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