| // Copyright 2009 Google Inc. |
| // Author: walken@google.com (Michel Lespinasse) |
| |
| #include <limits.h> |
| #include <sys/times.h> |
| #include <stdio.h> |
| #include <pthread.h> |
| |
| |
| struct thread_barrier { |
| futex_t threads; |
| futex_t unblock; |
| }; |
| |
| struct locktest_shared { |
| struct thread_barrier barrier_before; |
| struct thread_barrier barrier_after; |
| int loops; |
| futex_t futex; |
| }; |
| |
| /* Called by main thread to initialize barrier */ |
| static void barrier_init(struct thread_barrier *barrier, int threads) |
| { |
| barrier->threads = threads; |
| barrier->unblock = 0; |
| } |
| |
| /* Called by worker threads to synchronize with main thread */ |
| static void barrier_sync(struct thread_barrier *barrier) |
| { |
| futex_dec(&barrier->threads); |
| if (barrier->threads == 0) |
| futex_wake(&barrier->threads, 1, FUTEX_PRIVATE_FLAG); |
| while (barrier->unblock == 0) |
| futex_wait(&barrier->unblock, 0, NULL, FUTEX_PRIVATE_FLAG); |
| } |
| |
| /* Called by main thread to wait for all workers to reach sync point */ |
| static void barrier_wait(struct thread_barrier *barrier) |
| { |
| int threads; |
| while ((threads = barrier->threads) > 0) |
| futex_wait(&barrier->threads, threads, NULL, |
| FUTEX_PRIVATE_FLAG); |
| } |
| |
| /* Called by main thread to unblock worker threads from their sync point */ |
| static void barrier_unblock(struct thread_barrier *barrier) |
| { |
| barrier->unblock = 1; |
| futex_wake(&barrier->unblock, INT_MAX, FUTEX_PRIVATE_FLAG); |
| } |
| |
| |
| static void locktest(void * thread_function(void *), int iterations) |
| { |
| int threads[] = { 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 24, 32, |
| 64, 128, 256, 512, 1024, 0 }; |
| int t; |
| for (t = 0; threads[t]; t++) { |
| int num_threads = threads[t]; |
| struct locktest_shared shared; |
| pthread_t thread[num_threads]; |
| int i; |
| clock_t before, after; |
| struct tms tms_before, tms_after; |
| int wall, user, system; |
| double tick; |
| |
| barrier_init(&shared.barrier_before, num_threads); |
| barrier_init(&shared.barrier_after, num_threads); |
| shared.loops = iterations / num_threads; |
| shared.futex = 0; |
| |
| for (i = 0; i < num_threads; i++) |
| pthread_create(thread + i, NULL, thread_function, |
| &shared); |
| barrier_wait(&shared.barrier_before); |
| before = times(&tms_before); |
| barrier_unblock(&shared.barrier_before); |
| barrier_wait(&shared.barrier_after); |
| after = times(&tms_after); |
| wall = after - before; |
| user = tms_after.tms_utime - tms_before.tms_utime; |
| system = tms_after.tms_stime - tms_before.tms_stime; |
| tick = 1.0 / sysconf(_SC_CLK_TCK); |
| printf("%d threads: %.0f Kiter/s " |
| "(%.2fs user %.2fs system %.2fs wall %.2f cores)\n", |
| num_threads, |
| (num_threads * shared.loops) / (wall * tick * 1000), |
| user * tick, system * tick, wall * tick, |
| wall ? (user + system) * 1. / wall : 1.); |
| barrier_unblock(&shared.barrier_after); |
| for (i = 0; i < num_threads; i++) |
| pthread_join(thread[i], NULL); |
| } |
| } |