Davidlohr Bueso | d65817b | 2015-05-08 11:37:59 -0700 | [diff] [blame] | 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" |
Josh Poimboeuf | 4b6ab94 | 2015-12-15 09:39:39 -0600 | [diff] [blame^] | 13 | #include <subcmd/parse-options.h> |
Davidlohr Bueso | d65817b | 2015-05-08 11:37:59 -0700 | [diff] [blame] | 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 | } |