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/mutex.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 /* all threads will block on the same futex */ 34 static u_int32_t futex1 = 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 waketime_stats, wakeup_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 wakeups to do at a time. 47 * Default to 1 in order to make the kernel work more. 48 */ 49 .nwakes = 1, 50 }; 51 52 static const struct option options[] = { 53 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), 54 OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake 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 59 OPT_END() 60 }; 61 62 static const char * const bench_futex_wake_usage[] = { 63 "perf bench futex wake <options>", 64 NULL 65 }; 66 67 static void *workerfn(void *arg __maybe_unused) 68 { 69 mutex_lock(&thread_lock); 70 threads_starting--; 71 if (!threads_starting) 72 cond_signal(&thread_parent); 73 cond_wait(&thread_worker, &thread_lock); 74 mutex_unlock(&thread_lock); 75 76 while (1) { 77 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) 78 break; 79 } 80 81 pthread_exit(NULL); 82 return NULL; 83 } 84 85 static void print_summary(void) 86 { 87 double waketime_avg = avg_stats(&waketime_stats); 88 double waketime_stddev = stddev_stats(&waketime_stats); 89 unsigned int wakeup_avg = avg_stats(&wakeup_stats); 90 91 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n", 92 wakeup_avg, 93 params.nthreads, 94 waketime_avg / USEC_PER_MSEC, 95 rel_stddev_stats(waketime_stddev, waketime_avg)); 96 } 97 98 static void block_threads(pthread_t *w, 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 pthread_attr_t thread_attr; 113 114 pthread_attr_init(&thread_attr); 115 CPU_ZERO_S(size, cpuset); 116 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset); 117 118 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) { 119 CPU_FREE(cpuset); 120 err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); 121 } 122 123 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) { 124 CPU_FREE(cpuset); 125 err(EXIT_FAILURE, "pthread_create"); 126 } 127 pthread_attr_destroy(&thread_attr); 128 } 129 CPU_FREE(cpuset); 130 } 131 132 static void toggle_done(int sig __maybe_unused, 133 siginfo_t *info __maybe_unused, 134 void *uc __maybe_unused) 135 { 136 done = true; 137 } 138 139 int bench_futex_wake(int argc, const char **argv) 140 { 141 int ret = 0; 142 unsigned int i, j; 143 struct sigaction act; 144 struct perf_cpu_map *cpu; 145 146 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0); 147 if (argc) { 148 usage_with_options(bench_futex_wake_usage, options); 149 exit(EXIT_FAILURE); 150 } 151 152 cpu = perf_cpu_map__new(NULL); 153 if (!cpu) 154 err(EXIT_FAILURE, "calloc"); 155 156 memset(&act, 0, sizeof(act)); 157 sigfillset(&act.sa_mask); 158 act.sa_sigaction = toggle_done; 159 sigaction(SIGINT, &act, NULL); 160 161 if (params.mlockall) { 162 if (mlockall(MCL_CURRENT | MCL_FUTURE)) 163 err(EXIT_FAILURE, "mlockall"); 164 } 165 166 if (!params.nthreads) 167 params.nthreads = perf_cpu_map__nr(cpu); 168 169 worker = calloc(params.nthreads, sizeof(*worker)); 170 if (!worker) 171 err(EXIT_FAILURE, "calloc"); 172 173 if (!params.fshared) 174 futex_flag = FUTEX_PRIVATE_FLAG; 175 176 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " 177 "waking up %d at a time.\n\n", 178 getpid(), params.nthreads, params.fshared ? "shared":"private", 179 &futex1, params.nwakes); 180 181 init_stats(&wakeup_stats); 182 init_stats(&waketime_stats); 183 mutex_init(&thread_lock); 184 cond_init(&thread_parent); 185 cond_init(&thread_worker); 186 187 for (j = 0; j < bench_repeat && !done; j++) { 188 unsigned int nwoken = 0; 189 struct timeval start, end, runtime; 190 191 /* create, launch & block all threads */ 192 block_threads(worker, cpu); 193 194 /* make sure all threads are already blocked */ 195 mutex_lock(&thread_lock); 196 while (threads_starting) 197 cond_wait(&thread_parent, &thread_lock); 198 cond_broadcast(&thread_worker); 199 mutex_unlock(&thread_lock); 200 201 usleep(100000); 202 203 /* Ok, all threads are patiently blocked, start waking folks up */ 204 gettimeofday(&start, NULL); 205 while (nwoken != params.nthreads) 206 nwoken += futex_wake(&futex1, 207 params.nwakes, futex_flag); 208 gettimeofday(&end, NULL); 209 timersub(&end, &start, &runtime); 210 211 update_stats(&wakeup_stats, nwoken); 212 update_stats(&waketime_stats, runtime.tv_usec); 213 214 if (!params.silent) { 215 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n", 216 j + 1, nwoken, params.nthreads, 217 runtime.tv_usec / (double)USEC_PER_MSEC); 218 } 219 220 for (i = 0; i < params.nthreads; i++) { 221 ret = pthread_join(worker[i], NULL); 222 if (ret) 223 err(EXIT_FAILURE, "pthread_join"); 224 } 225 226 } 227 228 /* cleanup & report results */ 229 cond_destroy(&thread_parent); 230 cond_destroy(&thread_worker); 231 mutex_destroy(&thread_lock); 232 233 print_summary(); 234 235 free(worker); 236 perf_cpu_map__put(cpu); 237 return ret; 238 } 239