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
34 static u_int32_t futex1 = 0, futex2 = 0;
35
36 static pthread_t *worker;
37 static bool done = false;
38 static struct mutex thread_lock;
39 static struct cond thread_parent, thread_worker;
40 static struct stats requeuetime_stats, requeued_stats;
41 static unsigned int threads_starting;
42 static int futex_flag = 0;
43
44 static struct bench_futex_parameters params = {
45 .nbuckets = -1,
46 /*
47 * How many tasks to requeue at a time.
48 * Default to 1 in order to make the kernel work more.
49 */
50 .nrequeue = 1,
51 };
52
53 static const struct option options[] = {
54 OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"),
55 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
56 OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue at once"),
57 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
58 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
59 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
60 OPT_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"),
61 OPT_BOOLEAN( 'p', "pi", ¶ms.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),
62
63 OPT_END()
64 };
65
66 static const char * const bench_futex_requeue_usage[] = {
67 "perf bench futex requeue <options>",
68 NULL
69 };
70
print_summary(void)71 static void print_summary(void)
72 {
73 double requeuetime_avg = avg_stats(&requeuetime_stats);
74 double requeuetime_stddev = stddev_stats(&requeuetime_stats);
75 unsigned int requeued_avg = avg_stats(&requeued_stats);
76
77 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
78 requeued_avg,
79 params.nthreads,
80 requeuetime_avg / USEC_PER_MSEC,
81 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
82 futex_print_nbuckets(¶ms);
83 }
84
workerfn(void * arg __maybe_unused)85 static void *workerfn(void *arg __maybe_unused)
86 {
87 int ret;
88
89 mutex_lock(&thread_lock);
90 threads_starting--;
91 if (!threads_starting)
92 cond_signal(&thread_parent);
93 cond_wait(&thread_worker, &thread_lock);
94 mutex_unlock(&thread_lock);
95
96 while (1) {
97 if (!params.pi) {
98 ret = futex_wait(&futex1, 0, NULL, futex_flag);
99 if (!ret)
100 break;
101
102 if (ret && errno != EAGAIN) {
103 if (!params.silent)
104 warnx("futex_wait");
105 break;
106 }
107 } else {
108 ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
109 NULL, futex_flag);
110 if (!ret) {
111 /* got the lock at futex2 */
112 futex_unlock_pi(&futex2, futex_flag);
113 break;
114 }
115
116 if (ret && errno != EAGAIN) {
117 if (!params.silent)
118 warnx("futex_wait_requeue_pi");
119 break;
120 }
121 }
122 }
123
124 return NULL;
125 }
126
block_threads(pthread_t * w,struct perf_cpu_map * cpu)127 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
128 {
129 cpu_set_t *cpuset;
130 unsigned int i;
131 int nrcpus = cpu__max_cpu().cpu;
132 size_t size;
133
134 threads_starting = params.nthreads;
135
136 cpuset = CPU_ALLOC(nrcpus);
137 BUG_ON(!cpuset);
138 size = CPU_ALLOC_SIZE(nrcpus);
139
140 /* create and block all threads */
141 for (i = 0; i < params.nthreads; i++) {
142 pthread_attr_t thread_attr;
143
144 pthread_attr_init(&thread_attr);
145 CPU_ZERO_S(size, cpuset);
146 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
147
148 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
149 CPU_FREE(cpuset);
150 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
151 }
152
153 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
154 CPU_FREE(cpuset);
155 err(EXIT_FAILURE, "pthread_create");
156 }
157 pthread_attr_destroy(&thread_attr);
158 }
159 CPU_FREE(cpuset);
160 }
161
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)162 static void toggle_done(int sig __maybe_unused,
163 siginfo_t *info __maybe_unused,
164 void *uc __maybe_unused)
165 {
166 done = true;
167 }
168
bench_futex_requeue(int argc,const char ** argv)169 int bench_futex_requeue(int argc, const char **argv)
170 {
171 int ret = 0;
172 unsigned int i, j;
173 struct sigaction act;
174 struct perf_cpu_map *cpu;
175
176 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
177 if (argc)
178 goto err;
179
180 cpu = perf_cpu_map__new_online_cpus();
181 if (!cpu)
182 err(EXIT_FAILURE, "cpu_map__new");
183
184 memset(&act, 0, sizeof(act));
185 sigfillset(&act.sa_mask);
186 act.sa_sigaction = toggle_done;
187 sigaction(SIGINT, &act, NULL);
188
189 if (params.mlockall) {
190 if (mlockall(MCL_CURRENT | MCL_FUTURE))
191 err(EXIT_FAILURE, "mlockall");
192 }
193
194 if (!params.nthreads)
195 params.nthreads = perf_cpu_map__nr(cpu);
196
197 worker = calloc(params.nthreads, sizeof(*worker));
198 if (!worker)
199 err(EXIT_FAILURE, "calloc");
200
201 if (!params.fshared)
202 futex_flag = FUTEX_PRIVATE_FLAG;
203
204 if (params.nrequeue > params.nthreads)
205 params.nrequeue = params.nthreads;
206
207 if (params.broadcast)
208 params.nrequeue = params.nthreads;
209
210 futex_set_nbuckets_param(¶ms);
211
212 printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
213 "%d at a time.\n\n", getpid(), params.nthreads,
214 params.fshared ? "shared":"private", &futex1,
215 params.pi ? "PI ": "", &futex2, params.nrequeue);
216
217 init_stats(&requeued_stats);
218 init_stats(&requeuetime_stats);
219 mutex_init(&thread_lock);
220 cond_init(&thread_parent);
221 cond_init(&thread_worker);
222
223 for (j = 0; j < bench_repeat && !done; j++) {
224 unsigned int nrequeued = 0, wakeups = 0;
225 struct timeval start, end, runtime;
226
227 /* create, launch & block all threads */
228 block_threads(worker, cpu);
229
230 /* make sure all threads are already blocked */
231 mutex_lock(&thread_lock);
232 while (threads_starting)
233 cond_wait(&thread_parent, &thread_lock);
234 cond_broadcast(&thread_worker);
235 mutex_unlock(&thread_lock);
236
237 usleep(100000);
238
239 /* Ok, all threads are patiently blocked, start requeueing */
240 gettimeofday(&start, NULL);
241 while (nrequeued < params.nthreads) {
242 int r;
243
244 /*
245 * For the regular non-pi case, do not wakeup any tasks
246 * blocked on futex1, allowing us to really measure
247 * futex_wait functionality. For the PI case the first
248 * waiter is always awoken.
249 */
250 if (!params.pi) {
251 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
252 params.nrequeue,
253 futex_flag);
254 } else {
255 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
256 params.nrequeue,
257 futex_flag);
258 wakeups++; /* assume no error */
259 }
260
261 if (r < 0)
262 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
263 &futex1, &futex2);
264
265 nrequeued += r;
266 }
267
268 gettimeofday(&end, NULL);
269 timersub(&end, &start, &runtime);
270
271 update_stats(&requeued_stats, nrequeued);
272 update_stats(&requeuetime_stats, runtime.tv_usec);
273
274 if (!params.silent) {
275 if (!params.pi)
276 printf("[Run %d]: Requeued %d of %d threads in "
277 "%.4f ms\n", j + 1, nrequeued,
278 params.nthreads,
279 runtime.tv_usec / (double)USEC_PER_MSEC);
280 else {
281 nrequeued -= wakeups;
282 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
283 "%d threads in %.4f ms\n",
284 j + 1, wakeups, nrequeued,
285 params.nthreads,
286 runtime.tv_usec / (double)USEC_PER_MSEC);
287 }
288
289 }
290
291 if (!params.pi) {
292 /* everybody should be blocked on futex2, wake'em up */
293 nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
294 if (params.nthreads != nrequeued)
295 warnx("couldn't wakeup all tasks (%d/%d)",
296 nrequeued, params.nthreads);
297 }
298
299 for (i = 0; i < params.nthreads; i++) {
300 ret = pthread_join(worker[i], NULL);
301 if (ret)
302 err(EXIT_FAILURE, "pthread_join");
303 }
304 }
305
306 /* cleanup & report results */
307 cond_destroy(&thread_parent);
308 cond_destroy(&thread_worker);
309 mutex_destroy(&thread_lock);
310
311 print_summary();
312
313 free(worker);
314 perf_cpu_map__put(cpu);
315 return ret;
316 err:
317 usage_with_options(bench_futex_requeue_usage, options);
318 exit(EXIT_FAILURE);
319 }
320