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 /* 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 static u_int32_t futex1 = 0, futex2 = 0; 28 29 /* 30 * How many tasks to requeue at a time. 31 * Default to 1 in order to make the kernel work more. 32 */ 33 static unsigned int nrequeue = 1; 34 35 static pthread_t *worker; 36 static bool done = false, silent = false, fshared = false; 37 static pthread_mutex_t thread_lock; 38 static pthread_cond_t thread_parent, thread_worker; 39 static struct stats requeuetime_stats, requeued_stats; 40 static unsigned int ncpus, threads_starting, nthreads = 0; 41 static int futex_flag = 0; 42 43 static const struct option options[] = { 44 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), 45 OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"), 46 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 47 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 48 OPT_END() 49 }; 50 51 static const char * const bench_futex_requeue_usage[] = { 52 "perf bench futex requeue <options>", 53 NULL 54 }; 55 56 static void print_summary(void) 57 { 58 double requeuetime_avg = avg_stats(&requeuetime_stats); 59 double requeuetime_stddev = stddev_stats(&requeuetime_stats); 60 unsigned int requeued_avg = avg_stats(&requeued_stats); 61 62 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", 63 requeued_avg, 64 nthreads, 65 requeuetime_avg/1e3, 66 rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); 67 } 68 69 static void *workerfn(void *arg __maybe_unused) 70 { 71 pthread_mutex_lock(&thread_lock); 72 threads_starting--; 73 if (!threads_starting) 74 pthread_cond_signal(&thread_parent); 75 pthread_cond_wait(&thread_worker, &thread_lock); 76 pthread_mutex_unlock(&thread_lock); 77 78 futex_wait(&futex1, 0, NULL, futex_flag); 79 return NULL; 80 } 81 82 static void block_threads(pthread_t *w, 83 pthread_attr_t thread_attr) 84 { 85 cpu_set_t cpu; 86 unsigned int i; 87 88 threads_starting = nthreads; 89 90 /* create and block all threads */ 91 for (i = 0; i < nthreads; i++) { 92 CPU_ZERO(&cpu); 93 CPU_SET(i % ncpus, &cpu); 94 95 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 96 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 97 98 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) 99 err(EXIT_FAILURE, "pthread_create"); 100 } 101 } 102 103 static void toggle_done(int sig __maybe_unused, 104 siginfo_t *info __maybe_unused, 105 void *uc __maybe_unused) 106 { 107 done = true; 108 } 109 110 int bench_futex_requeue(int argc, const char **argv, 111 const char *prefix __maybe_unused) 112 { 113 int ret = 0; 114 unsigned int i, j; 115 struct sigaction act; 116 pthread_attr_t thread_attr; 117 118 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); 119 if (argc) 120 goto err; 121 122 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 123 124 sigfillset(&act.sa_mask); 125 act.sa_sigaction = toggle_done; 126 sigaction(SIGINT, &act, NULL); 127 128 if (!nthreads) 129 nthreads = ncpus; 130 131 worker = calloc(nthreads, sizeof(*worker)); 132 if (!worker) 133 err(EXIT_FAILURE, "calloc"); 134 135 if (!fshared) 136 futex_flag = FUTEX_PRIVATE_FLAG; 137 138 if (nrequeue > nthreads) 139 nrequeue = nthreads; 140 141 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), " 142 "%d at a time.\n\n", getpid(), nthreads, 143 fshared ? "shared":"private", &futex1, &futex2, nrequeue); 144 145 init_stats(&requeued_stats); 146 init_stats(&requeuetime_stats); 147 pthread_attr_init(&thread_attr); 148 pthread_mutex_init(&thread_lock, NULL); 149 pthread_cond_init(&thread_parent, NULL); 150 pthread_cond_init(&thread_worker, NULL); 151 152 for (j = 0; j < bench_repeat && !done; j++) { 153 unsigned int nrequeued = 0; 154 struct timeval start, end, runtime; 155 156 /* create, launch & block all threads */ 157 block_threads(worker, thread_attr); 158 159 /* make sure all threads are already blocked */ 160 pthread_mutex_lock(&thread_lock); 161 while (threads_starting) 162 pthread_cond_wait(&thread_parent, &thread_lock); 163 pthread_cond_broadcast(&thread_worker); 164 pthread_mutex_unlock(&thread_lock); 165 166 usleep(100000); 167 168 /* Ok, all threads are patiently blocked, start requeueing */ 169 gettimeofday(&start, NULL); 170 while (nrequeued < nthreads) { 171 /* 172 * Do not wakeup any tasks blocked on futex1, allowing 173 * us to really measure futex_wait functionality. 174 */ 175 nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0, 176 nrequeue, futex_flag); 177 } 178 179 gettimeofday(&end, NULL); 180 timersub(&end, &start, &runtime); 181 182 update_stats(&requeued_stats, nrequeued); 183 update_stats(&requeuetime_stats, runtime.tv_usec); 184 185 if (!silent) { 186 printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", 187 j + 1, nrequeued, nthreads, runtime.tv_usec/1e3); 188 } 189 190 /* everybody should be blocked on futex2, wake'em up */ 191 nrequeued = futex_wake(&futex2, nrequeued, futex_flag); 192 if (nthreads != nrequeued) 193 warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); 194 195 for (i = 0; i < nthreads; i++) { 196 ret = pthread_join(worker[i], NULL); 197 if (ret) 198 err(EXIT_FAILURE, "pthread_join"); 199 } 200 } 201 202 /* cleanup & report results */ 203 pthread_cond_destroy(&thread_parent); 204 pthread_cond_destroy(&thread_worker); 205 pthread_mutex_destroy(&thread_lock); 206 pthread_attr_destroy(&thread_attr); 207 208 print_summary(); 209 210 free(worker); 211 return ret; 212 err: 213 usage_with_options(bench_futex_requeue_usage, options); 214 exit(EXIT_FAILURE); 215 } 216