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1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2013  Davidlohr Bueso <[email protected]>
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         /*
46          * How many tasks to requeue at a time.
47          * Default to 1 in order to make the kernel work more.
48          */
49         .nrequeue = 1,
50 };
51
52 static const struct option options[] = {
53         OPT_UINTEGER('t', "threads",  &params.nthreads, "Specify amount of threads"),
54         OPT_UINTEGER('q', "nrequeue", &params.nrequeue, "Specify amount of threads to requeue at once"),
55         OPT_BOOLEAN( 's', "silent",   &params.silent, "Silent mode: do not display data/details"),
56         OPT_BOOLEAN( 'S', "shared",   &params.fshared, "Use shared futexes instead of private ones"),
57         OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
58         OPT_BOOLEAN( 'B', "broadcast", &params.broadcast, "Requeue all threads at once"),
59         OPT_BOOLEAN( 'p', "pi", &params.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),
60
61         OPT_END()
62 };
63
64 static const char * const bench_futex_requeue_usage[] = {
65         "perf bench futex requeue <options>",
66         NULL
67 };
68
69 static void print_summary(void)
70 {
71         double requeuetime_avg = avg_stats(&requeuetime_stats);
72         double requeuetime_stddev = stddev_stats(&requeuetime_stats);
73         unsigned int requeued_avg = avg_stats(&requeued_stats);
74
75         printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
76                requeued_avg,
77                params.nthreads,
78                requeuetime_avg / USEC_PER_MSEC,
79                rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
80 }
81
82 static void *workerfn(void *arg __maybe_unused)
83 {
84         int ret;
85
86         mutex_lock(&thread_lock);
87         threads_starting--;
88         if (!threads_starting)
89                 cond_signal(&thread_parent);
90         cond_wait(&thread_worker, &thread_lock);
91         mutex_unlock(&thread_lock);
92
93         while (1) {
94                 if (!params.pi) {
95                         ret = futex_wait(&futex1, 0, NULL, futex_flag);
96                         if (!ret)
97                                 break;
98
99                         if (ret && errno != EAGAIN) {
100                                 if (!params.silent)
101                                         warnx("futex_wait");
102                                 break;
103                         }
104                 } else {
105                         ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
106                                                     NULL, futex_flag);
107                         if (!ret) {
108                                 /* got the lock at futex2 */
109                                 futex_unlock_pi(&futex2, futex_flag);
110                                 break;
111                         }
112
113                         if (ret && errno != EAGAIN) {
114                                 if (!params.silent)
115                                         warnx("futex_wait_requeue_pi");
116                                 break;
117                         }
118                 }
119         }
120
121         return NULL;
122 }
123
124 static void block_threads(pthread_t *w,
125                           pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
126 {
127         cpu_set_t *cpuset;
128         unsigned int i;
129         int nrcpus = perf_cpu_map__nr(cpu);
130         size_t size;
131
132         threads_starting = params.nthreads;
133
134         cpuset = CPU_ALLOC(nrcpus);
135         BUG_ON(!cpuset);
136         size = CPU_ALLOC_SIZE(nrcpus);
137
138         /* create and block all threads */
139         for (i = 0; i < params.nthreads; i++) {
140                 CPU_ZERO_S(size, cpuset);
141                 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
142
143                 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
144                         CPU_FREE(cpuset);
145                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
146                 }
147
148                 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
149                         CPU_FREE(cpuset);
150                         err(EXIT_FAILURE, "pthread_create");
151                 }
152         }
153         CPU_FREE(cpuset);
154 }
155
156 static void toggle_done(int sig __maybe_unused,
157                         siginfo_t *info __maybe_unused,
158                         void *uc __maybe_unused)
159 {
160         done = true;
161 }
162
163 int bench_futex_requeue(int argc, const char **argv)
164 {
165         int ret = 0;
166         unsigned int i, j;
167         struct sigaction act;
168         pthread_attr_t thread_attr;
169         struct perf_cpu_map *cpu;
170
171         argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
172         if (argc)
173                 goto err;
174
175         cpu = perf_cpu_map__new(NULL);
176         if (!cpu)
177                 err(EXIT_FAILURE, "cpu_map__new");
178
179         memset(&act, 0, sizeof(act));
180         sigfillset(&act.sa_mask);
181         act.sa_sigaction = toggle_done;
182         sigaction(SIGINT, &act, NULL);
183
184         if (params.mlockall) {
185                 if (mlockall(MCL_CURRENT | MCL_FUTURE))
186                         err(EXIT_FAILURE, "mlockall");
187         }
188
189         if (!params.nthreads)
190                 params.nthreads = perf_cpu_map__nr(cpu);
191
192         worker = calloc(params.nthreads, sizeof(*worker));
193         if (!worker)
194                 err(EXIT_FAILURE, "calloc");
195
196         if (!params.fshared)
197                 futex_flag = FUTEX_PRIVATE_FLAG;
198
199         if (params.nrequeue > params.nthreads)
200                 params.nrequeue = params.nthreads;
201
202         if (params.broadcast)
203                 params.nrequeue = params.nthreads;
204
205         printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
206                "%d at a time.\n\n",  getpid(), params.nthreads,
207                params.fshared ? "shared":"private", &futex1,
208                params.pi ? "PI ": "", &futex2, params.nrequeue);
209
210         init_stats(&requeued_stats);
211         init_stats(&requeuetime_stats);
212         pthread_attr_init(&thread_attr);
213         mutex_init(&thread_lock);
214         cond_init(&thread_parent);
215         cond_init(&thread_worker);
216
217         for (j = 0; j < bench_repeat && !done; j++) {
218                 unsigned int nrequeued = 0, wakeups = 0;
219                 struct timeval start, end, runtime;
220
221                 /* create, launch & block all threads */
222                 block_threads(worker, thread_attr, cpu);
223
224                 /* make sure all threads are already blocked */
225                 mutex_lock(&thread_lock);
226                 while (threads_starting)
227                         cond_wait(&thread_parent, &thread_lock);
228                 cond_broadcast(&thread_worker);
229                 mutex_unlock(&thread_lock);
230
231                 usleep(100000);
232
233                 /* Ok, all threads are patiently blocked, start requeueing */
234                 gettimeofday(&start, NULL);
235                 while (nrequeued < params.nthreads) {
236                         int r;
237
238                         /*
239                          * For the regular non-pi case, do not wakeup any tasks
240                          * blocked on futex1, allowing us to really measure
241                          * futex_wait functionality. For the PI case the first
242                          * waiter is always awoken.
243                          */
244                         if (!params.pi) {
245                                 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
246                                                       params.nrequeue,
247                                                       futex_flag);
248                         } else {
249                                 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
250                                                          params.nrequeue,
251                                                          futex_flag);
252                                 wakeups++; /* assume no error */
253                         }
254
255                         if (r < 0)
256                                 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
257                                     &futex1, &futex2);
258
259                         nrequeued += r;
260                 }
261
262                 gettimeofday(&end, NULL);
263                 timersub(&end, &start, &runtime);
264
265                 update_stats(&requeued_stats, nrequeued);
266                 update_stats(&requeuetime_stats, runtime.tv_usec);
267
268                 if (!params.silent) {
269                         if (!params.pi)
270                                 printf("[Run %d]: Requeued %d of %d threads in "
271                                        "%.4f ms\n", j + 1, nrequeued,
272                                        params.nthreads,
273                                        runtime.tv_usec / (double)USEC_PER_MSEC);
274                         else {
275                                 nrequeued -= wakeups;
276                                 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
277                                        "%d threads in %.4f ms\n",
278                                        j + 1, wakeups, nrequeued,
279                                        params.nthreads,
280                                        runtime.tv_usec / (double)USEC_PER_MSEC);
281                         }
282
283                 }
284
285                 if (!params.pi) {
286                         /* everybody should be blocked on futex2, wake'em up */
287                         nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
288                         if (params.nthreads != nrequeued)
289                                 warnx("couldn't wakeup all tasks (%d/%d)",
290                                       nrequeued, params.nthreads);
291                 }
292
293                 for (i = 0; i < params.nthreads; i++) {
294                         ret = pthread_join(worker[i], NULL);
295                         if (ret)
296                                 err(EXIT_FAILURE, "pthread_join");
297                 }
298         }
299
300         /* cleanup & report results */
301         cond_destroy(&thread_parent);
302         cond_destroy(&thread_worker);
303         mutex_destroy(&thread_lock);
304         pthread_attr_destroy(&thread_attr);
305
306         print_summary();
307
308         free(worker);
309         perf_cpu_map__put(cpu);
310         return ret;
311 err:
312         usage_with_options(bench_futex_requeue_usage, options);
313         exit(EXIT_FAILURE);
314 }
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