parkinglot benchmark

Summary: Add benchmark vs. futex

Reviewed By: yfeldblum

Differential Revision: D6639280

fbshipit-source-id: 9735444a7f48011f31603159561675d472cc4411

folly/synchronization/test/ParkingLotBenchmark.cpp

+/*
+ * Copyright 2017-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 <thread>
+
+#include <folly/synchronization/ParkingLot.h>
+
+#include <folly/Benchmark.h>
+#include <folly/detail/Futex.h>
+#include <folly/synchronization/Baton.h>
+
+DEFINE_uint64(threads, 32, "Number of threads for benchmark");
+
+using namespace folly;
+
+namespace {
+struct SimpleBarrier {
+  explicit SimpleBarrier(size_t count) : lock_(), cv_(), count_(count) {}
+
+  void wait() {
+    std::unique_lock<std::mutex> lockHeld(lock_);
+    auto gen = gen_;
+    if (++num_ == count_) {
+      num_ = 0;
+      gen_++;
+      cv_.notify_all();
+    } else {
+      cv_.wait(lockHeld, [&]() { return gen == gen_; });
+    }
+  }
+
+ private:
+  std::mutex lock_;
+  std::condition_variable cv_;
+  size_t num_{0};
+  size_t count_;
+  size_t gen_{0};
+};
+} // namespace
+
+ParkingLot<> lot;
+
+BENCHMARK(FutexNoWaitersWake, iters) {
+  BenchmarkSuspender susp;
+  folly::detail::Futex<> fu;
+  SimpleBarrier b(FLAGS_threads + 1);
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      for (int i = 0; i < iters; i++) {
+        fu.futexWake(1);
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK_RELATIVE(ParkingLotNoWaitersWake, iters) {
+  BenchmarkSuspender susp;
+  folly::detail::Futex<> fu;
+  SimpleBarrier b(FLAGS_threads + 1);
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      for (int i = 0; i < iters; i++) {
+        lot.unpark(&lot, [](Unit) { return UnparkControl::RetainContinue; });
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK(FutexWakeOne, iters) {
+  BenchmarkSuspender susp;
+  folly::detail::Futex<> fu;
+  SimpleBarrier b(FLAGS_threads + 1);
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      while (true) {
+        fu.futexWait(0);
+        if (fu.load(std::memory_order_relaxed)) {
+          return;
+        }
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+  for (int i = 0; i < iters; i++) {
+    fu.futexWake(1);
+  }
+  fu.store(1);
+  fu.futexWake(threads.size());
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK_RELATIVE(ParkingLotWakeOne, iters) {
+  BenchmarkSuspender susp;
+  std::atomic<bool> done{false};
+  SimpleBarrier b(FLAGS_threads + 1);
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      while (true) {
+        Unit f;
+        lot.park(
+            &done,
+            f,
+            [&] { return done.load(std::memory_order_relaxed) == 0; },
+            [] {});
+        if (done.load(std::memory_order_relaxed)) {
+          return;
+        }
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+  for (int i = 0; i < iters; i++) {
+    lot.unpark(&done, [](Unit) { return UnparkControl::RemoveBreak; });
+  }
+  done = true;
+  lot.unpark(&done, [](Unit) { return UnparkControl::RemoveContinue; });
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK(FutexWakeAll, iters) {
+  BenchmarkSuspender susp;
+  SimpleBarrier b(FLAGS_threads + 1);
+  folly::detail::Futex<> fu;
+  std::atomic<bool> done{false};
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      while (true) {
+        fu.futexWait(0);
+        if (done.load(std::memory_order_relaxed)) {
+          return;
+        }
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+  for (int i = 0; i < iters; i++) {
+    fu.futexWake(threads.size());
+  }
+  fu.store(1);
+  done = true;
+  fu.futexWake(threads.size());
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+BENCHMARK_RELATIVE(ParkingLotWakeAll, iters) {
+  BenchmarkSuspender susp;
+  SimpleBarrier b(FLAGS_threads + 1);
+  std::atomic<bool> done{false};
+
+  std::vector<std::thread> threads{FLAGS_threads};
+  for (auto& t : threads) {
+    t = std::thread([&]() {
+      b.wait();
+      while (true) {
+        Unit f;
+        lot.park(
+            &done,
+            f,
+            [&] { return done.load(std::memory_order_relaxed) == 0; },
+            [] {});
+        if (done.load(std::memory_order_relaxed)) {
+          return;
+        }
+      }
+    });
+  }
+  susp.dismiss();
+  b.wait();
+  for (int i = 0; i < iters; i++) {
+    lot.unpark(&done, [](Unit) { return UnparkControl::RemoveContinue; });
+  }
+  done = true;
+  lot.unpark(&done, [](Unit) { return UnparkControl::RemoveContinue; });
+
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+int main(int argc, char** argv) {
+  gflags::ParseCommandLineFlags(&argc, &argv, true);
+
+  folly::runBenchmarks();
+}
+/*
+
+./buck-out/gen/folly/synchronization/test/parking_lot_test --benchmark
+--bm_min_iters=10000 --threads=4
+============================================================================
+folly/synchronization/test/ParkingLotBenchmark.cpprelative  time/iter  iters/s
+============================================================================
+FutexNoWaitersWake                                         163.43ns    6.12M
+ParkingLotNoWaitersWake                           29.64%   551.43ns    1.81M
+FutexWakeOne                                               156.78ns    6.38M
+ParkingLotWakeOne                                 37.49%   418.21ns    2.39M
+FutexWakeAll                                                 1.82us  549.52K
+ParkingLotWakeAll                                449.63%   404.73ns    2.47M
+============================================================================
+
+./buck-out/gen/folly/synchronization/test/parking_lot_test --benchmark
+--bm_min_iters=10000 --threads=32
+============================================================================
+folly/synchronization/test/ParkingLotBenchmark.cpprelative  time/iter  iters/s
+============================================================================
+FutexNoWaitersWake                                         379.59ns    2.63M
+ParkingLotNoWaitersWake                            7.94%     4.78us  209.08K
+FutexWakeOne                                               163.59ns    6.11M
+ParkingLotWakeOne                                  6.41%     2.55us  392.07K
+FutexWakeAll                                                12.46us   80.27K
+ParkingLotWakeAll                                784.76%     1.59us  629.92K
+============================================================================ */