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 <subcmd/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 static pthread_t *worker; 33 static bool done = false, silent = false, fshared = false; 34 static pthread_mutex_t thread_lock; 35 static pthread_cond_t thread_parent, thread_worker; 36 static struct stats requeuetime_stats, requeued_stats; 37 static unsigned int ncpus, threads_starting, nthreads = 0; 38 static int futex_flag = 0; 39 40 static const struct option options[] = { 41 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), 42 OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"), 43 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 44 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 45 OPT_END() 46 }; 47 48 static const char * const bench_futex_requeue_usage[] = { 49 "perf bench futex requeue <options>", 50 NULL 51 }; 52 53 static void print_summary(void) 54 { 55 double requeuetime_avg = avg_stats(&requeuetime_stats); 56 double requeuetime_stddev = stddev_stats(&requeuetime_stats); 57 unsigned int requeued_avg = avg_stats(&requeued_stats); 58 59 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", 60 requeued_avg, 61 nthreads, 62 requeuetime_avg/1e3, 63 rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); 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 futex_wait(&futex1, 0, NULL, futex_flag); 76 return NULL; 77 } 78 79 static void block_threads(pthread_t *w, 80 pthread_attr_t thread_attr) 81 { 82 cpu_set_t cpu; 83 unsigned int i; 84 85 threads_starting = nthreads; 86 87 /* create and block all threads */ 88 for (i = 0; i < nthreads; i++) { 89 CPU_ZERO(&cpu); 90 CPU_SET(i % ncpus, &cpu); 91 92 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 93 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 94 95 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 96 err(EXIT_FAILURE, "pthread_create"); 97 } 98 } 99 100 static void toggle_done(int sig __maybe_unused, 101 siginfo_t *info __maybe_unused, 102 void *uc __maybe_unused) 103 { 104 done = true; 105 } 106 107 int bench_futex_requeue(int argc, const char **argv, 108 const char *prefix __maybe_unused) 109 { 110 int ret = 0; 111 unsigned int i, j; 112 struct sigaction act; 113 pthread_attr_t thread_attr; 114 115 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); 116 if (argc) 117 goto err; 118 119 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 120 121 sigfillset(&act.sa_mask); 122 act.sa_sigaction = toggle_done; 123 sigaction(SIGINT, &act, NULL); 124 125 if (!nthreads) 126 nthreads = ncpus; 127 128 worker = calloc(nthreads, sizeof(*worker)); 129 if (!worker) 130 err(EXIT_FAILURE, "calloc"); 131 132 if (!fshared) 133 futex_flag = FUTEX_PRIVATE_FLAG; 134 135 if (nrequeue > nthreads) 136 nrequeue = nthreads; 137 138 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), " 139 "%d at a time.\n\n", getpid(), nthreads, 140 fshared ? "shared":"private", &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 < bench_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 while (nrequeued < nthreads) { 168 /* 169 * Do not wakeup any tasks blocked on futex1, allowing 170 * us to really measure futex_wait functionality. 171 */ 172 nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0, 173 nrequeue, futex_flag); 174 } 175 176 gettimeofday(&end, NULL); 177 timersub(&end, &start, &runtime); 178 179 update_stats(&requeued_stats, nrequeued); 180 update_stats(&requeuetime_stats, runtime.tv_usec); 181 182 if (!silent) { 183 printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", 184 j + 1, nrequeued, nthreads, runtime.tv_usec/1e3); 185 } 186 187 /* everybody should be blocked on futex2, wake'em up */ 188 nrequeued = futex_wake(&futex2, nrequeued, futex_flag); 189 if (nthreads != nrequeued) 190 warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); 191 192 for (i = 0; i < nthreads; i++) { 193 ret = pthread_join(worker[i], NULL); 194 if (ret) 195 err(EXIT_FAILURE, "pthread_join"); 196 } 197 } 198 199 /* cleanup & report results */ 200 pthread_cond_destroy(&thread_parent); 201 pthread_cond_destroy(&thread_worker); 202 pthread_mutex_destroy(&thread_lock); 203 pthread_attr_destroy(&thread_attr); 204 205 print_summary(); 206 207 free(worker); 208 return ret; 209 err: 210 usage_with_options(bench_futex_requeue_usage, options); 211 exit(EXIT_FAILURE); 212 } 213