1 /* 2 * Copyright (C) 2015 Davidlohr Bueso. 3 * 4 * Block a bunch of threads and let parallel waker threads wakeup an 5 * equal amount of them. The program output reflects the avg latency 6 * for each individual thread to service its share of work. Ultimately 7 * it can be used to measure futex_wake() changes. 8 */ 9 10 #include "../perf.h" 11 #include "../util/util.h" 12 #include "../util/stat.h" 13 #include <subcmd/parse-options.h> 14 #include "../util/header.h" 15 #include "bench.h" 16 #include "futex.h" 17 18 #include <err.h> 19 #include <stdlib.h> 20 #include <sys/time.h> 21 #include <pthread.h> 22 23 struct thread_data { 24 pthread_t worker; 25 unsigned int nwoken; 26 struct timeval runtime; 27 }; 28 29 static unsigned int nwakes = 1; 30 31 /* all threads will block on the same futex -- hash bucket chaos ;) */ 32 static u_int32_t futex = 0; 33 34 static pthread_t *blocked_worker; 35 static bool done = false, silent = false, fshared = false; 36 static unsigned int nblocked_threads = 0, nwaking_threads = 0; 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 ncpus, threads_starting; 41 static int futex_flag = 0; 42 43 static const struct option options[] = { 44 OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"), 45 OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"), 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_wake_parallel_usage[] = { 52 "perf bench futex wake-parallel <options>", 53 NULL 54 }; 55 56 static void *waking_workerfn(void *arg) 57 { 58 struct thread_data *waker = (struct thread_data *) arg; 59 struct timeval start, end; 60 61 gettimeofday(&start, NULL); 62 63 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 64 if (waker->nwoken != nwakes) 65 warnx("couldn't wakeup all tasks (%d/%d)", 66 waker->nwoken, nwakes); 67 68 gettimeofday(&end, NULL); 69 timersub(&end, &start, &waker->runtime); 70 71 pthread_exit(NULL); 72 return NULL; 73 } 74 75 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) 76 { 77 unsigned int i; 78 79 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 80 81 /* create and block all threads */ 82 for (i = 0; i < nwaking_threads; i++) { 83 /* 84 * Thread creation order will impact per-thread latency 85 * as it will affect the order to acquire the hb spinlock. 86 * For now let the scheduler decide. 87 */ 88 if (pthread_create(&td[i].worker, &thread_attr, 89 waking_workerfn, (void *)&td[i])) 90 err(EXIT_FAILURE, "pthread_create"); 91 } 92 93 for (i = 0; i < nwaking_threads; i++) 94 if (pthread_join(td[i].worker, NULL)) 95 err(EXIT_FAILURE, "pthread_join"); 96 } 97 98 static void *blocked_workerfn(void *arg __maybe_unused) 99 { 100 pthread_mutex_lock(&thread_lock); 101 threads_starting--; 102 if (!threads_starting) 103 pthread_cond_signal(&thread_parent); 104 pthread_cond_wait(&thread_worker, &thread_lock); 105 pthread_mutex_unlock(&thread_lock); 106 107 while (1) { /* handle spurious wakeups */ 108 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 109 break; 110 } 111 112 pthread_exit(NULL); 113 return NULL; 114 } 115 116 static void block_threads(pthread_t *w, pthread_attr_t thread_attr) 117 { 118 cpu_set_t cpu; 119 unsigned int i; 120 121 threads_starting = nblocked_threads; 122 123 /* create and block all threads */ 124 for (i = 0; i < nblocked_threads; i++) { 125 CPU_ZERO(&cpu); 126 CPU_SET(i % ncpus, &cpu); 127 128 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 129 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 130 131 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) 132 err(EXIT_FAILURE, "pthread_create"); 133 } 134 } 135 136 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 137 { 138 unsigned int i, wakeup_avg; 139 double waketime_avg, waketime_stddev; 140 struct stats __waketime_stats, __wakeup_stats; 141 142 init_stats(&__wakeup_stats); 143 init_stats(&__waketime_stats); 144 145 for (i = 0; i < nwaking_threads; i++) { 146 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 147 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 148 } 149 150 waketime_avg = avg_stats(&__waketime_stats); 151 waketime_stddev = stddev_stats(&__waketime_stats); 152 wakeup_avg = avg_stats(&__wakeup_stats); 153 154 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 155 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 156 nblocked_threads, waketime_avg/1e3, 157 rel_stddev_stats(waketime_stddev, waketime_avg)); 158 } 159 160 static void print_summary(void) 161 { 162 unsigned int wakeup_avg; 163 double waketime_avg, waketime_stddev; 164 165 waketime_avg = avg_stats(&waketime_stats); 166 waketime_stddev = stddev_stats(&waketime_stats); 167 wakeup_avg = avg_stats(&wakeup_stats); 168 169 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 170 wakeup_avg, 171 nblocked_threads, 172 waketime_avg/1e3, 173 rel_stddev_stats(waketime_stddev, waketime_avg)); 174 } 175 176 177 static void do_run_stats(struct thread_data *waking_worker) 178 { 179 unsigned int i; 180 181 for (i = 0; i < nwaking_threads; i++) { 182 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 183 update_stats(&wakeup_stats, waking_worker[i].nwoken); 184 } 185 186 } 187 188 static void toggle_done(int sig __maybe_unused, 189 siginfo_t *info __maybe_unused, 190 void *uc __maybe_unused) 191 { 192 done = true; 193 } 194 195 int bench_futex_wake_parallel(int argc, const char **argv, 196 const char *prefix __maybe_unused) 197 { 198 int ret = 0; 199 unsigned int i, j; 200 struct sigaction act; 201 pthread_attr_t thread_attr; 202 struct thread_data *waking_worker; 203 204 argc = parse_options(argc, argv, options, 205 bench_futex_wake_parallel_usage, 0); 206 if (argc) { 207 usage_with_options(bench_futex_wake_parallel_usage, options); 208 exit(EXIT_FAILURE); 209 } 210 211 sigfillset(&act.sa_mask); 212 act.sa_sigaction = toggle_done; 213 sigaction(SIGINT, &act, NULL); 214 215 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 216 if (!nblocked_threads) 217 nblocked_threads = ncpus; 218 219 /* some sanity checks */ 220 if (nwaking_threads > nblocked_threads || !nwaking_threads) 221 nwaking_threads = nblocked_threads; 222 223 if (nblocked_threads % nwaking_threads) 224 errx(EXIT_FAILURE, "Must be perfectly divisible"); 225 /* 226 * Each thread will wakeup nwakes tasks in 227 * a single futex_wait call. 228 */ 229 nwakes = nblocked_threads/nwaking_threads; 230 231 blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); 232 if (!blocked_worker) 233 err(EXIT_FAILURE, "calloc"); 234 235 if (!fshared) 236 futex_flag = FUTEX_PRIVATE_FLAG; 237 238 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 239 "futex %p), %d threads waking up %d at a time.\n\n", 240 getpid(), nblocked_threads, fshared ? "shared":"private", 241 &futex, nwaking_threads, nwakes); 242 243 init_stats(&wakeup_stats); 244 init_stats(&waketime_stats); 245 246 pthread_attr_init(&thread_attr); 247 pthread_mutex_init(&thread_lock, NULL); 248 pthread_cond_init(&thread_parent, NULL); 249 pthread_cond_init(&thread_worker, NULL); 250 251 for (j = 0; j < bench_repeat && !done; j++) { 252 waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); 253 if (!waking_worker) 254 err(EXIT_FAILURE, "calloc"); 255 256 /* create, launch & block all threads */ 257 block_threads(blocked_worker, thread_attr); 258 259 /* make sure all threads are already blocked */ 260 pthread_mutex_lock(&thread_lock); 261 while (threads_starting) 262 pthread_cond_wait(&thread_parent, &thread_lock); 263 pthread_cond_broadcast(&thread_worker); 264 pthread_mutex_unlock(&thread_lock); 265 266 usleep(100000); 267 268 /* Ok, all threads are patiently blocked, start waking folks up */ 269 wakeup_threads(waking_worker, thread_attr); 270 271 for (i = 0; i < nblocked_threads; i++) { 272 ret = pthread_join(blocked_worker[i], NULL); 273 if (ret) 274 err(EXIT_FAILURE, "pthread_join"); 275 } 276 277 do_run_stats(waking_worker); 278 if (!silent) 279 print_run(waking_worker, j); 280 281 free(waking_worker); 282 } 283 284 /* cleanup & report results */ 285 pthread_cond_destroy(&thread_parent); 286 pthread_cond_destroy(&thread_worker); 287 pthread_mutex_destroy(&thread_lock); 288 pthread_attr_destroy(&thread_attr); 289 290 print_summary(); 291 292 free(blocked_worker); 293 return ret; 294 } 295