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1/*
2 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
3 *
4 * futex-requeue: Block a bunch of threads on futex1 and requeue them
5 * on futex2, N at a time.
6 *
7 * This program is particularly useful to measure the latency of nthread
8 * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
9 */
10
11#include "../perf.h"
12#include "../util/util.h"
13#include "../util/stat.h"
14#include "../util/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
24static u_int32_t futex1 = 0, futex2 = 0;
25
26/*
27 * How many tasks to requeue at a time.
28 * Default to 1 in order to make the kernel work more.
29 */
30static unsigned int nrequeue = 1;
31
32/*
33 * There can be significant variance from run to run,
34 * the more repeats, the more exact the overall avg and
35 * the better idea of the futex latency.
36 */
37static unsigned int repeat = 10;
38
39static pthread_t *worker;
40static bool done = 0, silent = 0;
41static pthread_mutex_t thread_lock;
42static pthread_cond_t thread_parent, thread_worker;
43static struct stats requeuetime_stats, requeued_stats;
44static unsigned int ncpus, threads_starting, nthreads = 0;
45
46static const struct option options[] = {
47 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
48 OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"),
49 OPT_UINTEGER('r', "repeat", &repeat, "Specify amount of times to repeat the run"),
50 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
51 OPT_END()
52};
53
54static const char * const bench_futex_requeue_usage[] = {
55 "perf bench futex requeue <options>",
56 NULL
57};
58
59static void print_summary(void)
60{
61 double requeuetime_avg = avg_stats(&requeuetime_stats);
62 double requeuetime_stddev = stddev_stats(&requeuetime_stats);
63 unsigned int requeued_avg = avg_stats(&requeued_stats);
64
65 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
66 requeued_avg,
67 nthreads,
68 requeuetime_avg/1e3,
69 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
70}
71
72static void *workerfn(void *arg __maybe_unused)
73{
74 pthread_mutex_lock(&thread_lock);
75 threads_starting--;
76 if (!threads_starting)
77 pthread_cond_signal(&thread_parent);
78 pthread_cond_wait(&thread_worker, &thread_lock);
79 pthread_mutex_unlock(&thread_lock);
80
81 futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG);
82 return NULL;
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_requeue(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_requeue_usage, 0);
122 if (argc)
123 goto err;
124
125 ncpus = sysconf(_SC_NPROCESSORS_ONLN);
126
127 sigfillset(&act.sa_mask);
128 act.sa_sigaction = toggle_done;
129 sigaction(SIGINT, &act, NULL);
130
131 if (!nthreads)
132 nthreads = ncpus;
133
134 worker = calloc(nthreads, sizeof(*worker));
135 if (!worker)
136 err(EXIT_FAILURE, "calloc");
137
138 printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), "
139 "%d at a time.\n\n",
140 getpid(), nthreads, &futex1, &futex2, nrequeue);
141
142 init_stats(&requeued_stats);
143 init_stats(&requeuetime_stats);
144 pthread_attr_init(&thread_attr);
145 pthread_mutex_init(&thread_lock, NULL);
146 pthread_cond_init(&thread_parent, NULL);
147 pthread_cond_init(&thread_worker, NULL);
148
149 for (j = 0; j < repeat && !done; j++) {
150 unsigned int nrequeued = 0;
151 struct timeval start, end, runtime;
152
153 /* create, launch & block all threads */
154 block_threads(worker, thread_attr);
155
156 /* make sure all threads are already blocked */
157 pthread_mutex_lock(&thread_lock);
158 while (threads_starting)
159 pthread_cond_wait(&thread_parent, &thread_lock);
160 pthread_cond_broadcast(&thread_worker);
161 pthread_mutex_unlock(&thread_lock);
162
163 usleep(100000);
164
165 /* Ok, all threads are patiently blocked, start requeueing */
166 gettimeofday(&start, NULL);
167 for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue)
168 /*
169 * Do not wakeup any tasks blocked on futex1, allowing
170 * us to really measure futex_wait functionality.
171 */
172 futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue,
173 FUTEX_PRIVATE_FLAG);
174 gettimeofday(&end, NULL);
175 timersub(&end, &start, &runtime);
176
177 update_stats(&requeued_stats, nrequeued);
178 update_stats(&requeuetime_stats, runtime.tv_usec);
179
180 if (!silent) {
181 printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n",
182 j + 1, nrequeued, nthreads, runtime.tv_usec/1e3);
183 }
184
185 /* everybody should be blocked on futex2, wake'em up */
186 nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG);
187 if (nthreads != nrequeued)
188 warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);
189
190 for (i = 0; i < nthreads; i++) {
191 ret = pthread_join(worker[i], NULL);
192 if (ret)
193 err(EXIT_FAILURE, "pthread_join");
194 }
195
196 }
197
198 /* cleanup & report results */
199 pthread_cond_destroy(&thread_parent);
200 pthread_cond_destroy(&thread_worker);
201 pthread_mutex_destroy(&thread_lock);
202 pthread_attr_destroy(&thread_attr);
203
204 print_summary();
205
206 free(worker);
207 return ret;
208err:
209 usage_with_options(bench_futex_requeue_usage, options);
210 exit(EXIT_FAILURE);
211}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
4 *
5 * futex-requeue: Block a bunch of threads on futex1 and requeue them
6 * on futex2, N at a time.
7 *
8 * This program is particularly useful to measure the latency of nthread
9 * requeues without waking up any tasks (in the non-pi case) -- thus
10 * mimicking a regular futex_wait.
11 */
12
13/* For the CLR_() macros */
14#include <string.h>
15#include <pthread.h>
16
17#include <signal.h>
18#include "../util/mutex.h"
19#include "../util/stat.h"
20#include <subcmd/parse-options.h>
21#include <linux/compiler.h>
22#include <linux/kernel.h>
23#include <linux/time64.h>
24#include <errno.h>
25#include <perf/cpumap.h>
26#include "bench.h"
27#include "futex.h"
28
29#include <err.h>
30#include <stdlib.h>
31#include <sys/time.h>
32#include <sys/mman.h>
33
34static u_int32_t futex1 = 0, futex2 = 0;
35
36static pthread_t *worker;
37static bool done = false;
38static struct mutex thread_lock;
39static struct cond thread_parent, thread_worker;
40static struct stats requeuetime_stats, requeued_stats;
41static unsigned int threads_starting;
42static int futex_flag = 0;
43
44static struct bench_futex_parameters params = {
45 /*
46 * How many tasks to requeue at a time.
47 * Default to 1 in order to make the kernel work more.
48 */
49 .nrequeue = 1,
50};
51
52static const struct option options[] = {
53 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
54 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue 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 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"),
59 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),
60
61 OPT_END()
62};
63
64static const char * const bench_futex_requeue_usage[] = {
65 "perf bench futex requeue <options>",
66 NULL
67};
68
69static void print_summary(void)
70{
71 double requeuetime_avg = avg_stats(&requeuetime_stats);
72 double requeuetime_stddev = stddev_stats(&requeuetime_stats);
73 unsigned int requeued_avg = avg_stats(&requeued_stats);
74
75 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
76 requeued_avg,
77 params.nthreads,
78 requeuetime_avg / USEC_PER_MSEC,
79 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
80}
81
82static void *workerfn(void *arg __maybe_unused)
83{
84 int ret;
85
86 mutex_lock(&thread_lock);
87 threads_starting--;
88 if (!threads_starting)
89 cond_signal(&thread_parent);
90 cond_wait(&thread_worker, &thread_lock);
91 mutex_unlock(&thread_lock);
92
93 while (1) {
94 if (!params.pi) {
95 ret = futex_wait(&futex1, 0, NULL, futex_flag);
96 if (!ret)
97 break;
98
99 if (ret && errno != EAGAIN) {
100 if (!params.silent)
101 warnx("futex_wait");
102 break;
103 }
104 } else {
105 ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
106 NULL, futex_flag);
107 if (!ret) {
108 /* got the lock at futex2 */
109 futex_unlock_pi(&futex2, futex_flag);
110 break;
111 }
112
113 if (ret && errno != EAGAIN) {
114 if (!params.silent)
115 warnx("futex_wait_requeue_pi");
116 break;
117 }
118 }
119 }
120
121 return NULL;
122}
123
124static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
125{
126 cpu_set_t *cpuset;
127 unsigned int i;
128 int nrcpus = perf_cpu_map__nr(cpu);
129 size_t size;
130
131 threads_starting = params.nthreads;
132
133 cpuset = CPU_ALLOC(nrcpus);
134 BUG_ON(!cpuset);
135 size = CPU_ALLOC_SIZE(nrcpus);
136
137 /* create and block all threads */
138 for (i = 0; i < params.nthreads; i++) {
139 pthread_attr_t thread_attr;
140
141 pthread_attr_init(&thread_attr);
142 CPU_ZERO_S(size, cpuset);
143 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
144
145 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
146 CPU_FREE(cpuset);
147 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
148 }
149
150 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
151 CPU_FREE(cpuset);
152 err(EXIT_FAILURE, "pthread_create");
153 }
154 pthread_attr_destroy(&thread_attr);
155 }
156 CPU_FREE(cpuset);
157}
158
159static void toggle_done(int sig __maybe_unused,
160 siginfo_t *info __maybe_unused,
161 void *uc __maybe_unused)
162{
163 done = true;
164}
165
166int bench_futex_requeue(int argc, const char **argv)
167{
168 int ret = 0;
169 unsigned int i, j;
170 struct sigaction act;
171 struct perf_cpu_map *cpu;
172
173 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
174 if (argc)
175 goto err;
176
177 cpu = perf_cpu_map__new_online_cpus();
178 if (!cpu)
179 err(EXIT_FAILURE, "cpu_map__new");
180
181 memset(&act, 0, sizeof(act));
182 sigfillset(&act.sa_mask);
183 act.sa_sigaction = toggle_done;
184 sigaction(SIGINT, &act, NULL);
185
186 if (params.mlockall) {
187 if (mlockall(MCL_CURRENT | MCL_FUTURE))
188 err(EXIT_FAILURE, "mlockall");
189 }
190
191 if (!params.nthreads)
192 params.nthreads = perf_cpu_map__nr(cpu);
193
194 worker = calloc(params.nthreads, sizeof(*worker));
195 if (!worker)
196 err(EXIT_FAILURE, "calloc");
197
198 if (!params.fshared)
199 futex_flag = FUTEX_PRIVATE_FLAG;
200
201 if (params.nrequeue > params.nthreads)
202 params.nrequeue = params.nthreads;
203
204 if (params.broadcast)
205 params.nrequeue = params.nthreads;
206
207 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
208 "%d at a time.\n\n", getpid(), params.nthreads,
209 params.fshared ? "shared":"private", &futex1,
210 params.pi ? "PI ": "", &futex2, params.nrequeue);
211
212 init_stats(&requeued_stats);
213 init_stats(&requeuetime_stats);
214 mutex_init(&thread_lock);
215 cond_init(&thread_parent);
216 cond_init(&thread_worker);
217
218 for (j = 0; j < bench_repeat && !done; j++) {
219 unsigned int nrequeued = 0, wakeups = 0;
220 struct timeval start, end, runtime;
221
222 /* create, launch & block all threads */
223 block_threads(worker, cpu);
224
225 /* make sure all threads are already blocked */
226 mutex_lock(&thread_lock);
227 while (threads_starting)
228 cond_wait(&thread_parent, &thread_lock);
229 cond_broadcast(&thread_worker);
230 mutex_unlock(&thread_lock);
231
232 usleep(100000);
233
234 /* Ok, all threads are patiently blocked, start requeueing */
235 gettimeofday(&start, NULL);
236 while (nrequeued < params.nthreads) {
237 int r;
238
239 /*
240 * For the regular non-pi case, do not wakeup any tasks
241 * blocked on futex1, allowing us to really measure
242 * futex_wait functionality. For the PI case the first
243 * waiter is always awoken.
244 */
245 if (!params.pi) {
246 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
247 params.nrequeue,
248 futex_flag);
249 } else {
250 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
251 params.nrequeue,
252 futex_flag);
253 wakeups++; /* assume no error */
254 }
255
256 if (r < 0)
257 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
258 &futex1, &futex2);
259
260 nrequeued += r;
261 }
262
263 gettimeofday(&end, NULL);
264 timersub(&end, &start, &runtime);
265
266 update_stats(&requeued_stats, nrequeued);
267 update_stats(&requeuetime_stats, runtime.tv_usec);
268
269 if (!params.silent) {
270 if (!params.pi)
271 printf("[Run %d]: Requeued %d of %d threads in "
272 "%.4f ms\n", j + 1, nrequeued,
273 params.nthreads,
274 runtime.tv_usec / (double)USEC_PER_MSEC);
275 else {
276 nrequeued -= wakeups;
277 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
278 "%d threads in %.4f ms\n",
279 j + 1, wakeups, nrequeued,
280 params.nthreads,
281 runtime.tv_usec / (double)USEC_PER_MSEC);
282 }
283
284 }
285
286 if (!params.pi) {
287 /* everybody should be blocked on futex2, wake'em up */
288 nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
289 if (params.nthreads != nrequeued)
290 warnx("couldn't wakeup all tasks (%d/%d)",
291 nrequeued, params.nthreads);
292 }
293
294 for (i = 0; i < params.nthreads; i++) {
295 ret = pthread_join(worker[i], NULL);
296 if (ret)
297 err(EXIT_FAILURE, "pthread_join");
298 }
299 }
300
301 /* cleanup & report results */
302 cond_destroy(&thread_parent);
303 cond_destroy(&thread_worker);
304 mutex_destroy(&thread_lock);
305
306 print_summary();
307
308 free(worker);
309 perf_cpu_map__put(cpu);
310 return ret;
311err:
312 usage_with_options(bench_futex_requeue_usage, options);
313 exit(EXIT_FAILURE);
314}