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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 <internal/cpumap.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
32/* all threads will block on the same futex */
33static u_int32_t futex1 = 0;
34
35/*
36 * How many wakeups to do at a time.
37 * Default to 1 in order to make the kernel work more.
38 */
39static unsigned int nwakes = 1;
40
41pthread_t *worker;
42static bool done = false, silent = false, fshared = false;
43static pthread_mutex_t thread_lock;
44static pthread_cond_t thread_parent, thread_worker;
45static struct stats waketime_stats, wakeup_stats;
46static unsigned int ncpus, threads_starting, nthreads = 0;
47static int futex_flag = 0;
48
49static const struct option options[] = {
50 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
51 OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"),
52 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
53 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"),
54 OPT_END()
55};
56
57static const char * const bench_futex_wake_usage[] = {
58 "perf bench futex wake <options>",
59 NULL
60};
61
62static void *workerfn(void *arg __maybe_unused)
63{
64 pthread_mutex_lock(&thread_lock);
65 threads_starting--;
66 if (!threads_starting)
67 pthread_cond_signal(&thread_parent);
68 pthread_cond_wait(&thread_worker, &thread_lock);
69 pthread_mutex_unlock(&thread_lock);
70
71 while (1) {
72 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
73 break;
74 }
75
76 pthread_exit(NULL);
77 return NULL;
78}
79
80static void print_summary(void)
81{
82 double waketime_avg = avg_stats(&waketime_stats);
83 double waketime_stddev = stddev_stats(&waketime_stats);
84 unsigned int wakeup_avg = avg_stats(&wakeup_stats);
85
86 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
87 wakeup_avg,
88 nthreads,
89 waketime_avg / USEC_PER_MSEC,
90 rel_stddev_stats(waketime_stddev, waketime_avg));
91}
92
93static void block_threads(pthread_t *w,
94 pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
95{
96 cpu_set_t cpuset;
97 unsigned int i;
98
99 threads_starting = nthreads;
100
101 /* create and block all threads */
102 for (i = 0; i < nthreads; i++) {
103 CPU_ZERO(&cpuset);
104 CPU_SET(cpu->map[i % cpu->nr], &cpuset);
105
106 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset))
107 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
108
109 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
110 err(EXIT_FAILURE, "pthread_create");
111 }
112}
113
114static void toggle_done(int sig __maybe_unused,
115 siginfo_t *info __maybe_unused,
116 void *uc __maybe_unused)
117{
118 done = true;
119}
120
121int bench_futex_wake(int argc, const char **argv)
122{
123 int ret = 0;
124 unsigned int i, j;
125 struct sigaction act;
126 pthread_attr_t thread_attr;
127 struct perf_cpu_map *cpu;
128
129 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
130 if (argc) {
131 usage_with_options(bench_futex_wake_usage, options);
132 exit(EXIT_FAILURE);
133 }
134
135 cpu = perf_cpu_map__new(NULL);
136 if (!cpu)
137 err(EXIT_FAILURE, "calloc");
138
139 sigfillset(&act.sa_mask);
140 act.sa_sigaction = toggle_done;
141 sigaction(SIGINT, &act, NULL);
142
143 if (!nthreads)
144 nthreads = ncpus;
145
146 worker = calloc(nthreads, sizeof(*worker));
147 if (!worker)
148 err(EXIT_FAILURE, "calloc");
149
150 if (!fshared)
151 futex_flag = FUTEX_PRIVATE_FLAG;
152
153 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
154 "waking up %d at a time.\n\n",
155 getpid(), nthreads, fshared ? "shared":"private", &futex1, nwakes);
156
157 init_stats(&wakeup_stats);
158 init_stats(&waketime_stats);
159 pthread_attr_init(&thread_attr);
160 pthread_mutex_init(&thread_lock, NULL);
161 pthread_cond_init(&thread_parent, NULL);
162 pthread_cond_init(&thread_worker, NULL);
163
164 for (j = 0; j < bench_repeat && !done; j++) {
165 unsigned int nwoken = 0;
166 struct timeval start, end, runtime;
167
168 /* create, launch & block all threads */
169 block_threads(worker, thread_attr, cpu);
170
171 /* make sure all threads are already blocked */
172 pthread_mutex_lock(&thread_lock);
173 while (threads_starting)
174 pthread_cond_wait(&thread_parent, &thread_lock);
175 pthread_cond_broadcast(&thread_worker);
176 pthread_mutex_unlock(&thread_lock);
177
178 usleep(100000);
179
180 /* Ok, all threads are patiently blocked, start waking folks up */
181 gettimeofday(&start, NULL);
182 while (nwoken != nthreads)
183 nwoken += futex_wake(&futex1, nwakes, futex_flag);
184 gettimeofday(&end, NULL);
185 timersub(&end, &start, &runtime);
186
187 update_stats(&wakeup_stats, nwoken);
188 update_stats(&waketime_stats, runtime.tv_usec);
189
190 if (!silent) {
191 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
192 j + 1, nwoken, nthreads, runtime.tv_usec / (double)USEC_PER_MSEC);
193 }
194
195 for (i = 0; i < nthreads; i++) {
196 ret = pthread_join(worker[i], NULL);
197 if (ret)
198 err(EXIT_FAILURE, "pthread_join");
199 }
200
201 }
202
203 /* cleanup & report results */
204 pthread_cond_destroy(&thread_parent);
205 pthread_cond_destroy(&thread_worker);
206 pthread_mutex_destroy(&thread_lock);
207 pthread_attr_destroy(&thread_attr);
208
209 print_summary();
210
211 free(worker);
212 return ret;
213}
1/*
2 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
3 *
4 * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time.
5 *
6 * This program is particularly useful to measure the latency of nthread wakeups
7 * in non-error situations: all waiters are queued and all wake calls wakeup
8 * one or more tasks, and thus the waitqueue is never empty.
9 */
10
11#include "../perf.h"
12#include "../util/util.h"
13#include "../util/stat.h"
14#include <subcmd/parse-options.h>
15#include "../util/header.h"
16#include "bench.h"
17#include "futex.h"
18
19#include <err.h>
20#include <stdlib.h>
21#include <sys/time.h>
22#include <pthread.h>
23
24/* all threads will block on the same futex */
25static u_int32_t futex1 = 0;
26
27/*
28 * How many wakeups to do at a time.
29 * Default to 1 in order to make the kernel work more.
30 */
31static unsigned int nwakes = 1;
32
33pthread_t *worker;
34static bool done = false, silent = false, fshared = false;
35static pthread_mutex_t thread_lock;
36static pthread_cond_t thread_parent, thread_worker;
37static struct stats waketime_stats, wakeup_stats;
38static unsigned int ncpus, threads_starting, nthreads = 0;
39static int futex_flag = 0;
40
41static const struct option options[] = {
42 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
43 OPT_UINTEGER('w', "nwakes", &nwakes, "Specify amount of threads to wake at once"),
44 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
45 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"),
46 OPT_END()
47};
48
49static const char * const bench_futex_wake_usage[] = {
50 "perf bench futex wake <options>",
51 NULL
52};
53
54static void *workerfn(void *arg __maybe_unused)
55{
56 pthread_mutex_lock(&thread_lock);
57 threads_starting--;
58 if (!threads_starting)
59 pthread_cond_signal(&thread_parent);
60 pthread_cond_wait(&thread_worker, &thread_lock);
61 pthread_mutex_unlock(&thread_lock);
62
63 while (1) {
64 if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
65 break;
66 }
67
68 pthread_exit(NULL);
69 return NULL;
70}
71
72static void print_summary(void)
73{
74 double waketime_avg = avg_stats(&waketime_stats);
75 double waketime_stddev = stddev_stats(&waketime_stats);
76 unsigned int wakeup_avg = avg_stats(&wakeup_stats);
77
78 printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
79 wakeup_avg,
80 nthreads,
81 waketime_avg/1e3,
82 rel_stddev_stats(waketime_stddev, waketime_avg));
83}
84
85static void block_threads(pthread_t *w,
86 pthread_attr_t thread_attr)
87{
88 cpu_set_t cpu;
89 unsigned int i;
90
91 threads_starting = nthreads;
92
93 /* create and block all threads */
94 for (i = 0; i < nthreads; i++) {
95 CPU_ZERO(&cpu);
96 CPU_SET(i % ncpus, &cpu);
97
98 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
99 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
100
101 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
102 err(EXIT_FAILURE, "pthread_create");
103 }
104}
105
106static void toggle_done(int sig __maybe_unused,
107 siginfo_t *info __maybe_unused,
108 void *uc __maybe_unused)
109{
110 done = true;
111}
112
113int bench_futex_wake(int argc, const char **argv,
114 const char *prefix __maybe_unused)
115{
116 int ret = 0;
117 unsigned int i, j;
118 struct sigaction act;
119 pthread_attr_t thread_attr;
120
121 argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
122 if (argc) {
123 usage_with_options(bench_futex_wake_usage, options);
124 exit(EXIT_FAILURE);
125 }
126
127 ncpus = sysconf(_SC_NPROCESSORS_ONLN);
128
129 sigfillset(&act.sa_mask);
130 act.sa_sigaction = toggle_done;
131 sigaction(SIGINT, &act, NULL);
132
133 if (!nthreads)
134 nthreads = ncpus;
135
136 worker = calloc(nthreads, sizeof(*worker));
137 if (!worker)
138 err(EXIT_FAILURE, "calloc");
139
140 if (!fshared)
141 futex_flag = FUTEX_PRIVATE_FLAG;
142
143 printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
144 "waking up %d at a time.\n\n",
145 getpid(), nthreads, fshared ? "shared":"private", &futex1, nwakes);
146
147 init_stats(&wakeup_stats);
148 init_stats(&waketime_stats);
149 pthread_attr_init(&thread_attr);
150 pthread_mutex_init(&thread_lock, NULL);
151 pthread_cond_init(&thread_parent, NULL);
152 pthread_cond_init(&thread_worker, NULL);
153
154 for (j = 0; j < bench_repeat && !done; j++) {
155 unsigned int nwoken = 0;
156 struct timeval start, end, runtime;
157
158 /* create, launch & block all threads */
159 block_threads(worker, thread_attr);
160
161 /* make sure all threads are already blocked */
162 pthread_mutex_lock(&thread_lock);
163 while (threads_starting)
164 pthread_cond_wait(&thread_parent, &thread_lock);
165 pthread_cond_broadcast(&thread_worker);
166 pthread_mutex_unlock(&thread_lock);
167
168 usleep(100000);
169
170 /* Ok, all threads are patiently blocked, start waking folks up */
171 gettimeofday(&start, NULL);
172 while (nwoken != nthreads)
173 nwoken += futex_wake(&futex1, nwakes, futex_flag);
174 gettimeofday(&end, NULL);
175 timersub(&end, &start, &runtime);
176
177 update_stats(&wakeup_stats, nwoken);
178 update_stats(&waketime_stats, runtime.tv_usec);
179
180 if (!silent) {
181 printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
182 j + 1, nwoken, nthreads, runtime.tv_usec/1e3);
183 }
184
185 for (i = 0; i < nthreads; i++) {
186 ret = pthread_join(worker[i], NULL);
187 if (ret)
188 err(EXIT_FAILURE, "pthread_join");
189 }
190
191 }
192
193 /* cleanup & report results */
194 pthread_cond_destroy(&thread_parent);
195 pthread_cond_destroy(&thread_worker);
196 pthread_mutex_destroy(&thread_lock);
197 pthread_attr_destroy(&thread_attr);
198
199 print_summary();
200
201 free(worker);
202 return ret;
203}