315 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>4 *5 * futex-requeue: Block a bunch of threads on futex1 and requeue them6 * on futex2, N at a time.7 *8 * This program is particularly useful to measure the latency of nthread9 * requeues without waking up any tasks (in the non-pi case) -- thus10 * mimicking a regular futex_wait.11 */12 13/* For the CLR_() macros */14#include <string.h>15#include <pthread.h>16 17#include <signal.h>18#include "../util/mutex.h"19#include "../util/stat.h"20#include <subcmd/parse-options.h>21#include <linux/compiler.h>22#include <linux/kernel.h>23#include <linux/time64.h>24#include <errno.h>25#include <perf/cpumap.h>26#include "bench.h"27#include "futex.h"28 29#include <err.h>30#include <stdlib.h>31#include <sys/time.h>32#include <sys/mman.h>33 34static u_int32_t futex1 = 0, futex2 = 0;35 36static pthread_t *worker;37static bool done = false;38static struct mutex thread_lock;39static struct cond thread_parent, thread_worker;40static struct stats requeuetime_stats, requeued_stats;41static unsigned int threads_starting;42static int futex_flag = 0;43 44static struct bench_futex_parameters params = {45 /*46 * How many tasks to requeue at a time.47 * Default to 1 in order to make the kernel work more.48 */49 .nrequeue = 1,50};51 52static const struct option options[] = {53 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),54 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue at once"),55 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),56 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),57 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),58 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"),59 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),60 61 OPT_END()62};63 64static const char * const bench_futex_requeue_usage[] = {65 "perf bench futex requeue <options>",66 NULL67};68 69static void print_summary(void)70{71 double requeuetime_avg = avg_stats(&requeuetime_stats);72 double requeuetime_stddev = stddev_stats(&requeuetime_stats);73 unsigned int requeued_avg = avg_stats(&requeued_stats);74 75 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",76 requeued_avg,77 params.nthreads,78 requeuetime_avg / USEC_PER_MSEC,79 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));80}81 82static void *workerfn(void *arg __maybe_unused)83{84 int ret;85 86 mutex_lock(&thread_lock);87 threads_starting--;88 if (!threads_starting)89 cond_signal(&thread_parent);90 cond_wait(&thread_worker, &thread_lock);91 mutex_unlock(&thread_lock);92 93 while (1) {94 if (!params.pi) {95 ret = futex_wait(&futex1, 0, NULL, futex_flag);96 if (!ret)97 break;98 99 if (ret && errno != EAGAIN) {100 if (!params.silent)101 warnx("futex_wait");102 break;103 }104 } else {105 ret = futex_wait_requeue_pi(&futex1, 0, &futex2,106 NULL, futex_flag);107 if (!ret) {108 /* got the lock at futex2 */109 futex_unlock_pi(&futex2, futex_flag);110 break;111 }112 113 if (ret && errno != EAGAIN) {114 if (!params.silent)115 warnx("futex_wait_requeue_pi");116 break;117 }118 }119 }120 121 return NULL;122}123 124static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)125{126 cpu_set_t *cpuset;127 unsigned int i;128 int nrcpus = cpu__max_cpu().cpu;129 size_t size;130 131 threads_starting = params.nthreads;132 133 cpuset = CPU_ALLOC(nrcpus);134 BUG_ON(!cpuset);135 size = CPU_ALLOC_SIZE(nrcpus);136 137 /* create and block all threads */138 for (i = 0; i < params.nthreads; i++) {139 pthread_attr_t thread_attr;140 141 pthread_attr_init(&thread_attr);142 CPU_ZERO_S(size, cpuset);143 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);144 145 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {146 CPU_FREE(cpuset);147 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");148 }149 150 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {151 CPU_FREE(cpuset);152 err(EXIT_FAILURE, "pthread_create");153 }154 pthread_attr_destroy(&thread_attr);155 }156 CPU_FREE(cpuset);157}158 159static void toggle_done(int sig __maybe_unused,160 siginfo_t *info __maybe_unused,161 void *uc __maybe_unused)162{163 done = true;164}165 166int bench_futex_requeue(int argc, const char **argv)167{168 int ret = 0;169 unsigned int i, j;170 struct sigaction act;171 struct perf_cpu_map *cpu;172 173 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);174 if (argc)175 goto err;176 177 cpu = perf_cpu_map__new_online_cpus();178 if (!cpu)179 err(EXIT_FAILURE, "cpu_map__new");180 181 memset(&act, 0, sizeof(act));182 sigfillset(&act.sa_mask);183 act.sa_sigaction = toggle_done;184 sigaction(SIGINT, &act, NULL);185 186 if (params.mlockall) {187 if (mlockall(MCL_CURRENT | MCL_FUTURE))188 err(EXIT_FAILURE, "mlockall");189 }190 191 if (!params.nthreads)192 params.nthreads = perf_cpu_map__nr(cpu);193 194 worker = calloc(params.nthreads, sizeof(*worker));195 if (!worker)196 err(EXIT_FAILURE, "calloc");197 198 if (!params.fshared)199 futex_flag = FUTEX_PRIVATE_FLAG;200 201 if (params.nrequeue > params.nthreads)202 params.nrequeue = params.nthreads;203 204 if (params.broadcast)205 params.nrequeue = params.nthreads;206 207 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "208 "%d at a time.\n\n", getpid(), params.nthreads,209 params.fshared ? "shared":"private", &futex1,210 params.pi ? "PI ": "", &futex2, params.nrequeue);211 212 init_stats(&requeued_stats);213 init_stats(&requeuetime_stats);214 mutex_init(&thread_lock);215 cond_init(&thread_parent);216 cond_init(&thread_worker);217 218 for (j = 0; j < bench_repeat && !done; j++) {219 unsigned int nrequeued = 0, wakeups = 0;220 struct timeval start, end, runtime;221 222 /* create, launch & block all threads */223 block_threads(worker, cpu);224 225 /* make sure all threads are already blocked */226 mutex_lock(&thread_lock);227 while (threads_starting)228 cond_wait(&thread_parent, &thread_lock);229 cond_broadcast(&thread_worker);230 mutex_unlock(&thread_lock);231 232 usleep(100000);233 234 /* Ok, all threads are patiently blocked, start requeueing */235 gettimeofday(&start, NULL);236 while (nrequeued < params.nthreads) {237 int r;238 239 /*240 * For the regular non-pi case, do not wakeup any tasks241 * blocked on futex1, allowing us to really measure242 * futex_wait functionality. For the PI case the first243 * waiter is always awoken.244 */245 if (!params.pi) {246 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,247 params.nrequeue,248 futex_flag);249 } else {250 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,251 params.nrequeue,252 futex_flag);253 wakeups++; /* assume no error */254 }255 256 if (r < 0)257 err(EXIT_FAILURE, "couldn't requeue from %p to %p",258 &futex1, &futex2);259 260 nrequeued += r;261 }262 263 gettimeofday(&end, NULL);264 timersub(&end, &start, &runtime);265 266 update_stats(&requeued_stats, nrequeued);267 update_stats(&requeuetime_stats, runtime.tv_usec);268 269 if (!params.silent) {270 if (!params.pi)271 printf("[Run %d]: Requeued %d of %d threads in "272 "%.4f ms\n", j + 1, nrequeued,273 params.nthreads,274 runtime.tv_usec / (double)USEC_PER_MSEC);275 else {276 nrequeued -= wakeups;277 printf("[Run %d]: Awoke and Requeued (%d+%d) of "278 "%d threads in %.4f ms\n",279 j + 1, wakeups, nrequeued,280 params.nthreads,281 runtime.tv_usec / (double)USEC_PER_MSEC);282 }283 284 }285 286 if (!params.pi) {287 /* everybody should be blocked on futex2, wake'em up */288 nrequeued = futex_wake(&futex2, nrequeued, futex_flag);289 if (params.nthreads != nrequeued)290 warnx("couldn't wakeup all tasks (%d/%d)",291 nrequeued, params.nthreads);292 }293 294 for (i = 0; i < params.nthreads; i++) {295 ret = pthread_join(worker[i], NULL);296 if (ret)297 err(EXIT_FAILURE, "pthread_join");298 }299 }300 301 /* cleanup & report results */302 cond_destroy(&thread_parent);303 cond_destroy(&thread_worker);304 mutex_destroy(&thread_lock);305 306 print_summary();307 308 free(worker);309 perf_cpu_map__put(cpu);310 return ret;311err:312 usage_with_options(bench_futex_requeue_usage, options);313 exit(EXIT_FAILURE);314}315