diff options
Diffstat (limited to 'benchmarks/semaphore_benchmark.cpp')
-rw-r--r-- | benchmarks/semaphore_benchmark.cpp | 113 |
1 files changed, 2 insertions, 111 deletions
diff --git a/benchmarks/semaphore_benchmark.cpp b/benchmarks/semaphore_benchmark.cpp index cf5148983..ffccc82d7 100644 --- a/benchmarks/semaphore_benchmark.cpp +++ b/benchmarks/semaphore_benchmark.cpp @@ -28,8 +28,8 @@ static void BM_semaphore_sem_getvalue(benchmark::State& state) { sem_init(&semaphore, 1, 1); while (state.KeepRunning()) { - int dummy; - sem_getvalue(&semaphore, &dummy); + int unused; + sem_getvalue(&semaphore, &unused); } } BIONIC_BENCHMARK(BM_semaphore_sem_getvalue); @@ -44,112 +44,3 @@ static void BM_semaphore_sem_wait_sem_post(benchmark::State& state) { } } BIONIC_BENCHMARK(BM_semaphore_sem_wait_sem_post); - -// This test reports the overhead of the underlying futex wake syscall on -// the producer. It does not report the overhead from issuing the wake to the -// point where the posted consumer thread wakes up. It suffers from -// clock_gettime syscall overhead. Lock the CPU speed for consistent results -// as we may not reach >50% cpu utilization. -// -// We will run a background thread that catches the sem_post wakeup and -// loops immediately returning back to sleep in sem_wait for the next one. This -// thread is run with policy SCHED_OTHER (normal policy), a middle policy. -// -// The primary thread will run at SCHED_IDLE (lowest priority policy) when -// monitoring the background thread to detect when it hits sem_wait sleep. It -// will do so with no clock running. Once we are ready, we will switch to -// SCHED_FIFO (highest priority policy) to time the act of running sem_post -// with the benchmark clock running. This ensures nothing else in the system -// can preempt our timed activity, including the background thread. We are -// also protected with the scheduling policy of letting a process hit a -// resource limit rather than get hit with a context switch. -// -// The background thread will start executing either on another CPU, or -// after we back down from SCHED_FIFO, but certainly not in the context of -// the timing of the sem_post. - -static atomic_int BM_semaphore_sem_post_running; - -static void* BM_semaphore_sem_post_start_thread(void* arg) { - sem_t* semaphore = reinterpret_cast<sem_t*>(arg); - while ((BM_semaphore_sem_post_running > 0) && !sem_wait(semaphore)) { - } - BM_semaphore_sem_post_running = -1; - return nullptr; -} - -class SemaphoreFixture : public benchmark::Fixture { - public: - void SetUp(const benchmark::State&) override { - sem_init(&semaphore, 0, 0); - - pthread_attr_t attr; - pthread_attr_init(&attr); - - memset(¶m, 0, sizeof(param)); - pthread_attr_setschedparam(&attr, ¶m); - pthread_attr_setschedpolicy(&attr, SCHED_OTHER); - pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); - pthread_t pthread; - pthread_create(&pthread, &attr, BM_semaphore_sem_post_start_thread, &semaphore); - pthread_attr_destroy(&attr); - - sched_setscheduler(0, SCHED_IDLE, ¶m); - - BM_semaphore_sem_post_running = 1; - setup = true; - } - - ~SemaphoreFixture() override { - if (setup) { - // Only do this if the test was actually run. - sched_setscheduler(0, SCHED_OTHER, ¶m); - - if (BM_semaphore_sem_post_running > 0) { - BM_semaphore_sem_post_running = 0; - } - do { - sem_post(&semaphore); - sched_yield(); - } while (BM_semaphore_sem_post_running != -1); - } - } - - sem_t semaphore; - sched_param param; - bool setup = false; -}; - -// This is commented out because dynamic benchmark registering doesn't currently support fixtures. -// Uncomment it and recompile to run this benchmark on every run. -/* BENCHMARK_F(SemaphoreFixture, semaphore_sem_post)(benchmark::State& state) { - while (state.KeepRunning()) { - state.PauseTiming(); - - int trys = 3, dummy = 0; - do { - if (BM_semaphore_sem_post_running < 0) { - sched_setscheduler(0, SCHED_OTHER, ¶m); - fprintf(stderr, "BM_semaphore_sem_post: start_thread died unexpectedly\n"); - abort(); - } - sched_yield(); - sem_getvalue(&semaphore, &dummy); - if (dummy < 0) { // POSIX.1-2001 possibility 1 - break; - } - if (dummy == 0) { // POSIX.1-2001 possibility 2 - --trys; - } - } while (trys); - - param.sched_priority = 1; - sched_setscheduler(0, SCHED_FIFO, ¶m); - - state.ResumeTiming(); - sem_post(&semaphore); - - param.sched_priority = 0; - sched_setscheduler(0, SCHED_IDLE, ¶m); - } -}*/ |