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 #include "bench.h" 11 #include <linux/compiler.h> 12 #include "../util/debug.h" 13 #include "../util/mutex.h" 14 15 #ifndef HAVE_PTHREAD_BARRIER 16 int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused) 17 { 18 pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__); 19 return 0; 20 } 21 #else /* HAVE_PTHREAD_BARRIER */ 22 /* For the CLR_() macros */ 23 #include <string.h> 24 #include <pthread.h> 25 26 #include <signal.h> 27 #include "../util/stat.h" 28 #include <subcmd/parse-options.h> 29 #include <linux/kernel.h> 30 #include <linux/time64.h> 31 #include <errno.h> 32 #include "futex.h" 33 #include <perf/cpumap.h> 34 35 #include <err.h> 36 #include <stdlib.h> 37 #include <sys/time.h> 38 #include <sys/mman.h> 39 40 struct thread_data { 41 pthread_t worker; 42 unsigned int nwoken; 43 struct timeval runtime; 44 }; 45 46 static unsigned int nwakes = 1; 47 48 /* all threads will block on the same futex -- hash bucket chaos ;) */ 49 static u_int32_t futex = 0; 50 51 static pthread_t *blocked_worker; 52 static bool done = false; 53 static struct mutex thread_lock; 54 static struct cond thread_parent, thread_worker; 55 static pthread_barrier_t barrier; 56 static struct stats waketime_stats, wakeup_stats; 57 static unsigned int threads_starting; 58 static int futex_flag = 0; 59 60 static struct bench_futex_parameters params = { 61 .nbuckets = -1, 62 }; 63 64 static const struct option options[] = { 65 OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"), 66 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 67 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"), 68 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 69 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 70 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 71 72 OPT_END() 73 }; 74 75 static const char * const bench_futex_wake_parallel_usage[] = { 76 "perf bench futex wake-parallel <options>", 77 NULL 78 }; 79 80 static void *waking_workerfn(void *arg) 81 { 82 struct thread_data *waker = (struct thread_data *) arg; 83 struct timeval start, end; 84 85 pthread_barrier_wait(&barrier); 86 87 gettimeofday(&start, NULL); 88 89 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 90 if (waker->nwoken != nwakes) 91 warnx("couldn't wakeup all tasks (%d/%d)", 92 waker->nwoken, nwakes); 93 94 gettimeofday(&end, NULL); 95 timersub(&end, &start, &waker->runtime); 96 97 pthread_exit(NULL); 98 return NULL; 99 } 100 101 static void wakeup_threads(struct thread_data *td) 102 { 103 unsigned int i; 104 pthread_attr_t thread_attr; 105 106 pthread_attr_init(&thread_attr); 107 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 108 109 pthread_barrier_init(&barrier, NULL, params.nwakes + 1); 110 111 /* create and block all threads */ 112 for (i = 0; i < params.nwakes; i++) { 113 /* 114 * Thread creation order will impact per-thread latency 115 * as it will affect the order to acquire the hb spinlock. 116 * For now let the scheduler decide. 117 */ 118 if (pthread_create(&td[i].worker, &thread_attr, 119 waking_workerfn, (void *)&td[i])) 120 err(EXIT_FAILURE, "pthread_create"); 121 } 122 123 pthread_barrier_wait(&barrier); 124 125 for (i = 0; i < params.nwakes; i++) 126 if (pthread_join(td[i].worker, NULL)) 127 err(EXIT_FAILURE, "pthread_join"); 128 129 pthread_barrier_destroy(&barrier); 130 pthread_attr_destroy(&thread_attr); 131 } 132 133 static void *blocked_workerfn(void *arg __maybe_unused) 134 { 135 mutex_lock(&thread_lock); 136 threads_starting--; 137 if (!threads_starting) 138 cond_signal(&thread_parent); 139 cond_wait(&thread_worker, &thread_lock); 140 mutex_unlock(&thread_lock); 141 142 while (1) { /* handle spurious wakeups */ 143 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 144 break; 145 } 146 147 pthread_exit(NULL); 148 return NULL; 149 } 150 151 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu) 152 { 153 cpu_set_t *cpuset; 154 unsigned int i; 155 int nrcpus = cpu__max_cpu().cpu; 156 size_t size; 157 158 threads_starting = params.nthreads; 159 160 cpuset = CPU_ALLOC(nrcpus); 161 BUG_ON(!cpuset); 162 size = CPU_ALLOC_SIZE(nrcpus); 163 164 /* create and block all threads */ 165 for (i = 0; i < params.nthreads; i++) { 166 pthread_attr_t thread_attr; 167 168 pthread_attr_init(&thread_attr); 169 CPU_ZERO_S(size, cpuset); 170 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 171 172 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 173 CPU_FREE(cpuset); 174 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 175 } 176 177 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) { 178 CPU_FREE(cpuset); 179 err(EXIT_FAILURE, "pthread_create"); 180 } 181 pthread_attr_destroy(&thread_attr); 182 } 183 CPU_FREE(cpuset); 184 } 185 186 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 187 { 188 unsigned int i, wakeup_avg; 189 double waketime_avg, waketime_stddev; 190 struct stats __waketime_stats, __wakeup_stats; 191 192 init_stats(&__wakeup_stats); 193 init_stats(&__waketime_stats); 194 195 for (i = 0; i < params.nwakes; i++) { 196 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 197 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 198 } 199 200 waketime_avg = avg_stats(&__waketime_stats); 201 waketime_stddev = stddev_stats(&__waketime_stats); 202 wakeup_avg = avg_stats(&__wakeup_stats); 203 204 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 205 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 206 params.nthreads, waketime_avg / USEC_PER_MSEC, 207 rel_stddev_stats(waketime_stddev, waketime_avg)); 208 } 209 210 static void print_summary(void) 211 { 212 unsigned int wakeup_avg; 213 double waketime_avg, waketime_stddev; 214 215 waketime_avg = avg_stats(&waketime_stats); 216 waketime_stddev = stddev_stats(&waketime_stats); 217 wakeup_avg = avg_stats(&wakeup_stats); 218 219 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 220 wakeup_avg, 221 params.nthreads, 222 waketime_avg / USEC_PER_MSEC, 223 rel_stddev_stats(waketime_stddev, waketime_avg)); 224 futex_print_nbuckets(¶ms); 225 } 226 227 228 static void do_run_stats(struct thread_data *waking_worker) 229 { 230 unsigned int i; 231 232 for (i = 0; i < params.nwakes; i++) { 233 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 234 update_stats(&wakeup_stats, waking_worker[i].nwoken); 235 } 236 237 } 238 239 static void toggle_done(int sig __maybe_unused, 240 siginfo_t *info __maybe_unused, 241 void *uc __maybe_unused) 242 { 243 done = true; 244 } 245 246 int bench_futex_wake_parallel(int argc, const char **argv) 247 { 248 int ret = 0; 249 unsigned int i, j; 250 struct sigaction act; 251 struct thread_data *waking_worker; 252 struct perf_cpu_map *cpu; 253 254 argc = parse_options(argc, argv, options, 255 bench_futex_wake_parallel_usage, 0); 256 if (argc) { 257 usage_with_options(bench_futex_wake_parallel_usage, options); 258 exit(EXIT_FAILURE); 259 } 260 261 memset(&act, 0, sizeof(act)); 262 sigfillset(&act.sa_mask); 263 act.sa_sigaction = toggle_done; 264 sigaction(SIGINT, &act, NULL); 265 266 if (params.mlockall) { 267 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 268 err(EXIT_FAILURE, "mlockall"); 269 } 270 271 cpu = perf_cpu_map__new_online_cpus(); 272 if (!cpu) 273 err(EXIT_FAILURE, "calloc"); 274 275 if (!params.nthreads) 276 params.nthreads = perf_cpu_map__nr(cpu); 277 278 /* some sanity checks */ 279 if (params.nwakes > params.nthreads || 280 !params.nwakes) 281 params.nwakes = params.nthreads; 282 283 if (params.nthreads % params.nwakes) 284 errx(EXIT_FAILURE, "Must be perfectly divisible"); 285 /* 286 * Each thread will wakeup nwakes tasks in 287 * a single futex_wait call. 288 */ 289 nwakes = params.nthreads/params.nwakes; 290 291 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker)); 292 if (!blocked_worker) 293 err(EXIT_FAILURE, "calloc"); 294 295 if (!params.fshared) 296 futex_flag = FUTEX_PRIVATE_FLAG; 297 298 futex_set_nbuckets_param(¶ms); 299 300 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 301 "futex %p), %d threads waking up %d at a time.\n\n", 302 getpid(), params.nthreads, params.fshared ? "shared":"private", 303 &futex, params.nwakes, nwakes); 304 305 init_stats(&wakeup_stats); 306 init_stats(&waketime_stats); 307 308 mutex_init(&thread_lock); 309 cond_init(&thread_parent); 310 cond_init(&thread_worker); 311 312 for (j = 0; j < bench_repeat && !done; j++) { 313 waking_worker = calloc(params.nwakes, sizeof(*waking_worker)); 314 if (!waking_worker) 315 err(EXIT_FAILURE, "calloc"); 316 317 /* create, launch & block all threads */ 318 block_threads(blocked_worker, cpu); 319 320 /* make sure all threads are already blocked */ 321 mutex_lock(&thread_lock); 322 while (threads_starting) 323 cond_wait(&thread_parent, &thread_lock); 324 cond_broadcast(&thread_worker); 325 mutex_unlock(&thread_lock); 326 327 usleep(200000); 328 329 /* Ok, all threads are patiently blocked, start waking folks up */ 330 wakeup_threads(waking_worker); 331 332 for (i = 0; i < params.nthreads; i++) { 333 ret = pthread_join(blocked_worker[i], NULL); 334 if (ret) 335 err(EXIT_FAILURE, "pthread_join"); 336 } 337 338 do_run_stats(waking_worker); 339 if (!params.silent) 340 print_run(waking_worker, j); 341 342 free(waking_worker); 343 } 344 345 /* cleanup & report results */ 346 cond_destroy(&thread_parent); 347 cond_destroy(&thread_worker); 348 mutex_destroy(&thread_lock); 349 350 print_summary(); 351 352 free(blocked_worker); 353 perf_cpu_map__put(cpu); 354 return ret; 355 } 356 #endif /* HAVE_PTHREAD_BARRIER */ 357