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 /* For the CLR_() macros */ 12 #include <pthread.h> 13 14 #include <signal.h> 15 #include "../util/stat.h" 16 #include <subcmd/parse-options.h> 17 #include <linux/compiler.h> 18 #include <linux/kernel.h> 19 #include <errno.h> 20 #include "bench.h" 21 #include "futex.h" 22 23 #include <err.h> 24 #include <stdlib.h> 25 #include <sys/time.h> 26 27 /* all threads will block on the same futex */ 28 static u_int32_t futex1 = 0; 29 30 /* 31 * How many wakeups to do at a time. 32 * Default to 1 in order to make the kernel work more. 33 */ 34 static unsigned int nwakes = 1; 35 36 pthread_t *worker; 37 static bool done = false, silent = false, fshared = false; 38 static pthread_mutex_t thread_lock; 39 static pthread_cond_t thread_parent, thread_worker; 40 static struct stats waketime_stats, wakeup_stats; 41 static unsigned int ncpus, threads_starting, nthreads = 0; 42 static int futex_flag = 0; 43 44 static const struct option options[] = { 45 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), 46 OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"), 47 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 48 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 49 OPT_END() 50 }; 51 52 static const char * const bench_futex_wake_usage[] = { 53 "perf bench futex wake <options>", 54 NULL 55 }; 56 57 static void *workerfn(void *arg __maybe_unused) 58 { 59 pthread_mutex_lock(&thread_lock); 60 threads_starting--; 61 if (!threads_starting) 62 pthread_cond_signal(&thread_parent); 63 pthread_cond_wait(&thread_worker, &thread_lock); 64 pthread_mutex_unlock(&thread_lock); 65 66 while (1) { 67 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) 68 break; 69 } 70 71 pthread_exit(NULL); 72 return NULL; 73 } 74 75 static void print_summary(void) 76 { 77 double waketime_avg = avg_stats(&waketime_stats); 78 double waketime_stddev = stddev_stats(&waketime_stats); 79 unsigned int wakeup_avg = avg_stats(&wakeup_stats); 80 81 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", 82 wakeup_avg, 83 nthreads, 84 waketime_avg/1e3, 85 rel_stddev_stats(waketime_stddev, waketime_avg)); 86 } 87 88 static void block_threads(pthread_t *w, 89 pthread_attr_t thread_attr) 90 { 91 cpu_set_t cpu; 92 unsigned int i; 93 94 threads_starting = nthreads; 95 96 /* create and block all threads */ 97 for (i = 0; i < nthreads; i++) { 98 CPU_ZERO(&cpu); 99 CPU_SET(i % ncpus, &cpu); 100 101 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 102 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 103 104 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 105 err(EXIT_FAILURE, "pthread_create"); 106 } 107 } 108 109 static void toggle_done(int sig __maybe_unused, 110 siginfo_t *info __maybe_unused, 111 void *uc __maybe_unused) 112 { 113 done = true; 114 } 115 116 int bench_futex_wake(int argc, const char **argv, 117 const char *prefix __maybe_unused) 118 { 119 int ret = 0; 120 unsigned int i, j; 121 struct sigaction act; 122 pthread_attr_t thread_attr; 123 124 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); 125 if (argc) { 126 usage_with_options(bench_futex_wake_usage, options); 127 exit(EXIT_FAILURE); 128 } 129 130 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 131 132 sigfillset(&act.sa_mask); 133 act.sa_sigaction = toggle_done; 134 sigaction(SIGINT, &act, NULL); 135 136 if (!nthreads) 137 nthreads = ncpus; 138 139 worker = calloc(nthreads, sizeof(*worker)); 140 if (!worker) 141 err(EXIT_FAILURE, "calloc"); 142 143 if (!fshared) 144 futex_flag = FUTEX_PRIVATE_FLAG; 145 146 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " 147 "waking up %d at a time.\n\n", 148 getpid(), nthreads, fshared ? "shared":"private", &futex1, nwakes); 149 150 init_stats(&wakeup_stats); 151 init_stats(&waketime_stats); 152 pthread_attr_init(&thread_attr); 153 pthread_mutex_init(&thread_lock, NULL); 154 pthread_cond_init(&thread_parent, NULL); 155 pthread_cond_init(&thread_worker, NULL); 156 157 for (j = 0; j < bench_repeat && !done; j++) { 158 unsigned int nwoken = 0; 159 struct timeval start, end, runtime; 160 161 /* create, launch & block all threads */ 162 block_threads(worker, thread_attr); 163 164 /* make sure all threads are already blocked */ 165 pthread_mutex_lock(&thread_lock); 166 while (threads_starting) 167 pthread_cond_wait(&thread_parent, &thread_lock); 168 pthread_cond_broadcast(&thread_worker); 169 pthread_mutex_unlock(&thread_lock); 170 171 usleep(100000); 172 173 /* Ok, all threads are patiently blocked, start waking folks up */ 174 gettimeofday(&start, NULL); 175 while (nwoken != nthreads) 176 nwoken += futex_wake(&futex1, nwakes, futex_flag); 177 gettimeofday(&end, NULL); 178 timersub(&end, &start, &runtime); 179 180 update_stats(&wakeup_stats, nwoken); 181 update_stats(&waketime_stats, runtime.tv_usec); 182 183 if (!silent) { 184 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", 185 j + 1, nwoken, nthreads, runtime.tv_usec/1e3); 186 } 187 188 for (i = 0; i < nthreads; i++) { 189 ret = pthread_join(worker[i], NULL); 190 if (ret) 191 err(EXIT_FAILURE, "pthread_join"); 192 } 193 194 } 195 196 /* cleanup & report results */ 197 pthread_cond_destroy(&thread_parent); 198 pthread_cond_destroy(&thread_worker); 199 pthread_mutex_destroy(&thread_lock); 200 pthread_attr_destroy(&thread_attr); 201 202 print_summary(); 203 204 free(worker); 205 return ret; 206 } 207