GNU Linux-libre 4.19.211-gnu1
[releases.git] / tools / perf / bench / futex-wake.c
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 "bench.h"
24 #include "futex.h"
25 #include "cpumap.h"
26
27 #include <err.h>
28 #include <stdlib.h>
29 #include <sys/time.h>
30
31 /* all threads will block on the same futex */
32 static u_int32_t futex1 = 0;
33
34 /*
35  * How many wakeups to do at a time.
36  * Default to 1 in order to make the kernel work more.
37  */
38 static unsigned int nwakes = 1;
39
40 pthread_t *worker;
41 static bool done = false, silent = false, fshared = false;
42 static pthread_mutex_t thread_lock;
43 static pthread_cond_t thread_parent, thread_worker;
44 static struct stats waketime_stats, wakeup_stats;
45 static unsigned int threads_starting, nthreads = 0;
46 static int futex_flag = 0;
47
48 static const struct option options[] = {
49         OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
50         OPT_UINTEGER('w', "nwakes",  &nwakes,   "Specify amount of threads to wake at once"),
51         OPT_BOOLEAN( 's', "silent",  &silent,   "Silent mode: do not display data/details"),
52         OPT_BOOLEAN( 'S', "shared",  &fshared,  "Use shared futexes instead of private ones"),
53         OPT_END()
54 };
55
56 static const char * const bench_futex_wake_usage[] = {
57         "perf bench futex wake <options>",
58         NULL
59 };
60
61 static void *workerfn(void *arg __maybe_unused)
62 {
63         pthread_mutex_lock(&thread_lock);
64         threads_starting--;
65         if (!threads_starting)
66                 pthread_cond_signal(&thread_parent);
67         pthread_cond_wait(&thread_worker, &thread_lock);
68         pthread_mutex_unlock(&thread_lock);
69
70         while (1) {
71                 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
72                         break;
73         }
74
75         pthread_exit(NULL);
76         return NULL;
77 }
78
79 static void print_summary(void)
80 {
81         double waketime_avg = avg_stats(&waketime_stats);
82         double waketime_stddev = stddev_stats(&waketime_stats);
83         unsigned int wakeup_avg = avg_stats(&wakeup_stats);
84
85         printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
86                wakeup_avg,
87                nthreads,
88                waketime_avg / USEC_PER_MSEC,
89                rel_stddev_stats(waketime_stddev, waketime_avg));
90 }
91
92 static void block_threads(pthread_t *w,
93                           pthread_attr_t thread_attr, struct cpu_map *cpu)
94 {
95         cpu_set_t cpuset;
96         unsigned int i;
97
98         threads_starting = nthreads;
99
100         /* create and block all threads */
101         for (i = 0; i < nthreads; i++) {
102                 CPU_ZERO(&cpuset);
103                 CPU_SET(cpu->map[i % cpu->nr], &cpuset);
104
105                 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset))
106                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
107
108                 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
109                         err(EXIT_FAILURE, "pthread_create");
110         }
111 }
112
113 static void toggle_done(int sig __maybe_unused,
114                         siginfo_t *info __maybe_unused,
115                         void *uc __maybe_unused)
116 {
117         done = true;
118 }
119
120 int bench_futex_wake(int argc, const char **argv)
121 {
122         int ret = 0;
123         unsigned int i, j;
124         struct sigaction act;
125         pthread_attr_t thread_attr;
126         struct cpu_map *cpu;
127
128         argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
129         if (argc) {
130                 usage_with_options(bench_futex_wake_usage, options);
131                 exit(EXIT_FAILURE);
132         }
133
134         cpu = cpu_map__new(NULL);
135         if (!cpu)
136                 err(EXIT_FAILURE, "calloc");
137
138         sigfillset(&act.sa_mask);
139         act.sa_sigaction = toggle_done;
140         sigaction(SIGINT, &act, NULL);
141
142         if (!nthreads)
143                 nthreads = cpu->nr;
144
145         worker = calloc(nthreads, sizeof(*worker));
146         if (!worker)
147                 err(EXIT_FAILURE, "calloc");
148
149         if (!fshared)
150                 futex_flag = FUTEX_PRIVATE_FLAG;
151
152         printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
153                "waking up %d at a time.\n\n",
154                getpid(), nthreads, fshared ? "shared":"private",  &futex1, nwakes);
155
156         init_stats(&wakeup_stats);
157         init_stats(&waketime_stats);
158         pthread_attr_init(&thread_attr);
159         pthread_mutex_init(&thread_lock, NULL);
160         pthread_cond_init(&thread_parent, NULL);
161         pthread_cond_init(&thread_worker, NULL);
162
163         for (j = 0; j < bench_repeat && !done; j++) {
164                 unsigned int nwoken = 0;
165                 struct timeval start, end, runtime;
166
167                 /* create, launch & block all threads */
168                 block_threads(worker, thread_attr, cpu);
169
170                 /* make sure all threads are already blocked */
171                 pthread_mutex_lock(&thread_lock);
172                 while (threads_starting)
173                         pthread_cond_wait(&thread_parent, &thread_lock);
174                 pthread_cond_broadcast(&thread_worker);
175                 pthread_mutex_unlock(&thread_lock);
176
177                 usleep(100000);
178
179                 /* Ok, all threads are patiently blocked, start waking folks up */
180                 gettimeofday(&start, NULL);
181                 while (nwoken != nthreads)
182                         nwoken += futex_wake(&futex1, nwakes, futex_flag);
183                 gettimeofday(&end, NULL);
184                 timersub(&end, &start, &runtime);
185
186                 update_stats(&wakeup_stats, nwoken);
187                 update_stats(&waketime_stats, runtime.tv_usec);
188
189                 if (!silent) {
190                         printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
191                                j + 1, nwoken, nthreads, runtime.tv_usec / (double)USEC_PER_MSEC);
192                 }
193
194                 for (i = 0; i < nthreads; i++) {
195                         ret = pthread_join(worker[i], NULL);
196                         if (ret)
197                                 err(EXIT_FAILURE, "pthread_join");
198                 }
199
200         }
201
202         /* cleanup & report results */
203         pthread_cond_destroy(&thread_parent);
204         pthread_cond_destroy(&thread_worker);
205         pthread_mutex_destroy(&thread_lock);
206         pthread_attr_destroy(&thread_attr);
207
208         print_summary();
209
210         free(worker);
211         return ret;
212 }