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
workerfn(void * arg __maybe_unused)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
print_summary(void)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
block_threads(pthread_t * w,pthread_attr_t thread_attr,struct perf_cpu_map * cpu)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
103 threads_starting = params.nthreads;
104
105 /* create and block all threads */
106 for (i = 0; i < params.nthreads; i++) {
107 CPU_ZERO(&cpuset);
108 CPU_SET(cpu->map[i % cpu->nr], &cpuset);
109
110 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset))
111 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
112
113 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
114 err(EXIT_FAILURE, "pthread_create");
115 }
116 }
117
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)118 static void toggle_done(int sig __maybe_unused,
119 siginfo_t *info __maybe_unused,
120 void *uc __maybe_unused)
121 {
122 done = true;
123 }
124
bench_futex_wake(int argc,const char ** argv)125 int bench_futex_wake(int argc, const char **argv)
126 {
127 int ret = 0;
128 unsigned int i, j;
129 struct sigaction act;
130 pthread_attr_t thread_attr;
131 struct perf_cpu_map *cpu;
132
133 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
134 if (argc) {
135 usage_with_options(bench_futex_wake_usage, options);
136 exit(EXIT_FAILURE);
137 }
138
139 cpu = perf_cpu_map__new(NULL);
140 if (!cpu)
141 err(EXIT_FAILURE, "calloc");
142
143 memset(&act, 0, sizeof(act));
144 sigfillset(&act.sa_mask);
145 act.sa_sigaction = toggle_done;
146 sigaction(SIGINT, &act, NULL);
147
148 if (params.mlockall) {
149 if (mlockall(MCL_CURRENT | MCL_FUTURE))
150 err(EXIT_FAILURE, "mlockall");
151 }
152
153 if (!params.nthreads)
154 params.nthreads = cpu->nr;
155
156 worker = calloc(params.nthreads, sizeof(*worker));
157 if (!worker)
158 err(EXIT_FAILURE, "calloc");
159
160 if (!params.fshared)
161 futex_flag = FUTEX_PRIVATE_FLAG;
162
163 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
164 "waking up %d at a time.\n\n",
165 getpid(), params.nthreads, params.fshared ? "shared":"private",
166 &futex1, params.nwakes);
167
168 init_stats(&wakeup_stats);
169 init_stats(&waketime_stats);
170 pthread_attr_init(&thread_attr);
171 pthread_mutex_init(&thread_lock, NULL);
172 pthread_cond_init(&thread_parent, NULL);
173 pthread_cond_init(&thread_worker, NULL);
174
175 for (j = 0; j < bench_repeat && !done; j++) {
176 unsigned int nwoken = 0;
177 struct timeval start, end, runtime;
178
179 /* create, launch & block all threads */
180 block_threads(worker, thread_attr, cpu);
181
182 /* make sure all threads are already blocked */
183 pthread_mutex_lock(&thread_lock);
184 while (threads_starting)
185 pthread_cond_wait(&thread_parent, &thread_lock);
186 pthread_cond_broadcast(&thread_worker);
187 pthread_mutex_unlock(&thread_lock);
188
189 usleep(100000);
190
191 /* Ok, all threads are patiently blocked, start waking folks up */
192 gettimeofday(&start, NULL);
193 while (nwoken != params.nthreads)
194 nwoken += futex_wake(&futex1,
195 params.nwakes, futex_flag);
196 gettimeofday(&end, NULL);
197 timersub(&end, &start, &runtime);
198
199 update_stats(&wakeup_stats, nwoken);
200 update_stats(&waketime_stats, runtime.tv_usec);
201
202 if (!params.silent) {
203 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
204 j + 1, nwoken, params.nthreads,
205 runtime.tv_usec / (double)USEC_PER_MSEC);
206 }
207
208 for (i = 0; i < params.nthreads; i++) {
209 ret = pthread_join(worker[i], NULL);
210 if (ret)
211 err(EXIT_FAILURE, "pthread_join");
212 }
213
214 }
215
216 /* cleanup & report results */
217 pthread_cond_destroy(&thread_parent);
218 pthread_cond_destroy(&thread_worker);
219 pthread_mutex_destroy(&thread_lock);
220 pthread_attr_destroy(&thread_attr);
221
222 print_summary();
223
224 free(worker);
225 perf_cpu_map__put(cpu);
226 return ret;
227 }
228