1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> 4 * 5 * futex-requeue: Block a bunch of threads on futex1 and requeue them 6 * on futex2, N at a time. 7 * 8 * This program is particularly useful to measure the latency of nthread 9 * requeues without waking up any tasks (in the non-pi case) -- thus 10 * mimicking a regular futex_wait. 11 */ 12 13 /* For the CLR_() macros */ 14 #include <string.h> 15 #include <pthread.h> 16 17 #include <signal.h> 18 #include "../util/stat.h" 19 #include <subcmd/parse-options.h> 20 #include <linux/compiler.h> 21 #include <linux/kernel.h> 22 #include <linux/time64.h> 23 #include <errno.h> 24 #include <perf/cpumap.h> 25 #include "bench.h" 26 #include "futex.h" 27 28 #include <err.h> 29 #include <stdlib.h> 30 #include <sys/time.h> 31 #include <sys/mman.h> 32 33 static u_int32_t futex1 = 0, futex2 = 0; 34 35 static pthread_t *worker; 36 static bool done = false; 37 static pthread_mutex_t thread_lock; 38 static pthread_cond_t thread_parent, thread_worker; 39 static struct stats requeuetime_stats, requeued_stats; 40 static unsigned int threads_starting; 41 static int futex_flag = 0; 42 43 static struct bench_futex_parameters params = { 44 /* 45 * How many tasks to requeue at a time. 46 * Default to 1 in order to make the kernel work more. 47 */ 48 .nrequeue = 1, 49 }; 50 51 static const struct option options[] = { 52 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 53 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue at once"), 54 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 55 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 56 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 57 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"), 58 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"), 59 60 OPT_END() 61 }; 62 63 static const char * const bench_futex_requeue_usage[] = { 64 "perf bench futex requeue <options>", 65 NULL 66 }; 67 68 static void print_summary(void) 69 { 70 double requeuetime_avg = avg_stats(&requeuetime_stats); 71 double requeuetime_stddev = stddev_stats(&requeuetime_stats); 72 unsigned int requeued_avg = avg_stats(&requeued_stats); 73 74 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", 75 requeued_avg, 76 params.nthreads, 77 requeuetime_avg / USEC_PER_MSEC, 78 rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); 79 } 80 81 static void *workerfn(void *arg __maybe_unused) 82 { 83 int ret; 84 85 pthread_mutex_lock(&thread_lock); 86 threads_starting--; 87 if (!threads_starting) 88 pthread_cond_signal(&thread_parent); 89 pthread_cond_wait(&thread_worker, &thread_lock); 90 pthread_mutex_unlock(&thread_lock); 91 92 while (1) { 93 if (!params.pi) { 94 ret = futex_wait(&futex1, 0, NULL, futex_flag); 95 if (!ret) 96 break; 97 98 if (ret && errno != EAGAIN) { 99 if (!params.silent) 100 warnx("futex_wait"); 101 break; 102 } 103 } else { 104 ret = futex_wait_requeue_pi(&futex1, 0, &futex2, 105 NULL, futex_flag); 106 if (!ret) { 107 /* got the lock at futex2 */ 108 futex_unlock_pi(&futex2, futex_flag); 109 break; 110 } 111 112 if (ret && errno != EAGAIN) { 113 if (!params.silent) 114 warnx("futex_wait_requeue_pi"); 115 break; 116 } 117 } 118 } 119 120 return NULL; 121 } 122 123 static void block_threads(pthread_t *w, 124 pthread_attr_t thread_attr, struct perf_cpu_map *cpu) 125 { 126 cpu_set_t *cpuset; 127 unsigned int i; 128 int nrcpus = perf_cpu_map__nr(cpu); 129 size_t size; 130 131 threads_starting = params.nthreads; 132 133 cpuset = CPU_ALLOC(nrcpus); 134 BUG_ON(!cpuset); 135 size = CPU_ALLOC_SIZE(nrcpus); 136 137 /* create and block all threads */ 138 for (i = 0; i < params.nthreads; i++) { 139 CPU_ZERO_S(size, cpuset); 140 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 141 142 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 143 CPU_FREE(cpuset); 144 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 145 } 146 147 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) { 148 CPU_FREE(cpuset); 149 err(EXIT_FAILURE, "pthread_create"); 150 } 151 } 152 CPU_FREE(cpuset); 153 } 154 155 static void toggle_done(int sig __maybe_unused, 156 siginfo_t *info __maybe_unused, 157 void *uc __maybe_unused) 158 { 159 done = true; 160 } 161 162 int bench_futex_requeue(int argc, const char **argv) 163 { 164 int ret = 0; 165 unsigned int i, j; 166 struct sigaction act; 167 pthread_attr_t thread_attr; 168 struct perf_cpu_map *cpu; 169 170 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); 171 if (argc) 172 goto err; 173 174 cpu = perf_cpu_map__new(NULL); 175 if (!cpu) 176 err(EXIT_FAILURE, "cpu_map__new"); 177 178 memset(&act, 0, sizeof(act)); 179 sigfillset(&act.sa_mask); 180 act.sa_sigaction = toggle_done; 181 sigaction(SIGINT, &act, NULL); 182 183 if (params.mlockall) { 184 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 185 err(EXIT_FAILURE, "mlockall"); 186 } 187 188 if (!params.nthreads) 189 params.nthreads = perf_cpu_map__nr(cpu); 190 191 worker = calloc(params.nthreads, sizeof(*worker)); 192 if (!worker) 193 err(EXIT_FAILURE, "calloc"); 194 195 if (!params.fshared) 196 futex_flag = FUTEX_PRIVATE_FLAG; 197 198 if (params.nrequeue > params.nthreads) 199 params.nrequeue = params.nthreads; 200 201 if (params.broadcast) 202 params.nrequeue = params.nthreads; 203 204 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), " 205 "%d at a time.\n\n", getpid(), params.nthreads, 206 params.fshared ? "shared":"private", &futex1, 207 params.pi ? "PI ": "", &futex2, params.nrequeue); 208 209 init_stats(&requeued_stats); 210 init_stats(&requeuetime_stats); 211 pthread_attr_init(&thread_attr); 212 pthread_mutex_init(&thread_lock, NULL); 213 pthread_cond_init(&thread_parent, NULL); 214 pthread_cond_init(&thread_worker, NULL); 215 216 for (j = 0; j < bench_repeat && !done; j++) { 217 unsigned int nrequeued = 0, wakeups = 0; 218 struct timeval start, end, runtime; 219 220 /* create, launch & block all threads */ 221 block_threads(worker, thread_attr, cpu); 222 223 /* make sure all threads are already blocked */ 224 pthread_mutex_lock(&thread_lock); 225 while (threads_starting) 226 pthread_cond_wait(&thread_parent, &thread_lock); 227 pthread_cond_broadcast(&thread_worker); 228 pthread_mutex_unlock(&thread_lock); 229 230 usleep(100000); 231 232 /* Ok, all threads are patiently blocked, start requeueing */ 233 gettimeofday(&start, NULL); 234 while (nrequeued < params.nthreads) { 235 int r; 236 237 /* 238 * For the regular non-pi case, do not wakeup any tasks 239 * blocked on futex1, allowing us to really measure 240 * futex_wait functionality. For the PI case the first 241 * waiter is always awoken. 242 */ 243 if (!params.pi) { 244 r = futex_cmp_requeue(&futex1, 0, &futex2, 0, 245 params.nrequeue, 246 futex_flag); 247 } else { 248 r = futex_cmp_requeue_pi(&futex1, 0, &futex2, 249 params.nrequeue, 250 futex_flag); 251 wakeups++; /* assume no error */ 252 } 253 254 if (r < 0) 255 err(EXIT_FAILURE, "couldn't requeue from %p to %p", 256 &futex1, &futex2); 257 258 nrequeued += r; 259 } 260 261 gettimeofday(&end, NULL); 262 timersub(&end, &start, &runtime); 263 264 update_stats(&requeued_stats, nrequeued); 265 update_stats(&requeuetime_stats, runtime.tv_usec); 266 267 if (!params.silent) { 268 if (!params.pi) 269 printf("[Run %d]: Requeued %d of %d threads in " 270 "%.4f ms\n", j + 1, nrequeued, 271 params.nthreads, 272 runtime.tv_usec / (double)USEC_PER_MSEC); 273 else { 274 nrequeued -= wakeups; 275 printf("[Run %d]: Awoke and Requeued (%d+%d) of " 276 "%d threads in %.4f ms\n", 277 j + 1, wakeups, nrequeued, 278 params.nthreads, 279 runtime.tv_usec / (double)USEC_PER_MSEC); 280 } 281 282 } 283 284 if (!params.pi) { 285 /* everybody should be blocked on futex2, wake'em up */ 286 nrequeued = futex_wake(&futex2, nrequeued, futex_flag); 287 if (params.nthreads != nrequeued) 288 warnx("couldn't wakeup all tasks (%d/%d)", 289 nrequeued, params.nthreads); 290 } 291 292 for (i = 0; i < params.nthreads; i++) { 293 ret = pthread_join(worker[i], NULL); 294 if (ret) 295 err(EXIT_FAILURE, "pthread_join"); 296 } 297 } 298 299 /* cleanup & report results */ 300 pthread_cond_destroy(&thread_parent); 301 pthread_cond_destroy(&thread_worker); 302 pthread_mutex_destroy(&thread_lock); 303 pthread_attr_destroy(&thread_attr); 304 305 print_summary(); 306 307 free(worker); 308 perf_cpu_map__put(cpu); 309 return ret; 310 err: 311 usage_with_options(bench_futex_requeue_usage, options); 312 exit(EXIT_FAILURE); 313 } 314