replace StartingGate with folly::test::Barrier

Summary:
StartingGate was similar to std::barrier except that it guaranteed the
coordinating thread woke the worker threads. While this symmetry is
nice in concept, given enough threads, I doubt it pays for the
duplication.

Just adopt folly::test::Barrier (which is basically std::barrier)
instead.

Reviewed By: strager

Differential Revision: D16942136

fbshipit-source-id: 1691d8ef72b88c8867df74c8ed938f6c8d6ee094

eden/benchmarks/get_sha1_thrift.cpp

@@ -5,11 +5,11 @@
  * GNU General Public License version 2.
  */
 #include <boost/filesystem.hpp>
-#include <fb303/test/StartingGate.h>
 #include <folly/Benchmark.h>
 #include <folly/File.h>
 #include <folly/container/Array.h>
 #include <folly/init/Init.h>
+#include <folly/synchronization/test/Barrier.h>
 #include <thrift/lib/cpp/async/TAsyncSocket.h>
 #include <thrift/lib/cpp2/async/HeaderClientChannel.h>
 #include <iostream>
@@ -21,7 +21,6 @@
 #include "eden/fs/service/gen-cpp2/EdenService.h"
 
 using namespace facebook::eden;
-using namespace facebook::fb303;
 using namespace boost::filesystem;
 
 DEFINE_uint64(threads, 1, "The number of concurrent Thrift client threads");
@@ -67,7 +66,7 @@ int main(int argc, char** argv) {
   const auto samples_per_thread = 131072;
 
   std::vector<std::thread> threads;
-  StartingGate gate{static_cast<unsigned>(nthreads)};
+  folly::test::Barrier gate{static_cast<unsigned>(nthreads)};
   std::vector<uint64_t> samples(nthreads * samples_per_thread);
   for (unsigned i = 0; i < nthreads; ++i) {
     threads.emplace_back(
@@ -110,7 +109,6 @@ int main(int argc, char** argv) {
         });
   }
 
-  gate.waitThenOpen();
   for (auto& thread : threads) {
     thread.join();
   }

eden/benchmarks/open_close_parallel.cpp

@@ -4,11 +4,11 @@
  * This software may be used and distributed according to the terms of the
  * GNU General Public License version 2.
  */
-#include <fb303/test/StartingGate.h>
 #include <fcntl.h>
 #include <folly/Exception.h>
 #include <folly/Likely.h>
 #include <folly/init/Init.h>
+#include <folly/synchronization/test/Barrier.h>
 #include <gflags/gflags.h>
 #include <inttypes.h>
 #include <string.h>
@@ -23,7 +23,7 @@ DEFINE_uint64(threads, 1, "The number of concurrent open/close threads");
 DEFINE_uint64(iterations, 100000, "Number of open/close iterations per thread");
 
 using namespace facebook::eden;
-using facebook::fb303::StartingGate;
+using folly::test::Barrier;
 
 int main(int argc, char** argv) {
   folly::init(&argc, &argv);
@@ -54,7 +54,7 @@ int main(int argc, char** argv) {
     ::close(fd);
   }
 
-  StartingGate gate{FLAGS_threads};
+  folly::test::Barrier gate{FLAGS_threads};
 
   std::mutex result_mutex;
   StatAccumulator combined_open;
@@ -98,8 +98,6 @@ int main(int argc, char** argv) {
     threads.emplace_back([t, &thread] { thread(t); });
   }
 
-  gate.waitThenOpen();
-
   for (auto& thread : threads) {
     thread.join();
   }

eden/fs/tracing/test/TracingBenchmark.cpp

@@ -4,9 +4,9 @@
  * This software may be used and distributed according to the terms of the
  * GNU General Public License version 2.
  */
-#include <fb303/test/StartingGate.h>
 #include <folly/Benchmark.h>
 #include <folly/init/Init.h>
+#include <folly/synchronization/test/Barrier.h>
 #include "eden/fs/benchharness/Bench.h"
 #include "eden/fs/tracing/Tracing.h"
 
@@ -25,7 +25,7 @@ BENCHMARK(Tracer_repeatedly_create_trace_points, n) {
 BENCHMARK(Tracer_repeatedly_create_trace_points_from_multiple_threads, n) {
   constexpr unsigned threadCount = 8;
   std::vector<std::thread> threads;
-  facebook::fb303::StartingGate gate{threadCount};
+  folly::test::Barrier gate{1 + threadCount};
   {
     folly::BenchmarkSuspender suspender;
     enableTracing();
@@ -42,7 +42,7 @@ BENCHMARK(Tracer_repeatedly_create_trace_points_from_multiple_threads, n) {
         }
       });
     }
-    gate.waitThenOpen();
+    gate.wait();
   }
   for (unsigned i = 0; i < n; ++i) {
     TraceBlock block{"foo"};

eden/fs/utils/test/ProcessAccessLogBenchmark.cpp

@@ -6,13 +6,12 @@
  */
 #include "eden/fs/utils/ProcessAccessLog.h"
 
-#include <fb303/test/StartingGate.h>
 #include <folly/Benchmark.h>
+#include <folly/synchronization/test/Barrier.h>
 #include "eden/fs/benchharness/Bench.h"
 #include "eden/fs/utils/ProcessNameCache.h"
 
 using namespace facebook::eden;
-using namespace facebook::fb303;
 
 /**
  * A high but realistic amount of contention.
@@ -26,7 +25,7 @@ BENCHMARK(ProcessAccessLog_repeatedly_add_self, iters) {
   ProcessAccessLog processAccessLog{processNameCache};
 
   std::vector<std::thread> threads;
-  StartingGate gate{kThreadCount};
+  folly::test::Barrier gate{kThreadCount + 1};
 
   size_t remainingIterations = iters;
   size_t totalIterations = 0;
@@ -47,10 +46,10 @@ BENCHMARK(ProcessAccessLog_repeatedly_add_self, iters) {
 
   CHECK_EQ(totalIterations, iters);
 
-  suspender.dismiss();
-
   // Now wake the threads.
-  gate.waitThenOpen();
+  gate.wait();
+
+  suspender.dismiss();
 
   // Wait until they're done.
   for (auto& thread : threads) {

eden/fs/utils/test/ProcessNameCacheBenchmark.cpp

@@ -6,8 +6,8 @@
  */
 #include "eden/fs/utils/ProcessNameCache.h"
 
-#include <fb303/test/StartingGate.h>
 #include <folly/Benchmark.h>
+#include <folly/synchronization/test/Barrier.h>
 #include "eden/fs/benchharness/Bench.h"
 
 using namespace facebook::eden;
@@ -22,7 +22,7 @@ BENCHMARK(ProcessNameCache_repeatedly_add_self, iters) {
 
   ProcessNameCache processNameCache;
   std::vector<std::thread> threads;
-  facebook::fb303::StartingGate gate{kThreadCount};
+  folly::test::Barrier gate{1 + kThreadCount};
 
   size_t remainingIterations = iters;
   size_t totalIterations = 0;
@@ -42,10 +42,10 @@ BENCHMARK(ProcessNameCache_repeatedly_add_self, iters) {
 
   CHECK_EQ(totalIterations, iters);
 
-  suspender.dismiss();
-
   // Now wake the threads.
-  gate.waitThenOpen();
+  gate.wait();
+
+  suspender.dismiss();
 
   // Wait until they're done.
   for (auto& thread : threads) {