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
34static u_int32_t futex1 = 0, futex2 = 0;
35
36static pthread_t *worker;
37static bool done = false;
38static struct mutex thread_lock;
39static struct cond thread_parent, thread_worker;
40static struct stats requeuetime_stats, requeued_stats;
41static unsigned int threads_starting;
42static int futex_flag = 0;
43
44static 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
52static 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
64static const char * const bench_futex_requeue_usage[] = {
65	"perf bench futex requeue <options>",
66	NULL
67};
68
69static 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
82static 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
124static 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
159static void toggle_done(int sig __maybe_unused,
160			siginfo_t *info __maybe_unused,
161			void *uc __maybe_unused)
162{
163	done = true;
164}
165
166int 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_online_cpus();
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;
311err:
312	usage_with_options(bench_futex_requeue_usage, options);
313	exit(EXIT_FAILURE);
314}
315