xref: /openbmc/linux/tools/perf/bench/futex-requeue.c (revision 8351498d)
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 	/*
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 
print_summary(void)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 
workerfn(void * arg __maybe_unused)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 
block_threads(pthread_t * w,struct perf_cpu_map * cpu)124 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
125 {
126 	cpu_set_t *cpuset;
127 	unsigned int i;
128 	int nrcpus = perf_cpu_map__nr(cpu);
129 	size_t size;
130 
131 	threads_starting = params.nthreads;
132 
133 	cpuset = CPU_ALLOC(nrcpus);
134 	BUG_ON(!cpuset);
135 	size = CPU_ALLOC_SIZE(nrcpus);
136 
137 	/* create and block all threads */
138 	for (i = 0; i < params.nthreads; i++) {
139 		pthread_attr_t thread_attr;
140 
141 		pthread_attr_init(&thread_attr);
142 		CPU_ZERO_S(size, cpuset);
143 		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
144 
145 		if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
146 			CPU_FREE(cpuset);
147 			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
148 		}
149 
150 		if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
151 			CPU_FREE(cpuset);
152 			err(EXIT_FAILURE, "pthread_create");
153 		}
154 		pthread_attr_destroy(&thread_attr);
155 	}
156 	CPU_FREE(cpuset);
157 }
158 
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)159 static void toggle_done(int sig __maybe_unused,
160 			siginfo_t *info __maybe_unused,
161 			void *uc __maybe_unused)
162 {
163 	done = true;
164 }
165 
bench_futex_requeue(int argc,const char ** argv)166 int bench_futex_requeue(int argc, const char **argv)
167 {
168 	int ret = 0;
169 	unsigned int i, j;
170 	struct sigaction act;
171 	struct perf_cpu_map *cpu;
172 
173 	argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
174 	if (argc)
175 		goto err;
176 
177 	cpu = perf_cpu_map__new(NULL);
178 	if (!cpu)
179 		err(EXIT_FAILURE, "cpu_map__new");
180 
181 	memset(&act, 0, sizeof(act));
182 	sigfillset(&act.sa_mask);
183 	act.sa_sigaction = toggle_done;
184 	sigaction(SIGINT, &act, NULL);
185 
186 	if (params.mlockall) {
187 		if (mlockall(MCL_CURRENT | MCL_FUTURE))
188 			err(EXIT_FAILURE, "mlockall");
189 	}
190 
191 	if (!params.nthreads)
192 		params.nthreads = perf_cpu_map__nr(cpu);
193 
194 	worker = calloc(params.nthreads, sizeof(*worker));
195 	if (!worker)
196 		err(EXIT_FAILURE, "calloc");
197 
198 	if (!params.fshared)
199 		futex_flag = FUTEX_PRIVATE_FLAG;
200 
201 	if (params.nrequeue > params.nthreads)
202 		params.nrequeue = params.nthreads;
203 
204 	if (params.broadcast)
205 		params.nrequeue = params.nthreads;
206 
207 	printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
208 	       "%d at a time.\n\n",  getpid(), params.nthreads,
209 	       params.fshared ? "shared":"private", &futex1,
210 	       params.pi ? "PI ": "", &futex2, params.nrequeue);
211 
212 	init_stats(&requeued_stats);
213 	init_stats(&requeuetime_stats);
214 	mutex_init(&thread_lock);
215 	cond_init(&thread_parent);
216 	cond_init(&thread_worker);
217 
218 	for (j = 0; j < bench_repeat && !done; j++) {
219 		unsigned int nrequeued = 0, wakeups = 0;
220 		struct timeval start, end, runtime;
221 
222 		/* create, launch & block all threads */
223 		block_threads(worker, cpu);
224 
225 		/* make sure all threads are already blocked */
226 		mutex_lock(&thread_lock);
227 		while (threads_starting)
228 			cond_wait(&thread_parent, &thread_lock);
229 		cond_broadcast(&thread_worker);
230 		mutex_unlock(&thread_lock);
231 
232 		usleep(100000);
233 
234 		/* Ok, all threads are patiently blocked, start requeueing */
235 		gettimeofday(&start, NULL);
236 		while (nrequeued < params.nthreads) {
237 			int r;
238 
239 			/*
240 			 * For the regular non-pi case, do not wakeup any tasks
241 			 * blocked on futex1, allowing us to really measure
242 			 * futex_wait functionality. For the PI case the first
243 			 * waiter is always awoken.
244 			 */
245 			if (!params.pi) {
246 				r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
247 						      params.nrequeue,
248 						      futex_flag);
249 			} else {
250 				r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
251 							 params.nrequeue,
252 							 futex_flag);
253 				wakeups++; /* assume no error */
254 			}
255 
256 			if (r < 0)
257 				err(EXIT_FAILURE, "couldn't requeue from %p to %p",
258 				    &futex1, &futex2);
259 
260 			nrequeued += r;
261 		}
262 
263 		gettimeofday(&end, NULL);
264 		timersub(&end, &start, &runtime);
265 
266 		update_stats(&requeued_stats, nrequeued);
267 		update_stats(&requeuetime_stats, runtime.tv_usec);
268 
269 		if (!params.silent) {
270 			if (!params.pi)
271 				printf("[Run %d]: Requeued %d of %d threads in "
272 				       "%.4f ms\n", j + 1, nrequeued,
273 				       params.nthreads,
274 				       runtime.tv_usec / (double)USEC_PER_MSEC);
275 			else {
276 				nrequeued -= wakeups;
277 				printf("[Run %d]: Awoke and Requeued (%d+%d) of "
278 				       "%d threads in %.4f ms\n",
279 				       j + 1, wakeups, nrequeued,
280 				       params.nthreads,
281 				       runtime.tv_usec / (double)USEC_PER_MSEC);
282 			}
283 
284 		}
285 
286 		if (!params.pi) {
287 			/* everybody should be blocked on futex2, wake'em up */
288 			nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
289 			if (params.nthreads != nrequeued)
290 				warnx("couldn't wakeup all tasks (%d/%d)",
291 				      nrequeued, params.nthreads);
292 		}
293 
294 		for (i = 0; i < params.nthreads; i++) {
295 			ret = pthread_join(worker[i], NULL);
296 			if (ret)
297 				err(EXIT_FAILURE, "pthread_join");
298 		}
299 	}
300 
301 	/* cleanup & report results */
302 	cond_destroy(&thread_parent);
303 	cond_destroy(&thread_worker);
304 	mutex_destroy(&thread_lock);
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 }
315