diff options
Diffstat (limited to 'tools/perf/bench/futex-requeue.c')
| -rw-r--r-- | tools/perf/bench/futex-requeue.c | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c new file mode 100644 index 00000000000..a16255876f1 --- /dev/null +++ b/tools/perf/bench/futex-requeue.c @@ -0,0 +1,211 @@ +/* + * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> + * + * futex-requeue: Block a bunch of threads on futex1 and requeue them + * on futex2, N at a time. + * + * This program is particularly useful to measure the latency of nthread + * requeues without waking up any tasks -- thus mimicking a regular futex_wait. + */ + +#include "../perf.h" +#include "../util/util.h" +#include "../util/stat.h" +#include "../util/parse-options.h" +#include "../util/header.h" +#include "bench.h" +#include "futex.h" + +#include <err.h> +#include <stdlib.h> +#include <sys/time.h> +#include <pthread.h> + +static u_int32_t futex1 = 0, futex2 = 0; + +/* + * How many tasks to requeue at a time. + * Default to 1 in order to make the kernel work more. + */ +static unsigned int nrequeue = 1; + +/* + * There can be significant variance from run to run, + * the more repeats, the more exact the overall avg and + * the better idea of the futex latency. + */ +static unsigned int repeat = 10; + +static pthread_t *worker; +static bool done = 0, silent = 0; +static pthread_mutex_t thread_lock; +static pthread_cond_t thread_parent, thread_worker; +static struct stats requeuetime_stats, requeued_stats; +static unsigned int ncpus, threads_starting, nthreads = 0; + +static const struct option options[] = { + OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), + OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"), + OPT_UINTEGER('r', "repeat", &repeat, "Specify amount of times to repeat the run"), + OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), + OPT_END() +}; + +static const char * const bench_futex_requeue_usage[] = { + "perf bench futex requeue <options>", + NULL +}; + +static void print_summary(void) +{ + double requeuetime_avg = avg_stats(&requeuetime_stats); + double requeuetime_stddev = stddev_stats(&requeuetime_stats); + unsigned int requeued_avg = avg_stats(&requeued_stats); + + printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", + requeued_avg, + nthreads, + requeuetime_avg/1e3, + rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); +} + +static void *workerfn(void *arg __maybe_unused) +{ + pthread_mutex_lock(&thread_lock); + threads_starting--; + if (!threads_starting) + pthread_cond_signal(&thread_parent); + pthread_cond_wait(&thread_worker, &thread_lock); + pthread_mutex_unlock(&thread_lock); + + futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG); + return NULL; +} + +static void block_threads(pthread_t *w, + pthread_attr_t thread_attr) +{ + cpu_set_t cpu; + unsigned int i; + + threads_starting = nthreads; + + /* create and block all threads */ + for (i = 0; i < nthreads; i++) { + CPU_ZERO(&cpu); + CPU_SET(i % ncpus, &cpu); + + if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) + err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); + + if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) + err(EXIT_FAILURE, "pthread_create"); + } +} + +static void toggle_done(int sig __maybe_unused, + siginfo_t *info __maybe_unused, + void *uc __maybe_unused) +{ + done = true; +} + +int bench_futex_requeue(int argc, const char **argv, + const char *prefix __maybe_unused) +{ + int ret = 0; + unsigned int i, j; + struct sigaction act; + pthread_attr_t thread_attr; + + argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); + if (argc) + goto err; + + ncpus = sysconf(_SC_NPROCESSORS_ONLN); + + sigfillset(&act.sa_mask); + act.sa_sigaction = toggle_done; + sigaction(SIGINT, &act, NULL); + + if (!nthreads) + nthreads = ncpus; + + worker = calloc(nthreads, sizeof(*worker)); + if (!worker) + err(EXIT_FAILURE, "calloc"); + + printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), " + "%d at a time.\n\n", + getpid(), nthreads, &futex1, &futex2, nrequeue); + + init_stats(&requeued_stats); + init_stats(&requeuetime_stats); + pthread_attr_init(&thread_attr); + pthread_mutex_init(&thread_lock, NULL); + pthread_cond_init(&thread_parent, NULL); + pthread_cond_init(&thread_worker, NULL); + + for (j = 0; j < repeat && !done; j++) { + unsigned int nrequeued = 0; + struct timeval start, end, runtime; + + /* create, launch & block all threads */ + block_threads(worker, thread_attr); + + /* make sure all threads are already blocked */ + pthread_mutex_lock(&thread_lock); + while (threads_starting) + pthread_cond_wait(&thread_parent, &thread_lock); + pthread_cond_broadcast(&thread_worker); + pthread_mutex_unlock(&thread_lock); + + usleep(100000); + + /* Ok, all threads are patiently blocked, start requeueing */ + gettimeofday(&start, NULL); + for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue) + /* + * Do not wakeup any tasks blocked on futex1, allowing + * us to really measure futex_wait functionality. + */ + futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue, + FUTEX_PRIVATE_FLAG); + gettimeofday(&end, NULL); + timersub(&end, &start, &runtime); + + update_stats(&requeued_stats, nrequeued); + update_stats(&requeuetime_stats, runtime.tv_usec); + + if (!silent) { + printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", + j + 1, nrequeued, nthreads, runtime.tv_usec/1e3); + } + + /* everybody should be blocked on futex2, wake'em up */ + nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG); + if (nthreads != nrequeued) + warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); + + for (i = 0; i < nthreads; i++) { + ret = pthread_join(worker[i], NULL); + if (ret) + err(EXIT_FAILURE, "pthread_join"); + } + + } + + /* cleanup & report results */ + pthread_cond_destroy(&thread_parent); + pthread_cond_destroy(&thread_worker); + pthread_mutex_destroy(&thread_lock); + pthread_attr_destroy(&thread_attr); + + print_summary(); + + free(worker); + return ret; +err: + usage_with_options(bench_futex_requeue_usage, options); + exit(EXIT_FAILURE); +} |