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 .nbuckets = -1,
62 };
63
64 static const struct option options[] = {
65 OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"),
66 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
67 OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"),
68 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
69 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
70 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
71
72 OPT_END()
73 };
74
75 static const char * const bench_futex_wake_parallel_usage[] = {
76 "perf bench futex wake-parallel <options>",
77 NULL
78 };
79
waking_workerfn(void * arg)80 static void *waking_workerfn(void *arg)
81 {
82 struct thread_data *waker = (struct thread_data *) arg;
83 struct timeval start, end;
84
85 pthread_barrier_wait(&barrier);
86
87 gettimeofday(&start, NULL);
88
89 waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
90 if (waker->nwoken != nwakes)
91 warnx("couldn't wakeup all tasks (%d/%d)",
92 waker->nwoken, nwakes);
93
94 gettimeofday(&end, NULL);
95 timersub(&end, &start, &waker->runtime);
96
97 pthread_exit(NULL);
98 return NULL;
99 }
100
wakeup_threads(struct thread_data * td)101 static void wakeup_threads(struct thread_data *td)
102 {
103 unsigned int i;
104 pthread_attr_t thread_attr;
105
106 pthread_attr_init(&thread_attr);
107 pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
108
109 pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
110
111 /* create and block all threads */
112 for (i = 0; i < params.nwakes; i++) {
113 /*
114 * Thread creation order will impact per-thread latency
115 * as it will affect the order to acquire the hb spinlock.
116 * For now let the scheduler decide.
117 */
118 if (pthread_create(&td[i].worker, &thread_attr,
119 waking_workerfn, (void *)&td[i]))
120 err(EXIT_FAILURE, "pthread_create");
121 }
122
123 pthread_barrier_wait(&barrier);
124
125 for (i = 0; i < params.nwakes; i++)
126 if (pthread_join(td[i].worker, NULL))
127 err(EXIT_FAILURE, "pthread_join");
128
129 pthread_barrier_destroy(&barrier);
130 pthread_attr_destroy(&thread_attr);
131 }
132
blocked_workerfn(void * arg __maybe_unused)133 static void *blocked_workerfn(void *arg __maybe_unused)
134 {
135 mutex_lock(&thread_lock);
136 threads_starting--;
137 if (!threads_starting)
138 cond_signal(&thread_parent);
139 cond_wait(&thread_worker, &thread_lock);
140 mutex_unlock(&thread_lock);
141
142 while (1) { /* handle spurious wakeups */
143 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
144 break;
145 }
146
147 pthread_exit(NULL);
148 return NULL;
149 }
150
block_threads(pthread_t * w,struct perf_cpu_map * cpu)151 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
152 {
153 cpu_set_t *cpuset;
154 unsigned int i;
155 int nrcpus = cpu__max_cpu().cpu;
156 size_t size;
157
158 threads_starting = params.nthreads;
159
160 cpuset = CPU_ALLOC(nrcpus);
161 BUG_ON(!cpuset);
162 size = CPU_ALLOC_SIZE(nrcpus);
163
164 /* create and block all threads */
165 for (i = 0; i < params.nthreads; i++) {
166 pthread_attr_t thread_attr;
167
168 pthread_attr_init(&thread_attr);
169 CPU_ZERO_S(size, cpuset);
170 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
171
172 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
173 CPU_FREE(cpuset);
174 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
175 }
176
177 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
178 CPU_FREE(cpuset);
179 err(EXIT_FAILURE, "pthread_create");
180 }
181 pthread_attr_destroy(&thread_attr);
182 }
183 CPU_FREE(cpuset);
184 }
185
print_run(struct thread_data * waking_worker,unsigned int run_num)186 static void print_run(struct thread_data *waking_worker, unsigned int run_num)
187 {
188 unsigned int i, wakeup_avg;
189 double waketime_avg, waketime_stddev;
190 struct stats __waketime_stats, __wakeup_stats;
191
192 init_stats(&__wakeup_stats);
193 init_stats(&__waketime_stats);
194
195 for (i = 0; i < params.nwakes; i++) {
196 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
197 update_stats(&__wakeup_stats, waking_worker[i].nwoken);
198 }
199
200 waketime_avg = avg_stats(&__waketime_stats);
201 waketime_stddev = stddev_stats(&__waketime_stats);
202 wakeup_avg = avg_stats(&__wakeup_stats);
203
204 printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
205 "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
206 params.nthreads, waketime_avg / USEC_PER_MSEC,
207 rel_stddev_stats(waketime_stddev, waketime_avg));
208 }
209
print_summary(void)210 static void print_summary(void)
211 {
212 unsigned int wakeup_avg;
213 double waketime_avg, waketime_stddev;
214
215 waketime_avg = avg_stats(&waketime_stats);
216 waketime_stddev = stddev_stats(&waketime_stats);
217 wakeup_avg = avg_stats(&wakeup_stats);
218
219 printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
220 wakeup_avg,
221 params.nthreads,
222 waketime_avg / USEC_PER_MSEC,
223 rel_stddev_stats(waketime_stddev, waketime_avg));
224 futex_print_nbuckets(¶ms);
225 }
226
227
do_run_stats(struct thread_data * waking_worker)228 static void do_run_stats(struct thread_data *waking_worker)
229 {
230 unsigned int i;
231
232 for (i = 0; i < params.nwakes; i++) {
233 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
234 update_stats(&wakeup_stats, waking_worker[i].nwoken);
235 }
236
237 }
238
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)239 static void toggle_done(int sig __maybe_unused,
240 siginfo_t *info __maybe_unused,
241 void *uc __maybe_unused)
242 {
243 done = true;
244 }
245
bench_futex_wake_parallel(int argc,const char ** argv)246 int bench_futex_wake_parallel(int argc, const char **argv)
247 {
248 int ret = 0;
249 unsigned int i, j;
250 struct sigaction act;
251 struct thread_data *waking_worker;
252 struct perf_cpu_map *cpu;
253
254 argc = parse_options(argc, argv, options,
255 bench_futex_wake_parallel_usage, 0);
256 if (argc) {
257 usage_with_options(bench_futex_wake_parallel_usage, options);
258 exit(EXIT_FAILURE);
259 }
260
261 memset(&act, 0, sizeof(act));
262 sigfillset(&act.sa_mask);
263 act.sa_sigaction = toggle_done;
264 sigaction(SIGINT, &act, NULL);
265
266 if (params.mlockall) {
267 if (mlockall(MCL_CURRENT | MCL_FUTURE))
268 err(EXIT_FAILURE, "mlockall");
269 }
270
271 cpu = perf_cpu_map__new_online_cpus();
272 if (!cpu)
273 err(EXIT_FAILURE, "calloc");
274
275 if (!params.nthreads)
276 params.nthreads = perf_cpu_map__nr(cpu);
277
278 /* some sanity checks */
279 if (params.nwakes > params.nthreads ||
280 !params.nwakes)
281 params.nwakes = params.nthreads;
282
283 if (params.nthreads % params.nwakes)
284 errx(EXIT_FAILURE, "Must be perfectly divisible");
285 /*
286 * Each thread will wakeup nwakes tasks in
287 * a single futex_wait call.
288 */
289 nwakes = params.nthreads/params.nwakes;
290
291 blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
292 if (!blocked_worker)
293 err(EXIT_FAILURE, "calloc");
294
295 if (!params.fshared)
296 futex_flag = FUTEX_PRIVATE_FLAG;
297
298 futex_set_nbuckets_param(¶ms);
299
300 printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
301 "futex %p), %d threads waking up %d at a time.\n\n",
302 getpid(), params.nthreads, params.fshared ? "shared":"private",
303 &futex, params.nwakes, nwakes);
304
305 init_stats(&wakeup_stats);
306 init_stats(&waketime_stats);
307
308 mutex_init(&thread_lock);
309 cond_init(&thread_parent);
310 cond_init(&thread_worker);
311
312 for (j = 0; j < bench_repeat && !done; j++) {
313 waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
314 if (!waking_worker)
315 err(EXIT_FAILURE, "calloc");
316
317 /* create, launch & block all threads */
318 block_threads(blocked_worker, cpu);
319
320 /* make sure all threads are already blocked */
321 mutex_lock(&thread_lock);
322 while (threads_starting)
323 cond_wait(&thread_parent, &thread_lock);
324 cond_broadcast(&thread_worker);
325 mutex_unlock(&thread_lock);
326
327 usleep(200000);
328
329 /* Ok, all threads are patiently blocked, start waking folks up */
330 wakeup_threads(waking_worker);
331
332 for (i = 0; i < params.nthreads; i++) {
333 ret = pthread_join(blocked_worker[i], NULL);
334 if (ret)
335 err(EXIT_FAILURE, "pthread_join");
336 }
337
338 do_run_stats(waking_worker);
339 if (!params.silent)
340 print_run(waking_worker, j);
341
342 free(waking_worker);
343 }
344
345 /* cleanup & report results */
346 cond_destroy(&thread_parent);
347 cond_destroy(&thread_worker);
348 mutex_destroy(&thread_lock);
349
350 print_summary();
351
352 free(blocked_worker);
353 perf_cpu_map__put(cpu);
354 return ret;
355 }
356 #endif /* HAVE_PTHREAD_BARRIER */
357