1 // SPDX-License-Identifier: GPL-2.0 2 /* 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 wakeups 8 * in non-error situations: all waiters are queued and all wake calls wakeup 9 * 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/stat.h" 18 #include <subcmd/parse-options.h> 19 #include <linux/compiler.h> 20 #include <linux/kernel.h> 21 #include <linux/time64.h> 22 #include <errno.h> 23 #include "bench.h" 24 #include "futex.h" 25 26 #include <err.h> 27 #include <stdlib.h> 28 #include <sys/time.h> 29 30 /* all threads will block on the same futex */ 31 static u_int32_t futex1 = 0; 32 33 /* 34 * How many wakeups to do at a time. 35 * Default to 1 in order to make the kernel work more. 36 */ 37 static unsigned int nwakes = 1; 38 39 pthread_t *worker; 40 static bool done = false, silent = false, fshared = false; 41 static pthread_mutex_t thread_lock; 42 static pthread_cond_t thread_parent, thread_worker; 43 static struct stats waketime_stats, wakeup_stats; 44 static unsigned int ncpus, threads_starting, nthreads = 0; 45 static int futex_flag = 0; 46 47 static const struct option options[] = { 48 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), 49 OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"), 50 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 51 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 52 OPT_END() 53 }; 54 55 static const char * const bench_futex_wake_usage[] = { 56 "perf bench futex wake <options>", 57 NULL 58 }; 59 60 static void *workerfn(void *arg __maybe_unused) 61 { 62 pthread_mutex_lock(&thread_lock); 63 threads_starting--; 64 if (!threads_starting) 65 pthread_cond_signal(&thread_parent); 66 pthread_cond_wait(&thread_worker, &thread_lock); 67 pthread_mutex_unlock(&thread_lock); 68 69 while (1) { 70 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) 71 break; 72 } 73 74 pthread_exit(NULL); 75 return NULL; 76 } 77 78 static void print_summary(void) 79 { 80 double waketime_avg = avg_stats(&waketime_stats); 81 double waketime_stddev = stddev_stats(&waketime_stats); 82 unsigned int wakeup_avg = avg_stats(&wakeup_stats); 83 84 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", 85 wakeup_avg, 86 nthreads, 87 waketime_avg / USEC_PER_MSEC, 88 rel_stddev_stats(waketime_stddev, waketime_avg)); 89 } 90 91 static void block_threads(pthread_t *w, 92 pthread_attr_t thread_attr) 93 { 94 cpu_set_t cpu; 95 unsigned int i; 96 97 threads_starting = nthreads; 98 99 /* create and block all threads */ 100 for (i = 0; i < nthreads; i++) { 101 CPU_ZERO(&cpu); 102 CPU_SET(i % ncpus, &cpu); 103 104 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 105 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 106 107 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 108 err(EXIT_FAILURE, "pthread_create"); 109 } 110 } 111 112 static void toggle_done(int sig __maybe_unused, 113 siginfo_t *info __maybe_unused, 114 void *uc __maybe_unused) 115 { 116 done = true; 117 } 118 119 int bench_futex_wake(int argc, const char **argv) 120 { 121 int ret = 0; 122 unsigned int i, j; 123 struct sigaction act; 124 pthread_attr_t thread_attr; 125 126 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); 127 if (argc) { 128 usage_with_options(bench_futex_wake_usage, options); 129 exit(EXIT_FAILURE); 130 } 131 132 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 133 134 sigfillset(&act.sa_mask); 135 act.sa_sigaction = toggle_done; 136 sigaction(SIGINT, &act, NULL); 137 138 if (!nthreads) 139 nthreads = ncpus; 140 141 worker = calloc(nthreads, sizeof(*worker)); 142 if (!worker) 143 err(EXIT_FAILURE, "calloc"); 144 145 if (!fshared) 146 futex_flag = FUTEX_PRIVATE_FLAG; 147 148 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " 149 "waking up %d at a time.\n\n", 150 getpid(), nthreads, fshared ? "shared":"private", &futex1, nwakes); 151 152 init_stats(&wakeup_stats); 153 init_stats(&waketime_stats); 154 pthread_attr_init(&thread_attr); 155 pthread_mutex_init(&thread_lock, NULL); 156 pthread_cond_init(&thread_parent, NULL); 157 pthread_cond_init(&thread_worker, NULL); 158 159 for (j = 0; j < bench_repeat && !done; j++) { 160 unsigned int nwoken = 0; 161 struct timeval start, end, runtime; 162 163 /* create, launch & block all threads */ 164 block_threads(worker, thread_attr); 165 166 /* make sure all threads are already blocked */ 167 pthread_mutex_lock(&thread_lock); 168 while (threads_starting) 169 pthread_cond_wait(&thread_parent, &thread_lock); 170 pthread_cond_broadcast(&thread_worker); 171 pthread_mutex_unlock(&thread_lock); 172 173 usleep(100000); 174 175 /* Ok, all threads are patiently blocked, start waking folks up */ 176 gettimeofday(&start, NULL); 177 while (nwoken != nthreads) 178 nwoken += futex_wake(&futex1, nwakes, futex_flag); 179 gettimeofday(&end, NULL); 180 timersub(&end, &start, &runtime); 181 182 update_stats(&wakeup_stats, nwoken); 183 update_stats(&waketime_stats, runtime.tv_usec); 184 185 if (!silent) { 186 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", 187 j + 1, nwoken, nthreads, runtime.tv_usec / (double)USEC_PER_MSEC); 188 } 189 190 for (i = 0; i < nthreads; i++) { 191 ret = pthread_join(worker[i], NULL); 192 if (ret) 193 err(EXIT_FAILURE, "pthread_join"); 194 } 195 196 } 197 198 /* cleanup & report results */ 199 pthread_cond_destroy(&thread_parent); 200 pthread_cond_destroy(&thread_worker); 201 pthread_mutex_destroy(&thread_lock); 202 pthread_attr_destroy(&thread_attr); 203 204 print_summary(); 205 206 free(worker); 207 return ret; 208 } 209