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 */
34 static u_int32_t futex1 = 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 waketime_stats, wakeup_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 wakeups to do at a time.
47 	 * Default to 1 in order to make the kernel work more.
48 	 */
49 	.nwakes  = 1,
50 };
51 
52 static 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 
62 static const char * const bench_futex_wake_usage[] = {
63 	"perf bench futex wake <options>",
64 	NULL
65 };
66 
workerfn(void * arg __maybe_unused)67 static 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 
print_summary(void)85 static 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 
block_threads(pthread_t * w,pthread_attr_t thread_attr,struct perf_cpu_map * cpu)98 static 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 
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)129 static void toggle_done(int sig __maybe_unused,
130 			siginfo_t *info __maybe_unused,
131 			void *uc __maybe_unused)
132 {
133 	done = true;
134 }
135 
bench_futex_wake(int argc,const char ** argv)136 int 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 }
239