Merge remote-tracking branch 'upstream/master' into server_connection_timeout

26 files changed, 794 insertions, 269 deletions

diff --git a/test/core/end2end/cq_verifier.h b/test/core/end2end/cq_verifier.h
index 0b3b3fb349..959f849cb1 100644
--- a/test/core/end2end/cq_verifier.h
+++ b/test/core/end2end/cq_verifier.h
@@ -24,10 +24,6 @@
 #include <grpc/grpc.h>
 #include "test/core/util/test_config.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* A cq_verifier can verify that expected events arrive in a timely fashion
    on a single completion queue */
 
@@ -63,8 +59,4 @@ int contains_metadata(grpc_metadata_array* array, const char* key,
 int contains_metadata_slices(grpc_metadata_array* array, grpc_slice key,
                              grpc_slice value);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_TEST_CORE_END2END_CQ_VERIFIER_H */
diff --git a/test/core/end2end/data/client_certs.cc b/test/core/end2end/data/client_certs.cc
index 7e0b10da5c..46fc13927c 100644
--- a/test/core/end2end/data/client_certs.cc
+++ b/test/core/end2end/data/client_certs.cc
@@ -16,7 +16,7 @@
  *
  */
 
-extern "C" const char test_self_signed_client_cert[] = {
+extern const char test_self_signed_client_cert[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x43,
     0x45, 0x52, 0x54, 0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x6f, 0x44, 0x43, 0x43,
@@ -100,7 +100,7 @@ extern "C" const char test_self_signed_client_cert[] = {
     0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45, 0x2d, 0x2d, 0x2d, 0x2d, 0x2d,
     0x0a, 0x00};
 
-extern "C" const char test_self_signed_client_key[] = {
+extern const char test_self_signed_client_key[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x50,
     0x52, 0x49, 0x56, 0x41, 0x54, 0x45, 0x20, 0x4b, 0x45, 0x59, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x64, 0x77, 0x49, 0x42,
@@ -179,7 +179,7 @@ extern "C" const char test_self_signed_client_key[] = {
     0x52, 0x49, 0x56, 0x41, 0x54, 0x45, 0x20, 0x4b, 0x45, 0x59, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x00};
 
-extern "C" const char test_signed_client_cert[] = {
+extern const char test_signed_client_cert[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x43,
     0x45, 0x52, 0x54, 0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x48, 0x7a, 0x43, 0x43,
@@ -248,7 +248,7 @@ extern "C" const char test_signed_client_cert[] = {
     0x20, 0x43, 0x45, 0x52, 0x54, 0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45,
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x0a, 0x00};
 
-extern "C" const char test_signed_client_key[] = {
+extern const char test_signed_client_key[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x50,
     0x52, 0x49, 0x56, 0x41, 0x54, 0x45, 0x20, 0x4b, 0x45, 0x59, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x65, 0x51, 0x49, 0x42,
diff --git a/test/core/end2end/data/server1_cert.cc b/test/core/end2end/data/server1_cert.cc
index dd09810732..0943244ecc 100644
--- a/test/core/end2end/data/server1_cert.cc
+++ b/test/core/end2end/data/server1_cert.cc
@@ -16,7 +16,7 @@
  *
  */
 
-extern "C" const char test_server1_cert[] = {
+extern const char test_server1_cert[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x43,
     0x45, 0x52, 0x54, 0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x6e, 0x44, 0x43, 0x43,
diff --git a/test/core/end2end/data/server1_key.cc b/test/core/end2end/data/server1_key.cc
index 59dcaf6334..8f3ad15c26 100644
--- a/test/core/end2end/data/server1_key.cc
+++ b/test/core/end2end/data/server1_key.cc
@@ -16,7 +16,7 @@
  *
  */
 
-extern "C" const char test_server1_key[] = {
+extern const char test_server1_key[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x52,
     0x53, 0x41, 0x20, 0x50, 0x52, 0x49, 0x56, 0x41, 0x54, 0x45, 0x20, 0x4b,
     0x45, 0x59, 0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43,
diff --git a/test/core/end2end/data/ssl_test_data.h b/test/core/end2end/data/ssl_test_data.h
index e9c7dbceb2..303f3a6eda 100644
--- a/test/core/end2end/data/ssl_test_data.h
+++ b/test/core/end2end/data/ssl_test_data.h
@@ -19,10 +19,6 @@
 #ifndef GRPC_TEST_CORE_END2END_DATA_SSL_TEST_DATA_H
 #define GRPC_TEST_CORE_END2END_DATA_SSL_TEST_DATA_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 extern const char test_root_cert[];
 extern const char test_server1_cert[];
 extern const char test_server1_key[];
@@ -31,8 +27,4 @@ extern const char test_self_signed_client_key[];
 extern const char test_signed_client_cert[];
 extern const char test_signed_client_key[];
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_TEST_CORE_END2END_DATA_SSL_TEST_DATA_H */
diff --git a/test/core/end2end/data/test_root_cert.cc b/test/core/end2end/data/test_root_cert.cc
index 36fca2e45f..b4771b2cb8 100644
--- a/test/core/end2end/data/test_root_cert.cc
+++ b/test/core/end2end/data/test_root_cert.cc
@@ -16,7 +16,7 @@
  *
  */
 
-extern "C" const char test_root_cert[] = {
+extern const char test_root_cert[] = {
     0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x43,
     0x45, 0x52, 0x54, 0x49, 0x46, 0x49, 0x43, 0x41, 0x54, 0x45, 0x2d, 0x2d,
     0x2d, 0x2d, 0x2d, 0x0a, 0x4d, 0x49, 0x49, 0x43, 0x49, 0x7a, 0x43, 0x43,
diff --git a/test/core/end2end/end2end_tests.h b/test/core/end2end/end2end_tests.h
index 33943a7271..b42d90b55c 100644
--- a/test/core/end2end/end2end_tests.h
+++ b/test/core/end2end/end2end_tests.h
@@ -21,10 +21,6 @@
 
 #include <grpc/grpc.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct grpc_end2end_test_fixture grpc_end2end_test_fixture;
 typedef struct grpc_end2end_test_config grpc_end2end_test_config;
 
@@ -78,8 +74,4 @@ const grpc_slice* get_host_override_slice(const char* str,
 void validate_host_override_string(const char* pattern, grpc_slice str,
                                    grpc_end2end_test_config config);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_TEST_CORE_END2END_END2END_TESTS_H */
diff --git a/test/core/end2end/fuzzers/api_fuzzer.cc b/test/core/end2end/fuzzers/api_fuzzer.cc
index d84f8a31fa..75117218e4 100644
--- a/test/core/end2end/fuzzers/api_fuzzer.cc
+++ b/test/core/end2end/fuzzers/api_fuzzer.cc
@@ -56,7 +56,7 @@ static grpc_server* g_server;
 static grpc_channel* g_channel;
 static grpc_resource_quota* g_resource_quota;
 
-extern "C" gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type);
+extern gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type);
 
 static gpr_timespec now_impl(gpr_clock_type clock_type) {
   GPR_ASSERT(clock_type != GPR_TIMESPAN);
@@ -441,7 +441,7 @@ grpc_ares_request* my_dns_lookup_ares(
 // client connection
 
 // defined in tcp_client_posix.c
-extern "C" void (*grpc_tcp_client_connect_impl)(
+extern void (*grpc_tcp_client_connect_impl)(
     grpc_exec_ctx* exec_ctx, grpc_closure* closure, grpc_endpoint** ep,
     grpc_pollset_set* interested_parties, const grpc_channel_args* channel_args,
     const grpc_resolved_address* addr, grpc_millis deadline);
diff --git a/test/core/end2end/tests/no_logging.cc b/test/core/end2end/tests/no_logging.cc
index 55d211c44a..bf8651221a 100644
--- a/test/core/end2end/tests/no_logging.cc
+++ b/test/core/end2end/tests/no_logging.cc
@@ -36,7 +36,7 @@ enum { TIMEOUT = 200000 };
 
 static void* tag(intptr_t t) { return (void*)t; }
 
-extern "C" void gpr_default_log(gpr_log_func_args* args);
+void gpr_default_log(gpr_log_func_args* args);
 
 static void test_no_log(gpr_log_func_args* args) {
   char* message = nullptr;
diff --git a/test/core/end2end/tests/simple_request.cc b/test/core/end2end/tests/simple_request.cc
index ec7425aa09..7eb7467981 100644
--- a/test/core/end2end/tests/simple_request.cc
+++ b/test/core/end2end/tests/simple_request.cc
@@ -99,6 +99,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   grpc_metadata_array request_metadata_recv;
   grpc_call_details call_details;
   grpc_status_code status;
+  const char* error_string;
   grpc_call_error error;
   grpc_slice details;
   int was_cancelled = 2;
@@ -148,6 +149,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
   op->data.recv_status_on_client.status = &status;
   op->data.recv_status_on_client.status_details = &details;
+  op->data.recv_status_on_client.error_string = &error_string;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
@@ -199,6 +201,15 @@ static void simple_request_body(grpc_end2end_test_config config,
 
   GPR_ASSERT(status == GRPC_STATUS_UNIMPLEMENTED);
   GPR_ASSERT(0 == grpc_slice_str_cmp(details, "xyz"));
+  // the following sanity check makes sure that the requested error string is
+  // correctly populated by the core. It looks for certain substrings that are
+  // not likely to change much. Some parts of the error, like time created,
+  // obviously are not checked.
+  GPR_ASSERT(nullptr != strstr(error_string, "xyz"));
+  GPR_ASSERT(nullptr != strstr(error_string, "description"));
+  GPR_ASSERT(nullptr != strstr(error_string, "Error received from peer"));
+  GPR_ASSERT(nullptr != strstr(error_string, "grpc_message"));
+  GPR_ASSERT(nullptr != strstr(error_string, "grpc_status"));
   GPR_ASSERT(0 == grpc_slice_str_cmp(call_details.method, "/foo"));
   validate_host_override_string("foo.test.google.fr:1234", call_details.host,
                                 config);
@@ -206,6 +217,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   GPR_ASSERT(was_cancelled == 1);
 
   grpc_slice_unref(details);
+  gpr_free((void*)error_string);
   grpc_metadata_array_destroy(&initial_metadata_recv);
   grpc_metadata_array_destroy(&trailing_metadata_recv);
   grpc_metadata_array_destroy(&request_metadata_recv);
diff --git a/test/core/fling/client.cc b/test/core/fling/client.cc
index 544b66d480..69fb6dc7c7 100644
--- a/test/core/fling/client.cc
+++ b/test/core/fling/client.cc
@@ -22,15 +22,15 @@
 #include <string.h>
 
 #include <grpc/support/cmdline.h>
-#include <grpc/support/histogram.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
 #include <grpc/support/useful.h>
 #include "src/core/lib/profiling/timers.h"
 #include "test/core/util/grpc_profiler.h"
+#include "test/core/util/histogram.h"
 #include "test/core/util/test_config.h"
 
-static gpr_histogram* histogram;
+static grpc_histogram* histogram;
 static grpc_byte_buffer* the_buffer;
 static grpc_channel* channel;
 static grpc_completion_queue* cq;
@@ -195,7 +195,7 @@ int main(int argc, char** argv) {
   channel = grpc_insecure_channel_create(target, nullptr, nullptr);
   cq = grpc_completion_queue_create_for_next(nullptr);
   the_buffer = grpc_raw_byte_buffer_create(&slice, (size_t)payload_size);
-  histogram = gpr_histogram_create(0.01, 60e9);
+  histogram = grpc_histogram_create(0.01, 60e9);
 
   sc.init();
 
@@ -213,7 +213,7 @@ int main(int argc, char** argv) {
     start = now();
     sc.do_one_step();
     stop = now();
-    gpr_histogram_add(histogram, stop - start);
+    grpc_histogram_add(histogram, stop - start);
   }
   grpc_profiler_stop();
 
@@ -232,11 +232,11 @@ int main(int argc, char** argv) {
   grpc_slice_unref(slice);
 
   gpr_log(GPR_INFO, "latency (50/95/99/99.9): %f/%f/%f/%f",
-          gpr_histogram_percentile(histogram, 50),
-          gpr_histogram_percentile(histogram, 95),
-          gpr_histogram_percentile(histogram, 99),
-          gpr_histogram_percentile(histogram, 99.9));
-  gpr_histogram_destroy(histogram);
+          grpc_histogram_percentile(histogram, 50),
+          grpc_histogram_percentile(histogram, 95),
+          grpc_histogram_percentile(histogram, 99),
+          grpc_histogram_percentile(histogram, 99.9));
+  grpc_histogram_destroy(histogram);
 
   grpc_shutdown();
 
diff --git a/test/core/network_benchmarks/low_level_ping_pong.cc b/test/core/network_benchmarks/low_level_ping_pong.cc
index 687395d916..2ae9a45d7c 100644
--- a/test/core/network_benchmarks/low_level_ping_pong.cc
+++ b/test/core/network_benchmarks/low_level_ping_pong.cc
@@ -36,13 +36,13 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/cmdline.h>
-#include <grpc/support/histogram.h>
 #include <grpc/support/log.h>
 #include <grpc/support/thd.h>
 #include <grpc/support/time.h>
 #include <grpc/support/useful.h>
 #include "src/core/lib/iomgr/error.h"
 #include "src/core/lib/iomgr/socket_utils_posix.h"
+#include "test/core/util/histogram.h"
 
 typedef struct fd_pair {
   int read_fd;
@@ -275,14 +275,14 @@ static void server_thread_wrap(void* arg) {
   server_thread(args);
 }
 
-static void print_histogram(gpr_histogram* histogram) {
+static void print_histogram(grpc_histogram* histogram) {
   /* TODO(klempner): Print more detailed information, such as detailed histogram
      buckets */
   gpr_log(GPR_INFO, "latency (50/95/99/99.9): %f/%f/%f/%f",
-          gpr_histogram_percentile(histogram, 50),
-          gpr_histogram_percentile(histogram, 95),
-          gpr_histogram_percentile(histogram, 99),
-          gpr_histogram_percentile(histogram, 99.9));
+          grpc_histogram_percentile(histogram, 50),
+          grpc_histogram_percentile(histogram, 95),
+          grpc_histogram_percentile(histogram, 99),
+          grpc_histogram_percentile(histogram, 99.9));
 }
 
 static double now(void) {
@@ -293,7 +293,7 @@ static double now(void) {
 static void client_thread(thread_args* args) {
   char* buf = static_cast<char*>(gpr_malloc(args->msg_size * sizeof(char)));
   memset(buf, 0, args->msg_size * sizeof(char));
-  gpr_histogram* histogram = gpr_histogram_create(0.01, 60e9);
+  grpc_histogram* histogram = grpc_histogram_create(0.01, 60e9);
   double start_time;
   double end_time;
   double interval;
@@ -316,13 +316,13 @@ static void client_thread(thread_args* args) {
     end_time = now();
     if (i > kNumIters / 2) {
       interval = end_time - start_time;
-      gpr_histogram_add(histogram, interval);
+      grpc_histogram_add(histogram, interval);
     }
   }
   print_histogram(histogram);
 error:
   gpr_free(buf);
-  gpr_histogram_destroy(histogram);
+  grpc_histogram_destroy(histogram);
 }
 
 /* This roughly matches tcp_server's create_listening_socket */
diff --git a/test/core/support/BUILD b/test/core/support/BUILD
index 996166a371..4372b49b54 100644
--- a/test/core/support/BUILD
+++ b/test/core/support/BUILD
@@ -69,16 +69,6 @@ grpc_cc_test(
 )
 
 grpc_cc_test(
-    name = "histogram_test",
-    srcs = ["histogram_test.cc"],
-    language = "C++",
-    deps = [
-        "//:gpr",
-        "//test/core/util:gpr_test_util",
-    ],
-)
-
-grpc_cc_test(
     name = "host_port_test",
     srcs = ["host_port_test.cc"],
     language = "C++",
@@ -223,3 +213,30 @@ grpc_cc_test(
         "//test/core/util:gpr_test_util",
     ],
 )
+
+grpc_cc_test(
+    name = "ref_counted_test",
+    srcs = ["ref_counted_test.cc"],
+    language = "C++",
+    deps = [
+        "//:ref_counted",
+        "//test/core/util:gpr_test_util",
+    ],
+    external_deps = [
+        "gtest",
+    ],
+)
+
+grpc_cc_test(
+    name = "ref_counted_ptr_test",
+    srcs = ["ref_counted_ptr_test.cc"],
+    language = "C++",
+    deps = [
+        "//:ref_counted",
+        "//:ref_counted_ptr",
+        "//test/core/util:gpr_test_util",
+    ],
+    external_deps = [
+        "gtest",
+    ],
+)
diff --git a/test/core/support/histogram_test.cc b/test/core/support/histogram_test.cc
deleted file mode 100644
index 86b7d599e6..0000000000
--- a/test/core/support/histogram_test.cc
+++ /dev/null
@@ -1,163 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include <grpc/support/histogram.h>
-#include <grpc/support/log.h>
-
-#define LOG_TEST(x) gpr_log(GPR_INFO, "%s", x);
-
-static void test_no_op(void) {
-  gpr_histogram_destroy(gpr_histogram_create(0.01, 60e9));
-}
-
-static void expect_percentile(gpr_histogram* h, double percentile,
-                              double min_expect, double max_expect) {
-  double got = gpr_histogram_percentile(h, percentile);
-  gpr_log(GPR_INFO, "@%f%%, expect %f <= %f <= %f", percentile, min_expect, got,
-          max_expect);
-  GPR_ASSERT(min_expect <= got);
-  GPR_ASSERT(got <= max_expect);
-}
-
-static void test_simple(void) {
-  gpr_histogram* h;
-
-  LOG_TEST("test_simple");
-
-  h = gpr_histogram_create(0.01, 60e9);
-  gpr_histogram_add(h, 10000);
-  gpr_histogram_add(h, 10000);
-  gpr_histogram_add(h, 11000);
-  gpr_histogram_add(h, 11000);
-
-  expect_percentile(h, 50, 10001, 10999);
-  GPR_ASSERT(gpr_histogram_mean(h) == 10500);
-
-  gpr_histogram_destroy(h);
-}
-
-static void test_percentile(void) {
-  gpr_histogram* h;
-  double last;
-  double i;
-  double cur;
-
-  LOG_TEST("test_percentile");
-
-  h = gpr_histogram_create(0.05, 1e9);
-  gpr_histogram_add(h, 2.5);
-  gpr_histogram_add(h, 2.5);
-  gpr_histogram_add(h, 8);
-  gpr_histogram_add(h, 4);
-
-  GPR_ASSERT(gpr_histogram_count(h) == 4);
-  GPR_ASSERT(gpr_histogram_minimum(h) == 2.5);
-  GPR_ASSERT(gpr_histogram_maximum(h) == 8);
-  GPR_ASSERT(gpr_histogram_sum(h) == 17);
-  GPR_ASSERT(gpr_histogram_sum_of_squares(h) == 92.5);
-  GPR_ASSERT(gpr_histogram_mean(h) == 4.25);
-  GPR_ASSERT(gpr_histogram_variance(h) == 5.0625);
-  GPR_ASSERT(gpr_histogram_stddev(h) == 2.25);
-
-  expect_percentile(h, -10, 2.5, 2.5);
-  expect_percentile(h, 0, 2.5, 2.5);
-  expect_percentile(h, 12.5, 2.5, 2.5);
-  expect_percentile(h, 25, 2.5, 2.5);
-  expect_percentile(h, 37.5, 2.5, 2.8);
-  expect_percentile(h, 50, 3.0, 3.5);
-  expect_percentile(h, 62.5, 3.5, 4.5);
-  expect_percentile(h, 75, 5, 7.9);
-  expect_percentile(h, 100, 8, 8);
-  expect_percentile(h, 110, 8, 8);
-
-  /* test monotonicity */
-  last = 0.0;
-  for (i = 0; i < 100.0; i += 0.01) {
-    cur = gpr_histogram_percentile(h, i);
-    GPR_ASSERT(cur >= last);
-    last = cur;
-  }
-
-  gpr_histogram_destroy(h);
-}
-
-static void test_merge(void) {
-  gpr_histogram *h1, *h2;
-  double last;
-  double i;
-  double cur;
-
-  LOG_TEST("test_merge");
-
-  h1 = gpr_histogram_create(0.05, 1e9);
-  gpr_histogram_add(h1, 2.5);
-  gpr_histogram_add(h1, 2.5);
-  gpr_histogram_add(h1, 8);
-  gpr_histogram_add(h1, 4);
-
-  h2 = gpr_histogram_create(0.01, 1e9);
-  GPR_ASSERT(gpr_histogram_merge(h1, h2) == 0);
-  gpr_histogram_destroy(h2);
-
-  h2 = gpr_histogram_create(0.05, 1e10);
-  GPR_ASSERT(gpr_histogram_merge(h1, h2) == 0);
-  gpr_histogram_destroy(h2);
-
-  h2 = gpr_histogram_create(0.05, 1e9);
-  GPR_ASSERT(gpr_histogram_merge(h1, h2) == 1);
-  GPR_ASSERT(gpr_histogram_count(h1) == 4);
-  GPR_ASSERT(gpr_histogram_minimum(h1) == 2.5);
-  GPR_ASSERT(gpr_histogram_maximum(h1) == 8);
-  GPR_ASSERT(gpr_histogram_sum(h1) == 17);
-  GPR_ASSERT(gpr_histogram_sum_of_squares(h1) == 92.5);
-  GPR_ASSERT(gpr_histogram_mean(h1) == 4.25);
-  GPR_ASSERT(gpr_histogram_variance(h1) == 5.0625);
-  GPR_ASSERT(gpr_histogram_stddev(h1) == 2.25);
-  gpr_histogram_destroy(h2);
-
-  h2 = gpr_histogram_create(0.05, 1e9);
-  gpr_histogram_add(h2, 7.0);
-  gpr_histogram_add(h2, 17.0);
-  gpr_histogram_add(h2, 1.0);
-  GPR_ASSERT(gpr_histogram_merge(h1, h2) == 1);
-  GPR_ASSERT(gpr_histogram_count(h1) == 7);
-  GPR_ASSERT(gpr_histogram_minimum(h1) == 1.0);
-  GPR_ASSERT(gpr_histogram_maximum(h1) == 17.0);
-  GPR_ASSERT(gpr_histogram_sum(h1) == 42.0);
-  GPR_ASSERT(gpr_histogram_sum_of_squares(h1) == 431.5);
-  GPR_ASSERT(gpr_histogram_mean(h1) == 6.0);
-
-  /* test monotonicity */
-  last = 0.0;
-  for (i = 0; i < 100.0; i += 0.01) {
-    cur = gpr_histogram_percentile(h1, i);
-    GPR_ASSERT(cur >= last);
-    last = cur;
-  }
-
-  gpr_histogram_destroy(h1);
-  gpr_histogram_destroy(h2);
-}
-
-int main(void) {
-  test_no_op();
-  test_simple();
-  test_percentile();
-  test_merge();
-  return 0;
-}
diff --git a/test/core/support/ref_counted_ptr_test.cc b/test/core/support/ref_counted_ptr_test.cc
new file mode 100644
index 0000000000..1830edc4e5
--- /dev/null
+++ b/test/core/support/ref_counted_ptr_test.cc
@@ -0,0 +1,172 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/support/ref_counted_ptr.h"
+
+#include <gtest/gtest.h>
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/support/memory.h"
+#include "src/core/lib/support/ref_counted.h"
+#include "test/core/util/test_config.h"
+
+namespace grpc_core {
+namespace testing {
+namespace {
+
+class Foo : public RefCounted {
+ public:
+  Foo() : value_(0) {}
+
+  explicit Foo(int value) : value_(value) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+TEST(RefCountedPtr, DefaultConstructor) { RefCountedPtr<Foo> foo; }
+
+TEST(RefCountedPtr, ExplicitConstructorEmpty) {
+  RefCountedPtr<Foo> foo(nullptr);
+}
+
+TEST(RefCountedPtr, ExplicitConstructor) { RefCountedPtr<Foo> foo(New<Foo>()); }
+
+TEST(RefCountedPtr, MoveConstructor) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  RefCountedPtr<Foo> foo2(std::move(foo));
+  EXPECT_EQ(nullptr, foo.get());
+  EXPECT_NE(nullptr, foo2.get());
+}
+
+TEST(RefCountedPtr, MoveAssignment) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  RefCountedPtr<Foo> foo2 = std::move(foo);
+  EXPECT_EQ(nullptr, foo.get());
+  EXPECT_NE(nullptr, foo2.get());
+}
+
+TEST(RefCountedPtr, CopyConstructor) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  RefCountedPtr<Foo> foo2(foo);
+  EXPECT_NE(nullptr, foo.get());
+  EXPECT_EQ(foo.get(), foo2.get());
+}
+
+TEST(RefCountedPtr, CopyAssignment) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  RefCountedPtr<Foo> foo2 = foo;
+  EXPECT_NE(nullptr, foo.get());
+  EXPECT_EQ(foo.get(), foo2.get());
+}
+
+TEST(RefCountedPtr, CopyAssignmentWhenEmpty) {
+  RefCountedPtr<Foo> foo;
+  RefCountedPtr<Foo> foo2;
+  foo2 = foo;
+  EXPECT_EQ(nullptr, foo.get());
+  EXPECT_EQ(nullptr, foo2.get());
+}
+
+TEST(RefCountedPtr, CopyAssignmentToSelf) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  foo = foo;
+}
+
+TEST(RefCountedPtr, EnclosedScope) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  {
+    RefCountedPtr<Foo> foo2(std::move(foo));
+    EXPECT_EQ(nullptr, foo.get());
+    EXPECT_NE(nullptr, foo2.get());
+  }
+  EXPECT_EQ(nullptr, foo.get());
+}
+
+TEST(RefCountedPtr, ResetFromNullToNonNull) {
+  RefCountedPtr<Foo> foo;
+  EXPECT_EQ(nullptr, foo.get());
+  foo.reset(New<Foo>());
+  EXPECT_NE(nullptr, foo.get());
+}
+
+TEST(RefCountedPtr, ResetFromNonNullToNonNull) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  EXPECT_NE(nullptr, foo.get());
+  Foo* original = foo.get();
+  foo.reset(New<Foo>());
+  EXPECT_NE(nullptr, foo.get());
+  EXPECT_NE(original, foo.get());
+}
+
+TEST(RefCountedPtr, ResetFromNonNullToNull) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  EXPECT_NE(nullptr, foo.get());
+  foo.reset();
+  EXPECT_EQ(nullptr, foo.get());
+}
+
+TEST(RefCountedPtr, ResetFromNullToNull) {
+  RefCountedPtr<Foo> foo;
+  EXPECT_EQ(nullptr, foo.get());
+  foo.reset(nullptr);
+  EXPECT_EQ(nullptr, foo.get());
+}
+
+TEST(RefCountedPtr, DerefernceOperators) {
+  RefCountedPtr<Foo> foo(New<Foo>());
+  foo->value();
+  Foo& foo_ref = *foo;
+  foo_ref.value();
+}
+
+TEST(MakeRefCounted, NoArgs) {
+  RefCountedPtr<Foo> foo = MakeRefCounted<Foo>();
+  EXPECT_EQ(0, foo->value());
+}
+
+TEST(MakeRefCounted, Args) {
+  RefCountedPtr<Foo> foo = MakeRefCounted<Foo>(3);
+  EXPECT_EQ(3, foo->value());
+}
+
+TraceFlag foo_tracer(true, "foo");
+
+class FooWithTracing : public RefCountedWithTracing {
+ public:
+  FooWithTracing() : RefCountedWithTracing(&foo_tracer) {}
+};
+
+TEST(RefCountedPtr, RefCountedWithTracing) {
+  RefCountedPtr<FooWithTracing> foo(New<FooWithTracing>());
+  foo->Ref(DEBUG_LOCATION, "foo");
+  foo->Unref(DEBUG_LOCATION, "foo");
+}
+
+}  // namespace
+}  // namespace testing
+}  // namespace grpc_core
+
+int main(int argc, char** argv) {
+  grpc_test_init(argc, argv);
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/test/core/support/ref_counted_test.cc b/test/core/support/ref_counted_test.cc
new file mode 100644
index 0000000000..be9b6ff7c2
--- /dev/null
+++ b/test/core/support/ref_counted_test.cc
@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/support/ref_counted.h"
+
+#include <gtest/gtest.h>
+
+#include "src/core/lib/support/memory.h"
+#include "test/core/util/test_config.h"
+
+namespace grpc_core {
+namespace testing {
+namespace {
+
+class Foo : public RefCounted {
+ public:
+  Foo() {}
+};
+
+TEST(RefCounted, Basic) {
+  Foo* foo = New<Foo>();
+  foo->Unref();
+}
+
+TEST(RefCounted, ExtraRef) {
+  Foo* foo = New<Foo>();
+  foo->Ref();
+  foo->Unref();
+  foo->Unref();
+}
+
+TraceFlag foo_tracer(true, "foo");
+
+class FooWithTracing : public RefCountedWithTracing {
+ public:
+  FooWithTracing() : RefCountedWithTracing(&foo_tracer) {}
+};
+
+TEST(RefCountedWithTracing, Basic) {
+  FooWithTracing* foo = New<FooWithTracing>();
+  foo->Ref(DEBUG_LOCATION, "extra_ref");
+  foo->Unref(DEBUG_LOCATION, "extra_ref");
+  // Can use the no-argument methods, too.
+  foo->Ref();
+  foo->Unref();
+  foo->Unref(DEBUG_LOCATION, "original_ref");
+}
+
+}  // namespace
+}  // namespace testing
+}  // namespace grpc_core
+
+int main(int argc, char** argv) {
+  grpc_test_init(argc, argv);
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/test/core/surface/concurrent_connectivity_test.cc b/test/core/surface/concurrent_connectivity_test.cc
index 8fa15ab331..c7611b0dd1 100644
--- a/test/core/surface/concurrent_connectivity_test.cc
+++ b/test/core/surface/concurrent_connectivity_test.cc
@@ -49,10 +49,11 @@
 #define NUM_OUTER_LOOPS_SHORT_TIMEOUTS 10
 #define NUM_INNER_LOOPS_SHORT_TIMEOUTS 100
 #define DELAY_MILLIS_SHORT_TIMEOUTS 1
-// in a successful test run, POLL_MILLIS should never be reached beause all runs
-// should
-// end after the shorter delay_millis
+// in a successful test run, POLL_MILLIS should never be reached because all
+// runs should end after the shorter delay_millis
 #define POLL_MILLIS_SHORT_TIMEOUTS 30000
+// it should never take longer that this to shutdown the server
+#define SERVER_SHUTDOWN_TIMEOUT 30000
 
 static void* tag(int n) { return (void*)(uintptr_t)n; }
 static int detag(void* p) { return (int)(uintptr_t)p; }
@@ -95,7 +96,8 @@ struct server_thread_args {
 void server_thread(void* vargs) {
   struct server_thread_args* args = (struct server_thread_args*)vargs;
   grpc_event ev;
-  gpr_timespec deadline = gpr_inf_future(GPR_CLOCK_MONOTONIC);
+  gpr_timespec deadline =
+      grpc_timeout_milliseconds_to_deadline(SERVER_SHUTDOWN_TIMEOUT);
   ev = grpc_completion_queue_next(args->cq, deadline, nullptr);
   GPR_ASSERT(ev.type == GRPC_OP_COMPLETE);
   GPR_ASSERT(detag(ev.tag) == 0xd1e);
diff --git a/test/core/surface/public_headers_must_be_c89.c b/test/core/surface/public_headers_must_be_c89.c
index b5a83c8eed..8d2384ba61 100644
--- a/test/core/surface/public_headers_must_be_c89.c
+++ b/test/core/surface/public_headers_must_be_c89.c
@@ -20,6 +20,7 @@
 #include <grpc/byte_buffer_reader.h>
 #include <grpc/census.h>
 #include <grpc/compression.h>
+#include <grpc/fork.h>
 #include <grpc/grpc.h>
 #include <grpc/grpc_security.h>
 #include <grpc/grpc_security_constants.h>
@@ -29,6 +30,7 @@
 #include <grpc/impl/codegen/compression_types.h>
 #include <grpc/impl/codegen/connectivity_state.h>
 #include <grpc/impl/codegen/exec_ctx_fwd.h>
+#include <grpc/impl/codegen/fork.h>
 #include <grpc/impl/codegen/gpr_slice.h>
 #include <grpc/impl/codegen/gpr_types.h>
 #include <grpc/impl/codegen/grpc_types.h>
@@ -48,7 +50,6 @@
 #include <grpc/support/avl.h>
 #include <grpc/support/cmdline.h>
 #include <grpc/support/cpu.h>
-#include <grpc/support/histogram.h>
 #include <grpc/support/host_port.h>
 #include <grpc/support/log.h>
 #include <grpc/support/port_platform.h>
@@ -264,21 +265,6 @@ int main(int argc, char **argv) {
   printf("%lx", (unsigned long) gpr_cmdline_usage_string);
   printf("%lx", (unsigned long) gpr_cpu_num_cores);
   printf("%lx", (unsigned long) gpr_cpu_current_cpu);
-  printf("%lx", (unsigned long) gpr_histogram_create);
-  printf("%lx", (unsigned long) gpr_histogram_destroy);
-  printf("%lx", (unsigned long) gpr_histogram_add);
-  printf("%lx", (unsigned long) gpr_histogram_merge);
-  printf("%lx", (unsigned long) gpr_histogram_percentile);
-  printf("%lx", (unsigned long) gpr_histogram_mean);
-  printf("%lx", (unsigned long) gpr_histogram_stddev);
-  printf("%lx", (unsigned long) gpr_histogram_variance);
-  printf("%lx", (unsigned long) gpr_histogram_maximum);
-  printf("%lx", (unsigned long) gpr_histogram_minimum);
-  printf("%lx", (unsigned long) gpr_histogram_count);
-  printf("%lx", (unsigned long) gpr_histogram_sum);
-  printf("%lx", (unsigned long) gpr_histogram_sum_of_squares);
-  printf("%lx", (unsigned long) gpr_histogram_get_contents);
-  printf("%lx", (unsigned long) gpr_histogram_merge_contents);
   printf("%lx", (unsigned long) gpr_join_host_port);
   printf("%lx", (unsigned long) gpr_split_host_port);
   printf("%lx", (unsigned long) gpr_log_severity_string);
diff --git a/test/core/transport/bdp_estimator_test.cc b/test/core/transport/bdp_estimator_test.cc
index 2a6fa95162..d1272607f2 100644
--- a/test/core/transport/bdp_estimator_test.cc
+++ b/test/core/transport/bdp_estimator_test.cc
@@ -29,7 +29,7 @@
 #include "src/core/lib/support/string.h"
 #include "test/core/util/test_config.h"
 
-extern "C" gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type);
+extern gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type);
 
 namespace grpc_core {
 namespace testing {
diff --git a/test/core/util/BUILD b/test/core/util/BUILD
index 6443553466..268547f6c9 100644
--- a/test/core/util/BUILD
+++ b/test/core/util/BUILD
@@ -16,7 +16,10 @@ load("//bazel:grpc_build_system.bzl", "grpc_cc_library", "grpc_cc_test", "grpc_c
 
 licenses(["notice"])  # Apache v2
 
-grpc_package(name = "test/core/util", visibility = "public")
+grpc_package(
+    name = "test/core/util",
+    visibility = "public",
+)
 
 grpc_cc_library(
     name = "gpr_test_util",
@@ -49,6 +52,7 @@ grpc_cc_library(
     name = "grpc_test_util_base",
     srcs = [
         "grpc_profiler.cc",
+        "histogram.cc",
         "mock_endpoint.cc",
         "parse_hexstring.cc",
         "passthru_endpoint.cc",
@@ -62,6 +66,7 @@ grpc_cc_library(
     ],
     hdrs = [
         "grpc_profiler.h",
+        "histogram.h",
         "mock_endpoint.h",
         "parse_hexstring.h",
         "passthru_endpoint.h",
@@ -76,8 +81,8 @@ grpc_cc_library(
     language = "C++",
     deps = [
         ":gpr_test_util",
+        ":grpc_debugger_macros",
         "//:grpc_common",
-        ":grpc_debugger_macros"
     ],
 )
 
@@ -107,13 +112,23 @@ grpc_cc_library(
     name = "fuzzer_corpus_test",
     testonly = 1,
     srcs = ["fuzzer_corpus_test.cc"],
+    external_deps = [
+        "gtest",
+        "gflags",
+    ],
     deps = [
         ":gpr_test_util",
         "//:grpc",
     ],
-    external_deps = [
-        "gtest",
-        "gflags",
+)
+
+grpc_cc_test(
+    name = "histogram_test",
+    srcs = ["histogram_test.cc"],
+    language = "C++",
+    deps = [
+        ":grpc_test_util",
+        "//:gpr",
     ],
 )
 
diff --git a/test/core/util/fuzzer_corpus_test.cc b/test/core/util/fuzzer_corpus_test.cc
index d7aea54262..7849321257 100644
--- a/test/core/util/fuzzer_corpus_test.cc
+++ b/test/core/util/fuzzer_corpus_test.cc
@@ -29,8 +29,8 @@
 #include "test/core/util/test_config.h"
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
-extern "C" bool squelch;
-extern "C" bool leak_check;
+extern bool squelch;
+extern bool leak_check;
 
 // In some distros, gflags is in the namespace google, and in some others,
 // in gflags. This hack is enabling us to find both.
diff --git a/test/core/util/histogram.cc b/test/core/util/histogram.cc
new file mode 100644
index 0000000000..2f916f831d
--- /dev/null
+++ b/test/core/util/histogram.cc
@@ -0,0 +1,227 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <math.h>
+#include <stddef.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/useful.h>
+
+#include "test/core/util/histogram.h"
+
+/* Histograms are stored with exponentially increasing bucket sizes.
+   The first bucket is [0, m) where m = 1 + resolution
+   Bucket n (n>=1) contains [m**n, m**(n+1))
+   There are sufficient buckets to reach max_bucket_start */
+
+struct grpc_histogram {
+  /* Sum of all values seen so far */
+  double sum;
+  /* Sum of squares of all values seen so far */
+  double sum_of_squares;
+  /* number of values seen so far */
+  double count;
+  /* m in the description */
+  double multiplier;
+  double one_on_log_multiplier;
+  /* minimum value seen */
+  double min_seen;
+  /* maximum value seen */
+  double max_seen;
+  /* maximum representable value */
+  double max_possible;
+  /* number of buckets */
+  size_t num_buckets;
+  /* the buckets themselves */
+  uint32_t* buckets;
+};
+
+/* determine a bucket index given a value - does no bounds checking */
+static size_t bucket_for_unchecked(grpc_histogram* h, double x) {
+  return (size_t)(log(x) * h->one_on_log_multiplier);
+}
+
+/* bounds checked version of the above */
+static size_t bucket_for(grpc_histogram* h, double x) {
+  size_t bucket = bucket_for_unchecked(h, GPR_CLAMP(x, 1.0, h->max_possible));
+  GPR_ASSERT(bucket < h->num_buckets);
+  return bucket;
+}
+
+/* at what value does a bucket start? */
+static double bucket_start(grpc_histogram* h, double x) {
+  return pow(h->multiplier, x);
+}
+
+grpc_histogram* grpc_histogram_create(double resolution,
+                                      double max_bucket_start) {
+  grpc_histogram* h = (grpc_histogram*)gpr_malloc(sizeof(grpc_histogram));
+  GPR_ASSERT(resolution > 0.0);
+  GPR_ASSERT(max_bucket_start > resolution);
+  h->sum = 0.0;
+  h->sum_of_squares = 0.0;
+  h->multiplier = 1.0 + resolution;
+  h->one_on_log_multiplier = 1.0 / log(1.0 + resolution);
+  h->max_possible = max_bucket_start;
+  h->count = 0.0;
+  h->min_seen = max_bucket_start;
+  h->max_seen = 0.0;
+  h->num_buckets = bucket_for_unchecked(h, max_bucket_start) + 1;
+  GPR_ASSERT(h->num_buckets > 1);
+  GPR_ASSERT(h->num_buckets < 100000000);
+  h->buckets = (uint32_t*)gpr_zalloc(sizeof(uint32_t) * h->num_buckets);
+  return h;
+}
+
+void grpc_histogram_destroy(grpc_histogram* h) {
+  gpr_free(h->buckets);
+  gpr_free(h);
+}
+
+void grpc_histogram_add(grpc_histogram* h, double x) {
+  h->sum += x;
+  h->sum_of_squares += x * x;
+  h->count++;
+  if (x < h->min_seen) {
+    h->min_seen = x;
+  }
+  if (x > h->max_seen) {
+    h->max_seen = x;
+  }
+  h->buckets[bucket_for(h, x)]++;
+}
+
+int grpc_histogram_merge(grpc_histogram* dst, const grpc_histogram* src) {
+  if ((dst->num_buckets != src->num_buckets) ||
+      (dst->multiplier != src->multiplier)) {
+    /* Fail because these histograms don't match */
+    return 0;
+  }
+  grpc_histogram_merge_contents(dst, src->buckets, src->num_buckets,
+                                src->min_seen, src->max_seen, src->sum,
+                                src->sum_of_squares, src->count);
+  return 1;
+}
+
+void grpc_histogram_merge_contents(grpc_histogram* dst, const uint32_t* data,
+                                   size_t data_count, double min_seen,
+                                   double max_seen, double sum,
+                                   double sum_of_squares, double count) {
+  size_t i;
+  GPR_ASSERT(dst->num_buckets == data_count);
+  dst->sum += sum;
+  dst->sum_of_squares += sum_of_squares;
+  dst->count += count;
+  if (min_seen < dst->min_seen) {
+    dst->min_seen = min_seen;
+  }
+  if (max_seen > dst->max_seen) {
+    dst->max_seen = max_seen;
+  }
+  for (i = 0; i < dst->num_buckets; i++) {
+    dst->buckets[i] += data[i];
+  }
+}
+
+static double threshold_for_count_below(grpc_histogram* h, double count_below) {
+  double count_so_far;
+  double lower_bound;
+  double upper_bound;
+  size_t lower_idx;
+  size_t upper_idx;
+
+  if (h->count == 0) {
+    return 0.0;
+  }
+
+  if (count_below <= 0) {
+    return h->min_seen;
+  }
+  if (count_below >= h->count) {
+    return h->max_seen;
+  }
+
+  /* find the lowest bucket that gets us above count_below */
+  count_so_far = 0.0;
+  for (lower_idx = 0; lower_idx < h->num_buckets; lower_idx++) {
+    count_so_far += h->buckets[lower_idx];
+    if (count_so_far >= count_below) {
+      break;
+    }
+  }
+  if (count_so_far == count_below) {
+    /* this bucket hits the threshold exactly... we should be midway through
+       any run of zero values following the bucket */
+    for (upper_idx = lower_idx + 1; upper_idx < h->num_buckets; upper_idx++) {
+      if (h->buckets[upper_idx]) {
+        break;
+      }
+    }
+    return (bucket_start(h, (double)lower_idx) +
+            bucket_start(h, (double)upper_idx)) /
+           2.0;
+  } else {
+    /* treat values as uniform throughout the bucket, and find where this value
+       should lie */
+    lower_bound = bucket_start(h, (double)lower_idx);
+    upper_bound = bucket_start(h, (double)(lower_idx + 1));
+    return GPR_CLAMP(upper_bound - (upper_bound - lower_bound) *
+                                       (count_so_far - count_below) /
+                                       h->buckets[lower_idx],
+                     h->min_seen, h->max_seen);
+  }
+}
+
+double grpc_histogram_percentile(grpc_histogram* h, double percentile) {
+  return threshold_for_count_below(h, h->count * percentile / 100.0);
+}
+
+double grpc_histogram_mean(grpc_histogram* h) {
+  GPR_ASSERT(h->count != 0);
+  return h->sum / h->count;
+}
+
+double grpc_histogram_stddev(grpc_histogram* h) {
+  return sqrt(grpc_histogram_variance(h));
+}
+
+double grpc_histogram_variance(grpc_histogram* h) {
+  if (h->count == 0) return 0.0;
+  return (h->sum_of_squares * h->count - h->sum * h->sum) /
+         (h->count * h->count);
+}
+
+double grpc_histogram_maximum(grpc_histogram* h) { return h->max_seen; }
+
+double grpc_histogram_minimum(grpc_histogram* h) { return h->min_seen; }
+
+double grpc_histogram_count(grpc_histogram* h) { return h->count; }
+
+double grpc_histogram_sum(grpc_histogram* h) { return h->sum; }
+
+double grpc_histogram_sum_of_squares(grpc_histogram* h) {
+  return h->sum_of_squares;
+}
+
+const uint32_t* grpc_histogram_get_contents(grpc_histogram* h, size_t* size) {
+  *size = h->num_buckets;
+  return h->buckets;
+}
diff --git a/test/core/util/histogram.h b/test/core/util/histogram.h
new file mode 100644
index 0000000000..9d4985e64f
--- /dev/null
+++ b/test/core/util/histogram.h
@@ -0,0 +1,62 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_SUPPORT_HISTOGRAM_H
+#define GRPC_SUPPORT_HISTOGRAM_H
+
+#include <grpc/support/port_platform.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct grpc_histogram grpc_histogram;
+
+grpc_histogram* grpc_histogram_create(double resolution,
+                                      double max_bucket_start);
+void grpc_histogram_destroy(grpc_histogram* h);
+void grpc_histogram_add(grpc_histogram* h, double x);
+
+/** The following merges the second histogram into the first. It only works
+   if they have the same buckets and resolution. Returns 0 on failure, 1
+   on success */
+int grpc_histogram_merge(grpc_histogram* dst, const grpc_histogram* src);
+
+double grpc_histogram_percentile(grpc_histogram* histogram, double percentile);
+double grpc_histogram_mean(grpc_histogram* histogram);
+double grpc_histogram_stddev(grpc_histogram* histogram);
+double grpc_histogram_variance(grpc_histogram* histogram);
+double grpc_histogram_maximum(grpc_histogram* histogram);
+double grpc_histogram_minimum(grpc_histogram* histogram);
+double grpc_histogram_count(grpc_histogram* histogram);
+double grpc_histogram_sum(grpc_histogram* histogram);
+double grpc_histogram_sum_of_squares(grpc_histogram* histogram);
+
+const uint32_t* grpc_histogram_get_contents(grpc_histogram* histogram,
+                                            size_t* count);
+void grpc_histogram_merge_contents(grpc_histogram* histogram,
+                                   const uint32_t* data, size_t data_count,
+                                   double min_seen, double max_seen, double sum,
+                                   double sum_of_squares, double count);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GRPC_SUPPORT_HISTOGRAM_H */
diff --git a/test/core/util/histogram_test.cc b/test/core/util/histogram_test.cc
new file mode 100644
index 0000000000..b96ac7d841
--- /dev/null
+++ b/test/core/util/histogram_test.cc
@@ -0,0 +1,163 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/core/util/histogram.h"
+#include <grpc/support/log.h>
+
+#define LOG_TEST(x) gpr_log(GPR_INFO, "%s", x);
+
+static void test_no_op(void) {
+  grpc_histogram_destroy(grpc_histogram_create(0.01, 60e9));
+}
+
+static void expect_percentile(grpc_histogram* h, double percentile,
+                              double min_expect, double max_expect) {
+  double got = grpc_histogram_percentile(h, percentile);
+  gpr_log(GPR_INFO, "@%f%%, expect %f <= %f <= %f", percentile, min_expect, got,
+          max_expect);
+  GPR_ASSERT(min_expect <= got);
+  GPR_ASSERT(got <= max_expect);
+}
+
+static void test_simple(void) {
+  grpc_histogram* h;
+
+  LOG_TEST("test_simple");
+
+  h = grpc_histogram_create(0.01, 60e9);
+  grpc_histogram_add(h, 10000);
+  grpc_histogram_add(h, 10000);
+  grpc_histogram_add(h, 11000);
+  grpc_histogram_add(h, 11000);
+
+  expect_percentile(h, 50, 10001, 10999);
+  GPR_ASSERT(grpc_histogram_mean(h) == 10500);
+
+  grpc_histogram_destroy(h);
+}
+
+static void test_percentile(void) {
+  grpc_histogram* h;
+  double last;
+  double i;
+  double cur;
+
+  LOG_TEST("test_percentile");
+
+  h = grpc_histogram_create(0.05, 1e9);
+  grpc_histogram_add(h, 2.5);
+  grpc_histogram_add(h, 2.5);
+  grpc_histogram_add(h, 8);
+  grpc_histogram_add(h, 4);
+
+  GPR_ASSERT(grpc_histogram_count(h) == 4);
+  GPR_ASSERT(grpc_histogram_minimum(h) == 2.5);
+  GPR_ASSERT(grpc_histogram_maximum(h) == 8);
+  GPR_ASSERT(grpc_histogram_sum(h) == 17);
+  GPR_ASSERT(grpc_histogram_sum_of_squares(h) == 92.5);
+  GPR_ASSERT(grpc_histogram_mean(h) == 4.25);
+  GPR_ASSERT(grpc_histogram_variance(h) == 5.0625);
+  GPR_ASSERT(grpc_histogram_stddev(h) == 2.25);
+
+  expect_percentile(h, -10, 2.5, 2.5);
+  expect_percentile(h, 0, 2.5, 2.5);
+  expect_percentile(h, 12.5, 2.5, 2.5);
+  expect_percentile(h, 25, 2.5, 2.5);
+  expect_percentile(h, 37.5, 2.5, 2.8);
+  expect_percentile(h, 50, 3.0, 3.5);
+  expect_percentile(h, 62.5, 3.5, 4.5);
+  expect_percentile(h, 75, 5, 7.9);
+  expect_percentile(h, 100, 8, 8);
+  expect_percentile(h, 110, 8, 8);
+
+  /* test monotonicity */
+  last = 0.0;
+  for (i = 0; i < 100.0; i += 0.01) {
+    cur = grpc_histogram_percentile(h, i);
+    GPR_ASSERT(cur >= last);
+    last = cur;
+  }
+
+  grpc_histogram_destroy(h);
+}
+
+static void test_merge(void) {
+  grpc_histogram *h1, *h2;
+  double last;
+  double i;
+  double cur;
+
+  LOG_TEST("test_merge");
+
+  h1 = grpc_histogram_create(0.05, 1e9);
+  grpc_histogram_add(h1, 2.5);
+  grpc_histogram_add(h1, 2.5);
+  grpc_histogram_add(h1, 8);
+  grpc_histogram_add(h1, 4);
+
+  h2 = grpc_histogram_create(0.01, 1e9);
+  GPR_ASSERT(grpc_histogram_merge(h1, h2) == 0);
+  grpc_histogram_destroy(h2);
+
+  h2 = grpc_histogram_create(0.05, 1e10);
+  GPR_ASSERT(grpc_histogram_merge(h1, h2) == 0);
+  grpc_histogram_destroy(h2);
+
+  h2 = grpc_histogram_create(0.05, 1e9);
+  GPR_ASSERT(grpc_histogram_merge(h1, h2) == 1);
+  GPR_ASSERT(grpc_histogram_count(h1) == 4);
+  GPR_ASSERT(grpc_histogram_minimum(h1) == 2.5);
+  GPR_ASSERT(grpc_histogram_maximum(h1) == 8);
+  GPR_ASSERT(grpc_histogram_sum(h1) == 17);
+  GPR_ASSERT(grpc_histogram_sum_of_squares(h1) == 92.5);
+  GPR_ASSERT(grpc_histogram_mean(h1) == 4.25);
+  GPR_ASSERT(grpc_histogram_variance(h1) == 5.0625);
+  GPR_ASSERT(grpc_histogram_stddev(h1) == 2.25);
+  grpc_histogram_destroy(h2);
+
+  h2 = grpc_histogram_create(0.05, 1e9);
+  grpc_histogram_add(h2, 7.0);
+  grpc_histogram_add(h2, 17.0);
+  grpc_histogram_add(h2, 1.0);
+  GPR_ASSERT(grpc_histogram_merge(h1, h2) == 1);
+  GPR_ASSERT(grpc_histogram_count(h1) == 7);
+  GPR_ASSERT(grpc_histogram_minimum(h1) == 1.0);
+  GPR_ASSERT(grpc_histogram_maximum(h1) == 17.0);
+  GPR_ASSERT(grpc_histogram_sum(h1) == 42.0);
+  GPR_ASSERT(grpc_histogram_sum_of_squares(h1) == 431.5);
+  GPR_ASSERT(grpc_histogram_mean(h1) == 6.0);
+
+  /* test monotonicity */
+  last = 0.0;
+  for (i = 0; i < 100.0; i += 0.01) {
+    cur = grpc_histogram_percentile(h1, i);
+    GPR_ASSERT(cur >= last);
+    last = cur;
+  }
+
+  grpc_histogram_destroy(h1);
+  grpc_histogram_destroy(h2);
+}
+
+int main(void) {
+  test_no_op();
+  test_simple();
+  test_percentile();
+  test_merge();
+  return 0;
+}
diff --git a/test/core/util/port.h b/test/core/util/port.h
index 602099dea6..3a4cf4467a 100644
--- a/test/core/util/port.h
+++ b/test/core/util/port.h
@@ -19,10 +19,6 @@
 #ifndef GRPC_TEST_CORE_UTIL_PORT_H
 #define GRPC_TEST_CORE_UTIL_PORT_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct grpc_pick_port_functions {
   int (*pick_unused_port_fn)(void);
   int (*pick_unused_port_or_die_fn)(void);
@@ -45,8 +41,4 @@ void grpc_recycle_unused_port(int port);
 /** Request the family of pick_port functions in \a functions be used. */
 void grpc_set_pick_port_functions(grpc_pick_port_functions functions);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_TEST_CORE_UTIL_PORT_H */
diff --git a/test/core/util/test_config.h b/test/core/util/test_config.h
index 4383fbfce8..775ffac949 100644
--- a/test/core/util/test_config.h
+++ b/test/core/util/test_config.h
@@ -21,10 +21,6 @@
 
 #include <grpc/support/time.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 extern int64_t g_fixture_slowdown_factor;
 extern int64_t g_poller_slowdown_factor;
 
@@ -43,8 +39,4 @@ gpr_timespec grpc_timeout_milliseconds_to_deadline(int64_t time_ms);
 
 void grpc_test_init(int argc, char** argv);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_TEST_CORE_UTIL_TEST_CONFIG_H */