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 <perf/cpumap.h> 24 #include "bench.h" 25 #include "futex.h" 26 27 #include <err.h> 28 #include <stdlib.h> 29 #include <sys/time.h> 30 #include <sys/mman.h> 31 32 /* all threads will block on the same futex */ 33 static u_int32_t futex1 = 0; 34 35 static pthread_t *worker; 36 static bool done = false; 37 static pthread_mutex_t thread_lock; 38 static pthread_cond_t thread_parent, thread_worker; 39 static struct stats waketime_stats, wakeup_stats; 40 static unsigned int threads_starting; 41 static int futex_flag = 0; 42 43 static struct bench_futex_parameters params = { 44 /* 45 * How many wakeups to do at a time. 46 * Default to 1 in order to make the kernel work more. 47 */ 48 .nwakes = 1, 49 }; 50 51 static const struct option options[] = { 52 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 53 OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake at once"), 54 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 55 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 56 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 57 58 OPT_END() 59 }; 60 61 static const char * const bench_futex_wake_usage[] = { 62 "perf bench futex wake <options>", 63 NULL 64 }; 65 66 static void *workerfn(void *arg __maybe_unused) 67 { 68 pthread_mutex_lock(&thread_lock); 69 threads_starting--; 70 if (!threads_starting) 71 pthread_cond_signal(&thread_parent); 72 pthread_cond_wait(&thread_worker, &thread_lock); 73 pthread_mutex_unlock(&thread_lock); 74 75 while (1) { 76 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) 77 break; 78 } 79 80 pthread_exit(NULL); 81 return NULL; 82 } 83 84 static void print_summary(void) 85 { 86 double waketime_avg = avg_stats(&waketime_stats); 87 double waketime_stddev = stddev_stats(&waketime_stats); 88 unsigned int wakeup_avg = avg_stats(&wakeup_stats); 89 90 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", 91 wakeup_avg, 92 params.nthreads, 93 waketime_avg / USEC_PER_MSEC, 94 rel_stddev_stats(waketime_stddev, waketime_avg)); 95 } 96 97 static void block_threads(pthread_t *w, 98 pthread_attr_t thread_attr, struct perf_cpu_map *cpu) 99 { 100 cpu_set_t cpuset; 101 unsigned int i; 102 103 threads_starting = params.nthreads; 104 105 /* create and block all threads */ 106 for (i = 0; i < params.nthreads; i++) { 107 CPU_ZERO(&cpuset); 108 CPU_SET(cpu->map[i % cpu->nr], &cpuset); 109 110 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset)) 111 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 112 113 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 114 err(EXIT_FAILURE, "pthread_create"); 115 } 116 } 117 118 static void toggle_done(int sig __maybe_unused, 119 siginfo_t *info __maybe_unused, 120 void *uc __maybe_unused) 121 { 122 done = true; 123 } 124 125 int bench_futex_wake(int argc, const char **argv) 126 { 127 int ret = 0; 128 unsigned int i, j; 129 struct sigaction act; 130 pthread_attr_t thread_attr; 131 struct perf_cpu_map *cpu; 132 133 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); 134 if (argc) { 135 usage_with_options(bench_futex_wake_usage, options); 136 exit(EXIT_FAILURE); 137 } 138 139 cpu = perf_cpu_map__new(NULL); 140 if (!cpu) 141 err(EXIT_FAILURE, "calloc"); 142 143 memset(&act, 0, sizeof(act)); 144 sigfillset(&act.sa_mask); 145 act.sa_sigaction = toggle_done; 146 sigaction(SIGINT, &act, NULL); 147 148 if (params.mlockall) { 149 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 150 err(EXIT_FAILURE, "mlockall"); 151 } 152 153 if (!params.nthreads) 154 params.nthreads = cpu->nr; 155 156 worker = calloc(params.nthreads, sizeof(*worker)); 157 if (!worker) 158 err(EXIT_FAILURE, "calloc"); 159 160 if (!params.fshared) 161 futex_flag = FUTEX_PRIVATE_FLAG; 162 163 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " 164 "waking up %d at a time.\n\n", 165 getpid(), params.nthreads, params.fshared ? "shared":"private", 166 &futex1, params.nwakes); 167 168 init_stats(&wakeup_stats); 169 init_stats(&waketime_stats); 170 pthread_attr_init(&thread_attr); 171 pthread_mutex_init(&thread_lock, NULL); 172 pthread_cond_init(&thread_parent, NULL); 173 pthread_cond_init(&thread_worker, NULL); 174 175 for (j = 0; j < bench_repeat && !done; j++) { 176 unsigned int nwoken = 0; 177 struct timeval start, end, runtime; 178 179 /* create, launch & block all threads */ 180 block_threads(worker, thread_attr, cpu); 181 182 /* make sure all threads are already blocked */ 183 pthread_mutex_lock(&thread_lock); 184 while (threads_starting) 185 pthread_cond_wait(&thread_parent, &thread_lock); 186 pthread_cond_broadcast(&thread_worker); 187 pthread_mutex_unlock(&thread_lock); 188 189 usleep(100000); 190 191 /* Ok, all threads are patiently blocked, start waking folks up */ 192 gettimeofday(&start, NULL); 193 while (nwoken != params.nthreads) 194 nwoken += futex_wake(&futex1, 195 params.nwakes, futex_flag); 196 gettimeofday(&end, NULL); 197 timersub(&end, &start, &runtime); 198 199 update_stats(&wakeup_stats, nwoken); 200 update_stats(&waketime_stats, runtime.tv_usec); 201 202 if (!params.silent) { 203 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", 204 j + 1, nwoken, params.nthreads, 205 runtime.tv_usec / (double)USEC_PER_MSEC); 206 } 207 208 for (i = 0; i < params.nthreads; i++) { 209 ret = pthread_join(worker[i], NULL); 210 if (ret) 211 err(EXIT_FAILURE, "pthread_join"); 212 } 213 214 } 215 216 /* cleanup & report results */ 217 pthread_cond_destroy(&thread_parent); 218 pthread_cond_destroy(&thread_worker); 219 pthread_mutex_destroy(&thread_lock); 220 pthread_attr_destroy(&thread_attr); 221 222 print_summary(); 223 224 free(worker); 225 perf_cpu_map__put(cpu); 226 return ret; 227 } 228