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 #include "../util/mutex.h"
14
15 #ifndef HAVE_PTHREAD_BARRIER
bench_futex_wake_parallel(int argc __maybe_unused,const char ** argv __maybe_unused)16 int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
17 {
18 pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
19 return 0;
20 }
21 #else /* HAVE_PTHREAD_BARRIER */
22 /* For the CLR_() macros */
23 #include <string.h>
24 #include <pthread.h>
25
26 #include <signal.h>
27 #include "../util/stat.h"
28 #include <subcmd/parse-options.h>
29 #include <linux/kernel.h>
30 #include <linux/time64.h>
31 #include <errno.h>
32 #include "futex.h"
33 #include <perf/cpumap.h>
34
35 #include <err.h>
36 #include <stdlib.h>
37 #include <sys/time.h>
38 #include <sys/mman.h>
39
40 struct thread_data {
41 pthread_t worker;
42 unsigned int nwoken;
43 struct timeval runtime;
44 };
45
46 static unsigned int nwakes = 1;
47
48 /* all threads will block on the same futex -- hash bucket chaos ;) */
49 static u_int32_t futex = 0;
50
51 static pthread_t *blocked_worker;
52 static bool done = false;
53 static struct mutex thread_lock;
54 static struct cond thread_parent, thread_worker;
55 static pthread_barrier_t barrier;
56 static struct stats waketime_stats, wakeup_stats;
57 static unsigned int threads_starting;
58 static int futex_flag = 0;
59
60 static struct bench_futex_parameters params;
61
62 static const struct option options[] = {
63 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
64 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"),
65 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
66 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
67 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
68
69 OPT_END()
70 };
71
72 static const char * const bench_futex_wake_parallel_usage[] = {
73 "perf bench futex wake-parallel <options>",
74 NULL
75 };
76
waking_workerfn(void * arg)77 static void *waking_workerfn(void *arg)
78 {
79 struct thread_data *waker = (struct thread_data *) arg;
80 struct timeval start, end;
81
82 pthread_barrier_wait(&barrier);
83
84 gettimeofday(&start, NULL);
85
86 waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
87 if (waker->nwoken != nwakes)
88 warnx("couldn't wakeup all tasks (%d/%d)",
89 waker->nwoken, nwakes);
90
91 gettimeofday(&end, NULL);
92 timersub(&end, &start, &waker->runtime);
93
94 pthread_exit(NULL);
95 return NULL;
96 }
97
wakeup_threads(struct thread_data * td)98 static void wakeup_threads(struct thread_data *td)
99 {
100 unsigned int i;
101 pthread_attr_t thread_attr;
102
103 pthread_attr_init(&thread_attr);
104 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
105
106 pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
107
108 /* create and block all threads */
109 for (i = 0; i < params.nwakes; i++) {
110 /*
111 * Thread creation order will impact per-thread latency
112 * as it will affect the order to acquire the hb spinlock.
113 * For now let the scheduler decide.
114 */
115 if (pthread_create(&td[i].worker, &thread_attr,
116 waking_workerfn, (void *)&td[i]))
117 err(EXIT_FAILURE, "pthread_create");
118 }
119
120 pthread_barrier_wait(&barrier);
121
122 for (i = 0; i < params.nwakes; i++)
123 if (pthread_join(td[i].worker, NULL))
124 err(EXIT_FAILURE, "pthread_join");
125
126 pthread_barrier_destroy(&barrier);
127 pthread_attr_destroy(&thread_attr);
128 }
129
blocked_workerfn(void * arg __maybe_unused)130 static void *blocked_workerfn(void *arg __maybe_unused)
131 {
132 mutex_lock(&thread_lock);
133 threads_starting--;
134 if (!threads_starting)
135 cond_signal(&thread_parent);
136 cond_wait(&thread_worker, &thread_lock);
137 mutex_unlock(&thread_lock);
138
139 while (1) { /* handle spurious wakeups */
140 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
141 break;
142 }
143
144 pthread_exit(NULL);
145 return NULL;
146 }
147
block_threads(pthread_t * w,struct perf_cpu_map * cpu)148 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
149 {
150 cpu_set_t *cpuset;
151 unsigned int i;
152 int nrcpus = perf_cpu_map__nr(cpu);
153 size_t size;
154
155 threads_starting = params.nthreads;
156
157 cpuset = CPU_ALLOC(nrcpus);
158 BUG_ON(!cpuset);
159 size = CPU_ALLOC_SIZE(nrcpus);
160
161 /* create and block all threads */
162 for (i = 0; i < params.nthreads; i++) {
163 pthread_attr_t thread_attr;
164
165 pthread_attr_init(&thread_attr);
166 CPU_ZERO_S(size, cpuset);
167 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
168
169 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
170 CPU_FREE(cpuset);
171 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
172 }
173
174 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
175 CPU_FREE(cpuset);
176 err(EXIT_FAILURE, "pthread_create");
177 }
178 pthread_attr_destroy(&thread_attr);
179 }
180 CPU_FREE(cpuset);
181 }
182
print_run(struct thread_data * waking_worker,unsigned int run_num)183 static void print_run(struct thread_data *waking_worker, unsigned int run_num)
184 {
185 unsigned int i, wakeup_avg;
186 double waketime_avg, waketime_stddev;
187 struct stats __waketime_stats, __wakeup_stats;
188
189 init_stats(&__wakeup_stats);
190 init_stats(&__waketime_stats);
191
192 for (i = 0; i < params.nwakes; i++) {
193 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
194 update_stats(&__wakeup_stats, waking_worker[i].nwoken);
195 }
196
197 waketime_avg = avg_stats(&__waketime_stats);
198 waketime_stddev = stddev_stats(&__waketime_stats);
199 wakeup_avg = avg_stats(&__wakeup_stats);
200
201 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
202 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
203 params.nthreads, waketime_avg / USEC_PER_MSEC,
204 rel_stddev_stats(waketime_stddev, waketime_avg));
205 }
206
print_summary(void)207 static void print_summary(void)
208 {
209 unsigned int wakeup_avg;
210 double waketime_avg, waketime_stddev;
211
212 waketime_avg = avg_stats(&waketime_stats);
213 waketime_stddev = stddev_stats(&waketime_stats);
214 wakeup_avg = avg_stats(&wakeup_stats);
215
216 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
217 wakeup_avg,
218 params.nthreads,
219 waketime_avg / USEC_PER_MSEC,
220 rel_stddev_stats(waketime_stddev, waketime_avg));
221 }
222
223
do_run_stats(struct thread_data * waking_worker)224 static void do_run_stats(struct thread_data *waking_worker)
225 {
226 unsigned int i;
227
228 for (i = 0; i < params.nwakes; i++) {
229 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
230 update_stats(&wakeup_stats, waking_worker[i].nwoken);
231 }
232
233 }
234
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)235 static void toggle_done(int sig __maybe_unused,
236 siginfo_t *info __maybe_unused,
237 void *uc __maybe_unused)
238 {
239 done = true;
240 }
241
bench_futex_wake_parallel(int argc,const char ** argv)242 int bench_futex_wake_parallel(int argc, const char **argv)
243 {
244 int ret = 0;
245 unsigned int i, j;
246 struct sigaction act;
247 struct thread_data *waking_worker;
248 struct perf_cpu_map *cpu;
249
250 argc = parse_options(argc, argv, options,
251 bench_futex_wake_parallel_usage, 0);
252 if (argc) {
253 usage_with_options(bench_futex_wake_parallel_usage, options);
254 exit(EXIT_FAILURE);
255 }
256
257 memset(&act, 0, sizeof(act));
258 sigfillset(&act.sa_mask);
259 act.sa_sigaction = toggle_done;
260 sigaction(SIGINT, &act, NULL);
261
262 if (params.mlockall) {
263 if (mlockall(MCL_CURRENT | MCL_FUTURE))
264 err(EXIT_FAILURE, "mlockall");
265 }
266
267 cpu = perf_cpu_map__new(NULL);
268 if (!cpu)
269 err(EXIT_FAILURE, "calloc");
270
271 if (!params.nthreads)
272 params.nthreads = perf_cpu_map__nr(cpu);
273
274 /* some sanity checks */
275 if (params.nwakes > params.nthreads ||
276 !params.nwakes)
277 params.nwakes = params.nthreads;
278
279 if (params.nthreads % params.nwakes)
280 errx(EXIT_FAILURE, "Must be perfectly divisible");
281 /*
282 * Each thread will wakeup nwakes tasks in
283 * a single futex_wait call.
284 */
285 nwakes = params.nthreads/params.nwakes;
286
287 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
288 if (!blocked_worker)
289 err(EXIT_FAILURE, "calloc");
290
291 if (!params.fshared)
292 futex_flag = FUTEX_PRIVATE_FLAG;
293
294 printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
295 "futex %p), %d threads waking up %d at a time.\n\n",
296 getpid(), params.nthreads, params.fshared ? "shared":"private",
297 &futex, params.nwakes, nwakes);
298
299 init_stats(&wakeup_stats);
300 init_stats(&waketime_stats);
301
302 mutex_init(&thread_lock);
303 cond_init(&thread_parent);
304 cond_init(&thread_worker);
305
306 for (j = 0; j < bench_repeat && !done; j++) {
307 waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
308 if (!waking_worker)
309 err(EXIT_FAILURE, "calloc");
310
311 /* create, launch & block all threads */
312 block_threads(blocked_worker, cpu);
313
314 /* make sure all threads are already blocked */
315 mutex_lock(&thread_lock);
316 while (threads_starting)
317 cond_wait(&thread_parent, &thread_lock);
318 cond_broadcast(&thread_worker);
319 mutex_unlock(&thread_lock);
320
321 usleep(100000);
322
323 /* Ok, all threads are patiently blocked, start waking folks up */
324 wakeup_threads(waking_worker);
325
326 for (i = 0; i < params.nthreads; i++) {
327 ret = pthread_join(blocked_worker[i], NULL);
328 if (ret)
329 err(EXIT_FAILURE, "pthread_join");
330 }
331
332 do_run_stats(waking_worker);
333 if (!params.silent)
334 print_run(waking_worker, j);
335
336 free(waking_worker);
337 }
338
339 /* cleanup & report results */
340 cond_destroy(&thread_parent);
341 cond_destroy(&thread_worker);
342 mutex_destroy(&thread_lock);
343
344 print_summary();
345
346 free(blocked_worker);
347 perf_cpu_map__put(cpu);
348 return ret;
349 }
350 #endif /* HAVE_PTHREAD_BARRIER */
351