Merge branch 'flow_control_v2' into bwest

1 files changed, 36 insertions, 94 deletions

diff --git a/src/core/lib/iomgr/resource_quota.h b/src/core/lib/iomgr/resource_quota.h
index d9e7d8fa90..e3ff99e0aa 100644
--- a/src/core/lib/iomgr/resource_quota.h
+++ b/src/core/lib/iomgr/resource_quota.h
@@ -49,7 +49,8 @@
     resource constrained, grpc_resource_user instances are asked (in turn) to
     free up whatever they can so that the system as a whole can make progress.
 
-    There are three kinds of reclamation that take place:
+    There are three kinds of reclamation that take place, in order of increasing
+    invasiveness:
     - an internal reclamation, where cached resource at the resource user level
       is returned to the quota
     - a benign reclamation phase, whereby resources that are in use but are not
@@ -58,9 +59,14 @@
       make progress may be enacted so that at least one part of the system can
       complete.
 
-    These reclamations are tried in priority order, and only one reclamation
-    is outstanding for a quota at any given time (meaning that if a destructive
-    reclamation makes progress, we may follow up with a benign reclamation).
+    Only one reclamation will be outstanding for a given quota at a given time.
+    On each reclamation attempt, the kinds of reclamation are tried in order of
+    increasing invasiveness, stopping at the first one that succeeds. Thus, on a
+    given reclamation attempt, if internal and benign reclamation both fail, it
+    will wind up doing a destructive reclamation. However, the next reclamation
+    attempt may then be able to get what it needs via internal or benign
+    reclamation, due to resources that may have been freed up by the destructive
+    reclamation in the previous attempt.
 
     Future work will be to expose the current resource pressure so that back
     pressure can be applied to avoid reclamation phases starting.
@@ -84,96 +90,19 @@ grpc_resource_quota *grpc_resource_quota_from_channel_args(
 double grpc_resource_quota_get_memory_pressure(
     grpc_resource_quota *resource_quota);
 
-/* Resource users are kept in (potentially) several intrusive linked lists
-   at once. These are the list names. */
-typedef enum {
-  /* Resource users that are waiting for an allocation */
-  GRPC_RULIST_AWAITING_ALLOCATION,
-  /* Resource users that have free memory available for internal reclamation */
-  GRPC_RULIST_NON_EMPTY_FREE_POOL,
-  /* Resource users that have published a benign reclamation is available */
-  GRPC_RULIST_RECLAIMER_BENIGN,
-  /* Resource users that have published a destructive reclamation is
-     available */
-  GRPC_RULIST_RECLAIMER_DESTRUCTIVE,
-  /* Number of lists: must be last */
-  GRPC_RULIST_COUNT
-} grpc_rulist;
-
 typedef struct grpc_resource_user grpc_resource_user;
 
-/* Internal linked list pointers for a resource user */
-typedef struct {
-  grpc_resource_user *next;
-  grpc_resource_user *prev;
-} grpc_resource_user_link;
-
-struct grpc_resource_user {
-  /* The quota this resource user consumes from */
-  grpc_resource_quota *resource_quota;
-
-  /* Closure to schedule an allocation onder the resource quota combiner lock */
-  grpc_closure allocate_closure;
-  /* Closure to publish a non empty free pool under the resource quota combiner
-     lock */
-  grpc_closure add_to_free_pool_closure;
-
-#ifndef NDEBUG
-  /* Canary object to detect leaked resource users with ASAN */
-  void *asan_canary;
-#endif
-
-  gpr_mu mu;
-  /* Total allocated memory outstanding by this resource user;
-     always positive */
-  int64_t allocated;
-  /* The amount of memory this user has cached for its own use: to avoid quota
-     contention, each resource user can keep some memory aside from the quota,
-     and the quota can pull it back under memory pressure.
-     This value can become negative if more memory has been requested than
-     existed in the free pool, at which point the quota is consulted to bring
-     this value non-negative (asynchronously). */
-  int64_t free_pool;
-  /* A list of closures to call once free_pool becomes non-negative - ie when
-     all outstanding allocations have been granted. */
-  grpc_closure_list on_allocated;
-  /* True if we are currently trying to allocate from the quota, false if not */
-  bool allocating;
-  /* True if we are currently trying to add ourselves to the non-free quota
-     list, false otherwise */
-  bool added_to_free_pool;
-
-  /* Reclaimers: index 0 is the benign reclaimer, 1 is the destructive reclaimer
-   */
-  grpc_closure *reclaimers[2];
-  /* Trampoline closures to finish reclamation and re-enter the quota combiner
-     lock */
-  grpc_closure post_reclaimer_closure[2];
-
-  /* Closure to execute under the quota combiner to de-register and shutdown the
-     resource user */
-  grpc_closure destroy_closure;
-  /* User supplied closure to call once the user has finished shutting down AND
-     all outstanding allocations have been freed */
-  gpr_atm on_done_destroy_closure;
-
-  /* Links in the various grpc_rulist lists */
-  grpc_resource_user_link links[GRPC_RULIST_COUNT];
-
-  /* The name of this resource user, for debugging/tracing */
-  char *name;
-};
-
-void grpc_resource_user_init(grpc_resource_user *resource_user,
-                             grpc_resource_quota *resource_quota,
-                             const char *name);
+grpc_resource_user *grpc_resource_user_create(
+    grpc_resource_quota *resource_quota, const char *name);
+void grpc_resource_user_ref(grpc_resource_user *resource_user);
+void grpc_resource_user_unref(grpc_exec_ctx *exec_ctx,
+                              grpc_resource_user *resource_user);
 void grpc_resource_user_shutdown(grpc_exec_ctx *exec_ctx,
-                                 grpc_resource_user *resource_user,
-                                 grpc_closure *on_done);
-void grpc_resource_user_destroy(grpc_exec_ctx *exec_ctx,
-                                grpc_resource_user *resource_user);
+                                 grpc_resource_user *resource_user);
+grpc_resource_quota *grpc_resource_user_get_quota(
+    grpc_resource_user *resource_user);
 
-/* Allocate from the resource user (and it's quota).
+/* Allocate from the resource user (and its quota).
    If optional_on_done is NULL, then allocate immediately. This may push the
    quota over-limit, at which point reclamation will kick in.
    If optional_on_done is non-NULL, it will be scheduled when the allocation has
@@ -197,23 +126,36 @@ void grpc_resource_user_finish_reclamation(grpc_exec_ctx *exec_ctx,
 
 /* Helper to allocate slices from a resource user */
 typedef struct grpc_resource_user_slice_allocator {
+  /* Closure for when a resource user allocation completes */
   grpc_closure on_allocated;
+  /* Closure to call when slices have been allocated */
   grpc_closure on_done;
+  /* Length of slices to allocate on the current request */
   size_t length;
+  /* Number of slices to allocate on the current request */
   size_t count;
-  gpr_slice_buffer *dest;
+  /* Destination for slices to allocate on the current request */
+  grpc_slice_buffer *dest;
+  /* Parent resource user */
   grpc_resource_user *resource_user;
 } grpc_resource_user_slice_allocator;
 
-/* Initialize a slice allocator */
+/* Initialize a slice allocator.
+   When an allocation is completed, calls \a cb with arg \p. */
 void grpc_resource_user_slice_allocator_init(
     grpc_resource_user_slice_allocator *slice_allocator,
     grpc_resource_user *resource_user, grpc_iomgr_cb_func cb, void *p);
 
-/* Allocate \a count slices of length \a length into \a dest. */
+/* Allocate \a count slices of length \a length into \a dest. Only one request
+   can be outstanding at a time. */
 void grpc_resource_user_alloc_slices(
     grpc_exec_ctx *exec_ctx,
     grpc_resource_user_slice_allocator *slice_allocator, size_t length,
-    size_t count, gpr_slice_buffer *dest);
+    size_t count, grpc_slice_buffer *dest);
+
+/* Allocate one slice of length \a size synchronously. */
+grpc_slice grpc_resource_user_slice_malloc(grpc_exec_ctx *exec_ctx,
+                                           grpc_resource_user *resource_user,
+                                           size_t size);
 
 #endif /* GRPC_CORE_LIB_IOMGR_RESOURCE_QUOTA_H */