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
print_summary(void)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
workerfn(void * arg __maybe_unused)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
block_threads(pthread_t * w,pthread_attr_t thread_attr,struct perf_cpu_map * cpu)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 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 CPU_ZERO_S(size, cpuset);
140 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
141
142 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
143 CPU_FREE(cpuset);
144 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
145 }
146
147 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
148 CPU_FREE(cpuset);
149 err(EXIT_FAILURE, "pthread_create");
150 }
151 }
152 CPU_FREE(cpuset);
153 }
154
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)155 static void toggle_done(int sig __maybe_unused,
156 siginfo_t *info __maybe_unused,
157 void *uc __maybe_unused)
158 {
159 done = true;
160 }
161
bench_futex_requeue(int argc,const char ** argv)162 int bench_futex_requeue(int argc, const char **argv)
163 {
164 int ret = 0;
165 unsigned int i, j;
166 struct sigaction act;
167 pthread_attr_t thread_attr;
168 struct perf_cpu_map *cpu;
169
170 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
171 if (argc)
172 goto err;
173
174 cpu = perf_cpu_map__new(NULL);
175 if (!cpu)
176 err(EXIT_FAILURE, "cpu_map__new");
177
178 memset(&act, 0, sizeof(act));
179 sigfillset(&act.sa_mask);
180 act.sa_sigaction = toggle_done;
181 sigaction(SIGINT, &act, NULL);
182
183 if (params.mlockall) {
184 if (mlockall(MCL_CURRENT | MCL_FUTURE))
185 err(EXIT_FAILURE, "mlockall");
186 }
187
188 if (!params.nthreads)
189 params.nthreads = perf_cpu_map__nr(cpu);
190
191 worker = calloc(params.nthreads, sizeof(*worker));
192 if (!worker)
193 err(EXIT_FAILURE, "calloc");
194
195 if (!params.fshared)
196 futex_flag = FUTEX_PRIVATE_FLAG;
197
198 if (params.nrequeue > params.nthreads)
199 params.nrequeue = params.nthreads;
200
201 if (params.broadcast)
202 params.nrequeue = params.nthreads;
203
204 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
205 "%d at a time.\n\n", getpid(), params.nthreads,
206 params.fshared ? "shared":"private", &futex1,
207 params.pi ? "PI ": "", &futex2, params.nrequeue);
208
209 init_stats(&requeued_stats);
210 init_stats(&requeuetime_stats);
211 pthread_attr_init(&thread_attr);
212 pthread_mutex_init(&thread_lock, NULL);
213 pthread_cond_init(&thread_parent, NULL);
214 pthread_cond_init(&thread_worker, NULL);
215
216 for (j = 0; j < bench_repeat && !done; j++) {
217 unsigned int nrequeued = 0, wakeups = 0;
218 struct timeval start, end, runtime;
219
220 /* create, launch & block all threads */
221 block_threads(worker, thread_attr, cpu);
222
223 /* make sure all threads are already blocked */
224 pthread_mutex_lock(&thread_lock);
225 while (threads_starting)
226 pthread_cond_wait(&thread_parent, &thread_lock);
227 pthread_cond_broadcast(&thread_worker);
228 pthread_mutex_unlock(&thread_lock);
229
230 usleep(100000);
231
232 /* Ok, all threads are patiently blocked, start requeueing */
233 gettimeofday(&start, NULL);
234 while (nrequeued < params.nthreads) {
235 int r;
236
237 /*
238 * For the regular non-pi case, do not wakeup any tasks
239 * blocked on futex1, allowing us to really measure
240 * futex_wait functionality. For the PI case the first
241 * waiter is always awoken.
242 */
243 if (!params.pi) {
244 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
245 params.nrequeue,
246 futex_flag);
247 } else {
248 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
249 params.nrequeue,
250 futex_flag);
251 wakeups++; /* assume no error */
252 }
253
254 if (r < 0)
255 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
256 &futex1, &futex2);
257
258 nrequeued += r;
259 }
260
261 gettimeofday(&end, NULL);
262 timersub(&end, &start, &runtime);
263
264 update_stats(&requeued_stats, nrequeued);
265 update_stats(&requeuetime_stats, runtime.tv_usec);
266
267 if (!params.silent) {
268 if (!params.pi)
269 printf("[Run %d]: Requeued %d of %d threads in "
270 "%.4f ms\n", j + 1, nrequeued,
271 params.nthreads,
272 runtime.tv_usec / (double)USEC_PER_MSEC);
273 else {
274 nrequeued -= wakeups;
275 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
276 "%d threads in %.4f ms\n",
277 j + 1, wakeups, nrequeued,
278 params.nthreads,
279 runtime.tv_usec / (double)USEC_PER_MSEC);
280 }
281
282 }
283
284 if (!params.pi) {
285 /* everybody should be blocked on futex2, wake'em up */
286 nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
287 if (params.nthreads != nrequeued)
288 warnx("couldn't wakeup all tasks (%d/%d)",
289 nrequeued, params.nthreads);
290 }
291
292 for (i = 0; i < params.nthreads; i++) {
293 ret = pthread_join(worker[i], NULL);
294 if (ret)
295 err(EXIT_FAILURE, "pthread_join");
296 }
297 }
298
299 /* cleanup & report results */
300 pthread_cond_destroy(&thread_parent);
301 pthread_cond_destroy(&thread_worker);
302 pthread_mutex_destroy(&thread_lock);
303 pthread_attr_destroy(&thread_attr);
304
305 print_summary();
306
307 free(worker);
308 perf_cpu_map__put(cpu);
309 return ret;
310 err:
311 usage_with_options(bench_futex_requeue_usage, options);
312 exit(EXIT_FAILURE);
313 }
314