc_plugins\macosx_x64\protoc" target="tools\macosx_x64\protoc" />
-    <file src="protoc_plugins\macosx_x64\grpc_csharp_plugin" target="tools\macosx_x64\grpc_csharp_plugin" />
+    <!-- forward slashes in src path enable building on Linux -->
+    <file src="protoc_plugins/windows_x86/protoc.exe" target="tools\windows_x86\protoc.exe" />
+    <file src="protoc_plugins/windows_x86/grpc_csharp_plugin.exe" target="tools\windows_x86\grpc_csharp_plugin.exe" />
+    <file src="protoc_plugins/windows_x64/protoc.exe" target="tools\windows_x64\protoc.exe" />
+    <file src="protoc_plugins/windows_x64/grpc_csharp_plugin.exe" target="tools\windows_x64\grpc_csharp_plugin.exe" />
+    <file src="protoc_plugins/linux_x86/protoc" target="tools\linux_x86\protoc" />
+    <file src="protoc_plugins/linux_x86/grpc_csharp_plugin" target="tools\linux_x86\grpc_csharp_plugin" />
+    <file src="protoc_plugins/linux_x64/protoc" target="tools\linux_x64\protoc" />
+    <file src="protoc_plugins/linux_x64/grpc_csharp_plugin" target="tools\linux_x64\grpc_csharp_plugin" />
+    <file src="protoc_plugins/macosx_x86/protoc" target="tools\macosx_x86\protoc" />
+    <file src="protoc_plugins/macosx_x86/grpc_csharp_plugin" target="tools\macosx_x86\grpc_csharp_plugin" />
+    <file src="protoc_plugins/macosx_x64/protoc" target="tools\macosx_x64\protoc" />
+    <file src="protoc_plugins/macosx_x64/grpc_csharp_plugin" target="tools\macosx_x64\grpc_csharp_plugin" />
   </files>
 </package>
diff --git a/src/csharp/build_packages.bat b/src/csharp/build_packages.bat
index b92189c840..c0036df13f 100644
--- a/src/csharp/build_packages.bat
+++ b/src/csharp/build_packages.bat
@@ -29,6 +29,10 @@
 
 @rem Builds gRPC NuGet packages
 
+@rem This way of building nuget packages is now obsolete. C# nuget packages
+@rem with CoreCLR support are now being built using the dotnet cli
+@rem in build_packages_dotnetcli.sh
+
 @rem Current package versions
 set VERSION=1.1.0-dev
 set PROTOBUF_VERSION=3.0.0
@@ -77,8 +81,8 @@ endlocal
 xcopy /Y /I *.nupkg ..\..\artifacts\
 
 @rem create a zipfile with the artifacts as well
-powershell -Command "Add-Type -Assembly 'System.IO.Compression.FileSystem'; [System.IO.Compression.ZipFile]::CreateFromDirectory('..\..\artifacts', 'csharp_nugets.zip');"
-xcopy /Y /I csharp_nugets.zip ..\..\artifacts\
+powershell -Command "Add-Type -Assembly 'System.IO.Compression.FileSystem'; [System.IO.Compression.ZipFile]::CreateFromDirectory('..\..\artifacts', 'csharp_nugets_obsolete.zip');"
+xcopy /Y /I csharp_nugets_obsolete.zip ..\..\artifacts\
 
 goto :EOF
 
diff --git a/src/csharp/build_packages_dotnetcli.sh b/src/csharp/build_packages_dotnetcli.sh
index 2807278de6..3c127f320b 100755
--- a/src/csharp/build_packages_dotnetcli.sh
+++ b/src/csharp/build_packages_dotnetcli.sh
@@ -34,9 +34,6 @@ cd $(dirname $0)
 
 mkdir -p ../../artifacts/
 
-# IMPORTANT: NuGet packages generated by dotnet CLI are considered experimental.
-# The official nugets are generated by src/csharp/build_packages.bat
-
 mkdir -p nativelibs/windows_x86 nativelibs/windows_x64 \
     nativelibs/linux_x86 nativelibs/linux_x64 \
     nativelibs/macosx_x86 nativelibs/macosx_x64
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.m b/src/objective-c/GRPCClient/private/GRPCHost.m
index 9cd9593d17..1159aac7a7 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.m
+++ b/src/objective-c/GRPCClient/private/GRPCHost.m
@@ -217,7 +217,7 @@ static NSMutableDictionary *kHostCache;
   }
 
   if (_responseSizeLimitOverride) {
-    args[@GRPC_ARG_MAX_MESSAGE_LENGTH] = _responseSizeLimitOverride;
+    args[@GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH] = _responseSizeLimitOverride;
   }
   return args;
 }
diff --git a/src/objective-c/tests/InteropTests.m b/src/objective-c/tests/InteropTests.m
index f04a7e6441..44f22c9e85 100644
--- a/src/objective-c/tests/InteropTests.m
+++ b/src/objective-c/tests/InteropTests.m
@@ -180,7 +180,7 @@
     // - If you're developing the server, consider using response streaming, or let clients filter
     //   responses by setting a google.protobuf.FieldMask in the request:
     //   https://github.com/google/protobuf/blob/master/src/google/protobuf/field_mask.proto
-    XCTAssertEqualObjects(error.localizedDescription, @"Max message size exceeded");
+    XCTAssertEqualObjects(error.localizedDescription, @"Received message larger than max (4194305 vs. 4194304)");
     [expectation fulfill];
   }];
 
diff --git a/src/objective-c/tests/run_tests.sh b/src/objective-c/tests/run_tests.sh
index a265149f48..81c2885320 100755
--- a/src/objective-c/tests/run_tests.sh
+++ b/src/objective-c/tests/run_tests.sh
@@ -44,8 +44,8 @@ BINDIR=../../../bins/$CONFIG
              "interop_server before calling this script."
     exit 1
 }
-$BINDIR/interop_server --port=5050 &
-$BINDIR/interop_server --port=5051 --use_tls &
+$BINDIR/interop_server --port=5050 --max_send_message_size=8388608 &
+$BINDIR/interop_server --port=5051 --max_send_message_size=8388608 --use_tls &
 # Kill them when this script exits.
 trap 'kill -9 `jobs -p`' EXIT
 
diff --git a/src/php/lib/Grpc/BaseStub.php b/src/php/lib/Grpc/BaseStub.php
index d850eebc78..8a7f6572a6 100644
--- a/src/php/lib/Grpc/BaseStub.php
+++ b/src/php/lib/Grpc/BaseStub.php
@@ -182,6 +182,7 @@ class BaseStub
         } else {
             $hostname = $this->hostname;
         }
+
         return 'https://'.$hostname.$service_name;
     }
 
diff --git a/src/php/tests/interop/interop_client.php b/src/php/tests/interop/interop_client.php
index 94ceeda02c..4bc4589956 100755
--- a/src/php/tests/interop/interop_client.php
+++ b/src/php/tests/interop/interop_client.php
@@ -70,7 +70,8 @@ function hardAssertIfStatusOk($status)
  */
 function emptyUnary($stub)
 {
-    list($result, $status) = $stub->EmptyCall(new grpc\testing\EmptyMessage())->wait();
+    list($result, $status) =
+        $stub->EmptyCall(new grpc\testing\EmptyMessage())->wait();
     hardAssertIfStatusOk($status);
     hardAssert($result !== null, 'Call completed with a null response');
 }
@@ -92,8 +93,8 @@ function largeUnary($stub)
  * @param $fillUsername boolean whether to fill result with username
  * @param $fillOauthScope boolean whether to fill result with oauth scope
  */
-function performLargeUnary($stub, $fillUsername = false, $fillOauthScope = false,
-                           $callback = false)
+function performLargeUnary($stub, $fillUsername = false,
+                           $fillOauthScope = false, $callback = false)
 {
     $request_len = 271828;
     $response_len = 314159;
@@ -118,11 +119,11 @@ function performLargeUnary($stub, $fillUsername = false, $fillOauthScope = false
     hardAssert($result !== null, 'Call returned a null response');
     $payload = $result->getPayload();
     hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-         'Payload had the wrong type');
+               'Payload had the wrong type');
     hardAssert(strlen($payload->getBody()) === $response_len,
-         'Payload had the wrong length');
+               'Payload had the wrong length');
     hardAssert($payload->getBody() === str_repeat("\0", $response_len),
-         'Payload had the wrong content');
+               'Payload had the wrong content');
 
     return $result;
 }
@@ -141,11 +142,12 @@ function serviceAccountCreds($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
     hardAssert(strpos($args['oauth_scope'], $result->getOauthScope()) !== false,
-             'invalid oauth scope returned');
+               'invalid oauth scope returned');
 }
 
 /**
@@ -163,9 +165,10 @@ function computeEngineCreds($stub, $args)
     if (!array_key_exists('default_service_account', $args)) {
         throw new Exception('Missing default_service_account');
     }
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($args['default_service_account'] == $result->getUsername(),
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($args['default_service_account'] === $result->getUsername(),
+               'invalid email returned');
 }
 
 /**
@@ -179,9 +182,10 @@ function jwtTokenCreds($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 /**
@@ -195,9 +199,10 @@ function oauth2AuthToken($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 function updateAuthMetadataCallback($context)
@@ -209,8 +214,9 @@ function updateAuthMetadataCallback($context)
     $metadata = [];
     $result = $auth_credentials->updateMetadata([], $authUri);
     foreach ($result as $key => $value) {
-      $metadata[strtolower($key)] = $value;
+        $metadata[strtolower($key)] = $value;
     }
+
     return $metadata;
 }
 
@@ -226,10 +232,11 @@ function perRpcCreds($stub, $args)
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
 
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true,
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true,
                                 'updateAuthMetadataCallback');
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 /**
@@ -258,7 +265,7 @@ function clientStreaming($stub)
     list($result, $status) = $call->wait();
     hardAssertIfStatusOk($status);
     hardAssert($result->getAggregatedPayloadSize() === 74922,
-              'aggregated_payload_size was incorrect');
+               'aggregated_payload_size was incorrect');
 }
 
 /**
@@ -283,10 +290,11 @@ function serverStreaming($stub)
     foreach ($call->responses() as $value) {
         hardAssert($i < 4, 'Too many responses');
         $payload = $value->getPayload();
-        hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-                'Payload '.$i.' had the wrong type');
+        hardAssert(
+            $payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
+            'Payload '.$i.' had the wrong type');
         hardAssert(strlen($payload->getBody()) === $sizes[$i],
-                'Response '.$i.' had the wrong length');
+                   'Response '.$i.' had the wrong length');
         $i += 1;
     }
     hardAssertIfStatusOk($call->getStatus());
@@ -318,10 +326,11 @@ function pingPong($stub)
 
         hardAssert($response !== null, 'Server returned too few responses');
         $payload = $response->getPayload();
-        hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-                'Payload '.$i.' had the wrong type');
+        hardAssert(
+            $payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
+            'Payload '.$i.' had the wrong type');
         hardAssert(strlen($payload->getBody()) === $response_lengths[$i],
-                'Payload '.$i.' had the wrong length');
+                   'Payload '.$i.' had the wrong length');
     }
     $call->writesDone();
     hardAssert($call->read() === null, 'Server returned too many responses');
@@ -352,7 +361,7 @@ function cancelAfterBegin($stub)
     $call->cancel();
     list($result, $status) = $call->wait();
     hardAssert($status->code === Grpc\STATUS_CANCELLED,
-             'Call status was not CANCELLED');
+               'Call status was not CANCELLED');
 }
 
 /**
@@ -377,7 +386,7 @@ function cancelAfterFirstResponse($stub)
 
     $call->cancel();
     hardAssert($call->getStatus()->code === Grpc\STATUS_CANCELLED,
-             'Call status was not CANCELLED');
+               'Call status was not CANCELLED');
 }
 
 function timeoutOnSleepingServer($stub)
@@ -396,7 +405,7 @@ function timeoutOnSleepingServer($stub)
     $response = $call->read();
 
     hardAssert($call->getStatus()->code === Grpc\STATUS_DEADLINE_EXCEEDED,
-             'Call status was not DEADLINE_EXCEEDED');
+               'Call status was not DEADLINE_EXCEEDED');
 }
 
 function customMetadata($stub)
@@ -425,9 +434,9 @@ function customMetadata($stub)
     $initial_metadata = $call->getMetadata();
     hardAssert(array_key_exists($ECHO_INITIAL_KEY, $initial_metadata),
                'Initial metadata does not contain expected key');
-    hardAssert($initial_metadata[$ECHO_INITIAL_KEY][0] ==
-               $ECHO_INITIAL_VALUE,
-               'Incorrect initial metadata value');
+    hardAssert(
+        $initial_metadata[$ECHO_INITIAL_KEY][0] === $ECHO_INITIAL_VALUE,
+        'Incorrect initial metadata value');
 
     list($result, $status) = $call->wait();
     hardAssertIfStatusOk($status);
@@ -435,8 +444,9 @@ function customMetadata($stub)
     $trailing_metadata = $call->getTrailingMetadata();
     hardAssert(array_key_exists($ECHO_TRAILING_KEY, $trailing_metadata),
                'Trailing metadata does not contain expected key');
-    hardAssert($trailing_metadata[$ECHO_TRAILING_KEY][0] ==
-               $ECHO_TRAILING_VALUE, 'Incorrect trailing metadata value');
+    hardAssert(
+        $trailing_metadata[$ECHO_TRAILING_KEY][0] === $ECHO_TRAILING_VALUE,
+        'Incorrect trailing metadata value');
 
     $streaming_call = $stub->FullDuplexCall($metadata);
 
@@ -451,7 +461,7 @@ function customMetadata($stub)
     hardAssert(array_key_exists($ECHO_TRAILING_KEY,
                                 $streaming_trailing_metadata),
                'Trailing metadata does not contain expected key');
-    hardAssert($streaming_trailing_metadata[$ECHO_TRAILING_KEY][0] ==
+    hardAssert($streaming_trailing_metadata[$ECHO_TRAILING_KEY][0] ===
                $ECHO_TRAILING_VALUE, 'Incorrect trailing metadata value');
 }
 
@@ -506,7 +516,7 @@ function _makeStub($args)
         throw new Exception('Missing argument: --test_case is required');
     }
 
-    if ($args['server_port'] == 443) {
+    if ($args['server_port'] === 443) {
         $server_address = $args['server_host'];
     } else {
         $server_address = $args['server_host'].':'.$args['server_port'];
@@ -548,7 +558,7 @@ function _makeStub($args)
 
     if (in_array($test_case, ['service_account_creds',
                               'compute_engine_creds', 'jwt_token_creds', ])) {
-        if ($test_case == 'jwt_token_creds') {
+        if ($test_case === 'jwt_token_creds') {
             $auth_credentials = ApplicationDefaultCredentials::getCredentials();
         } else {
             $auth_credentials = ApplicationDefaultCredentials::getCredentials(
@@ -558,7 +568,7 @@ function _makeStub($args)
         $opts['update_metadata'] = $auth_credentials->getUpdateMetadataFunc();
     }
 
-    if ($test_case == 'oauth2_auth_token') {
+    if ($test_case === 'oauth2_auth_token') {
         $auth_credentials = ApplicationDefaultCredentials::getCredentials(
             $args['oauth_scope']
         );
@@ -578,8 +588,9 @@ function _makeStub($args)
         $opts['update_metadata'] = $update_metadata;
     }
 
-    if ($test_case == 'unimplemented_method') {
-        $stub = new grpc\testing\UnimplementedServiceClient($server_address, $opts);
+    if ($test_case === 'unimplemented_method') {
+        $stub = new grpc\testing\UnimplementedServiceClient($server_address,
+                                                            $opts);
     } else {
         $stub = new grpc\testing\TestServiceClient($server_address, $opts);
     }
@@ -656,7 +667,8 @@ function interop_main($args, $stub = false)
     return $stub;
 }
 
-if (isset($_SERVER['PHP_SELF']) && preg_match('/interop_client/', $_SERVER['PHP_SELF'])) {
+if (isset($_SERVER['PHP_SELF']) &&
+    preg_match('/interop_client/', $_SERVER['PHP_SELF'])) {
     $args = getopt('', ['server_host:', 'server_port:', 'test_case:',
                         'use_tls::', 'use_test_ca::',
                         'server_host_override:', 'oauth_scope:',
diff --git a/src/php/tests/unit_tests/CallCredentials2Test.php b/src/php/tests/unit_tests/CallCredentials2Test.php
index b3b98a22ca..fa31439c54 100644
--- a/src/php/tests/unit_tests/CallCredentials2Test.php
+++ b/src/php/tests/unit_tests/CallCredentials2Test.php
@@ -170,7 +170,7 @@ class CallCredentials2Test extends PHPUnit_Framework_TestCase
         $this->assertTrue(is_string($context->service_url));
         $this->assertTrue(is_string($context->method_name));
 
-        return "a string";
+        return 'a string';
     }
 
     public function testCallbackWithInvalidReturnValue()
@@ -196,5 +196,4 @@ class CallCredentials2Test extends PHPUnit_Framework_TestCase
         $this->assertTrue($event->send_close);
         $this->assertTrue($event->status->code == Grpc\STATUS_UNAUTHENTICATED);
     }
-
 }
diff --git a/src/proto/grpc/lb/v1/load_balancer.options b/src/proto/grpc/lb/v1/load_balancer.options
index d90366996e..a9398d5f47 100644
--- a/src/proto/grpc/lb/v1/load_balancer.options
+++ b/src/proto/grpc/lb/v1/load_balancer.options
@@ -1,6 +1,6 @@
 grpc.lb.v1.InitialLoadBalanceRequest.name max_size:128
 grpc.lb.v1.InitialLoadBalanceResponse.client_config max_size:64
 grpc.lb.v1.InitialLoadBalanceResponse.load_balancer_delegate max_size:64
-grpc.lb.v1.Server.ip_address max_size:46
-grpc.lb.v1.Server.load_balance_token max_size:64
+grpc.lb.v1.Server.ip_address max_size:16
+grpc.lb.v1.Server.load_balance_token max_size:65
 load_balancer.proto no_unions:true
diff --git a/src/proto/grpc/lb/v1/load_balancer.proto b/src/proto/grpc/lb/v1/load_balancer.proto
index 1bcad0b1d4..210fba1323 100644
--- a/src/proto/grpc/lb/v1/load_balancer.proto
+++ b/src/proto/grpc/lb/v1/load_balancer.proto
@@ -32,7 +32,6 @@ syntax = "proto3";
 package grpc.lb.v1;
 
 message Duration {
-
   // Signed seconds of the span of time. Must be from -315,576,000,000
   // to +315,576,000,000 inclusive.
   int64 seconds = 1;
@@ -93,21 +92,16 @@ message LoadBalanceResponse {
 }
 
 message InitialLoadBalanceResponse {
-  oneof initial_response_type {
-    // TODO(zhangkun83): ClientConfig not yet defined
-    //ClientConfig client_config = 1;
-
-    // This is an application layer redirect that indicates the client should
-    // use the specified server for load balancing. When this field is set in
-    // the response, the client should open a separate connection to the
-    // load_balancer_delegate and call the BalanceLoad method.
-    string load_balancer_delegate = 2;
-  }
+  // This is an application layer redirect that indicates the client should use
+  // the specified server for load balancing. When this field is non-empty in
+  // the response, the client should open a separate connection to the
+  // load_balancer_delegate and call the BalanceLoad method.
+  string load_balancer_delegate = 1;
 
   // This interval defines how often the client should send the client stats
   // to the load balancer. Stats should only be reported when the duration is
   // positive.
-  Duration client_stats_report_interval = 3;
+  Duration client_stats_report_interval = 2;
 }
 
 message ServerList {
@@ -125,14 +119,17 @@ message ServerList {
 }
 
 message Server {
-  // A resolved address and port for the server. The IP address string may
+  // A resolved address for the server, serialized in network-byte-order. It may
   // either be an IPv4 or IPv6 address.
-  string ip_address = 1;
+  bytes ip_address = 1;
+
+  // A resolved port number for the server.
   int32 port = 2;
 
-  // An opaque token that is passed from the client to the server in metadata.
-  // The server may expect this token to indicate that the request from the
-  // client was load balanced.
+  // An opaque but printable token given to the frontend for each pick. All
+  // frontend requests for that pick must include the token in its initial
+  // metadata. The token is used by the backend to verify the request and to
+  // allow the backend to report load to the gRPC LB system.
   string load_balance_token = 3;
 
   // Indicates whether this particular request should be dropped by the client
diff --git a/src/python/grpcio/commands.py b/src/python/grpcio/commands.py
index d36ac23305..ea3b6f3391 100644
--- a/src/python/grpcio/commands.py
+++ b/src/python/grpcio/commands.py
@@ -53,6 +53,7 @@ PYTHON_STEM = os.path.dirname(os.path.abspath(__file__))
 GRPC_STEM = os.path.abspath(PYTHON_STEM + '../../../../')
 PROTO_STEM = os.path.join(GRPC_STEM, 'src', 'proto')
 PROTO_GEN_STEM = os.path.join(GRPC_STEM, 'src', 'python', 'gens')
+CYTHON_STEM = os.path.join(PYTHON_STEM, 'grpc', '_cython')
 
 CONF_PY_ADDENDUM = """
 extensions.append('sphinx.ext.napoleon')
@@ -244,7 +245,7 @@ def try_cythonize(extensions, linetracing=False, mandatory=True):
     extensions,
     include_path=[
       include_dir for extension in extensions for include_dir in extension.include_dirs
-    ],
+    ] + [CYTHON_STEM],
     compiler_directives=cython_compiler_directives
   )
 
diff --git a/src/python/grpcio/grpc/__init__.py b/src/python/grpcio/grpc/__init__.py
index faf3ab5f0d..b9b662c032 100644
--- a/src/python/grpcio/grpc/__init__.py
+++ b/src/python/grpcio/grpc/__init__.py
@@ -1189,7 +1189,7 @@ def insecure_channel(target, options=None):
     A Channel to the target through which RPCs may be conducted.
   """
   from grpc import _channel
-  return _channel.Channel(target, options, None)
+  return _channel.Channel(target, () if options is None else options, None)
 
 
 def secure_channel(target, credentials, options=None):
@@ -1205,10 +1205,11 @@ def secure_channel(target, credentials, options=None):
     A Channel to the target through which RPCs may be conducted.
   """
   from grpc import _channel
-  return _channel.Channel(target, options, credentials._credentials)
+  return _channel.Channel(target, () if options is None else options,
+                          credentials._credentials)
 
 
-def server(thread_pool, handlers=None):
+def server(thread_pool, handlers=None, options=None):
   """Creates a Server with which RPCs can be serviced.
 
   Args:
@@ -1219,12 +1220,15 @@ def server(thread_pool, handlers=None):
       only handlers the server will use to service RPCs; other handlers may
       later be added by calling add_generic_rpc_handlers any time before the
       returned Server is started.
+    options: A sequence of string-value pairs according to which to configure
+      the created server.
 
   Returns:
     A Server with which RPCs can be serviced.
   """
   from grpc import _server
-  return _server.Server(thread_pool, () if handlers is None else handlers)
+  return _server.Server(thread_pool, () if handlers is None else handlers,
+                        () if options is None else options)
 
 
 ###################################  __all__  #################################
diff --git a/src/python/grpcio/grpc/_channel.py b/src/python/grpcio/grpc/_channel.py
index 3117dd1cb3..53a26727ab 100644
--- a/src/python/grpcio/grpc/_channel.py
+++ b/src/python/grpcio/grpc/_channel.py
@@ -842,18 +842,8 @@ def _unsubscribe(state, callback):
 
 
 def _options(options):
-  if options is None:
-    pairs = ((cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT),)
-  else:
-    pairs = list(options) + [
-        (cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT)]
-  encoded_pairs = [
-      (_common.encode(arg_name), arg_value) if isinstance(arg_value, int)
-      else (_common.encode(arg_name), _common.encode(arg_value))
-      for arg_name, arg_value in pairs]
-  return cygrpc.ChannelArgs([
-      cygrpc.ChannelArg(arg_name, arg_value)
-      for arg_name, arg_value in encoded_pairs])
+  return list(options) + [
+      (cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT)]
 
 
 class Channel(grpc.Channel):
@@ -867,7 +857,8 @@ class Channel(grpc.Channel):
       credentials: A cygrpc.ChannelCredentials or None.
     """
     self._channel = cygrpc.Channel(
-        _common.encode(target), _options(options), credentials)
+        _common.encode(target), _common.channel_args(_options(options)),
+        credentials)
     self._call_state = _ChannelCallState(self._channel)
     self._connectivity_state = _ChannelConnectivityState(self._channel)
 
diff --git a/src/python/grpcio/grpc/_common.py b/src/python/grpcio/grpc/_common.py
index 4d7d521419..cc0984c8c6 100644
--- a/src/python/grpcio/grpc/_common.py
+++ b/src/python/grpcio/grpc/_common.py
@@ -94,6 +94,16 @@ def decode(b):
       return b.decode('latin1')
 
 
+def channel_args(options):
+  channel_args = []
+  for key, value in options:
+    if isinstance(value, six.string_types):
+      channel_args.append(cygrpc.ChannelArg(encode(key), encode(value)))
+    else:
+      channel_args.append(cygrpc.ChannelArg(encode(key), value))
+  return cygrpc.ChannelArgs(channel_args)
+
+
 def cygrpc_metadata(application_metadata):
   return _EMPTY_METADATA if application_metadata is None else cygrpc.Metadata(
       cygrpc.Metadatum(encode(key), encode(value))
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
index 3df937eb14..73d1ff7b97 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
@@ -32,15 +32,16 @@ cimport cpython
 
 cdef class Channel:
 
-  def __cinit__(self, bytes target, ChannelArgs arguments=None,
+  def __cinit__(self, bytes target, ChannelArgs arguments,
                 ChannelCredentials channel_credentials=None):
     grpc_init()
     cdef grpc_channel_args *c_arguments = NULL
     cdef char *c_target = NULL
     self.c_channel = NULL
     self.references = []
-    if arguments is not None:
+    if len(arguments) > 0:
       c_arguments = &arguments.c_args
+      self.references.append(arguments)
     c_target = target
     if channel_credentials is None:
       with nogil:
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
index 42fced6545..dae28e15f2 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
@@ -135,7 +135,7 @@ cdef extern from "grpc/grpc.h":
   const char *GRPC_ARG_PRIMARY_USER_AGENT_STRING
   const char *GRPC_ARG_ENABLE_CENSUS
   const char *GRPC_ARG_MAX_CONCURRENT_STREAMS
-  const char *GRPC_ARG_MAX_MESSAGE_LENGTH
+  const char *GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH
   const char *GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER
   const char *GRPC_ARG_DEFAULT_AUTHORITY
   const char *GRPC_ARG_PRIMARY_USER_AGENT_STRING
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
index 834a44123d..f444e33cf0 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
@@ -39,7 +39,7 @@ class ConnectivityState:
 class ChannelArgKey:
   enable_census = GRPC_ARG_ENABLE_CENSUS
   max_concurrent_streams = GRPC_ARG_MAX_CONCURRENT_STREAMS
-  max_message_length = GRPC_ARG_MAX_MESSAGE_LENGTH
+  max_message_length = GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH
   http2_initial_sequence_number = GRPC_ARG_HTTP2_INITIAL_SEQUENCE_NUMBER
   default_authority = GRPC_ARG_DEFAULT_AUTHORITY
   primary_user_agent_string = GRPC_ARG_PRIMARY_USER_AGENT_STRING
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi
index 23cee7bd6e..20fc1c5fce 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi
@@ -35,7 +35,7 @@ import pkg_resources
 cdef grpc_ssl_roots_override_result ssl_roots_override_callback(
     char **pem_root_certs) with gil:
   temporary_pem_root_certs = pkg_resources.resource_string(
-      'grpc._cython', '_credentials/roots.pem')
+      __name__.rstrip('.cygrpc'), '_credentials/roots.pem')
   pem_root_certs[0] = <char *>gpr_malloc(len(temporary_pem_root_certs) + 1)
   memcpy(
       pem_root_certs[0], <char *>temporary_pem_root_certs,
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
index ca2b831114..18db38b686 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
@@ -34,12 +34,12 @@ import time
 
 cdef class Server:
 
-  def __cinit__(self, ChannelArgs arguments=None):
+  def __cinit__(self, ChannelArgs arguments):
     grpc_init()
     cdef grpc_channel_args *c_arguments = NULL
     self.references = []
     self.registered_completion_queues = []
-    if arguments is not None:
+    if len(arguments) > 0:
       c_arguments = &arguments.c_args
       self.references.append(arguments)
     with nogil:
diff --git a/src/python/grpcio/grpc/_cython/cygrpc.pxd b/src/python/grpcio/grpc/_cython/cygrpc.pxd
index 9779534e38..26454634a1 100644
--- a/src/python/grpcio/grpc/_cython/cygrpc.pxd
+++ b/src/python/grpcio/grpc/_cython/cygrpc.pxd
@@ -27,12 +27,12 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-include "grpc/_cython/_cygrpc/grpc.pxi"
+include "_cygrpc/grpc.pxi"
 
-include "grpc/_cython/_cygrpc/call.pxd.pxi"
-include "grpc/_cython/_cygrpc/channel.pxd.pxi"
-include "grpc/_cython/_cygrpc/credentials.pxd.pxi"
-include "grpc/_cython/_cygrpc/completion_queue.pxd.pxi"
-include "grpc/_cython/_cygrpc/records.pxd.pxi"
-include "grpc/_cython/_cygrpc/security.pxd.pxi"
-include "grpc/_cython/_cygrpc/server.pxd.pxi"
+include "_cygrpc/call.pxd.pxi"
+include "_cygrpc/channel.pxd.pxi"
+include "_cygrpc/credentials.pxd.pxi"
+include "_cygrpc/completion_queue.pxd.pxi"
+include "_cygrpc/records.pxd.pxi"
+include "_cygrpc/security.pxd.pxi"
+include "_cygrpc/server.pxd.pxi"
diff --git a/src/python/grpcio/grpc/_cython/cygrpc.pyx b/src/python/grpcio/grpc/_cython/cygrpc.pyx
index 08089994a9..e1bd046a1a 100644
--- a/src/python/grpcio/grpc/_cython/cygrpc.pyx
+++ b/src/python/grpcio/grpc/_cython/cygrpc.pyx
@@ -35,14 +35,14 @@ import sys
 
 # TODO(atash): figure out why the coverage tool gets confused about the Cython
 # coverage plugin when the following files don't have a '.pxi' suffix.
-include "grpc/_cython/_cygrpc/grpc_string.pyx.pxi"
-include "grpc/_cython/_cygrpc/call.pyx.pxi"
-include "grpc/_cython/_cygrpc/channel.pyx.pxi"
-include "grpc/_cython/_cygrpc/credentials.pyx.pxi"
-include "grpc/_cython/_cygrpc/completion_queue.pyx.pxi"
-include "grpc/_cython/_cygrpc/records.pyx.pxi"
-include "grpc/_cython/_cygrpc/security.pyx.pxi"
-include "grpc/_cython/_cygrpc/server.pyx.pxi"
+include "_cygrpc/grpc_string.pyx.pxi"
+include "_cygrpc/call.pyx.pxi"
+include "_cygrpc/channel.pyx.pxi"
+include "_cygrpc/credentials.pyx.pxi"
+include "_cygrpc/completion_queue.pyx.pxi"
+include "_cygrpc/records.pyx.pxi"
+include "_cygrpc/security.pyx.pxi"
+include "_cygrpc/server.pyx.pxi"
 
 #
 # initialize gRPC
diff --git a/src/python/grpcio/grpc/_server.py b/src/python/grpcio/grpc/_server.py
index 94a13bfb2f..5f846ce773 100644
--- a/src/python/grpcio/grpc/_server.py
+++ b/src/python/grpcio/grpc/_server.py
@@ -728,12 +728,11 @@ def _start(state):
         cleanup_server, target=_serve, args=(state,))
     thread.start()
 
-
 class Server(grpc.Server):
 
-  def __init__(self, thread_pool, generic_handlers):
+  def __init__(self, thread_pool, generic_handlers, options):
     completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(_common.channel_args(options))
     server.register_completion_queue(completion_queue)
     self._state = _ServerState(
         completion_queue, server, generic_handlers, thread_pool)
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index be7f30c29b..288f02042e 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -50,6 +50,7 @@ CORE_SOURCE_FILES = [
   'src/core/lib/support/log_linux.c',
   'src/core/lib/support/log_posix.c',
   'src/core/lib/support/log_windows.c',
+  'src/core/lib/support/mpscq.c',
   'src/core/lib/support/murmur_hash.c',
   'src/core/lib/support/percent_encoding.c',
   'src/core/lib/support/slice.c',
@@ -85,6 +86,7 @@ CORE_SOURCE_FILES = [
   'src/core/lib/channel/handshaker.c',
   'src/core/lib/channel/http_client_filter.c',
   'src/core/lib/channel/http_server_filter.c',
+  'src/core/lib/channel/message_size_filter.c',
   'src/core/lib/compression/compression.c',
   'src/core/lib/compression/message_compress.c',
   'src/core/lib/debug/trace.c',
@@ -92,6 +94,7 @@ CORE_SOURCE_FILES = [
   'src/core/lib/http/httpcli.c',
   'src/core/lib/http/parser.c',
   'src/core/lib/iomgr/closure.c',
+  'src/core/lib/iomgr/combiner.c',
   'src/core/lib/iomgr/endpoint.c',
   'src/core/lib/iomgr/endpoint_pair_posix.c',
   'src/core/lib/iomgr/endpoint_pair_windows.c',
@@ -134,7 +137,6 @@ CORE_SOURCE_FILES = [
   'src/core/lib/iomgr/wakeup_fd_nospecial.c',
   'src/core/lib/iomgr/wakeup_fd_pipe.c',
   'src/core/lib/iomgr/wakeup_fd_posix.c',
-  'src/core/lib/iomgr/workqueue_posix.c',
   'src/core/lib/iomgr/workqueue_windows.c',
   'src/core/lib/json/json.c',
   'src/core/lib/json/json_reader.c',
@@ -264,6 +266,7 @@ CORE_SOURCE_FILES = [
   'src/core/ext/census/operation.c',
   'src/core/ext/census/placeholders.c',
   'src/core/ext/census/resource.c',
+  'src/core/ext/census/trace_context.c',
   'src/core/ext/census/tracing.c',
   'src/core/plugin_registry/grpc_plugin_registry.c',
   'src/boringssl/err_data.c',
diff --git a/src/python/grpcio_tests/tests/tests.json b/src/python/grpcio_tests/tests/tests.json
index dcaef0db1f..2071a33e13 100644
--- a/src/python/grpcio_tests/tests/tests.json
+++ b/src/python/grpcio_tests/tests/tests.json
@@ -7,6 +7,7 @@
   "_beta_features_test.BetaFeaturesTest", 
   "_beta_features_test.ContextManagementAndLifecycleTest", 
   "_cancel_many_calls_test.CancelManyCallsTest",
+  "_channel_args_test.ChannelArgsTest",
   "_channel_connectivity_test.ChannelConnectivityTest",
   "_channel_ready_future_test.ChannelReadyFutureTest",
   "_channel_test.ChannelTest", 
diff --git a/src/python/grpcio_tests/tests/unit/_channel_args_test.py b/src/python/grpcio_tests/tests/unit/_channel_args_test.py
new file mode 100644
index 0000000000..6a636d7993
--- /dev/null
+++ b/src/python/grpcio_tests/tests/unit/_channel_args_test.py
@@ -0,0 +1,53 @@
+# Copyright 2016, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests of Channel Args on client/server side."""
+
+import unittest
+
+import grpc
+
+TEST_CHANNEL_ARGS = (
+    ('arg1', b'bytes_val'),
+    ('arg2', 'str_val'),
+    ('arg3', 1),
+    (b'arg4', 'str_val'),
+)
+
+
+class ChannelArgsTest(unittest.TestCase):
+
+  def test_client(self):
+    grpc.insecure_channel('localhost:8080', options=TEST_CHANNEL_ARGS)
+
+  def test_server(self):
+    grpc.server(None, options=TEST_CHANNEL_ARGS)
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)
diff --git a/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py b/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
index 9cae96a00d..1324ad37b6 100644
--- a/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
+++ b/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
@@ -78,7 +78,7 @@ class ChannelConnectivityTest(unittest.TestCase):
   def test_lonely_channel_connectivity(self):
     callback = _Callback()
 
-    channel = _channel.Channel('localhost:12345', None, None)
+    channel = _channel.Channel('localhost:12345', (), None)
     channel.subscribe(callback.update, try_to_connect=False)
     first_connectivities = callback.block_until_connectivities_satisfy(bool)
     channel.subscribe(callback.update, try_to_connect=True)
@@ -105,13 +105,13 @@ class ChannelConnectivityTest(unittest.TestCase):
 
   def test_immediately_connectable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     first_callback = _Callback()
     second_callback = _Callback()
 
-    channel = _channel.Channel('localhost:{}'.format(port), None, None)
+    channel = _channel.Channel('localhost:{}'.format(port), (), None)
     channel.subscribe(first_callback.update, try_to_connect=False)
     first_connectivities = first_callback.block_until_connectivities_satisfy(
         bool)
@@ -146,12 +146,12 @@ class ChannelConnectivityTest(unittest.TestCase):
 
   def test_reachable_then_unreachable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     callback = _Callback()
 
-    channel = _channel.Channel('localhost:{}'.format(port), None, None)
+    channel = _channel.Channel('localhost:{}'.format(port), (), None)
     channel.subscribe(callback.update, try_to_connect=True)
     callback.block_until_connectivities_satisfy(_ready_in_connectivities)
     # Now take down the server and confirm that channel readiness is repudiated.
diff --git a/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py b/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
index 24f5b45b18..60d478bcd9 100644
--- a/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
+++ b/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
@@ -79,7 +79,7 @@ class ChannelReadyFutureTest(unittest.TestCase):
 
   def test_immediately_connectable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     channel = grpc.insecure_channel('localhost:{}'.format(port))
diff --git a/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py b/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
index cf212c5653..20115fb22c 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
@@ -157,11 +157,12 @@ class CancelManyCallsTest(unittest.TestCase):
     server_thread_pool = logging_pool.pool(test_constants.THREAD_CONCURRENCY)
 
     server_completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.register_completion_queue(server_completion_queue)
     port = server.add_http2_port(b'[::]:0')
     server.start()
-    channel = cygrpc.Channel('localhost:{}'.format(port).encode())
+    channel = cygrpc.Channel('localhost:{}'.format(port).encode(),
+                             cygrpc.ChannelArgs([]))
 
     state = _State()
 
diff --git a/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py b/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
index 152d8edde3..2ae5285232 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
@@ -124,11 +124,12 @@ class ReadSomeButNotAllResponsesTest(unittest.TestCase):
 
   def testReadSomeButNotAllResponses(self):
     server_completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.register_completion_queue(server_completion_queue)
     port = server.add_http2_port(b'[::]:0')
     server.start()
-    channel = cygrpc.Channel('localhost:{}'.format(port).encode())
+    channel = cygrpc.Channel('localhost:{}'.format(port).encode(),
+                             cygrpc.ChannelArgs([]))
 
     server_shutdown_tag = 'server_shutdown_tag'
     server_driver = _ServerDriver(server_completion_queue, server_shutdown_tag)
diff --git a/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py b/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
index 142387d810..8dedebfabe 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
@@ -121,7 +121,7 @@ class TypeSmokeTest(unittest.TestCase):
     del call_credentials
 
   def testServerStartNoExplicitShutdown(self):
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     completion_queue = cygrpc.CompletionQueue()
     server.register_completion_queue(completion_queue)
     port = server.add_http2_port(b'[::]:0')
@@ -131,7 +131,7 @@ class TypeSmokeTest(unittest.TestCase):
 
   def testServerStartShutdown(self):
     completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.add_http2_port(b'[::]:0')
     server.register_completion_queue(completion_queue)
     server.start()
@@ -148,7 +148,7 @@ class ServerClientMixin(object):
 
   def setUpMixin(self, server_credentials, client_credentials, host_override):
     self.server_completion_queue = cygrpc.CompletionQueue()
-    self.server = cygrpc.Server()
+    self.server = cygrpc.Server(cygrpc.ChannelArgs([]))
     self.server.register_completion_queue(self.server_completion_queue)
     if server_credentials:
       self.port = self.server.add_http2_port(b'[::]:0', server_credentials)
@@ -164,7 +164,8 @@ class ServerClientMixin(object):
           'localhost:{}'.format(self.port).encode(), client_channel_arguments,
           client_credentials)
     else:
-      self.client_channel = cygrpc.Channel('localhost:{}'.format(self.port).encode())
+      self.client_channel = cygrpc.Channel(
+          'localhost:{}'.format(self.port).encode(), cygrpc.ChannelArgs([]))
     if host_override:
       self.host_argument = None  # default host
       self.expected_host = host_override
diff --git a/src/ruby/ext/grpc/rb_channel.c b/src/ruby/ext/grpc/rb_channel.c
index e6d30a174b..3b2b88eb77 100644
--- a/src/ruby/ext/grpc/rb_channel.c
+++ b/src/ruby/ext/grpc/rb_channel.c
@@ -386,7 +386,7 @@ void Init_grpc_channel() {
   rb_define_const(grpc_rb_cChannel, "MAX_CONCURRENT_STREAMS",
                   ID2SYM(rb_intern(GRPC_ARG_MAX_CONCURRENT_STREAMS)));
   rb_define_const(grpc_rb_cChannel, "MAX_MESSAGE_LENGTH",
-                  ID2SYM(rb_intern(GRPC_ARG_MAX_MESSAGE_LENGTH)));
+                  ID2SYM(rb_intern(GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH)));
   id_insecure_channel = rb_intern("this_channel_is_insecure");
   Init_grpc_propagate_masks();
   Init_grpc_connectivity_states();