1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com> 4 * 5 * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time. 6 * 7 * This program is particularly useful to measure the latency of nthread wakeups 8 * in non-error situations: all waiters are queued and all wake calls wakeup 9 * one or more tasks, and thus the waitqueue is never empty. 10 */ 11 12 /* For the CLR_() macros */ 13 #include <string.h> 14 #include <pthread.h> 15 16 #include <signal.h> 17 #include "../util/stat.h" 18 #include <subcmd/parse-options.h> 19 #include <linux/compiler.h> 20 #include <linux/kernel.h> 21 #include <linux/time64.h> 22 #include <errno.h> 23 #include <perf/cpumap.h> 24 #include "bench.h" 25 #include "futex.h" 26 27 #include <err.h> 28 #include <stdlib.h> 29 #include <sys/time.h> 30 #include <sys/mman.h> 31 32 /* all threads will block on the same futex */ 33 static u_int32_t futex1 = 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 waketime_stats, wakeup_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 wakeups to do at a time. 46 * Default to 1 in order to make the kernel work more. 47 */ 48 .nwakes = 1, 49 }; 50 51 static const struct option options[] = { 52 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 53 OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake 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 58 OPT_END() 59 }; 60 61 static const char * const bench_futex_wake_usage[] = { 62 "perf bench futex wake <options>", 63 NULL 64 }; 65 66 static void *workerfn(void *arg __maybe_unused) 67 { 68 pthread_mutex_lock(&thread_lock); 69 threads_starting--; 70 if (!threads_starting) 71 pthread_cond_signal(&thread_parent); 72 pthread_cond_wait(&thread_worker, &thread_lock); 73 pthread_mutex_unlock(&thread_lock); 74 75 while (1) { 76 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) 77 break; 78 } 79 80 pthread_exit(NULL); 81 return NULL; 82 } 83 84 static void print_summary(void) 85 { 86 double waketime_avg = avg_stats(&waketime_stats); 87 double waketime_stddev = stddev_stats(&waketime_stats); 88 unsigned int wakeup_avg = avg_stats(&wakeup_stats); 89 90 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", 91 wakeup_avg, 92 params.nthreads, 93 waketime_avg / USEC_PER_MSEC, 94 rel_stddev_stats(waketime_stddev, waketime_avg)); 95 } 96 97 static void block_threads(pthread_t *w, 98 pthread_attr_t thread_attr, struct perf_cpu_map *cpu) 99 { 100 cpu_set_t *cpuset; 101 unsigned int i; 102 size_t size; 103 int nrcpus = perf_cpu_map__nr(cpu); 104 threads_starting = params.nthreads; 105 106 cpuset = CPU_ALLOC(nrcpus); 107 BUG_ON(!cpuset); 108 size = CPU_ALLOC_SIZE(nrcpus); 109 110 /* create and block all threads */ 111 for (i = 0; i < params.nthreads; i++) { 112 CPU_ZERO_S(size, cpuset); 113 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 114 115 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 116 CPU_FREE(cpuset); 117 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 118 } 119 120 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) { 121 CPU_FREE(cpuset); 122 err(EXIT_FAILURE, "pthread_create"); 123 } 124 } 125 CPU_FREE(cpuset); 126 } 127 128 static void toggle_done(int sig __maybe_unused, 129 siginfo_t *info __maybe_unused, 130 void *uc __maybe_unused) 131 { 132 done = true; 133 } 134 135 int bench_futex_wake(int argc, const char **argv) 136 { 137 int ret = 0; 138 unsigned int i, j; 139 struct sigaction act; 140 pthread_attr_t thread_attr; 141 struct perf_cpu_map *cpu; 142 143 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); 144 if (argc) { 145 usage_with_options(bench_futex_wake_usage, options); 146 exit(EXIT_FAILURE); 147 } 148 149 cpu = perf_cpu_map__new(NULL); 150 if (!cpu) 151 err(EXIT_FAILURE, "calloc"); 152 153 memset(&act, 0, sizeof(act)); 154 sigfillset(&act.sa_mask); 155 act.sa_sigaction = toggle_done; 156 sigaction(SIGINT, &act, NULL); 157 158 if (params.mlockall) { 159 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 160 err(EXIT_FAILURE, "mlockall"); 161 } 162 163 if (!params.nthreads) 164 params.nthreads = perf_cpu_map__nr(cpu); 165 166 worker = calloc(params.nthreads, sizeof(*worker)); 167 if (!worker) 168 err(EXIT_FAILURE, "calloc"); 169 170 if (!params.fshared) 171 futex_flag = FUTEX_PRIVATE_FLAG; 172 173 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " 174 "waking up %d at a time.\n\n", 175 getpid(), params.nthreads, params.fshared ? "shared":"private", 176 &futex1, params.nwakes); 177 178 init_stats(&wakeup_stats); 179 init_stats(&waketime_stats); 180 pthread_attr_init(&thread_attr); 181 pthread_mutex_init(&thread_lock, NULL); 182 pthread_cond_init(&thread_parent, NULL); 183 pthread_cond_init(&thread_worker, NULL); 184 185 for (j = 0; j < bench_repeat && !done; j++) { 186 unsigned int nwoken = 0; 187 struct timeval start, end, runtime; 188 189 /* create, launch & block all threads */ 190 block_threads(worker, thread_attr, cpu); 191 192 /* make sure all threads are already blocked */ 193 pthread_mutex_lock(&thread_lock); 194 while (threads_starting) 195 pthread_cond_wait(&thread_parent, &thread_lock); 196 pthread_cond_broadcast(&thread_worker); 197 pthread_mutex_unlock(&thread_lock); 198 199 usleep(100000); 200 201 /* Ok, all threads are patiently blocked, start waking folks up */ 202 gettimeofday(&start, NULL); 203 while (nwoken != params.nthreads) 204 nwoken += futex_wake(&futex1, 205 params.nwakes, futex_flag); 206 gettimeofday(&end, NULL); 207 timersub(&end, &start, &runtime); 208 209 update_stats(&wakeup_stats, nwoken); 210 update_stats(&waketime_stats, runtime.tv_usec); 211 212 if (!params.silent) { 213 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", 214 j + 1, nwoken, params.nthreads, 215 runtime.tv_usec / (double)USEC_PER_MSEC); 216 } 217 218 for (i = 0; i < params.nthreads; i++) { 219 ret = pthread_join(worker[i], NULL); 220 if (ret) 221 err(EXIT_FAILURE, "pthread_join"); 222 } 223 224 } 225 226 /* cleanup & report results */ 227 pthread_cond_destroy(&thread_parent); 228 pthread_cond_destroy(&thread_worker); 229 pthread_mutex_destroy(&thread_lock); 230 pthread_attr_destroy(&thread_attr); 231 232 print_summary(); 233 234 free(worker); 235 perf_cpu_map__put(cpu); 236 return ret; 237 } 238