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 /* For the CLR_() macros */ 11 #include <pthread.h> 12 13 #include <signal.h> 14 #include "../util/stat.h" 15 #include <subcmd/parse-options.h> 16 #include <linux/compiler.h> 17 #include <linux/kernel.h> 18 #include <errno.h> 19 #include "bench.h" 20 #include "futex.h" 21 22 #include <err.h> 23 #include <stdlib.h> 24 #include <sys/time.h> 25 26 struct thread_data { 27 pthread_t worker; 28 unsigned int nwoken; 29 struct timeval runtime; 30 }; 31 32 static unsigned int nwakes = 1; 33 34 /* all threads will block on the same futex -- hash bucket chaos ;) */ 35 static u_int32_t futex = 0; 36 37 static pthread_t *blocked_worker; 38 static bool done = false, silent = false, fshared = false; 39 static unsigned int nblocked_threads = 0, nwaking_threads = 0; 40 static pthread_mutex_t thread_lock; 41 static pthread_cond_t thread_parent, thread_worker; 42 static struct stats waketime_stats, wakeup_stats; 43 static unsigned int ncpus, threads_starting; 44 static int futex_flag = 0; 45 46 static const struct option options[] = { 47 OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"), 48 OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"), 49 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 50 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 51 OPT_END() 52 }; 53 54 static const char * const bench_futex_wake_parallel_usage[] = { 55 "perf bench futex wake-parallel <options>", 56 NULL 57 }; 58 59 static void *waking_workerfn(void *arg) 60 { 61 struct thread_data *waker = (struct thread_data *) arg; 62 struct timeval start, end; 63 64 gettimeofday(&start, NULL); 65 66 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 67 if (waker->nwoken != nwakes) 68 warnx("couldn't wakeup all tasks (%d/%d)", 69 waker->nwoken, nwakes); 70 71 gettimeofday(&end, NULL); 72 timersub(&end, &start, &waker->runtime); 73 74 pthread_exit(NULL); 75 return NULL; 76 } 77 78 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) 79 { 80 unsigned int i; 81 82 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 83 84 /* create and block all threads */ 85 for (i = 0; i < nwaking_threads; i++) { 86 /* 87 * Thread creation order will impact per-thread latency 88 * as it will affect the order to acquire the hb spinlock. 89 * For now let the scheduler decide. 90 */ 91 if (pthread_create(&td[i].worker, &thread_attr, 92 waking_workerfn, (void *)&td[i])) 93 err(EXIT_FAILURE, "pthread_create"); 94 } 95 96 for (i = 0; i < nwaking_threads; i++) 97 if (pthread_join(td[i].worker, NULL)) 98 err(EXIT_FAILURE, "pthread_join"); 99 } 100 101 static void *blocked_workerfn(void *arg __maybe_unused) 102 { 103 pthread_mutex_lock(&thread_lock); 104 threads_starting--; 105 if (!threads_starting) 106 pthread_cond_signal(&thread_parent); 107 pthread_cond_wait(&thread_worker, &thread_lock); 108 pthread_mutex_unlock(&thread_lock); 109 110 while (1) { /* handle spurious wakeups */ 111 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 112 break; 113 } 114 115 pthread_exit(NULL); 116 return NULL; 117 } 118 119 static void block_threads(pthread_t *w, pthread_attr_t thread_attr) 120 { 121 cpu_set_t cpu; 122 unsigned int i; 123 124 threads_starting = nblocked_threads; 125 126 /* create and block all threads */ 127 for (i = 0; i < nblocked_threads; i++) { 128 CPU_ZERO(&cpu); 129 CPU_SET(i % ncpus, &cpu); 130 131 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 132 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 133 134 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) 135 err(EXIT_FAILURE, "pthread_create"); 136 } 137 } 138 139 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 140 { 141 unsigned int i, wakeup_avg; 142 double waketime_avg, waketime_stddev; 143 struct stats __waketime_stats, __wakeup_stats; 144 145 init_stats(&__wakeup_stats); 146 init_stats(&__waketime_stats); 147 148 for (i = 0; i < nwaking_threads; i++) { 149 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 150 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 151 } 152 153 waketime_avg = avg_stats(&__waketime_stats); 154 waketime_stddev = stddev_stats(&__waketime_stats); 155 wakeup_avg = avg_stats(&__wakeup_stats); 156 157 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 158 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 159 nblocked_threads, waketime_avg/1e3, 160 rel_stddev_stats(waketime_stddev, waketime_avg)); 161 } 162 163 static void print_summary(void) 164 { 165 unsigned int wakeup_avg; 166 double waketime_avg, waketime_stddev; 167 168 waketime_avg = avg_stats(&waketime_stats); 169 waketime_stddev = stddev_stats(&waketime_stats); 170 wakeup_avg = avg_stats(&wakeup_stats); 171 172 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 173 wakeup_avg, 174 nblocked_threads, 175 waketime_avg/1e3, 176 rel_stddev_stats(waketime_stddev, waketime_avg)); 177 } 178 179 180 static void do_run_stats(struct thread_data *waking_worker) 181 { 182 unsigned int i; 183 184 for (i = 0; i < nwaking_threads; i++) { 185 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 186 update_stats(&wakeup_stats, waking_worker[i].nwoken); 187 } 188 189 } 190 191 static void toggle_done(int sig __maybe_unused, 192 siginfo_t *info __maybe_unused, 193 void *uc __maybe_unused) 194 { 195 done = true; 196 } 197 198 int bench_futex_wake_parallel(int argc, const char **argv, 199 const char *prefix __maybe_unused) 200 { 201 int ret = 0; 202 unsigned int i, j; 203 struct sigaction act; 204 pthread_attr_t thread_attr; 205 struct thread_data *waking_worker; 206 207 argc = parse_options(argc, argv, options, 208 bench_futex_wake_parallel_usage, 0); 209 if (argc) { 210 usage_with_options(bench_futex_wake_parallel_usage, options); 211 exit(EXIT_FAILURE); 212 } 213 214 sigfillset(&act.sa_mask); 215 act.sa_sigaction = toggle_done; 216 sigaction(SIGINT, &act, NULL); 217 218 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 219 if (!nblocked_threads) 220 nblocked_threads = ncpus; 221 222 /* some sanity checks */ 223 if (nwaking_threads > nblocked_threads || !nwaking_threads) 224 nwaking_threads = nblocked_threads; 225 226 if (nblocked_threads % nwaking_threads) 227 errx(EXIT_FAILURE, "Must be perfectly divisible"); 228 /* 229 * Each thread will wakeup nwakes tasks in 230 * a single futex_wait call. 231 */ 232 nwakes = nblocked_threads/nwaking_threads; 233 234 blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); 235 if (!blocked_worker) 236 err(EXIT_FAILURE, "calloc"); 237 238 if (!fshared) 239 futex_flag = FUTEX_PRIVATE_FLAG; 240 241 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 242 "futex %p), %d threads waking up %d at a time.\n\n", 243 getpid(), nblocked_threads, fshared ? "shared":"private", 244 &futex, nwaking_threads, nwakes); 245 246 init_stats(&wakeup_stats); 247 init_stats(&waketime_stats); 248 249 pthread_attr_init(&thread_attr); 250 pthread_mutex_init(&thread_lock, NULL); 251 pthread_cond_init(&thread_parent, NULL); 252 pthread_cond_init(&thread_worker, NULL); 253 254 for (j = 0; j < bench_repeat && !done; j++) { 255 waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); 256 if (!waking_worker) 257 err(EXIT_FAILURE, "calloc"); 258 259 /* create, launch & block all threads */ 260 block_threads(blocked_worker, thread_attr); 261 262 /* make sure all threads are already blocked */ 263 pthread_mutex_lock(&thread_lock); 264 while (threads_starting) 265 pthread_cond_wait(&thread_parent, &thread_lock); 266 pthread_cond_broadcast(&thread_worker); 267 pthread_mutex_unlock(&thread_lock); 268 269 usleep(100000); 270 271 /* Ok, all threads are patiently blocked, start waking folks up */ 272 wakeup_threads(waking_worker, thread_attr); 273 274 for (i = 0; i < nblocked_threads; i++) { 275 ret = pthread_join(blocked_worker[i], NULL); 276 if (ret) 277 err(EXIT_FAILURE, "pthread_join"); 278 } 279 280 do_run_stats(waking_worker); 281 if (!silent) 282 print_run(waking_worker, j); 283 284 free(waking_worker); 285 } 286 287 /* cleanup & report results */ 288 pthread_cond_destroy(&thread_parent); 289 pthread_cond_destroy(&thread_worker); 290 pthread_mutex_destroy(&thread_lock); 291 pthread_attr_destroy(&thread_attr); 292 293 print_summary(); 294 295 free(blocked_worker); 296 return ret; 297 } 298