1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2015 Davidlohr Bueso.
4 *
5 * Block a bunch of threads and let parallel waker threads wakeup an
6 * equal amount of them. The program output reflects the avg latency
7 * for each individual thread to service its share of work. Ultimately
8 * it can be used to measure futex_wake() changes.
9 */
10 #include "bench.h"
11 #include <linux/compiler.h>
12 #include "../util/debug.h"
13
14 #ifndef HAVE_PTHREAD_BARRIER
bench_futex_wake_parallel(int argc __maybe_unused,const char ** argv __maybe_unused)15 int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
16 {
17 pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
18 return 0;
19 }
20 #else /* HAVE_PTHREAD_BARRIER */
21 /* For the CLR_() macros */
22 #include <string.h>
23 #include <pthread.h>
24
25 #include <signal.h>
26 #include "../util/stat.h"
27 #include <subcmd/parse-options.h>
28 #include <linux/kernel.h>
29 #include <linux/time64.h>
30 #include <errno.h>
31 #include "futex.h"
32 #include <perf/cpumap.h>
33
34 #include <err.h>
35 #include <stdlib.h>
36 #include <sys/time.h>
37 #include <sys/mman.h>
38
39 struct thread_data {
40 pthread_t worker;
41 unsigned int nwoken;
42 struct timeval runtime;
43 };
44
45 static unsigned int nwakes = 1;
46
47 /* all threads will block on the same futex -- hash bucket chaos ;) */
48 static u_int32_t futex = 0;
49
50 static pthread_t *blocked_worker;
51 static bool done = false;
52 static pthread_mutex_t thread_lock;
53 static pthread_cond_t thread_parent, thread_worker;
54 static pthread_barrier_t barrier;
55 static struct stats waketime_stats, wakeup_stats;
56 static unsigned int threads_starting;
57 static int futex_flag = 0;
58
59 static struct bench_futex_parameters params;
60
61 static const struct option options[] = {
62 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
63 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"),
64 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
65 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
66 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
67
68 OPT_END()
69 };
70
71 static const char * const bench_futex_wake_parallel_usage[] = {
72 "perf bench futex wake-parallel <options>",
73 NULL
74 };
75
waking_workerfn(void * arg)76 static void *waking_workerfn(void *arg)
77 {
78 struct thread_data *waker = (struct thread_data *) arg;
79 struct timeval start, end;
80
81 pthread_barrier_wait(&barrier);
82
83 gettimeofday(&start, NULL);
84
85 waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
86 if (waker->nwoken != nwakes)
87 warnx("couldn't wakeup all tasks (%d/%d)",
88 waker->nwoken, nwakes);
89
90 gettimeofday(&end, NULL);
91 timersub(&end, &start, &waker->runtime);
92
93 pthread_exit(NULL);
94 return NULL;
95 }
96
wakeup_threads(struct thread_data * td,pthread_attr_t thread_attr)97 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr)
98 {
99 unsigned int i;
100
101 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
102
103 pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
104
105 /* create and block all threads */
106 for (i = 0; i < params.nwakes; i++) {
107 /*
108 * Thread creation order will impact per-thread latency
109 * as it will affect the order to acquire the hb spinlock.
110 * For now let the scheduler decide.
111 */
112 if (pthread_create(&td[i].worker, &thread_attr,
113 waking_workerfn, (void *)&td[i]))
114 err(EXIT_FAILURE, "pthread_create");
115 }
116
117 pthread_barrier_wait(&barrier);
118
119 for (i = 0; i < params.nwakes; i++)
120 if (pthread_join(td[i].worker, NULL))
121 err(EXIT_FAILURE, "pthread_join");
122
123 pthread_barrier_destroy(&barrier);
124 }
125
blocked_workerfn(void * arg __maybe_unused)126 static void *blocked_workerfn(void *arg __maybe_unused)
127 {
128 pthread_mutex_lock(&thread_lock);
129 threads_starting--;
130 if (!threads_starting)
131 pthread_cond_signal(&thread_parent);
132 pthread_cond_wait(&thread_worker, &thread_lock);
133 pthread_mutex_unlock(&thread_lock);
134
135 while (1) { /* handle spurious wakeups */
136 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
137 break;
138 }
139
140 pthread_exit(NULL);
141 return NULL;
142 }
143
block_threads(pthread_t * w,pthread_attr_t thread_attr,struct perf_cpu_map * cpu)144 static void block_threads(pthread_t *w, pthread_attr_t thread_attr,
145 struct perf_cpu_map *cpu)
146 {
147 cpu_set_t *cpuset;
148 unsigned int i;
149 int nrcpus = perf_cpu_map__nr(cpu);
150 size_t size;
151
152 threads_starting = params.nthreads;
153
154 cpuset = CPU_ALLOC(nrcpus);
155 BUG_ON(!cpuset);
156 size = CPU_ALLOC_SIZE(nrcpus);
157
158 /* create and block all threads */
159 for (i = 0; i < params.nthreads; i++) {
160 CPU_ZERO_S(size, cpuset);
161 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
162
163 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
164 CPU_FREE(cpuset);
165 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
166 }
167
168 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
169 CPU_FREE(cpuset);
170 err(EXIT_FAILURE, "pthread_create");
171 }
172 }
173 CPU_FREE(cpuset);
174 }
175
print_run(struct thread_data * waking_worker,unsigned int run_num)176 static void print_run(struct thread_data *waking_worker, unsigned int run_num)
177 {
178 unsigned int i, wakeup_avg;
179 double waketime_avg, waketime_stddev;
180 struct stats __waketime_stats, __wakeup_stats;
181
182 init_stats(&__wakeup_stats);
183 init_stats(&__waketime_stats);
184
185 for (i = 0; i < params.nwakes; i++) {
186 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
187 update_stats(&__wakeup_stats, waking_worker[i].nwoken);
188 }
189
190 waketime_avg = avg_stats(&__waketime_stats);
191 waketime_stddev = stddev_stats(&__waketime_stats);
192 wakeup_avg = avg_stats(&__wakeup_stats);
193
194 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
195 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
196 params.nthreads, waketime_avg / USEC_PER_MSEC,
197 rel_stddev_stats(waketime_stddev, waketime_avg));
198 }
199
print_summary(void)200 static void print_summary(void)
201 {
202 unsigned int wakeup_avg;
203 double waketime_avg, waketime_stddev;
204
205 waketime_avg = avg_stats(&waketime_stats);
206 waketime_stddev = stddev_stats(&waketime_stats);
207 wakeup_avg = avg_stats(&wakeup_stats);
208
209 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
210 wakeup_avg,
211 params.nthreads,
212 waketime_avg / USEC_PER_MSEC,
213 rel_stddev_stats(waketime_stddev, waketime_avg));
214 }
215
216
do_run_stats(struct thread_data * waking_worker)217 static void do_run_stats(struct thread_data *waking_worker)
218 {
219 unsigned int i;
220
221 for (i = 0; i < params.nwakes; i++) {
222 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
223 update_stats(&wakeup_stats, waking_worker[i].nwoken);
224 }
225
226 }
227
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)228 static void toggle_done(int sig __maybe_unused,
229 siginfo_t *info __maybe_unused,
230 void *uc __maybe_unused)
231 {
232 done = true;
233 }
234
bench_futex_wake_parallel(int argc,const char ** argv)235 int bench_futex_wake_parallel(int argc, const char **argv)
236 {
237 int ret = 0;
238 unsigned int i, j;
239 struct sigaction act;
240 pthread_attr_t thread_attr;
241 struct thread_data *waking_worker;
242 struct perf_cpu_map *cpu;
243
244 argc = parse_options(argc, argv, options,
245 bench_futex_wake_parallel_usage, 0);
246 if (argc) {
247 usage_with_options(bench_futex_wake_parallel_usage, options);
248 exit(EXIT_FAILURE);
249 }
250
251 memset(&act, 0, sizeof(act));
252 sigfillset(&act.sa_mask);
253 act.sa_sigaction = toggle_done;
254 sigaction(SIGINT, &act, NULL);
255
256 if (params.mlockall) {
257 if (mlockall(MCL_CURRENT | MCL_FUTURE))
258 err(EXIT_FAILURE, "mlockall");
259 }
260
261 cpu = perf_cpu_map__new(NULL);
262 if (!cpu)
263 err(EXIT_FAILURE, "calloc");
264
265 if (!params.nthreads)
266 params.nthreads = perf_cpu_map__nr(cpu);
267
268 /* some sanity checks */
269 if (params.nwakes > params.nthreads ||
270 !params.nwakes)
271 params.nwakes = params.nthreads;
272
273 if (params.nthreads % params.nwakes)
274 errx(EXIT_FAILURE, "Must be perfectly divisible");
275 /*
276 * Each thread will wakeup nwakes tasks in
277 * a single futex_wait call.
278 */
279 nwakes = params.nthreads/params.nwakes;
280
281 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
282 if (!blocked_worker)
283 err(EXIT_FAILURE, "calloc");
284
285 if (!params.fshared)
286 futex_flag = FUTEX_PRIVATE_FLAG;
287
288 printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
289 "futex %p), %d threads waking up %d at a time.\n\n",
290 getpid(), params.nthreads, params.fshared ? "shared":"private",
291 &futex, params.nwakes, nwakes);
292
293 init_stats(&wakeup_stats);
294 init_stats(&waketime_stats);
295
296 pthread_attr_init(&thread_attr);
297 pthread_mutex_init(&thread_lock, NULL);
298 pthread_cond_init(&thread_parent, NULL);
299 pthread_cond_init(&thread_worker, NULL);
300
301 for (j = 0; j < bench_repeat && !done; j++) {
302 waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
303 if (!waking_worker)
304 err(EXIT_FAILURE, "calloc");
305
306 /* create, launch & block all threads */
307 block_threads(blocked_worker, thread_attr, cpu);
308
309 /* make sure all threads are already blocked */
310 pthread_mutex_lock(&thread_lock);
311 while (threads_starting)
312 pthread_cond_wait(&thread_parent, &thread_lock);
313 pthread_cond_broadcast(&thread_worker);
314 pthread_mutex_unlock(&thread_lock);
315
316 usleep(100000);
317
318 /* Ok, all threads are patiently blocked, start waking folks up */
319 wakeup_threads(waking_worker, thread_attr);
320
321 for (i = 0; i < params.nthreads; i++) {
322 ret = pthread_join(blocked_worker[i], NULL);
323 if (ret)
324 err(EXIT_FAILURE, "pthread_join");
325 }
326
327 do_run_stats(waking_worker);
328 if (!params.silent)
329 print_run(waking_worker, j);
330
331 free(waking_worker);
332 }
333
334 /* cleanup & report results */
335 pthread_cond_destroy(&thread_parent);
336 pthread_cond_destroy(&thread_worker);
337 pthread_mutex_destroy(&thread_lock);
338 pthread_attr_destroy(&thread_attr);
339
340 print_summary();
341
342 free(blocked_worker);
343 perf_cpu_map__put(cpu);
344 return ret;
345 }
346 #endif /* HAVE_PTHREAD_BARRIER */
347