text: /*
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * 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/synchronization/Baton.h>
  
  #include <thread>
  
  #include <folly/Benchmark.h>
  #include <folly/synchronization/NativeSemaphore.h>
  #include <folly/synchronization/test/BatonTestHelpers.h>
  #include <folly/test/DeterministicSchedule.h>
  
  using namespace folly::test;
  using folly::detail::EmulatedFutexAtomic;
  
  BENCHMARK(baton_pingpong_blocking, iters) {
    run_pingpong_test<true, std::atomic>(iters);
  }
  
  BENCHMARK(baton_pingpong_nonblocking, iters) {
    run_pingpong_test<false, std::atomic>(iters);
  }
  
  BENCHMARK_DRAW_LINE();
  
  BENCHMARK(baton_pingpong_emulated_futex_blocking, iters) {
    run_pingpong_test<true, EmulatedFutexAtomic>(iters);
  }
  
  BENCHMARK(baton_pingpong_emulated_futex_nonblocking, iters) {
    run_pingpong_test<false, EmulatedFutexAtomic>(iters);
  }
  
  BENCHMARK_DRAW_LINE();
  
  BENCHMARK(native_sem_pingpong, iters) {
    alignas(folly::hardware_destructive_interference_size)
        folly::NativeSemaphore a;
    alignas(folly::hardware_destructive_interference_size)
        folly::NativeSemaphore b;
  
    auto thr = std::thread([&] {
      for (size_t i = 0; i < iters; ++i) {
        a.wait();
        b.post();
      }
    });
    for (size_t i = 0; i < iters; ++i) {
      a.post();
      b.wait();
    }
    thr.join();
  }
  
  // I am omitting a benchmark result snapshot because these microbenchmarks
  // mainly illustrate that PreBlockAttempts is very effective for rapid
  // handoffs.  The performance of Baton and sem_t is essentially identical
  // to the required futex calls for the blocking case
  
  int main(int argc, char** argv) {
    gflags::ParseCommandLineFlags(&argc, &argv, true);
    folly::runBenchmarks();
    return 0;
  }
  