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 14 #ifndef HAVE_PTHREAD_BARRIER 15 int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused) 16 { 17 pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__); 18 return 0; 19 } 20 #else /* HAVE_PTHREAD_BARRIER */ 21 /* For the CLR_() macros */ 22 #include <string.h> 23 #include <pthread.h> 24 25 #include <signal.h> 26 #include "../util/stat.h" 27 #include <subcmd/parse-options.h> 28 #include <linux/kernel.h> 29 #include <linux/time64.h> 30 #include <errno.h> 31 #include "futex.h" 32 #include <perf/cpumap.h> 33 34 #include <err.h> 35 #include <stdlib.h> 36 #include <sys/time.h> 37 #include <sys/mman.h> 38 39 struct thread_data { 40 pthread_t worker; 41 unsigned int nwoken; 42 struct timeval runtime; 43 }; 44 45 static unsigned int nwakes = 1; 46 47 /* all threads will block on the same futex -- hash bucket chaos ;) */ 48 static u_int32_t futex = 0; 49 50 static pthread_t *blocked_worker; 51 static bool done = false; 52 static pthread_mutex_t thread_lock; 53 static pthread_cond_t thread_parent, thread_worker; 54 static pthread_barrier_t barrier; 55 static struct stats waketime_stats, wakeup_stats; 56 static unsigned int threads_starting; 57 static int futex_flag = 0; 58 59 static struct bench_futex_parameters params; 60 61 static const struct option options[] = { 62 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 63 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"), 64 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 65 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 66 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 67 68 OPT_END() 69 }; 70 71 static const char * const bench_futex_wake_parallel_usage[] = { 72 "perf bench futex wake-parallel <options>", 73 NULL 74 }; 75 76 static void *waking_workerfn(void *arg) 77 { 78 struct thread_data *waker = (struct thread_data *) arg; 79 struct timeval start, end; 80 81 pthread_barrier_wait(&barrier); 82 83 gettimeofday(&start, NULL); 84 85 waker->nwoken = futex_wake(&futex, nwakes, futex_flag); 86 if (waker->nwoken != nwakes) 87 warnx("couldn't wakeup all tasks (%d/%d)", 88 waker->nwoken, nwakes); 89 90 gettimeofday(&end, NULL); 91 timersub(&end, &start, &waker->runtime); 92 93 pthread_exit(NULL); 94 return NULL; 95 } 96 97 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) 98 { 99 unsigned int i; 100 101 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 102 103 pthread_barrier_init(&barrier, NULL, params.nwakes + 1); 104 105 /* create and block all threads */ 106 for (i = 0; i < params.nwakes; i++) { 107 /* 108 * Thread creation order will impact per-thread latency 109 * as it will affect the order to acquire the hb spinlock. 110 * For now let the scheduler decide. 111 */ 112 if (pthread_create(&td[i].worker, &thread_attr, 113 waking_workerfn, (void *)&td[i])) 114 err(EXIT_FAILURE, "pthread_create"); 115 } 116 117 pthread_barrier_wait(&barrier); 118 119 for (i = 0; i < params.nwakes; i++) 120 if (pthread_join(td[i].worker, NULL)) 121 err(EXIT_FAILURE, "pthread_join"); 122 123 pthread_barrier_destroy(&barrier); 124 } 125 126 static void *blocked_workerfn(void *arg __maybe_unused) 127 { 128 pthread_mutex_lock(&thread_lock); 129 threads_starting--; 130 if (!threads_starting) 131 pthread_cond_signal(&thread_parent); 132 pthread_cond_wait(&thread_worker, &thread_lock); 133 pthread_mutex_unlock(&thread_lock); 134 135 while (1) { /* handle spurious wakeups */ 136 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 137 break; 138 } 139 140 pthread_exit(NULL); 141 return NULL; 142 } 143 144 static void block_threads(pthread_t *w, pthread_attr_t thread_attr, 145 struct perf_cpu_map *cpu) 146 { 147 cpu_set_t *cpuset; 148 unsigned int i; 149 int nrcpus = perf_cpu_map__nr(cpu); 150 size_t size; 151 152 threads_starting = params.nthreads; 153 154 cpuset = CPU_ALLOC(nrcpus); 155 BUG_ON(!cpuset); 156 size = CPU_ALLOC_SIZE(nrcpus); 157 158 /* create and block all threads */ 159 for (i = 0; i < params.nthreads; i++) { 160 CPU_ZERO_S(size, cpuset); 161 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 162 163 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 164 CPU_FREE(cpuset); 165 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 166 } 167 168 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) { 169 CPU_FREE(cpuset); 170 err(EXIT_FAILURE, "pthread_create"); 171 } 172 } 173 CPU_FREE(cpuset); 174 } 175 176 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 177 { 178 unsigned int i, wakeup_avg; 179 double waketime_avg, waketime_stddev; 180 struct stats __waketime_stats, __wakeup_stats; 181 182 init_stats(&__wakeup_stats); 183 init_stats(&__waketime_stats); 184 185 for (i = 0; i < params.nwakes; i++) { 186 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 187 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 188 } 189 190 waketime_avg = avg_stats(&__waketime_stats); 191 waketime_stddev = stddev_stats(&__waketime_stats); 192 wakeup_avg = avg_stats(&__wakeup_stats); 193 194 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 195 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 196 params.nthreads, waketime_avg / USEC_PER_MSEC, 197 rel_stddev_stats(waketime_stddev, waketime_avg)); 198 } 199 200 static void print_summary(void) 201 { 202 unsigned int wakeup_avg; 203 double waketime_avg, waketime_stddev; 204 205 waketime_avg = avg_stats(&waketime_stats); 206 waketime_stddev = stddev_stats(&waketime_stats); 207 wakeup_avg = avg_stats(&wakeup_stats); 208 209 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 210 wakeup_avg, 211 params.nthreads, 212 waketime_avg / USEC_PER_MSEC, 213 rel_stddev_stats(waketime_stddev, waketime_avg)); 214 } 215 216 217 static void do_run_stats(struct thread_data *waking_worker) 218 { 219 unsigned int i; 220 221 for (i = 0; i < params.nwakes; i++) { 222 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 223 update_stats(&wakeup_stats, waking_worker[i].nwoken); 224 } 225 226 } 227 228 static void toggle_done(int sig __maybe_unused, 229 siginfo_t *info __maybe_unused, 230 void *uc __maybe_unused) 231 { 232 done = true; 233 } 234 235 int bench_futex_wake_parallel(int argc, const char **argv) 236 { 237 int ret = 0; 238 unsigned int i, j; 239 struct sigaction act; 240 pthread_attr_t thread_attr; 241 struct thread_data *waking_worker; 242 struct perf_cpu_map *cpu; 243 244 argc = parse_options(argc, argv, options, 245 bench_futex_wake_parallel_usage, 0); 246 if (argc) { 247 usage_with_options(bench_futex_wake_parallel_usage, options); 248 exit(EXIT_FAILURE); 249 } 250 251 memset(&act, 0, sizeof(act)); 252 sigfillset(&act.sa_mask); 253 act.sa_sigaction = toggle_done; 254 sigaction(SIGINT, &act, NULL); 255 256 if (params.mlockall) { 257 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 258 err(EXIT_FAILURE, "mlockall"); 259 } 260 261 cpu = perf_cpu_map__new(NULL); 262 if (!cpu) 263 err(EXIT_FAILURE, "calloc"); 264 265 if (!params.nthreads) 266 params.nthreads = perf_cpu_map__nr(cpu); 267 268 /* some sanity checks */ 269 if (params.nwakes > params.nthreads || 270 !params.nwakes) 271 params.nwakes = params.nthreads; 272 273 if (params.nthreads % params.nwakes) 274 errx(EXIT_FAILURE, "Must be perfectly divisible"); 275 /* 276 * Each thread will wakeup nwakes tasks in 277 * a single futex_wait call. 278 */ 279 nwakes = params.nthreads/params.nwakes; 280 281 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker)); 282 if (!blocked_worker) 283 err(EXIT_FAILURE, "calloc"); 284 285 if (!params.fshared) 286 futex_flag = FUTEX_PRIVATE_FLAG; 287 288 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 289 "futex %p), %d threads waking up %d at a time.\n\n", 290 getpid(), params.nthreads, params.fshared ? "shared":"private", 291 &futex, params.nwakes, nwakes); 292 293 init_stats(&wakeup_stats); 294 init_stats(&waketime_stats); 295 296 pthread_attr_init(&thread_attr); 297 pthread_mutex_init(&thread_lock, NULL); 298 pthread_cond_init(&thread_parent, NULL); 299 pthread_cond_init(&thread_worker, NULL); 300 301 for (j = 0; j < bench_repeat && !done; j++) { 302 waking_worker = calloc(params.nwakes, sizeof(*waking_worker)); 303 if (!waking_worker) 304 err(EXIT_FAILURE, "calloc"); 305 306 /* create, launch & block all threads */ 307 block_threads(blocked_worker, thread_attr, cpu); 308 309 /* make sure all threads are already blocked */ 310 pthread_mutex_lock(&thread_lock); 311 while (threads_starting) 312 pthread_cond_wait(&thread_parent, &thread_lock); 313 pthread_cond_broadcast(&thread_worker); 314 pthread_mutex_unlock(&thread_lock); 315 316 usleep(100000); 317 318 /* Ok, all threads are patiently blocked, start waking folks up */ 319 wakeup_threads(waking_worker, thread_attr); 320 321 for (i = 0; i < params.nthreads; i++) { 322 ret = pthread_join(blocked_worker[i], NULL); 323 if (ret) 324 err(EXIT_FAILURE, "pthread_join"); 325 } 326 327 do_run_stats(waking_worker); 328 if (!params.silent) 329 print_run(waking_worker, j); 330 331 free(waking_worker); 332 } 333 334 /* cleanup & report results */ 335 pthread_cond_destroy(&thread_parent); 336 pthread_cond_destroy(&thread_worker); 337 pthread_mutex_destroy(&thread_lock); 338 pthread_attr_destroy(&thread_attr); 339 340 print_summary(); 341 342 free(blocked_worker); 343 perf_cpu_map__put(cpu); 344 return ret; 345 } 346 #endif /* HAVE_PTHREAD_BARRIER */ 347