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/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 static u_int32_t futex1 = 0, futex2 = 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 requeuetime_stats, requeued_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 tasks to requeue at a time.
46 * Default to 1 in order to make the kernel work more.
47 */
48 .nrequeue = 1,
49 };
50
51 static const struct option options[] = {
52 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
53 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue 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 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"),
58 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),
59
60 OPT_END()
61 };
62
63 static const char * const bench_futex_requeue_usage[] = {
64 "perf bench futex requeue <options>",
65 NULL
66 };
67
68 static void print_summary(void)
69 {
70 double requeuetime_avg = avg_stats(&requeuetime_stats);
71 double requeuetime_stddev = stddev_stats(&requeuetime_stats);
72 unsigned int requeued_avg = avg_stats(&requeued_stats);
73
74 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
75 requeued_avg,
76 params.nthreads,
77 requeuetime_avg / USEC_PER_MSEC,
78 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
79 }
80
81 static void *workerfn(void *arg __maybe_unused)
82 {
83 int ret;
84
85 pthread_mutex_lock(&thread_lock);
86 threads_starting--;
87 if (!threads_starting)
88 pthread_cond_signal(&thread_parent);
89 pthread_cond_wait(&thread_worker, &thread_lock);
90 pthread_mutex_unlock(&thread_lock);
91
92 while (1) {
93 if (!params.pi) {
94 ret = futex_wait(&futex1, 0, NULL, futex_flag);
95 if (!ret)
96 break;
97
98 if (ret && errno != EAGAIN) {
99 if (!params.silent)
100 warnx("futex_wait");
101 break;
102 }
103 } else {
104 ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
105 NULL, futex_flag);
106 if (!ret) {
107 /* got the lock at futex2 */
108 futex_unlock_pi(&futex2, futex_flag);
109 break;
110 }
111
112 if (ret && errno != EAGAIN) {
113 if (!params.silent)
114 warnx("futex_wait_requeue_pi");
115 break;
116 }
117 }
118 }
119
120 return NULL;
121 }
122
123 static void block_threads(pthread_t *w,
124 pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
125 {
126 cpu_set_t cpuset;
127 unsigned int i;
128
129 threads_starting = params.nthreads;
130
131 /* create and block all threads */
132 for (i = 0; i < params.nthreads; i++) {
133 CPU_ZERO(&cpuset);
134 CPU_SET(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, &cpuset);
135
136 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset))
137 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
138
139 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
140 err(EXIT_FAILURE, "pthread_create");
141 }
142 }
143
144 static void toggle_done(int sig __maybe_unused,
145 siginfo_t *info __maybe_unused,
146 void *uc __maybe_unused)
147 {
148 done = true;
149 }
150
151 int bench_futex_requeue(int argc, const char **argv)
152 {
153 int ret = 0;
154 unsigned int i, j;
155 struct sigaction act;
156 pthread_attr_t thread_attr;
157 struct perf_cpu_map *cpu;
158
159 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
160 if (argc)
161 goto err;
162
163 cpu = perf_cpu_map__new(NULL);
164 if (!cpu)
165 err(EXIT_FAILURE, "cpu_map__new");
166
167 memset(&act, 0, sizeof(act));
168 sigfillset(&act.sa_mask);
169 act.sa_sigaction = toggle_done;
170 sigaction(SIGINT, &act, NULL);
171
172 if (params.mlockall) {
173 if (mlockall(MCL_CURRENT | MCL_FUTURE))
174 err(EXIT_FAILURE, "mlockall");
175 }
176
177 if (!params.nthreads)
178 params.nthreads = perf_cpu_map__nr(cpu);
179
180 worker = calloc(params.nthreads, sizeof(*worker));
181 if (!worker)
182 err(EXIT_FAILURE, "calloc");
183
184 if (!params.fshared)
185 futex_flag = FUTEX_PRIVATE_FLAG;
186
187 if (params.nrequeue > params.nthreads)
188 params.nrequeue = params.nthreads;
189
190 if (params.broadcast)
191 params.nrequeue = params.nthreads;
192
193 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
194 "%d at a time.\n\n", getpid(), params.nthreads,
195 params.fshared ? "shared":"private", &futex1,
196 params.pi ? "PI ": "", &futex2, params.nrequeue);
197
198 init_stats(&requeued_stats);
199 init_stats(&requeuetime_stats);
200 pthread_attr_init(&thread_attr);
201 pthread_mutex_init(&thread_lock, NULL);
202 pthread_cond_init(&thread_parent, NULL);
203 pthread_cond_init(&thread_worker, NULL);
204
205 for (j = 0; j < bench_repeat && !done; j++) {
206 unsigned int nrequeued = 0, wakeups = 0;
207 struct timeval start, end, runtime;
208
209 /* create, launch & block all threads */
210 block_threads(worker, thread_attr, cpu);
211
212 /* make sure all threads are already blocked */
213 pthread_mutex_lock(&thread_lock);
214 while (threads_starting)
215 pthread_cond_wait(&thread_parent, &thread_lock);
216 pthread_cond_broadcast(&thread_worker);
217 pthread_mutex_unlock(&thread_lock);
218
219 usleep(100000);
220
221 /* Ok, all threads are patiently blocked, start requeueing */
222 gettimeofday(&start, NULL);
223 while (nrequeued < params.nthreads) {
224 int r;
225
226 /*
227 * For the regular non-pi case, do not wakeup any tasks
228 * blocked on futex1, allowing us to really measure
229 * futex_wait functionality. For the PI case the first
230 * waiter is always awoken.
231 */
232 if (!params.pi) {
233 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
234 params.nrequeue,
235 futex_flag);
236 } else {
237 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
238 params.nrequeue,
239 futex_flag);
240 wakeups++; /* assume no error */
241 }
242
243 if (r < 0)
244 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
245 &futex1, &futex2);
246
247 nrequeued += r;
248 }
249
250 gettimeofday(&end, NULL);
251 timersub(&end, &start, &runtime);
252
253 update_stats(&requeued_stats, nrequeued);
254 update_stats(&requeuetime_stats, runtime.tv_usec);
255
256 if (!params.silent) {
257 if (!params.pi)
258 printf("[Run %d]: Requeued %d of %d threads in "
259 "%.4f ms\n", j + 1, nrequeued,
260 params.nthreads,
261 runtime.tv_usec / (double)USEC_PER_MSEC);
262 else {
263 nrequeued -= wakeups;
264 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
265 "%d threads in %.4f ms\n",
266 j + 1, wakeups, nrequeued,
267 params.nthreads,
268 runtime.tv_usec / (double)USEC_PER_MSEC);
269 }
270
271 }
272
273 if (!params.pi) {
274 /* everybody should be blocked on futex2, wake'em up */
275 nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
276 if (params.nthreads != nrequeued)
277 warnx("couldn't wakeup all tasks (%d/%d)",
278 nrequeued, params.nthreads);
279 }
280
281 for (i = 0; i < params.nthreads; i++) {
282 ret = pthread_join(worker[i], NULL);
283 if (ret)
284 err(EXIT_FAILURE, "pthread_join");
285 }
286 }
287
288 /* cleanup & report results */
289 pthread_cond_destroy(&thread_parent);
290 pthread_cond_destroy(&thread_worker);
291 pthread_mutex_destroy(&thread_lock);
292 pthread_attr_destroy(&thread_attr);
293
294 print_summary();
295
296 free(worker);
297 perf_cpu_map__put(cpu);
298 return ret;
299 err:
300 usage_with_options(bench_futex_requeue_usage, options);
301 exit(EXIT_FAILURE);
302 }
303
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.