libcxx/test/benchmarks/shared_mutex_vs_mutex.bench.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14
  10
  11 // This benchmark compares the performance of std::mutex and std::shared_mutex in contended scenarios.
  12 // it's meant to establish a baseline overhead for std::shared_mutex and std::mutex, and to help inform decisions about
  13 // which mutex to use when selecting a mutex type for a given use case.
  14
  15 #include <atomic>
  16 #include <mutex>
  17 #include <numeric>
  18 #include <shared_mutex>
  19 #include <thread>
  20
  21 #include "benchmark/benchmark.h"
  22
  23 int global_value = 42;
  24 std::mutex m;
  25 std::shared_mutex sm;
  26
  27 static void BM_shared_mutex(benchmark::State& state) {
  28   for (auto _ : state) {
  29     std::shared_lock<std::shared_mutex> lock(sm);
  30     benchmark::DoNotOptimize(global_value);
  31   }
  32 }
  33
  34 static void BM_mutex(benchmark::State& state) {
  35   for (auto _ : state) {
  36     std::lock_guard<std::mutex> lock(m);
  37     benchmark::DoNotOptimize(global_value);
  38   }
  39 }
  40
  41 BENCHMARK(BM_shared_mutex)->Threads(1)->Threads(2)->Threads(4)->Threads(8)->Threads(32);
  42 BENCHMARK(BM_mutex)->Threads(1)->Threads(2)->Threads(4)->Threads(8)->Threads(32);
  43
  44 BENCHMARK_MAIN();