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 62 static const struct option options[] = { 63 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 64 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"), 65 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 66 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 67 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 68 69 OPT_END() 70 }; 71 72 static const char * const bench_futex_wake_parallel_usage[] = { 73 "perf bench futex wake-parallel <options>", 74 NULL 75 }; 76 77 static void *waking_workerfn(void *arg) 78 { 79 struct thread_data *waker = (struct thread_data *) arg; 80 struct timeval start, end; 81 82 pthread_barrier_wait(&barrier); 83 84 gettimeofday(&start, NULL); 85 86 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 87 if (waker->nwoken != nwakes) 88 warnx("couldn't wakeup all tasks (%d/%d)", 89 waker->nwoken, nwakes); 90 91 gettimeofday(&end, NULL); 92 timersub(&end, &start, &waker->runtime); 93 94 pthread_exit(NULL); 95 return NULL; 96 } 97 98 static void wakeup_threads(struct thread_data *td) 99 { 100 unsigned int i; 101 pthread_attr_t thread_attr; 102 103 pthread_attr_init(&thread_attr); 104 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 105 106 pthread_barrier_init(&barrier, NULL, params.nwakes + 1); 107 108 /* create and block all threads */ 109 for (i = 0; i < params.nwakes; i++) { 110 /* 111 * Thread creation order will impact per-thread latency 112 * as it will affect the order to acquire the hb spinlock. 113 * For now let the scheduler decide. 114 */ 115 if (pthread_create(&td[i].worker, &thread_attr, 116 waking_workerfn, (void *)&td[i])) 117 err(EXIT_FAILURE, "pthread_create"); 118 } 119 120 pthread_barrier_wait(&barrier); 121 122 for (i = 0; i < params.nwakes; i++) 123 if (pthread_join(td[i].worker, NULL)) 124 err(EXIT_FAILURE, "pthread_join"); 125 126 pthread_barrier_destroy(&barrier); 127 pthread_attr_destroy(&thread_attr); 128 } 129 130 static void *blocked_workerfn(void *arg __maybe_unused) 131 { 132 mutex_lock(&thread_lock); 133 threads_starting--; 134 if (!threads_starting) 135 cond_signal(&thread_parent); 136 cond_wait(&thread_worker, &thread_lock); 137 mutex_unlock(&thread_lock); 138 139 while (1) { /* handle spurious wakeups */ 140 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 141 break; 142 } 143 144 pthread_exit(NULL); 145 return NULL; 146 } 147 148 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu) 149 { 150 cpu_set_t *cpuset; 151 unsigned int i; 152 int nrcpus = perf_cpu_map__nr(cpu); 153 size_t size; 154 155 threads_starting = params.nthreads; 156 157 cpuset = CPU_ALLOC(nrcpus); 158 BUG_ON(!cpuset); 159 size = CPU_ALLOC_SIZE(nrcpus); 160 161 /* create and block all threads */ 162 for (i = 0; i < params.nthreads; i++) { 163 pthread_attr_t thread_attr; 164 165 pthread_attr_init(&thread_attr); 166 CPU_ZERO_S(size, cpuset); 167 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 168 169 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 170 CPU_FREE(cpuset); 171 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 172 } 173 174 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) { 175 CPU_FREE(cpuset); 176 err(EXIT_FAILURE, "pthread_create"); 177 } 178 pthread_attr_destroy(&thread_attr); 179 } 180 CPU_FREE(cpuset); 181 } 182 183 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 184 { 185 unsigned int i, wakeup_avg; 186 double waketime_avg, waketime_stddev; 187 struct stats __waketime_stats, __wakeup_stats; 188 189 init_stats(&__wakeup_stats); 190 init_stats(&__waketime_stats); 191 192 for (i = 0; i < params.nwakes; i++) { 193 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 194 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 195 } 196 197 waketime_avg = avg_stats(&__waketime_stats); 198 waketime_stddev = stddev_stats(&__waketime_stats); 199 wakeup_avg = avg_stats(&__wakeup_stats); 200 201 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 202 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 203 params.nthreads, waketime_avg / USEC_PER_MSEC, 204 rel_stddev_stats(waketime_stddev, waketime_avg)); 205 } 206 207 static void print_summary(void) 208 { 209 unsigned int wakeup_avg; 210 double waketime_avg, waketime_stddev; 211 212 waketime_avg = avg_stats(&waketime_stats); 213 waketime_stddev = stddev_stats(&waketime_stats); 214 wakeup_avg = avg_stats(&wakeup_stats); 215 216 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 217 wakeup_avg, 218 params.nthreads, 219 waketime_avg / USEC_PER_MSEC, 220 rel_stddev_stats(waketime_stddev, waketime_avg)); 221 } 222 223 224 static void do_run_stats(struct thread_data *waking_worker) 225 { 226 unsigned int i; 227 228 for (i = 0; i < params.nwakes; i++) { 229 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 230 update_stats(&wakeup_stats, waking_worker[i].nwoken); 231 } 232 233 } 234 235 static void toggle_done(int sig __maybe_unused, 236 siginfo_t *info __maybe_unused, 237 void *uc __maybe_unused) 238 { 239 done = true; 240 } 241 242 int bench_futex_wake_parallel(int argc, const char **argv) 243 { 244 int ret = 0; 245 unsigned int i, j; 246 struct sigaction act; 247 struct thread_data *waking_worker; 248 struct perf_cpu_map *cpu; 249 250 argc = parse_options(argc, argv, options, 251 bench_futex_wake_parallel_usage, 0); 252 if (argc) { 253 usage_with_options(bench_futex_wake_parallel_usage, options); 254 exit(EXIT_FAILURE); 255 } 256 257 memset(&act, 0, sizeof(act)); 258 sigfillset(&act.sa_mask); 259 act.sa_sigaction = toggle_done; 260 sigaction(SIGINT, &act, NULL); 261 262 if (params.mlockall) { 263 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 264 err(EXIT_FAILURE, "mlockall"); 265 } 266 267 cpu = perf_cpu_map__new(NULL); 268 if (!cpu) 269 err(EXIT_FAILURE, "calloc"); 270 271 if (!params.nthreads) 272 params.nthreads = perf_cpu_map__nr(cpu); 273 274 /* some sanity checks */ 275 if (params.nwakes > params.nthreads || 276 !params.nwakes) 277 params.nwakes = params.nthreads; 278 279 if (params.nthreads % params.nwakes) 280 errx(EXIT_FAILURE, "Must be perfectly divisible"); 281 /* 282 * Each thread will wakeup nwakes tasks in 283 * a single futex_wait call. 284 */ 285 nwakes = params.nthreads/params.nwakes; 286 287 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker)); 288 if (!blocked_worker) 289 err(EXIT_FAILURE, "calloc"); 290 291 if (!params.fshared) 292 futex_flag = FUTEX_PRIVATE_FLAG; 293 294 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 295 "futex %p), %d threads waking up %d at a time.\n\n", 296 getpid(), params.nthreads, params.fshared ? "shared":"private", 297 &futex, params.nwakes, nwakes); 298 299 init_stats(&wakeup_stats); 300 init_stats(&waketime_stats); 301 302 mutex_init(&thread_lock); 303 cond_init(&thread_parent); 304 cond_init(&thread_worker); 305 306 for (j = 0; j < bench_repeat && !done; j++) { 307 waking_worker = calloc(params.nwakes, sizeof(*waking_worker)); 308 if (!waking_worker) 309 err(EXIT_FAILURE, "calloc"); 310 311 /* create, launch & block all threads */ 312 block_threads(blocked_worker, cpu); 313 314 /* make sure all threads are already blocked */ 315 mutex_lock(&thread_lock); 316 while (threads_starting) 317 cond_wait(&thread_parent, &thread_lock); 318 cond_broadcast(&thread_worker); 319 mutex_unlock(&thread_lock); 320 321 usleep(100000); 322 323 /* Ok, all threads are patiently blocked, start waking folks up */ 324 wakeup_threads(waking_worker); 325 326 for (i = 0; i < params.nthreads; i++) { 327 ret = pthread_join(blocked_worker[i], NULL); 328 if (ret) 329 err(EXIT_FAILURE, "pthread_join"); 330 } 331 332 do_run_stats(waking_worker); 333 if (!params.silent) 334 print_run(waking_worker, j); 335 336 free(waking_worker); 337 } 338 339 /* cleanup & report results */ 340 cond_destroy(&thread_parent); 341 cond_destroy(&thread_worker); 342 mutex_destroy(&thread_lock); 343 344 print_summary(); 345 346 free(blocked_worker); 347 perf_cpu_map__put(cpu); 348 return ret; 349 } 350 #endif /* HAVE_PTHREAD_BARRIER */ 351