Add ThreadLocal::accessAllThreads benchmark

Summary: Add ThreadLocal::accessAllThreads benchmark

Reviewed By: djwatson

Differential Revision: D8555358

fbshipit-source-id: 44da3830df96183158d3641fc4611c8e36364c00

folly/test/ThreadLocalAccessBenchmark.cpp

+/*
+ * Copyright 2018-present Facebook, Inc.
+ *
+ * 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 <folly/Benchmark.h>
+#include <folly/ThreadLocal.h>
+#include <condition_variable>
+#include <mutex>
+#include <thread>
+
+using namespace folly;
+
+namespace {
+class SimpleThreadCachedInt {
+  class NewTag;
+  ThreadLocal<int, NewTag> val_;
+
+ public:
+  void set() {
+    *val_ = 0;
+  }
+
+  void access() {
+    for (const auto& i : val_.accessAllThreads()) {
+      (void)i;
+    }
+  }
+};
+} // namespace
+void runTest(int iters, int numThreads) {
+  BenchmarkSuspender susp;
+
+  std::vector<SimpleThreadCachedInt> stci(numThreads);
+
+  std::mutex m, mw;
+  std::condition_variable cv, cvw;
+  bool running = true;
+  int numRunning = 0;
+
+  std::vector<std::thread> threads;
+  for (int i = 0; i < numThreads; i++) {
+    threads.push_back(std::thread([i,
+                                   numThreads,
+                                   &stci,
+                                   &m,
+                                   &mw,
+                                   &cv,
+                                   &cvw,
+                                   &running,
+                                   &numRunning]() mutable {
+      stci[i].set();
+
+      // notify if all the threads have created the
+      // thread local var
+      bool notify = false;
+      {
+        std::lock_guard<std::mutex> lk(m);
+        if (++numRunning == numThreads) {
+          notify = true;
+        }
+      }
+
+      if (notify) {
+        cv.notify_one();
+      }
+
+      // now wait
+      {
+        std::unique_lock<std::mutex> lk(mw);
+        cvw.wait(lk, [&]() { return !running; });
+      }
+    }));
+  }
+
+  // wait for the threads to create the thread locals
+  {
+    std::unique_lock<std::mutex> lk(m);
+    cv.wait(lk, [&]() { return numRunning == numThreads; });
+  }
+
+  susp.dismiss();
+
+  // run the test loop
+  for (int i = 0; i < iters; i++) {
+    stci[i % numThreads].access();
+  }
+
+  susp.rehire();
+
+  {
+    std::lock_guard<std::mutex> lk(mw);
+    running = false;
+  }
+
+  cvw.notify_all();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK_DRAW_LINE();
+BENCHMARK_PARAM(runTest, 1)
+BENCHMARK_PARAM(runTest, 128)
+BENCHMARK_PARAM(runTest, 256)
+BENCHMARK_PARAM(runTest, 512)
+BENCHMARK_PARAM(runTest, 1024)
+BENCHMARK_PARAM(runTest, 2048)
+BENCHMARK_DRAW_LINE();
+
+int main(int argc, char* argv[]) {
+  gflags::ParseCommandLineFlags(&argc, &argv, true);
+  folly::runBenchmarks();
+
+  return 0;
+}