1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2015 Davidlohr Bueso. 4 * 5 * Block a bunch of threads and let parallel waker threads wakeup an 6 * equal amount of them. The program output reflects the avg latency 7 * for each individual thread to service its share of work. Ultimately 8 * it can be used to measure futex_wake() changes. 9 */ 10 11 /* For the CLR_() macros */ 12 #include <string.h> 13 #include <pthread.h> 14 15 #include <signal.h> 16 #include "../util/stat.h" 17 #include <subcmd/parse-options.h> 18 #include <linux/compiler.h> 19 #include <linux/kernel.h> 20 #include <linux/time64.h> 21 #include <errno.h> 22 #include "bench.h" 23 #include "futex.h" 24 25 #include <err.h> 26 #include <stdlib.h> 27 #include <sys/time.h> 28 29 struct thread_data { 30 pthread_t worker; 31 unsigned int nwoken; 32 struct timeval runtime; 33 }; 34 35 static unsigned int nwakes = 1; 36 37 /* all threads will block on the same futex -- hash bucket chaos ;) */ 38 static u_int32_t futex = 0; 39 40 static pthread_t *blocked_worker; 41 static bool done = false, silent = false, fshared = false; 42 static unsigned int nblocked_threads = 0, nwaking_threads = 0; 43 static pthread_mutex_t thread_lock; 44 static pthread_cond_t thread_parent, thread_worker; 45 static struct stats waketime_stats, wakeup_stats; 46 static unsigned int ncpus, threads_starting; 47 static int futex_flag = 0; 48 49 static const struct option options[] = { 50 OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"), 51 OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"), 52 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), 53 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), 54 OPT_END() 55 }; 56 57 static const char * const bench_futex_wake_parallel_usage[] = { 58 "perf bench futex wake-parallel <options>", 59 NULL 60 }; 61 62 static void *waking_workerfn(void *arg) 63 { 64 struct thread_data *waker = (struct thread_data *) arg; 65 struct timeval start, end; 66 67 gettimeofday(&start, NULL); 68 69 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 70 if (waker->nwoken != nwakes) 71 warnx("couldn't wakeup all tasks (%d/%d)", 72 waker->nwoken, nwakes); 73 74 gettimeofday(&end, NULL); 75 timersub(&end, &start, &waker->runtime); 76 77 pthread_exit(NULL); 78 return NULL; 79 } 80 81 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) 82 { 83 unsigned int i; 84 85 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 86 87 /* create and block all threads */ 88 for (i = 0; i < nwaking_threads; i++) { 89 /* 90 * Thread creation order will impact per-thread latency 91 * as it will affect the order to acquire the hb spinlock. 92 * For now let the scheduler decide. 93 */ 94 if (pthread_create(&td[i].worker, &thread_attr, 95 waking_workerfn, (void *)&td[i])) 96 err(EXIT_FAILURE, "pthread_create"); 97 } 98 99 for (i = 0; i < nwaking_threads; i++) 100 if (pthread_join(td[i].worker, NULL)) 101 err(EXIT_FAILURE, "pthread_join"); 102 } 103 104 static void *blocked_workerfn(void *arg __maybe_unused) 105 { 106 pthread_mutex_lock(&thread_lock); 107 threads_starting--; 108 if (!threads_starting) 109 pthread_cond_signal(&thread_parent); 110 pthread_cond_wait(&thread_worker, &thread_lock); 111 pthread_mutex_unlock(&thread_lock); 112 113 while (1) { /* handle spurious wakeups */ 114 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 115 break; 116 } 117 118 pthread_exit(NULL); 119 return NULL; 120 } 121 122 static void block_threads(pthread_t *w, pthread_attr_t thread_attr) 123 { 124 cpu_set_t cpu; 125 unsigned int i; 126 127 threads_starting = nblocked_threads; 128 129 /* create and block all threads */ 130 for (i = 0; i < nblocked_threads; i++) { 131 CPU_ZERO(&cpu); 132 CPU_SET(i % ncpus, &cpu); 133 134 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) 135 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 136 137 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) 138 err(EXIT_FAILURE, "pthread_create"); 139 } 140 } 141 142 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 143 { 144 unsigned int i, wakeup_avg; 145 double waketime_avg, waketime_stddev; 146 struct stats __waketime_stats, __wakeup_stats; 147 148 init_stats(&__wakeup_stats); 149 init_stats(&__waketime_stats); 150 151 for (i = 0; i < nwaking_threads; i++) { 152 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 153 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 154 } 155 156 waketime_avg = avg_stats(&__waketime_stats); 157 waketime_stddev = stddev_stats(&__waketime_stats); 158 wakeup_avg = avg_stats(&__wakeup_stats); 159 160 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 161 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 162 nblocked_threads, waketime_avg / USEC_PER_MSEC, 163 rel_stddev_stats(waketime_stddev, waketime_avg)); 164 } 165 166 static void print_summary(void) 167 { 168 unsigned int wakeup_avg; 169 double waketime_avg, waketime_stddev; 170 171 waketime_avg = avg_stats(&waketime_stats); 172 waketime_stddev = stddev_stats(&waketime_stats); 173 wakeup_avg = avg_stats(&wakeup_stats); 174 175 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 176 wakeup_avg, 177 nblocked_threads, 178 waketime_avg / USEC_PER_MSEC, 179 rel_stddev_stats(waketime_stddev, waketime_avg)); 180 } 181 182 183 static void do_run_stats(struct thread_data *waking_worker) 184 { 185 unsigned int i; 186 187 for (i = 0; i < nwaking_threads; i++) { 188 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 189 update_stats(&wakeup_stats, waking_worker[i].nwoken); 190 } 191 192 } 193 194 static void toggle_done(int sig __maybe_unused, 195 siginfo_t *info __maybe_unused, 196 void *uc __maybe_unused) 197 { 198 done = true; 199 } 200 201 int bench_futex_wake_parallel(int argc, const char **argv) 202 { 203 int ret = 0; 204 unsigned int i, j; 205 struct sigaction act; 206 pthread_attr_t thread_attr; 207 struct thread_data *waking_worker; 208 209 argc = parse_options(argc, argv, options, 210 bench_futex_wake_parallel_usage, 0); 211 if (argc) { 212 usage_with_options(bench_futex_wake_parallel_usage, options); 213 exit(EXIT_FAILURE); 214 } 215 216 sigfillset(&act.sa_mask); 217 act.sa_sigaction = toggle_done; 218 sigaction(SIGINT, &act, NULL); 219 220 ncpus = sysconf(_SC_NPROCESSORS_ONLN); 221 if (!nblocked_threads) 222 nblocked_threads = ncpus; 223 224 /* some sanity checks */ 225 if (nwaking_threads > nblocked_threads || !nwaking_threads) 226 nwaking_threads = nblocked_threads; 227 228 if (nblocked_threads % nwaking_threads) 229 errx(EXIT_FAILURE, "Must be perfectly divisible"); 230 /* 231 * Each thread will wakeup nwakes tasks in 232 * a single futex_wait call. 233 */ 234 nwakes = nblocked_threads/nwaking_threads; 235 236 blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); 237 if (!blocked_worker) 238 err(EXIT_FAILURE, "calloc"); 239 240 if (!fshared) 241 futex_flag = FUTEX_PRIVATE_FLAG; 242 243 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 244 "futex %p), %d threads waking up %d at a time.\n\n", 245 getpid(), nblocked_threads, fshared ? "shared":"private", 246 &futex, nwaking_threads, nwakes); 247 248 init_stats(&wakeup_stats); 249 init_stats(&waketime_stats); 250 251 pthread_attr_init(&thread_attr); 252 pthread_mutex_init(&thread_lock, NULL); 253 pthread_cond_init(&thread_parent, NULL); 254 pthread_cond_init(&thread_worker, NULL); 255 256 for (j = 0; j < bench_repeat && !done; j++) { 257 waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); 258 if (!waking_worker) 259 err(EXIT_FAILURE, "calloc"); 260 261 /* create, launch & block all threads */ 262 block_threads(blocked_worker, thread_attr); 263 264 /* make sure all threads are already blocked */ 265 pthread_mutex_lock(&thread_lock); 266 while (threads_starting) 267 pthread_cond_wait(&thread_parent, &thread_lock); 268 pthread_cond_broadcast(&thread_worker); 269 pthread_mutex_unlock(&thread_lock); 270 271 usleep(100000); 272 273 /* Ok, all threads are patiently blocked, start waking folks up */ 274 wakeup_threads(waking_worker, thread_attr); 275 276 for (i = 0; i < nblocked_threads; i++) { 277 ret = pthread_join(blocked_worker[i], NULL); 278 if (ret) 279 err(EXIT_FAILURE, "pthread_join"); 280 } 281 282 do_run_stats(waking_worker); 283 if (!silent) 284 print_run(waking_worker, j); 285 286 free(waking_worker); 287 } 288 289 /* cleanup & report results */ 290 pthread_cond_destroy(&thread_parent); 291 pthread_cond_destroy(&thread_worker); 292 pthread_mutex_destroy(&thread_lock); 293 pthread_attr_destroy(&thread_attr); 294 295 print_summary(); 296 297 free(blocked_worker); 298 return ret; 299 } 300