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[perf-counters] Fix pause/resume (#1643)
* [perf-counters] Fix pause/resume Using `state.PauseTiming() / state.ResumeTiming()` was broken. Thanks [@virajbshah] for the the repro testcase. * ran clang-format over the whole perf_counters_test.cc * Remove check that perf counters are 0 on `Pause`, since `Pause`/`Resume` sequences would cause a non-0 counter value * both upper and lower bound for the with/without resume counters --------- Co-authored-by: dominic <510002+dmah42@users.noreply.github.com>
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@ -229,8 +229,7 @@ void State::PauseTiming() {
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for (const auto& name_and_measurement : measurements) {
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auto name = name_and_measurement.first;
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auto measurement = name_and_measurement.second;
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BM_CHECK_EQ(std::fpclassify(double{counters[name]}), FP_ZERO);
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counters[name] = Counter(measurement, Counter::kAvgIterations);
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counters[name] += Counter(measurement, Counter::kAvgIterations);
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}
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}
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}
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@ -1,8 +1,8 @@
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#include <cstdarg>
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#undef NDEBUG
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#include "../src/perf_counters.h"
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#include "../src/commandlineflags.h"
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#include "../src/perf_counters.h"
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#include "benchmark/benchmark.h"
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#include "output_test.h"
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@ -21,17 +21,78 @@ static void BM_Simple(benchmark::State& state) {
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BENCHMARK(BM_Simple);
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ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Simple\",$"}});
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const int kIters = 1000000;
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void BM_WithoutPauseResume(benchmark::State& state) {
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int n = 0;
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for (auto _ : state) {
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for (auto i = 0; i < kIters; ++i) {
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n = 1 - n;
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benchmark::DoNotOptimize(n);
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}
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}
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}
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BENCHMARK(BM_WithoutPauseResume);
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ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_WithoutPauseResume\",$"}});
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void BM_WithPauseResume(benchmark::State& state) {
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int m = 0, n = 0;
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for (auto _ : state) {
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for (auto i = 0; i < kIters; ++i) {
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n = 1 - n;
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benchmark::DoNotOptimize(n);
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}
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state.PauseTiming();
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for (auto j = 0; j < kIters; ++j) {
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m = 1 - m;
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benchmark::DoNotOptimize(m);
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}
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state.ResumeTiming();
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}
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}
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BENCHMARK(BM_WithPauseResume);
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ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_WithPauseResume\",$"}});
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static void CheckSimple(Results const& e) {
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CHECK_COUNTER_VALUE(e, double, "CYCLES", GT, 0);
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CHECK_COUNTER_VALUE(e, double, "BRANCHES", GT, 0.0);
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}
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double withoutPauseResumeInstrCount = 0.0;
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double withPauseResumeInstrCount = 0.0;
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static void CheckInstrCount(double* counter, Results const& e) {
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BM_CHECK_GT(e.NumIterations(), 0);
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*counter = e.GetAs<double>("INSTRUCTIONS") / e.NumIterations();
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}
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static void CheckInstrCountWithoutResume(Results const& e) {
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CheckInstrCount(&withoutPauseResumeInstrCount, e);
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}
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static void CheckInstrCountWithResume(Results const& e) {
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CheckInstrCount(&withPauseResumeInstrCount, e);
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}
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CHECK_BENCHMARK_RESULTS("BM_Simple", &CheckSimple);
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CHECK_BENCHMARK_RESULTS("BM_WithoutPauseResume", &CheckInstrCountWithoutResume);
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CHECK_BENCHMARK_RESULTS("BM_WithPauseResume", &CheckInstrCountWithResume);
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int main(int argc, char* argv[]) {
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if (!benchmark::internal::PerfCounters::kSupported) {
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return 0;
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}
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benchmark::FLAGS_benchmark_perf_counters = "CYCLES,BRANCHES";
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benchmark::FLAGS_benchmark_perf_counters = "CYCLES,BRANCHES,INSTRUCTIONS";
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benchmark::internal::PerfCounters::Initialize();
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RunOutputTests(argc, argv);
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BM_CHECK_GT(withPauseResumeInstrCount, kIters);
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BM_CHECK_GT(withoutPauseResumeInstrCount, kIters);
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BM_CHECK_LT(withPauseResumeInstrCount, 1.5 * withoutPauseResumeInstrCount);
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}
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