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, pthread_attr_t thread_attr) 99 { 100 unsigned int i; 101 102 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); 103 104 pthread_barrier_init(&barrier, NULL, params.nwakes + 1); 105 106 /* create and block all threads */ 107 for (i = 0; i < params.nwakes; i++) { 108 /* 109 * Thread creation order will impact per-thread latency 110 * as it will affect the order to acquire the hb spinlock. 111 * For now let the scheduler decide. 112 */ 113 if (pthread_create(&td[i].worker, &thread_attr, 114 waking_workerfn, (void *)&td[i])) 115 err(EXIT_FAILURE, "pthread_create"); 116 } 117 118 pthread_barrier_wait(&barrier); 119 120 for (i = 0; i < params.nwakes; i++) 121 if (pthread_join(td[i].worker, NULL)) 122 err(EXIT_FAILURE, "pthread_join"); 123 124 pthread_barrier_destroy(&barrier); 125 } 126 127 static void *blocked_workerfn(void *arg __maybe_unused) 128 { 129 mutex_lock(&thread_lock); 130 threads_starting--; 131 if (!threads_starting) 132 cond_signal(&thread_parent); 133 cond_wait(&thread_worker, &thread_lock); 134 mutex_unlock(&thread_lock); 135 136 while (1) { /* handle spurious wakeups */ 137 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) 138 break; 139 } 140 141 pthread_exit(NULL); 142 return NULL; 143 } 144 145 static void block_threads(pthread_t *w, pthread_attr_t thread_attr, 146 struct perf_cpu_map *cpu) 147 { 148 cpu_set_t *cpuset; 149 unsigned int i; 150 int nrcpus = perf_cpu_map__nr(cpu); 151 size_t size; 152 153 threads_starting = params.nthreads; 154 155 cpuset = CPU_ALLOC(nrcpus); 156 BUG_ON(!cpuset); 157 size = CPU_ALLOC_SIZE(nrcpus); 158 159 /* create and block all threads */ 160 for (i = 0; i < params.nthreads; i++) { 161 CPU_ZERO_S(size, cpuset); 162 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 163 164 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 165 CPU_FREE(cpuset); 166 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 167 } 168 169 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) { 170 CPU_FREE(cpuset); 171 err(EXIT_FAILURE, "pthread_create"); 172 } 173 } 174 CPU_FREE(cpuset); 175 } 176 177 static void print_run(struct thread_data *waking_worker, unsigned int run_num) 178 { 179 unsigned int i, wakeup_avg; 180 double waketime_avg, waketime_stddev; 181 struct stats __waketime_stats, __wakeup_stats; 182 183 init_stats(&__wakeup_stats); 184 init_stats(&__waketime_stats); 185 186 for (i = 0; i < params.nwakes; i++) { 187 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); 188 update_stats(&__wakeup_stats, waking_worker[i].nwoken); 189 } 190 191 waketime_avg = avg_stats(&__waketime_stats); 192 waketime_stddev = stddev_stats(&__waketime_stats); 193 wakeup_avg = avg_stats(&__wakeup_stats); 194 195 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " 196 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, 197 params.nthreads, waketime_avg / USEC_PER_MSEC, 198 rel_stddev_stats(waketime_stddev, waketime_avg)); 199 } 200 201 static void print_summary(void) 202 { 203 unsigned int wakeup_avg; 204 double waketime_avg, waketime_stddev; 205 206 waketime_avg = avg_stats(&waketime_stats); 207 waketime_stddev = stddev_stats(&waketime_stats); 208 wakeup_avg = avg_stats(&wakeup_stats); 209 210 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", 211 wakeup_avg, 212 params.nthreads, 213 waketime_avg / USEC_PER_MSEC, 214 rel_stddev_stats(waketime_stddev, waketime_avg)); 215 } 216 217 218 static void do_run_stats(struct thread_data *waking_worker) 219 { 220 unsigned int i; 221 222 for (i = 0; i < params.nwakes; i++) { 223 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); 224 update_stats(&wakeup_stats, waking_worker[i].nwoken); 225 } 226 227 } 228 229 static void toggle_done(int sig __maybe_unused, 230 siginfo_t *info __maybe_unused, 231 void *uc __maybe_unused) 232 { 233 done = true; 234 } 235 236 int bench_futex_wake_parallel(int argc, const char **argv) 237 { 238 int ret = 0; 239 unsigned int i, j; 240 struct sigaction act; 241 pthread_attr_t thread_attr; 242 struct thread_data *waking_worker; 243 struct perf_cpu_map *cpu; 244 245 argc = parse_options(argc, argv, options, 246 bench_futex_wake_parallel_usage, 0); 247 if (argc) { 248 usage_with_options(bench_futex_wake_parallel_usage, options); 249 exit(EXIT_FAILURE); 250 } 251 252 memset(&act, 0, sizeof(act)); 253 sigfillset(&act.sa_mask); 254 act.sa_sigaction = toggle_done; 255 sigaction(SIGINT, &act, NULL); 256 257 if (params.mlockall) { 258 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 259 err(EXIT_FAILURE, "mlockall"); 260 } 261 262 cpu = perf_cpu_map__new(NULL); 263 if (!cpu) 264 err(EXIT_FAILURE, "calloc"); 265 266 if (!params.nthreads) 267 params.nthreads = perf_cpu_map__nr(cpu); 268 269 /* some sanity checks */ 270 if (params.nwakes > params.nthreads || 271 !params.nwakes) 272 params.nwakes = params.nthreads; 273 274 if (params.nthreads % params.nwakes) 275 errx(EXIT_FAILURE, "Must be perfectly divisible"); 276 /* 277 * Each thread will wakeup nwakes tasks in 278 * a single futex_wait call. 279 */ 280 nwakes = params.nthreads/params.nwakes; 281 282 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker)); 283 if (!blocked_worker) 284 err(EXIT_FAILURE, "calloc"); 285 286 if (!params.fshared) 287 futex_flag = FUTEX_PRIVATE_FLAG; 288 289 printf("Run summary [PID %d]: blocking on %d threads (at [%s] " 290 "futex %p), %d threads waking up %d at a time.\n\n", 291 getpid(), params.nthreads, params.fshared ? "shared":"private", 292 &futex, params.nwakes, nwakes); 293 294 init_stats(&wakeup_stats); 295 init_stats(&waketime_stats); 296 297 pthread_attr_init(&thread_attr); 298 mutex_init(&thread_lock); 299 cond_init(&thread_parent); 300 cond_init(&thread_worker); 301 302 for (j = 0; j < bench_repeat && !done; j++) { 303 waking_worker = calloc(params.nwakes, sizeof(*waking_worker)); 304 if (!waking_worker) 305 err(EXIT_FAILURE, "calloc"); 306 307 /* create, launch & block all threads */ 308 block_threads(blocked_worker, thread_attr, cpu); 309 310 /* make sure all threads are already blocked */ 311 mutex_lock(&thread_lock); 312 while (threads_starting) 313 cond_wait(&thread_parent, &thread_lock); 314 cond_broadcast(&thread_worker); 315 mutex_unlock(&thread_lock); 316 317 usleep(100000); 318 319 /* Ok, all threads are patiently blocked, start waking folks up */ 320 wakeup_threads(waking_worker, thread_attr); 321 322 for (i = 0; i < params.nthreads; i++) { 323 ret = pthread_join(blocked_worker[i], NULL); 324 if (ret) 325 err(EXIT_FAILURE, "pthread_join"); 326 } 327 328 do_run_stats(waking_worker); 329 if (!params.silent) 330 print_run(waking_worker, j); 331 332 free(waking_worker); 333 } 334 335 /* cleanup & report results */ 336 cond_destroy(&thread_parent); 337 cond_destroy(&thread_worker); 338 mutex_destroy(&thread_lock); 339 pthread_attr_destroy(&thread_attr); 340 341 print_summary(); 342 343 free(blocked_worker); 344 perf_cpu_map__put(cpu); 345 return ret; 346 } 347 #endif /* HAVE_PTHREAD_BARRIER */ 348