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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>4 *5 * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time.6 *7 * This program is particularly useful to measure the latency of nthread wakeups8 * in non-error situations: all waiters are queued and all wake calls wakeup9 * one or more tasks, and thus the waitqueue is never empty.10 */11 12/* For the CLR_() macros */13#include <string.h>14#include <pthread.h>15 16#include <signal.h>17#include "../util/mutex.h"18#include "../util/stat.h"19#include <subcmd/parse-options.h>20#include <linux/compiler.h>21#include <linux/kernel.h>22#include <linux/time64.h>23#include <errno.h>24#include <perf/cpumap.h>25#include "bench.h"26#include "futex.h"27 28#include <err.h>29#include <stdlib.h>30#include <sys/time.h>31#include <sys/mman.h>32 33/* all threads will block on the same futex */34static u_int32_t futex1 = 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 waketime_stats, wakeup_stats;41static unsigned int threads_starting;42static int futex_flag = 0;43 44static struct bench_futex_parameters params = {45 /*46 * How many wakeups to do at a time.47 * Default to 1 in order to make the kernel work more.48 */49 .nwakes = 1,50};51 52static const struct option options[] = {53 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),54 OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake 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 59 OPT_END()60};61 62static const char * const bench_futex_wake_usage[] = {63 "perf bench futex wake <options>",64 NULL65};66 67static void *workerfn(void *arg __maybe_unused)68{69 mutex_lock(&thread_lock);70 threads_starting--;71 if (!threads_starting)72 cond_signal(&thread_parent);73 cond_wait(&thread_worker, &thread_lock);74 mutex_unlock(&thread_lock);75 76 while (1) {77 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)78 break;79 }80 81 pthread_exit(NULL);82 return NULL;83}84 85static void print_summary(void)86{87 double waketime_avg = avg_stats(&waketime_stats);88 double waketime_stddev = stddev_stats(&waketime_stats);89 unsigned int wakeup_avg = avg_stats(&wakeup_stats);90 91 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",92 wakeup_avg,93 params.nthreads,94 waketime_avg / USEC_PER_MSEC,95 rel_stddev_stats(waketime_stddev, waketime_avg));96}97 98static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)99{100 cpu_set_t *cpuset;101 unsigned int i;102 size_t size;103 int nrcpus = cpu__max_cpu().cpu;104 threads_starting = params.nthreads;105 106 cpuset = CPU_ALLOC(nrcpus);107 BUG_ON(!cpuset);108 size = CPU_ALLOC_SIZE(nrcpus);109 110 /* create and block all threads */111 for (i = 0; i < params.nthreads; i++) {112 pthread_attr_t thread_attr;113 114 pthread_attr_init(&thread_attr);115 CPU_ZERO_S(size, cpuset);116 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);117 118 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {119 CPU_FREE(cpuset);120 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");121 }122 123 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {124 CPU_FREE(cpuset);125 err(EXIT_FAILURE, "pthread_create");126 }127 pthread_attr_destroy(&thread_attr);128 }129 CPU_FREE(cpuset);130}131 132static void toggle_done(int sig __maybe_unused,133 siginfo_t *info __maybe_unused,134 void *uc __maybe_unused)135{136 done = true;137}138 139int bench_futex_wake(int argc, const char **argv)140{141 int ret = 0;142 unsigned int i, j;143 struct sigaction act;144 struct perf_cpu_map *cpu;145 146 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);147 if (argc) {148 usage_with_options(bench_futex_wake_usage, options);149 exit(EXIT_FAILURE);150 }151 152 cpu = perf_cpu_map__new_online_cpus();153 if (!cpu)154 err(EXIT_FAILURE, "calloc");155 156 memset(&act, 0, sizeof(act));157 sigfillset(&act.sa_mask);158 act.sa_sigaction = toggle_done;159 sigaction(SIGINT, &act, NULL);160 161 if (params.mlockall) {162 if (mlockall(MCL_CURRENT | MCL_FUTURE))163 err(EXIT_FAILURE, "mlockall");164 }165 166 if (!params.nthreads)167 params.nthreads = perf_cpu_map__nr(cpu);168 169 worker = calloc(params.nthreads, sizeof(*worker));170 if (!worker)171 err(EXIT_FAILURE, "calloc");172 173 if (!params.fshared)174 futex_flag = FUTEX_PRIVATE_FLAG;175 176 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "177 "waking up %d at a time.\n\n",178 getpid(), params.nthreads, params.fshared ? "shared":"private",179 &futex1, params.nwakes);180 181 init_stats(&wakeup_stats);182 init_stats(&waketime_stats);183 mutex_init(&thread_lock);184 cond_init(&thread_parent);185 cond_init(&thread_worker);186 187 for (j = 0; j < bench_repeat && !done; j++) {188 unsigned int nwoken = 0;189 struct timeval start, end, runtime;190 191 /* create, launch & block all threads */192 block_threads(worker, cpu);193 194 /* make sure all threads are already blocked */195 mutex_lock(&thread_lock);196 while (threads_starting)197 cond_wait(&thread_parent, &thread_lock);198 cond_broadcast(&thread_worker);199 mutex_unlock(&thread_lock);200 201 usleep(100000);202 203 /* Ok, all threads are patiently blocked, start waking folks up */204 gettimeofday(&start, NULL);205 while (nwoken != params.nthreads)206 nwoken += futex_wake(&futex1,207 params.nwakes, futex_flag);208 gettimeofday(&end, NULL);209 timersub(&end, &start, &runtime);210 211 update_stats(&wakeup_stats, nwoken);212 update_stats(&waketime_stats, runtime.tv_usec);213 214 if (!params.silent) {215 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",216 j + 1, nwoken, params.nthreads,217 runtime.tv_usec / (double)USEC_PER_MSEC);218 }219 220 for (i = 0; i < params.nthreads; i++) {221 ret = pthread_join(worker[i], NULL);222 if (ret)223 err(EXIT_FAILURE, "pthread_join");224 }225 226 }227 228 /* cleanup & report results */229 cond_destroy(&thread_parent);230 cond_destroy(&thread_worker);231 mutex_destroy(&thread_lock);232 233 print_summary();234 235 free(worker);236 perf_cpu_map__put(cpu);237 return ret;238}239