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 <linux/time64.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 struct thread_data { 28 pthread_t worker; 29 unsigned int nwoken; 30 struct timeval runtime; 31 }; 32 33 static unsigned int nwakes = 1; 34 35 /* all threads will block on the same futex -- hash bucket chaos ;) */ 36 static u_int32_t futex = 0; 37 38 static pthread_t *blocked_worker; 39 static bool done = false, silent = false, fshared = false; 40 static unsigned int nblocked_threads = 0, nwaking_threads = 0; 41 static pthread_mutex_t thread_lock; 42 static pthread_cond_t thread_parent, thread_worker; 43 static struct stats waketime_stats, wakeup_stats; 44 static unsigned int ncpus, threads_starting; 45 static int futex_flag = 0; 46 47 static const struct option options[] = { 48 OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"), 49 OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"), 50 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 51 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 52 OPT_END() 53 }; 54 55 static const char * const bench_futex_wake_parallel_usage[] = { 56 "perf bench futex wake-parallel <options>", 57 NULL 58 }; 59 60 static void *waking_workerfn(void *arg) 61 { 62 struct thread_data *waker = (struct thread_data *) arg; 63 struct timeval start, end; 64 65 gettimeofday(&start, NULL); 66 67 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 68 if (waker->nwoken != nwakes) 69 warnx("couldn't wakeup all tasks (%d/%d)", 70 waker->nwoken, nwakes); 71 72 gettimeofday(&end, NULL); 73 timersub(&end, &start, &waker->runtime); 74 75 pthread_exit(NULL); 76 return NULL; 77 } 78 79 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) 80 { 81 unsigned int i; 82 83 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 84 85 /* create and block all threads */ 86 for (i = 0; i < nwaking_threads; i++) { 87 /* 88 * Thread creation order will impact per-thread latency 89 * as it will affect the order to acquire the hb spinlock. 90 * For now let the scheduler decide. 91 */ 92 if (pthread_create(&td[i].worker, &thread_attr, 93 waking_workerfn, (void *)&td[i])) 94 err(EXIT_FAILURE, "pthread_create"); 95 } 96 97 for (i = 0; i < nwaking_threads; i++) 98 if (pthread_join(td[i].worker, NULL)) 99 err(EXIT_FAILURE, "pthread_join"); 100 } 101 102 static void *blocked_workerfn(void *arg __maybe_unused) 103 { 104 pthread_mutex_lock(&thread_lock); 105 threads_starting--; 106 if (!threads_starting) 107 pthread_cond_signal(&thread_parent); 108 pthread_cond_wait(&thread_worker, &thread_lock); 109 pthread_mutex_unlock(&thread_lock); 110 111 while (1) { /* handle spurious wakeups */ 112 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 113 break; 114 } 115 116 pthread_exit(NULL); 117 return NULL; 118 } 119 120 static void block_threads(pthread_t *w, pthread_attr_t thread_attr) 121 { 122 cpu_set_t cpu; 123 unsigned int i; 124 125 threads_starting = nblocked_threads; 126 127 /* create and block all threads */ 128 for (i = 0; i < nblocked_threads; i++) { 129 CPU_ZERO(&cpu); 130 CPU_SET(i % ncpus, &cpu); 131 132 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 133 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 134 135 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) 136 err(EXIT_FAILURE, "pthread_create"); 137 } 138 } 139 140 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 141 { 142 unsigned int i, wakeup_avg; 143 double waketime_avg, waketime_stddev; 144 struct stats __waketime_stats, __wakeup_stats; 145 146 init_stats(&__wakeup_stats); 147 init_stats(&__waketime_stats); 148 149 for (i = 0; i < nwaking_threads; i++) { 150 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 151 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 152 } 153 154 waketime_avg = avg_stats(&__waketime_stats); 155 waketime_stddev = stddev_stats(&__waketime_stats); 156 wakeup_avg = avg_stats(&__wakeup_stats); 157 158 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 159 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 160 nblocked_threads, waketime_avg / USEC_PER_MSEC, 161 rel_stddev_stats(waketime_stddev, waketime_avg)); 162 } 163 164 static void print_summary(void) 165 { 166 unsigned int wakeup_avg; 167 double waketime_avg, waketime_stddev; 168 169 waketime_avg = avg_stats(&waketime_stats); 170 waketime_stddev = stddev_stats(&waketime_stats); 171 wakeup_avg = avg_stats(&wakeup_stats); 172 173 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 174 wakeup_avg, 175 nblocked_threads, 176 waketime_avg / USEC_PER_MSEC, 177 rel_stddev_stats(waketime_stddev, waketime_avg)); 178 } 179 180 181 static void do_run_stats(struct thread_data *waking_worker) 182 { 183 unsigned int i; 184 185 for (i = 0; i < nwaking_threads; i++) { 186 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 187 update_stats(&wakeup_stats, waking_worker[i].nwoken); 188 } 189 190 } 191 192 static void toggle_done(int sig __maybe_unused, 193 siginfo_t *info __maybe_unused, 194 void *uc __maybe_unused) 195 { 196 done = true; 197 } 198 199 int bench_futex_wake_parallel(int argc, const char **argv, 200 const char *prefix __maybe_unused) 201 { 202 int ret = 0; 203 unsigned int i, j; 204 struct sigaction act; 205 pthread_attr_t thread_attr; 206 struct thread_data *waking_worker; 207 208 argc = parse_options(argc, argv, options, 209 bench_futex_wake_parallel_usage, 0); 210 if (argc) { 211 usage_with_options(bench_futex_wake_parallel_usage, options); 212 exit(EXIT_FAILURE); 213 } 214 215 sigfillset(&act.sa_mask); 216 act.sa_sigaction = toggle_done; 217 sigaction(SIGINT, &act, NULL); 218 219 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 220 if (!nblocked_threads) 221 nblocked_threads = ncpus; 222 223 /* some sanity checks */ 224 if (nwaking_threads > nblocked_threads || !nwaking_threads) 225 nwaking_threads = nblocked_threads; 226 227 if (nblocked_threads % nwaking_threads) 228 errx(EXIT_FAILURE, "Must be perfectly divisible"); 229 /* 230 * Each thread will wakeup nwakes tasks in 231 * a single futex_wait call. 232 */ 233 nwakes = nblocked_threads/nwaking_threads; 234 235 blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); 236 if (!blocked_worker) 237 err(EXIT_FAILURE, "calloc"); 238 239 if (!fshared) 240 futex_flag = FUTEX_PRIVATE_FLAG; 241 242 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 243 "futex %p), %d threads waking up %d at a time.\n\n", 244 getpid(), nblocked_threads, fshared ? "shared":"private", 245 &futex, nwaking_threads, nwakes); 246 247 init_stats(&wakeup_stats); 248 init_stats(&waketime_stats); 249 250 pthread_attr_init(&thread_attr); 251 pthread_mutex_init(&thread_lock, NULL); 252 pthread_cond_init(&thread_parent, NULL); 253 pthread_cond_init(&thread_worker, NULL); 254 255 for (j = 0; j < bench_repeat && !done; j++) { 256 waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); 257 if (!waking_worker) 258 err(EXIT_FAILURE, "calloc"); 259 260 /* create, launch & block all threads */ 261 block_threads(blocked_worker, thread_attr); 262 263 /* make sure all threads are already blocked */ 264 pthread_mutex_lock(&thread_lock); 265 while (threads_starting) 266 pthread_cond_wait(&thread_parent, &thread_lock); 267 pthread_cond_broadcast(&thread_worker); 268 pthread_mutex_unlock(&thread_lock); 269 270 usleep(100000); 271 272 /* Ok, all threads are patiently blocked, start waking folks up */ 273 wakeup_threads(waking_worker, thread_attr); 274 275 for (i = 0; i < nblocked_threads; i++) { 276 ret = pthread_join(blocked_worker[i], NULL); 277 if (ret) 278 err(EXIT_FAILURE, "pthread_join"); 279 } 280 281 do_run_stats(waking_worker); 282 if (!silent) 283 print_run(waking_worker, j); 284 285 free(waking_worker); 286 } 287 288 /* cleanup & report results */ 289 pthread_cond_destroy(&thread_parent); 290 pthread_cond_destroy(&thread_worker); 291 pthread_mutex_destroy(&thread_lock); 292 pthread_attr_destroy(&thread_attr); 293 294 print_summary(); 295 296 free(blocked_worker); 297 return ret; 298 } 299