1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
  4 *
  5 * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time.
  6 *
  7 * This program is particularly useful to measure the latency of nthread wakeups
  8 * in non-error situations:  all waiters are queued and all wake calls wakeup
  9 * one or more tasks, and thus the waitqueue is never empty.
 10 */
 11
 12/* For the CLR_() macros */
 13#include <string.h>
 14#include <pthread.h>
 15
 16#include <signal.h>
 17#include "../util/mutex.h"
 18#include "../util/stat.h"
 19#include <subcmd/parse-options.h>
 20#include <linux/compiler.h>
 21#include <linux/kernel.h>
 22#include <linux/time64.h>
 23#include <errno.h>
 24#include <perf/cpumap.h>
 25#include "bench.h"
 26#include "futex.h"
 27
 28#include <err.h>
 29#include <stdlib.h>
 30#include <sys/time.h>
 31#include <sys/mman.h>
 32
 33/* all threads will block on the same futex */
 34static u_int32_t futex1 = 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 waketime_stats, wakeup_stats;
 41static unsigned int threads_starting;
 42static int futex_flag = 0;
 43
 44static struct bench_futex_parameters params = {
 45	/*
 46	 * How many wakeups to do at a time.
 47	 * Default to 1 in order to make the kernel work more.
 48	 */
 49	.nwakes  = 1,
 50};
 51
 52static const struct option options[] = {
 53	OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
 54	OPT_UINTEGER('w', "nwakes",  &params.nwakes, "Specify amount of threads to wake 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
 59	OPT_END()
 60};
 61
 62static const char * const bench_futex_wake_usage[] = {
 63	"perf bench futex wake <options>",
 64	NULL
 65};
 66
 67static void *workerfn(void *arg __maybe_unused)
 68{
 69	mutex_lock(&thread_lock);
 70	threads_starting--;
 71	if (!threads_starting)
 72		cond_signal(&thread_parent);
 73	cond_wait(&thread_worker, &thread_lock);
 74	mutex_unlock(&thread_lock);
 75
 76	while (1) {
 77		if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
 78			break;
 79	}
 80
 81	pthread_exit(NULL);
 82	return NULL;
 83}
 84
 85static void print_summary(void)
 86{
 87	double waketime_avg = avg_stats(&waketime_stats);
 88	double waketime_stddev = stddev_stats(&waketime_stats);
 89	unsigned int wakeup_avg = avg_stats(&wakeup_stats);
 90
 91	printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
 92	       wakeup_avg,
 93	       params.nthreads,
 94	       waketime_avg / USEC_PER_MSEC,
 95	       rel_stddev_stats(waketime_stddev, waketime_avg));
 96}
 97
 98static void block_threads(pthread_t *w,
 99			  pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
100{
101	cpu_set_t *cpuset;
102	unsigned int i;
103	size_t size;
104	int nrcpus = perf_cpu_map__nr(cpu);
105	threads_starting = params.nthreads;
106
107	cpuset = CPU_ALLOC(nrcpus);
108	BUG_ON(!cpuset);
109	size = CPU_ALLOC_SIZE(nrcpus);
110
111	/* create and block all threads */
112	for (i = 0; i < params.nthreads; i++) {
113		CPU_ZERO_S(size, cpuset);
114		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
115
116		if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
117			CPU_FREE(cpuset);
118			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
119		}
120
121		if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
122			CPU_FREE(cpuset);
123			err(EXIT_FAILURE, "pthread_create");
124		}
125	}
126	CPU_FREE(cpuset);
127}
128
129static void toggle_done(int sig __maybe_unused,
130			siginfo_t *info __maybe_unused,
131			void *uc __maybe_unused)
132{
133	done = true;
134}
135
136int bench_futex_wake(int argc, const char **argv)
137{
138	int ret = 0;
139	unsigned int i, j;
140	struct sigaction act;
141	pthread_attr_t thread_attr;
142	struct perf_cpu_map *cpu;
143
144	argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
145	if (argc) {
146		usage_with_options(bench_futex_wake_usage, options);
147		exit(EXIT_FAILURE);
148	}
149
150	cpu = perf_cpu_map__new(NULL);
151	if (!cpu)
152		err(EXIT_FAILURE, "calloc");
153
154	memset(&act, 0, sizeof(act));
155	sigfillset(&act.sa_mask);
156	act.sa_sigaction = toggle_done;
157	sigaction(SIGINT, &act, NULL);
158
159	if (params.mlockall) {
160		if (mlockall(MCL_CURRENT | MCL_FUTURE))
161			err(EXIT_FAILURE, "mlockall");
162	}
163
164	if (!params.nthreads)
165		params.nthreads = perf_cpu_map__nr(cpu);
166
167	worker = calloc(params.nthreads, sizeof(*worker));
168	if (!worker)
169		err(EXIT_FAILURE, "calloc");
170
171	if (!params.fshared)
172		futex_flag = FUTEX_PRIVATE_FLAG;
173
174	printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
175	       "waking up %d at a time.\n\n",
176	       getpid(), params.nthreads, params.fshared ? "shared":"private",
177	       &futex1, params.nwakes);
178
179	init_stats(&wakeup_stats);
180	init_stats(&waketime_stats);
181	pthread_attr_init(&thread_attr);
182	mutex_init(&thread_lock);
183	cond_init(&thread_parent);
184	cond_init(&thread_worker);
185
186	for (j = 0; j < bench_repeat && !done; j++) {
187		unsigned int nwoken = 0;
188		struct timeval start, end, runtime;
189
190		/* create, launch & block all threads */
191		block_threads(worker, thread_attr, cpu);
192
193		/* make sure all threads are already blocked */
194		mutex_lock(&thread_lock);
195		while (threads_starting)
196			cond_wait(&thread_parent, &thread_lock);
197		cond_broadcast(&thread_worker);
198		mutex_unlock(&thread_lock);
199
200		usleep(100000);
201
202		/* Ok, all threads are patiently blocked, start waking folks up */
203		gettimeofday(&start, NULL);
204		while (nwoken != params.nthreads)
205			nwoken += futex_wake(&futex1,
206					     params.nwakes, futex_flag);
207		gettimeofday(&end, NULL);
208		timersub(&end, &start, &runtime);
209
210		update_stats(&wakeup_stats, nwoken);
211		update_stats(&waketime_stats, runtime.tv_usec);
212
213		if (!params.silent) {
214			printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
215			       j + 1, nwoken, params.nthreads,
216			       runtime.tv_usec / (double)USEC_PER_MSEC);
217		}
218
219		for (i = 0; i < params.nthreads; i++) {
220			ret = pthread_join(worker[i], NULL);
221			if (ret)
222				err(EXIT_FAILURE, "pthread_join");
223		}
224
225	}
226
227	/* cleanup & report results */
228	cond_destroy(&thread_parent);
229	cond_destroy(&thread_worker);
230	mutex_destroy(&thread_lock);
231	pthread_attr_destroy(&thread_attr);
232
233	print_summary();
234
235	free(worker);
236	perf_cpu_map__put(cpu);
237	return ret;
238}