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/mutex.h" 19 #include "../util/stat.h" 20 #include <subcmd/parse-options.h> 21 #include <linux/compiler.h> 22 #include <linux/kernel.h> 23 #include <linux/time64.h> 24 #include <errno.h> 25 #include <perf/cpumap.h> 26 #include "bench.h" 27 #include "futex.h" 28 29 #include <err.h> 30 #include <stdlib.h> 31 #include <sys/time.h> 32 #include <sys/mman.h> 33 34 static u_int32_t futex1 = 0, futex2 = 0; 35 36 static pthread_t *worker; 37 static bool done = false; 38 static struct mutex thread_lock; 39 static struct cond thread_parent, thread_worker; 40 static struct stats requeuetime_stats, requeued_stats; 41 static unsigned int threads_starting; 42 static int futex_flag = 0; 43 44 static struct bench_futex_parameters params = { 45 .nbuckets = -1, 46 /* 47 * How many tasks to requeue at a time. 48 * Default to 1 in order to make the kernel work more. 49 */ 50 .nrequeue = 1, 51 }; 52 53 static const struct option options[] = { 54 OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"), 55 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 56 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue at once"), 57 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), 58 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"), 59 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"), 60 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"), 61 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"), 62 63 OPT_END() 64 }; 65 66 static const char * const bench_futex_requeue_usage[] = { 67 "perf bench futex requeue <options>", 68 NULL 69 }; 70 71 static void print_summary(void) 72 { 73 double requeuetime_avg = avg_stats(&requeuetime_stats); 74 double requeuetime_stddev = stddev_stats(&requeuetime_stats); 75 unsigned int requeued_avg = avg_stats(&requeued_stats); 76 77 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", 78 requeued_avg, 79 params.nthreads, 80 requeuetime_avg / USEC_PER_MSEC, 81 rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); 82 futex_print_nbuckets(¶ms); 83 } 84 85 static void *workerfn(void *arg __maybe_unused) 86 { 87 int ret; 88 89 mutex_lock(&thread_lock); 90 threads_starting--; 91 if (!threads_starting) 92 cond_signal(&thread_parent); 93 cond_wait(&thread_worker, &thread_lock); 94 mutex_unlock(&thread_lock); 95 96 while (1) { 97 if (!params.pi) { 98 ret = futex_wait(&futex1, 0, NULL, futex_flag); 99 if (!ret) 100 break; 101 102 if (ret && errno != EAGAIN) { 103 if (!params.silent) 104 warnx("futex_wait"); 105 break; 106 } 107 } else { 108 ret = futex_wait_requeue_pi(&futex1, 0, &futex2, 109 NULL, futex_flag); 110 if (!ret) { 111 /* got the lock at futex2 */ 112 futex_unlock_pi(&futex2, futex_flag); 113 break; 114 } 115 116 if (ret && errno != EAGAIN) { 117 if (!params.silent) 118 warnx("futex_wait_requeue_pi"); 119 break; 120 } 121 } 122 } 123 124 return NULL; 125 } 126 127 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu) 128 { 129 cpu_set_t *cpuset; 130 unsigned int i; 131 int nrcpus = cpu__max_cpu().cpu; 132 size_t size; 133 134 threads_starting = params.nthreads; 135 136 cpuset = CPU_ALLOC(nrcpus); 137 BUG_ON(!cpuset); 138 size = CPU_ALLOC_SIZE(nrcpus); 139 140 /* create and block all threads */ 141 for (i = 0; i < params.nthreads; i++) { 142 pthread_attr_t thread_attr; 143 144 pthread_attr_init(&thread_attr); 145 CPU_ZERO_S(size, cpuset); 146 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 147 148 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 149 CPU_FREE(cpuset); 150 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 151 } 152 153 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) { 154 CPU_FREE(cpuset); 155 err(EXIT_FAILURE, "pthread_create"); 156 } 157 pthread_attr_destroy(&thread_attr); 158 } 159 CPU_FREE(cpuset); 160 } 161 162 static void toggle_done(int sig __maybe_unused, 163 siginfo_t *info __maybe_unused, 164 void *uc __maybe_unused) 165 { 166 done = true; 167 } 168 169 int bench_futex_requeue(int argc, const char **argv) 170 { 171 int ret = 0; 172 unsigned int i, j; 173 struct sigaction act; 174 struct perf_cpu_map *cpu; 175 176 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); 177 if (argc) 178 goto err; 179 180 cpu = perf_cpu_map__new_online_cpus(); 181 if (!cpu) 182 err(EXIT_FAILURE, "cpu_map__new"); 183 184 memset(&act, 0, sizeof(act)); 185 sigfillset(&act.sa_mask); 186 act.sa_sigaction = toggle_done; 187 sigaction(SIGINT, &act, NULL); 188 189 if (params.mlockall) { 190 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 191 err(EXIT_FAILURE, "mlockall"); 192 } 193 194 if (!params.nthreads) 195 params.nthreads = perf_cpu_map__nr(cpu); 196 197 worker = calloc(params.nthreads, sizeof(*worker)); 198 if (!worker) 199 err(EXIT_FAILURE, "calloc"); 200 201 if (!params.fshared) 202 futex_flag = FUTEX_PRIVATE_FLAG; 203 204 if (params.nrequeue > params.nthreads) 205 params.nrequeue = params.nthreads; 206 207 if (params.broadcast) 208 params.nrequeue = params.nthreads; 209 210 futex_set_nbuckets_param(¶ms); 211 212 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), " 213 "%d at a time.\n\n", getpid(), params.nthreads, 214 params.fshared ? "shared":"private", &futex1, 215 params.pi ? "PI ": "", &futex2, params.nrequeue); 216 217 init_stats(&requeued_stats); 218 init_stats(&requeuetime_stats); 219 mutex_init(&thread_lock); 220 cond_init(&thread_parent); 221 cond_init(&thread_worker); 222 223 for (j = 0; j < bench_repeat && !done; j++) { 224 unsigned int nrequeued = 0, wakeups = 0; 225 struct timeval start, end, runtime; 226 227 /* create, launch & block all threads */ 228 block_threads(worker, cpu); 229 230 /* make sure all threads are already blocked */ 231 mutex_lock(&thread_lock); 232 while (threads_starting) 233 cond_wait(&thread_parent, &thread_lock); 234 cond_broadcast(&thread_worker); 235 mutex_unlock(&thread_lock); 236 237 usleep(100000); 238 239 /* Ok, all threads are patiently blocked, start requeueing */ 240 gettimeofday(&start, NULL); 241 while (nrequeued < params.nthreads) { 242 int r; 243 244 /* 245 * For the regular non-pi case, do not wakeup any tasks 246 * blocked on futex1, allowing us to really measure 247 * futex_wait functionality. For the PI case the first 248 * waiter is always awoken. 249 */ 250 if (!params.pi) { 251 r = futex_cmp_requeue(&futex1, 0, &futex2, 0, 252 params.nrequeue, 253 futex_flag); 254 } else { 255 r = futex_cmp_requeue_pi(&futex1, 0, &futex2, 256 params.nrequeue, 257 futex_flag); 258 wakeups++; /* assume no error */ 259 } 260 261 if (r < 0) 262 err(EXIT_FAILURE, "couldn't requeue from %p to %p", 263 &futex1, &futex2); 264 265 nrequeued += r; 266 } 267 268 gettimeofday(&end, NULL); 269 timersub(&end, &start, &runtime); 270 271 update_stats(&requeued_stats, nrequeued); 272 update_stats(&requeuetime_stats, runtime.tv_usec); 273 274 if (!params.silent) { 275 if (!params.pi) 276 printf("[Run %d]: Requeued %d of %d threads in " 277 "%.4f ms\n", j + 1, nrequeued, 278 params.nthreads, 279 runtime.tv_usec / (double)USEC_PER_MSEC); 280 else { 281 nrequeued -= wakeups; 282 printf("[Run %d]: Awoke and Requeued (%d+%d) of " 283 "%d threads in %.4f ms\n", 284 j + 1, wakeups, nrequeued, 285 params.nthreads, 286 runtime.tv_usec / (double)USEC_PER_MSEC); 287 } 288 289 } 290 291 if (!params.pi) { 292 /* everybody should be blocked on futex2, wake'em up */ 293 nrequeued = futex_wake(&futex2, nrequeued, futex_flag); 294 if (params.nthreads != nrequeued) 295 warnx("couldn't wakeup all tasks (%d/%d)", 296 nrequeued, params.nthreads); 297 } 298 299 for (i = 0; i < params.nthreads; i++) { 300 ret = pthread_join(worker[i], NULL); 301 if (ret) 302 err(EXIT_FAILURE, "pthread_join"); 303 } 304 } 305 306 /* cleanup & report results */ 307 cond_destroy(&thread_parent); 308 cond_destroy(&thread_worker); 309 mutex_destroy(&thread_lock); 310 311 print_summary(); 312 313 free(worker); 314 perf_cpu_map__put(cpu); 315 return ret; 316 err: 317 usage_with_options(bench_futex_requeue_usage, options); 318 exit(EXIT_FAILURE); 319 } 320