Davidlohr Bueso | 27db783 | 2013-12-14 20:31:56 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> |
| 3 | * |
| 4 | * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time. |
| 5 | * |
| 6 | * This program is particularly useful to measure the latency of nthread wakeups |
| 7 | * in non-error situations: all waiters are queued and all wake calls wakeup |
| 8 | * one or more tasks, and thus the waitqueue is never empty. |
| 9 | */ |
| 10 | |
| 11 | #include "../perf.h" |
| 12 | #include "../util/util.h" |
| 13 | #include "../util/stat.h" |
| 14 | #include "../util/parse-options.h" |
| 15 | #include "../util/header.h" |
| 16 | #include "bench.h" |
| 17 | #include "futex.h" |
| 18 | |
| 19 | #include <err.h> |
| 20 | #include <stdlib.h> |
| 21 | #include <sys/time.h> |
| 22 | #include <pthread.h> |
| 23 | |
| 24 | /* all threads will block on the same futex */ |
| 25 | static u_int32_t futex1 = 0; |
| 26 | |
| 27 | /* |
| 28 | * How many wakeups to do at a time. |
| 29 | * Default to 1 in order to make the kernel work more. |
| 30 | */ |
| 31 | static unsigned int nwakes = 1; |
| 32 | |
Davidlohr Bueso | 27db783 | 2013-12-14 20:31:56 -0800 | [diff] [blame] | 33 | pthread_t *worker; |
Davidlohr Bueso | d9de84a | 2014-06-16 11:14:23 -0700 | [diff] [blame^] | 34 | static bool done = false, silent = false; |
Davidlohr Bueso | 27db783 | 2013-12-14 20:31:56 -0800 | [diff] [blame] | 35 | static pthread_mutex_t thread_lock; |
| 36 | static pthread_cond_t thread_parent, thread_worker; |
| 37 | static struct stats waketime_stats, wakeup_stats; |
| 38 | static unsigned int ncpus, threads_starting, nthreads = 0; |
| 39 | |
| 40 | static const struct option options[] = { |
| 41 | OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), |
| 42 | OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"), |
Davidlohr Bueso | 27db783 | 2013-12-14 20:31:56 -0800 | [diff] [blame] | 43 | OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), |
| 44 | OPT_END() |
| 45 | }; |
| 46 | |
| 47 | static const char * const bench_futex_wake_usage[] = { |
| 48 | "perf bench futex wake <options>", |
| 49 | NULL |
| 50 | }; |
| 51 | |
| 52 | static void *workerfn(void *arg __maybe_unused) |
| 53 | { |
| 54 | pthread_mutex_lock(&thread_lock); |
| 55 | threads_starting--; |
| 56 | if (!threads_starting) |
| 57 | pthread_cond_signal(&thread_parent); |
| 58 | pthread_cond_wait(&thread_worker, &thread_lock); |
| 59 | pthread_mutex_unlock(&thread_lock); |
| 60 | |
| 61 | futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG); |
| 62 | return NULL; |
| 63 | } |
| 64 | |
| 65 | static void print_summary(void) |
| 66 | { |
| 67 | double waketime_avg = avg_stats(&waketime_stats); |
| 68 | double waketime_stddev = stddev_stats(&waketime_stats); |
| 69 | unsigned int wakeup_avg = avg_stats(&wakeup_stats); |
| 70 | |
| 71 | printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", |
| 72 | wakeup_avg, |
| 73 | nthreads, |
| 74 | waketime_avg/1e3, |
| 75 | rel_stddev_stats(waketime_stddev, waketime_avg)); |
| 76 | } |
| 77 | |
| 78 | static void block_threads(pthread_t *w, |
| 79 | pthread_attr_t thread_attr) |
| 80 | { |
| 81 | cpu_set_t cpu; |
| 82 | unsigned int i; |
| 83 | |
| 84 | threads_starting = nthreads; |
| 85 | |
| 86 | /* create and block all threads */ |
| 87 | for (i = 0; i < nthreads; i++) { |
| 88 | CPU_ZERO(&cpu); |
| 89 | CPU_SET(i % ncpus, &cpu); |
| 90 | |
| 91 | if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) |
| 92 | err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); |
| 93 | |
| 94 | if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) |
| 95 | err(EXIT_FAILURE, "pthread_create"); |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | static void toggle_done(int sig __maybe_unused, |
| 100 | siginfo_t *info __maybe_unused, |
| 101 | void *uc __maybe_unused) |
| 102 | { |
| 103 | done = true; |
| 104 | } |
| 105 | |
| 106 | int bench_futex_wake(int argc, const char **argv, |
| 107 | const char *prefix __maybe_unused) |
| 108 | { |
| 109 | int ret = 0; |
| 110 | unsigned int i, j; |
| 111 | struct sigaction act; |
| 112 | pthread_attr_t thread_attr; |
| 113 | |
| 114 | argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); |
| 115 | if (argc) { |
| 116 | usage_with_options(bench_futex_wake_usage, options); |
| 117 | exit(EXIT_FAILURE); |
| 118 | } |
| 119 | |
| 120 | ncpus = sysconf(_SC_NPROCESSORS_ONLN); |
| 121 | |
| 122 | sigfillset(&act.sa_mask); |
| 123 | act.sa_sigaction = toggle_done; |
| 124 | sigaction(SIGINT, &act, NULL); |
| 125 | |
| 126 | if (!nthreads) |
| 127 | nthreads = ncpus; |
| 128 | |
| 129 | worker = calloc(nthreads, sizeof(*worker)); |
| 130 | if (!worker) |
| 131 | err(EXIT_FAILURE, "calloc"); |
| 132 | |
| 133 | printf("Run summary [PID %d]: blocking on %d threads (at futex %p), " |
| 134 | "waking up %d at a time.\n\n", |
| 135 | getpid(), nthreads, &futex1, nwakes); |
| 136 | |
| 137 | init_stats(&wakeup_stats); |
| 138 | init_stats(&waketime_stats); |
| 139 | pthread_attr_init(&thread_attr); |
| 140 | pthread_mutex_init(&thread_lock, NULL); |
| 141 | pthread_cond_init(&thread_parent, NULL); |
| 142 | pthread_cond_init(&thread_worker, NULL); |
| 143 | |
Davidlohr Bueso | d9de84a | 2014-06-16 11:14:23 -0700 | [diff] [blame^] | 144 | for (j = 0; j < bench_repeat && !done; j++) { |
Davidlohr Bueso | 27db783 | 2013-12-14 20:31:56 -0800 | [diff] [blame] | 145 | unsigned int nwoken = 0; |
| 146 | struct timeval start, end, runtime; |
| 147 | |
| 148 | /* create, launch & block all threads */ |
| 149 | block_threads(worker, thread_attr); |
| 150 | |
| 151 | /* make sure all threads are already blocked */ |
| 152 | pthread_mutex_lock(&thread_lock); |
| 153 | while (threads_starting) |
| 154 | pthread_cond_wait(&thread_parent, &thread_lock); |
| 155 | pthread_cond_broadcast(&thread_worker); |
| 156 | pthread_mutex_unlock(&thread_lock); |
| 157 | |
| 158 | usleep(100000); |
| 159 | |
| 160 | /* Ok, all threads are patiently blocked, start waking folks up */ |
| 161 | gettimeofday(&start, NULL); |
| 162 | while (nwoken != nthreads) |
| 163 | nwoken += futex_wake(&futex1, nwakes, FUTEX_PRIVATE_FLAG); |
| 164 | gettimeofday(&end, NULL); |
| 165 | timersub(&end, &start, &runtime); |
| 166 | |
| 167 | update_stats(&wakeup_stats, nwoken); |
| 168 | update_stats(&waketime_stats, runtime.tv_usec); |
| 169 | |
| 170 | if (!silent) { |
| 171 | printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", |
| 172 | j + 1, nwoken, nthreads, runtime.tv_usec/1e3); |
| 173 | } |
| 174 | |
| 175 | for (i = 0; i < nthreads; i++) { |
| 176 | ret = pthread_join(worker[i], NULL); |
| 177 | if (ret) |
| 178 | err(EXIT_FAILURE, "pthread_join"); |
| 179 | } |
| 180 | |
| 181 | } |
| 182 | |
| 183 | /* cleanup & report results */ |
| 184 | pthread_cond_destroy(&thread_parent); |
| 185 | pthread_cond_destroy(&thread_worker); |
| 186 | pthread_mutex_destroy(&thread_lock); |
| 187 | pthread_attr_destroy(&thread_attr); |
| 188 | |
| 189 | print_summary(); |
| 190 | |
| 191 | free(worker); |
| 192 | return ret; |
| 193 | } |