summaryrefslogtreecommitdiffstats
path: root/tools/perf/bench/futex-requeue.c
blob: 732403bfd31a9391e50719c182577047a8eb508b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
/*
 * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
 *
 * futex-requeue: Block a bunch of threads on futex1 and requeue them
 *                on futex2, N at a time.
 *
 * This program is particularly useful to measure the latency of nthread
 * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
 */

#include "../perf.h"
#include "../util/util.h"
#include "../util/stat.h"
#include "../util/parse-options.h"
#include "../util/header.h"
#include "bench.h"
#include "futex.h"

#include <err.h>
#include <stdlib.h>
#include <sys/time.h>
#include <pthread.h>

static u_int32_t futex1 = 0, futex2 = 0;

/*
 * How many tasks to requeue at a time.
 * Default to 1 in order to make the kernel work more.
 */
static unsigned int nrequeue = 1;

static pthread_t *worker;
static bool done = 0, silent = 0;
static pthread_mutex_t thread_lock;
static pthread_cond_t thread_parent, thread_worker;
static struct stats requeuetime_stats, requeued_stats;
static unsigned int ncpus, threads_starting, nthreads = 0;

static const struct option options[] = {
	OPT_UINTEGER('t', "threads",  &nthreads, "Specify amount of threads"),
	OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"),
	OPT_BOOLEAN( 's', "silent",   &silent,   "Silent mode: do not display data/details"),
	OPT_END()
};

static const char * const bench_futex_requeue_usage[] = {
	"perf bench futex requeue <options>",
	NULL
};

static void print_summary(void)
{
	double requeuetime_avg = avg_stats(&requeuetime_stats);
	double requeuetime_stddev = stddev_stats(&requeuetime_stats);
	unsigned int requeued_avg = avg_stats(&requeued_stats);

	printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
	       requeued_avg,
	       nthreads,
	       requeuetime_avg/1e3,
	       rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
}

static void *workerfn(void *arg __maybe_unused)
{
	pthread_mutex_lock(&thread_lock);
	threads_starting--;
	if (!threads_starting)
		pthread_cond_signal(&thread_parent);
	pthread_cond_wait(&thread_worker, &thread_lock);
	pthread_mutex_unlock(&thread_lock);

	futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG);
	return NULL;
}

static void block_threads(pthread_t *w,
			  pthread_attr_t thread_attr)
{
	cpu_set_t cpu;
	unsigned int i;

	threads_starting = nthreads;

	/* create and block all threads */
	for (i = 0; i < nthreads; i++) {
		CPU_ZERO(&cpu);
		CPU_SET(i % ncpus, &cpu);

		if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");

		if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
			err(EXIT_FAILURE, "pthread_create");
	}
}

static void toggle_done(int sig __maybe_unused,
			siginfo_t *info __maybe_unused,
			void *uc __maybe_unused)
{
	done = true;
}

int bench_futex_requeue(int argc, const char **argv,
			const char *prefix __maybe_unused)
{
	int ret = 0;
	unsigned int i, j;
	struct sigaction act;
	pthread_attr_t thread_attr;

	argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
	if (argc)
		goto err;

	ncpus = sysconf(_SC_NPROCESSORS_ONLN);

	sigfillset(&act.sa_mask);
	act.sa_sigaction = toggle_done;
	sigaction(SIGINT, &act, NULL);

	if (!nthreads)
		nthreads = ncpus;

	worker = calloc(nthreads, sizeof(*worker));
	if (!worker)
		err(EXIT_FAILURE, "calloc");

	printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), "
	       "%d at a time.\n\n",
	       getpid(), nthreads, &futex1, &futex2, nrequeue);

	init_stats(&requeued_stats);
	init_stats(&requeuetime_stats);
	pthread_attr_init(&thread_attr);
	pthread_mutex_init(&thread_lock, NULL);
	pthread_cond_init(&thread_parent, NULL);
	pthread_cond_init(&thread_worker, NULL);

	for (j = 0; j < bench_repeat && !done; j++) {
		unsigned int nrequeued = 0;
		struct timeval start, end, runtime;

		/* create, launch & block all threads */
		block_threads(worker, thread_attr);

		/* make sure all threads are already blocked */
		pthread_mutex_lock(&thread_lock);
		while (threads_starting)
			pthread_cond_wait(&thread_parent, &thread_lock);
		pthread_cond_broadcast(&thread_worker);
		pthread_mutex_unlock(&thread_lock);

		usleep(100000);

		/* Ok, all threads are patiently blocked, start requeueing */
		gettimeofday(&start, NULL);
		for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue)
			/*
			 * Do not wakeup any tasks blocked on futex1, allowing
			 * us to really measure futex_wait functionality.
			 */
			futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue,
					  FUTEX_PRIVATE_FLAG);
		gettimeofday(&end, NULL);
		timersub(&end, &start, &runtime);

		update_stats(&requeued_stats, nrequeued);
		update_stats(&requeuetime_stats, runtime.tv_usec);

		if (!silent) {
			printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n",
			       j + 1, nrequeued, nthreads, runtime.tv_usec/1e3);
		}

		/* everybody should be blocked on futex2, wake'em up */
		nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG);
		if (nthreads != nrequeued)
			warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);

		for (i = 0; i < nthreads; i++) {
			ret = pthread_join(worker[i], NULL);
			if (ret)
				err(EXIT_FAILURE, "pthread_join");
		}

	}

	/* cleanup & report results */
	pthread_cond_destroy(&thread_parent);
	pthread_cond_destroy(&thread_worker);
	pthread_mutex_destroy(&thread_lock);
	pthread_attr_destroy(&thread_attr);

	print_summary();

	free(worker);
	return ret;
err:
	usage_with_options(bench_futex_requeue_usage, options);
	exit(EXIT_FAILURE);
}