1 /* 2 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> 3 * 4 * futex-requeue: Block a bunch of threads on futex1 and requeue them 5 * on futex2, N at a time. 6 * 7 * This program is particularly useful to measure the latency of nthread 8 * requeues without waking up any tasks -- thus mimicking a regular futex_wait. 9 */ 10 11 #include "../perf.h" 12 #include "../util/util.h" 13 #include "../util/stat.h" 14 #include "../util/parse-options.h" 15 #include "../util/header.h" 16 #include "bench.h" 17 #include "futex.h" 18 19 #include <err.h> 20 #include <stdlib.h> 21 #include <sys/time.h> 22 #include <pthread.h> 23 24 static u_int32_t futex1 = 0, futex2 = 0; 25 26 /* 27 * How many tasks to requeue at a time. 28 * Default to 1 in order to make the kernel work more. 29 */ 30 static unsigned int nrequeue = 1; 31 32 /* 33 * There can be significant variance from run to run, 34 * the more repeats, the more exact the overall avg and 35 * the better idea of the futex latency. 36 */ 37 static unsigned int repeat = 10; 38 39 static pthread_t *worker; 40 static bool done = 0, silent = 0; 41 static pthread_mutex_t thread_lock; 42 static pthread_cond_t thread_parent, thread_worker; 43 static struct stats requeuetime_stats, requeued_stats; 44 static unsigned int ncpus, threads_starting, nthreads = 0; 45 46 static const struct option options[] = { 47 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), 48 OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"), 49 OPT_UINTEGER('r', "repeat", &repeat, "Specify amount of times to repeat the run"), 50 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 51 OPT_END() 52 }; 53 54 static const char * const bench_futex_requeue_usage[] = { 55 "perf bench futex requeue <options>", 56 NULL 57 }; 58 59 static void print_summary(void) 60 { 61 double requeuetime_avg = avg_stats(&requeuetime_stats); 62 double requeuetime_stddev = stddev_stats(&requeuetime_stats); 63 unsigned int requeued_avg = avg_stats(&requeued_stats); 64 65 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", 66 requeued_avg, 67 nthreads, 68 requeuetime_avg/1e3, 69 rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); 70 } 71 72 static void *workerfn(void *arg __maybe_unused) 73 { 74 pthread_mutex_lock(&thread_lock); 75 threads_starting--; 76 if (!threads_starting) 77 pthread_cond_signal(&thread_parent); 78 pthread_cond_wait(&thread_worker, &thread_lock); 79 pthread_mutex_unlock(&thread_lock); 80 81 futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG); 82 return NULL; 83 } 84 85 static void block_threads(pthread_t *w, 86 pthread_attr_t thread_attr) 87 { 88 cpu_set_t cpu; 89 unsigned int i; 90 91 threads_starting = nthreads; 92 93 /* create and block all threads */ 94 for (i = 0; i < nthreads; i++) { 95 CPU_ZERO(&cpu); 96 CPU_SET(i % ncpus, &cpu); 97 98 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 99 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 100 101 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 102 err(EXIT_FAILURE, "pthread_create"); 103 } 104 } 105 106 static void toggle_done(int sig __maybe_unused, 107 siginfo_t *info __maybe_unused, 108 void *uc __maybe_unused) 109 { 110 done = true; 111 } 112 113 int bench_futex_requeue(int argc, const char **argv, 114 const char *prefix __maybe_unused) 115 { 116 int ret = 0; 117 unsigned int i, j; 118 struct sigaction act; 119 pthread_attr_t thread_attr; 120 121 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); 122 if (argc) 123 goto err; 124 125 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 126 127 sigfillset(&act.sa_mask); 128 act.sa_sigaction = toggle_done; 129 sigaction(SIGINT, &act, NULL); 130 131 if (!nthreads) 132 nthreads = ncpus; 133 134 worker = calloc(nthreads, sizeof(*worker)); 135 if (!worker) 136 err(EXIT_FAILURE, "calloc"); 137 138 printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), " 139 "%d at a time.\n\n", 140 getpid(), nthreads, &futex1, &futex2, nrequeue); 141 142 init_stats(&requeued_stats); 143 init_stats(&requeuetime_stats); 144 pthread_attr_init(&thread_attr); 145 pthread_mutex_init(&thread_lock, NULL); 146 pthread_cond_init(&thread_parent, NULL); 147 pthread_cond_init(&thread_worker, NULL); 148 149 for (j = 0; j < repeat && !done; j++) { 150 unsigned int nrequeued = 0; 151 struct timeval start, end, runtime; 152 153 /* create, launch & block all threads */ 154 block_threads(worker, thread_attr); 155 156 /* make sure all threads are already blocked */ 157 pthread_mutex_lock(&thread_lock); 158 while (threads_starting) 159 pthread_cond_wait(&thread_parent, &thread_lock); 160 pthread_cond_broadcast(&thread_worker); 161 pthread_mutex_unlock(&thread_lock); 162 163 usleep(100000); 164 165 /* Ok, all threads are patiently blocked, start requeueing */ 166 gettimeofday(&start, NULL); 167 for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue) 168 /* 169 * Do not wakeup any tasks blocked on futex1, allowing 170 * us to really measure futex_wait functionality. 171 */ 172 futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue, 173 FUTEX_PRIVATE_FLAG); 174 gettimeofday(&end, NULL); 175 timersub(&end, &start, &runtime); 176 177 update_stats(&requeued_stats, nrequeued); 178 update_stats(&requeuetime_stats, runtime.tv_usec); 179 180 if (!silent) { 181 printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", 182 j + 1, nrequeued, nthreads, runtime.tv_usec/1e3); 183 } 184 185 /* everybody should be blocked on futex2, wake'em up */ 186 nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG); 187 if (nthreads != nrequeued) 188 warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); 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 err: 209 usage_with_options(bench_futex_requeue_usage, options); 210 exit(EXIT_FAILURE); 211 } 212