diff options
Diffstat (limited to 'kernel/tools/perf/bench/futex-wake.c')
| -rw-r--r-- | kernel/tools/perf/bench/futex-wake.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/kernel/tools/perf/bench/futex-wake.c b/kernel/tools/perf/bench/futex-wake.c new file mode 100644 index 000000000..929f762be --- /dev/null +++ b/kernel/tools/perf/bench/futex-wake.c @@ -0,0 +1,198 @@ +/* + * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> + * + * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time. + * + * This program is particularly useful to measure the latency of nthread wakeups + * in non-error situations: all waiters are queued and all wake calls wakeup + * one or more tasks, and thus the waitqueue is never empty. + */ + +#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> + +/* all threads will block on the same futex */ +static u_int32_t futex1 = 0; + +/* + * How many wakeups to do at a time. + * Default to 1 in order to make the kernel work more. + */ +static unsigned int nwakes = 1; + +pthread_t *worker; +static bool done = false, silent = false, fshared = false; +static pthread_mutex_t thread_lock; +static pthread_cond_t thread_parent, thread_worker; +static struct stats waketime_stats, wakeup_stats; +static unsigned int ncpus, threads_starting, nthreads = 0; +static int futex_flag = 0; + +static const struct option options[] = { + OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), + OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"), + OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), + OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), + OPT_END() +}; + +static const char * const bench_futex_wake_usage[] = { + "perf bench futex wake <options>", + NULL +}; + +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_flag); + return NULL; +} + +static void print_summary(void) +{ + double waketime_avg = avg_stats(&waketime_stats); + double waketime_stddev = stddev_stats(&waketime_stats); + unsigned int wakeup_avg = avg_stats(&wakeup_stats); + + printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", + wakeup_avg, + nthreads, + waketime_avg/1e3, + rel_stddev_stats(waketime_stddev, waketime_avg)); +} + +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_wake(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_wake_usage, 0); + if (argc) { + usage_with_options(bench_futex_wake_usage, options); + exit(EXIT_FAILURE); + } + + 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"); + + if (!fshared) + futex_flag = FUTEX_PRIVATE_FLAG; + + printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " + "waking up %d at a time.\n\n", + getpid(), nthreads, fshared ? "shared":"private", &futex1, nwakes); + + init_stats(&wakeup_stats); + init_stats(&waketime_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 < bench_repeat && !done; j++) { + unsigned int nwoken = 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 waking folks up */ + gettimeofday(&start, NULL); + while (nwoken != nthreads) + nwoken += futex_wake(&futex1, nwakes, futex_flag); + gettimeofday(&end, NULL); + timersub(&end, &start, &runtime); + + update_stats(&wakeup_stats, nwoken); + update_stats(&waketime_stats, runtime.tv_usec); + + if (!silent) { + printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", + j + 1, nwoken, nthreads, runtime.tv_usec/1e3); + } + + 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; +} |