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-rw-r--r--absl/synchronization/mutex_benchmark.cc151
1 files changed, 140 insertions, 11 deletions
diff --git a/absl/synchronization/mutex_benchmark.cc b/absl/synchronization/mutex_benchmark.cc
index 1e019e00..2652bb97 100644
--- a/absl/synchronization/mutex_benchmark.cc
+++ b/absl/synchronization/mutex_benchmark.cc
@@ -12,16 +12,154 @@
// See the License for the specific language governing permissions and
// limitations under the License.
+#include <cstdint>
+#include <mutex> // NOLINT(build/c++11)
#include <vector>
-#include "benchmark/benchmark.h"
-#include "absl/base/internal/sysinfo.h"
+#include "absl/base/internal/cycleclock.h"
+#include "absl/base/internal/spinlock.h"
#include "absl/synchronization/blocking_counter.h"
#include "absl/synchronization/internal/thread_pool.h"
#include "absl/synchronization/mutex.h"
+#include "benchmark/benchmark.h"
namespace {
+void BM_Mutex(benchmark::State& state) {
+ static absl::Mutex* mu = new absl::Mutex;
+ for (auto _ : state) {
+ absl::MutexLock lock(mu);
+ }
+}
+BENCHMARK(BM_Mutex)->UseRealTime()->Threads(1)->ThreadPerCpu();
+
+static void DelayNs(int64_t ns, int* data) {
+ int64_t end = absl::base_internal::CycleClock::Now() +
+ ns * absl::base_internal::CycleClock::Frequency() / 1e9;
+ while (absl::base_internal::CycleClock::Now() < end) {
+ ++(*data);
+ benchmark::DoNotOptimize(*data);
+ }
+}
+
+template <typename MutexType>
+class RaiiLocker {
+ public:
+ explicit RaiiLocker(MutexType* mu) : mu_(mu) { mu_->Lock(); }
+ ~RaiiLocker() { mu_->Unlock(); }
+ private:
+ MutexType* mu_;
+};
+
+template <>
+class RaiiLocker<std::mutex> {
+ public:
+ explicit RaiiLocker(std::mutex* mu) : mu_(mu) { mu_->lock(); }
+ ~RaiiLocker() { mu_->unlock(); }
+ private:
+ std::mutex* mu_;
+};
+
+template <typename MutexType>
+void BM_Contended(benchmark::State& state) {
+ struct Shared {
+ MutexType mu;
+ int data = 0;
+ };
+ static auto* shared = new Shared;
+ int local = 0;
+ for (auto _ : state) {
+ // Here we model both local work outside of the critical section as well as
+ // some work inside of the critical section. The idea is to capture some
+ // more or less realisitic contention levels.
+ // If contention is too low, the benchmark won't measure anything useful.
+ // If contention is unrealistically high, the benchmark will favor
+ // bad mutex implementations that block and otherwise distract threads
+ // from the mutex and shared state for as much as possible.
+ // To achieve this amount of local work is multiplied by number of threads
+ // to keep ratio between local work and critical section approximately
+ // equal regardless of number of threads.
+ DelayNs(100 * state.threads, &local);
+ RaiiLocker<MutexType> locker(&shared->mu);
+ DelayNs(state.range(0), &shared->data);
+ }
+}
+
+BENCHMARK_TEMPLATE(BM_Contended, absl::Mutex)
+ ->UseRealTime()
+ // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+ ->Threads(1)
+ ->Threads(2)
+ ->Threads(4)
+ ->Threads(6)
+ ->Threads(8)
+ ->Threads(12)
+ ->Threads(16)
+ ->Threads(24)
+ ->Threads(32)
+ ->Threads(48)
+ ->Threads(64)
+ ->Threads(96)
+ ->Threads(128)
+ ->Threads(192)
+ ->Threads(256)
+ // Some empirically chosen amounts of work in critical section.
+ // 1 is low contention, 200 is high contention and few values in between.
+ ->Arg(1)
+ ->Arg(20)
+ ->Arg(50)
+ ->Arg(200);
+
+BENCHMARK_TEMPLATE(BM_Contended, absl::base_internal::SpinLock)
+ ->UseRealTime()
+ // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+ ->Threads(1)
+ ->Threads(2)
+ ->Threads(4)
+ ->Threads(6)
+ ->Threads(8)
+ ->Threads(12)
+ ->Threads(16)
+ ->Threads(24)
+ ->Threads(32)
+ ->Threads(48)
+ ->Threads(64)
+ ->Threads(96)
+ ->Threads(128)
+ ->Threads(192)
+ ->Threads(256)
+ // Some empirically chosen amounts of work in critical section.
+ // 1 is low contention, 200 is high contention and few values in between.
+ ->Arg(1)
+ ->Arg(20)
+ ->Arg(50)
+ ->Arg(200);
+
+BENCHMARK_TEMPLATE(BM_Contended, std::mutex)
+ ->UseRealTime()
+ // ThreadPerCpu poorly handles non-power-of-two CPU counts.
+ ->Threads(1)
+ ->Threads(2)
+ ->Threads(4)
+ ->Threads(6)
+ ->Threads(8)
+ ->Threads(12)
+ ->Threads(16)
+ ->Threads(24)
+ ->Threads(32)
+ ->Threads(48)
+ ->Threads(64)
+ ->Threads(96)
+ ->Threads(128)
+ ->Threads(192)
+ ->Threads(256)
+ // Some empirically chosen amounts of work in critical section.
+ // 1 is low contention, 200 is high contention and few values in between.
+ ->Arg(1)
+ ->Arg(20)
+ ->Arg(50)
+ ->Arg(200);
+
// Measure the overhead of conditions on mutex release (when they must be
// evaluated). Mutex has (some) support for equivalence classes allowing
// Conditions with the same function/argument to potentially not be multiply
@@ -82,13 +220,4 @@ constexpr int kMaxConditionWaiters = 1024;
#endif
BENCHMARK(BM_ConditionWaiters)->RangePair(0, 2, 1, kMaxConditionWaiters);
-void BM_ContendedMutex(benchmark::State& state) {
- static absl::Mutex* mu = new absl::Mutex;
- for (auto _ : state) {
- absl::MutexLock lock(mu);
- }
-}
-BENCHMARK(BM_ContendedMutex)->Threads(1);
-BENCHMARK(BM_ContendedMutex)->ThreadPerCpu();
-
} // namespace