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/*
* Copyright 2020 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "benchmark/benchmark.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/system/unused.h"
namespace webrtc {
class PerfTestData {
public:
PerfTestData() : cache_line_barrier_1_(), cache_line_barrier_2_() {
cache_line_barrier_1_[0]++; // Avoid 'is not used'.
cache_line_barrier_2_[0]++; // Avoid 'is not used'.
}
int AddToCounter(int add) {
MutexLock mu(&mu_);
my_counter_ += add;
return 0;
}
private:
uint8_t cache_line_barrier_1_[64];
Mutex mu_;
uint8_t cache_line_barrier_2_[64];
int64_t my_counter_ = 0;
};
void BM_LockWithMutex(benchmark::State& state) {
static PerfTestData test_data;
for (auto s : state) {
RTC_UNUSED(s);
int add_to_counter = test_data.AddToCounter(2);
benchmark::DoNotOptimize(add_to_counter);
}
}
BENCHMARK(BM_LockWithMutex)->Threads(1);
BENCHMARK(BM_LockWithMutex)->Threads(2);
BENCHMARK(BM_LockWithMutex)->Threads(4);
BENCHMARK(BM_LockWithMutex)->ThreadPerCpu();
} // namespace webrtc
/*
Results:
NB when reproducing: Remember to turn of power management features such as CPU
scaling before running!
pthreads (Linux):
----------------------------------------------------------------------
Run on (12 X 4500 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x6)
L1 Instruction 32 KiB (x6)
L2 Unified 1024 KiB (x6)
L3 Unified 8448 KiB (x1)
Load Average: 0.26, 0.28, 0.44
----------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------
BM_LockWithMutex/threads:1 13.4 ns 13.4 ns 52192906
BM_LockWithMutex/threads:2 44.2 ns 88.4 ns 8189944
BM_LockWithMutex/threads:4 52.0 ns 198 ns 3743244
BM_LockWithMutex/threads:12 84.9 ns 944 ns 733524
std::mutex performs like the pthread implementation (Linux).
Abseil (Linux):
----------------------------------------------------------------------
Run on (12 X 4500 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x6)
L1 Instruction 32 KiB (x6)
L2 Unified 1024 KiB (x6)
L3 Unified 8448 KiB (x1)
Load Average: 0.27, 0.24, 0.37
----------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------
BM_LockWithMutex/threads:1 15.0 ns 15.0 ns 46550231
BM_LockWithMutex/threads:2 91.1 ns 182 ns 4059212
BM_LockWithMutex/threads:4 40.8 ns 131 ns 5496560
BM_LockWithMutex/threads:12 37.0 ns 130 ns 5377668
*/
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