2 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
4 * futex-requeue: Block a bunch of threads on futex1 and requeue them
5 * on futex2, N at a time.
7 * This program is particularly useful to measure the latency of nthread
8 * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
12 #include "../util/util.h"
13 #include "../util/stat.h"
14 #include "../util/parse-options.h"
15 #include "../util/header.h"
24 static u_int32_t futex1 = 0, futex2 = 0;
27 * How many tasks to requeue at a time.
28 * Default to 1 in order to make the kernel work more.
30 static unsigned int nrequeue = 1;
32 static pthread_t *worker;
33 static bool done = 0, silent = 0;
34 static pthread_mutex_t thread_lock;
35 static pthread_cond_t thread_parent, thread_worker;
36 static struct stats requeuetime_stats, requeued_stats;
37 static unsigned int ncpus, threads_starting, nthreads = 0;
39 static const struct option options[] = {
40 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
41 OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"),
42 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
46 static const char * const bench_futex_requeue_usage[] = {
47 "perf bench futex requeue <options>",
51 static void print_summary(void)
53 double requeuetime_avg = avg_stats(&requeuetime_stats);
54 double requeuetime_stddev = stddev_stats(&requeuetime_stats);
55 unsigned int requeued_avg = avg_stats(&requeued_stats);
57 printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
61 rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
64 static void *workerfn(void *arg __maybe_unused)
66 pthread_mutex_lock(&thread_lock);
68 if (!threads_starting)
69 pthread_cond_signal(&thread_parent);
70 pthread_cond_wait(&thread_worker, &thread_lock);
71 pthread_mutex_unlock(&thread_lock);
73 futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG);
77 static void block_threads(pthread_t *w,
78 pthread_attr_t thread_attr)
83 threads_starting = nthreads;
85 /* create and block all threads */
86 for (i = 0; i < nthreads; i++) {
88 CPU_SET(i % ncpus, &cpu);
90 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
91 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
93 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
94 err(EXIT_FAILURE, "pthread_create");
98 static void toggle_done(int sig __maybe_unused,
99 siginfo_t *info __maybe_unused,
100 void *uc __maybe_unused)
105 int bench_futex_requeue(int argc, const char **argv,
106 const char *prefix __maybe_unused)
110 struct sigaction act;
111 pthread_attr_t thread_attr;
113 argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
117 ncpus = sysconf(_SC_NPROCESSORS_ONLN);
119 sigfillset(&act.sa_mask);
120 act.sa_sigaction = toggle_done;
121 sigaction(SIGINT, &act, NULL);
126 worker = calloc(nthreads, sizeof(*worker));
128 err(EXIT_FAILURE, "calloc");
130 printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), "
132 getpid(), nthreads, &futex1, &futex2, nrequeue);
134 init_stats(&requeued_stats);
135 init_stats(&requeuetime_stats);
136 pthread_attr_init(&thread_attr);
137 pthread_mutex_init(&thread_lock, NULL);
138 pthread_cond_init(&thread_parent, NULL);
139 pthread_cond_init(&thread_worker, NULL);
141 for (j = 0; j < bench_repeat && !done; j++) {
142 unsigned int nrequeued = 0;
143 struct timeval start, end, runtime;
145 /* create, launch & block all threads */
146 block_threads(worker, thread_attr);
148 /* make sure all threads are already blocked */
149 pthread_mutex_lock(&thread_lock);
150 while (threads_starting)
151 pthread_cond_wait(&thread_parent, &thread_lock);
152 pthread_cond_broadcast(&thread_worker);
153 pthread_mutex_unlock(&thread_lock);
157 /* Ok, all threads are patiently blocked, start requeueing */
158 gettimeofday(&start, NULL);
159 for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue)
161 * Do not wakeup any tasks blocked on futex1, allowing
162 * us to really measure futex_wait functionality.
164 futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue,
166 gettimeofday(&end, NULL);
167 timersub(&end, &start, &runtime);
169 update_stats(&requeued_stats, nrequeued);
170 update_stats(&requeuetime_stats, runtime.tv_usec);
173 printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n",
174 j + 1, nrequeued, nthreads, runtime.tv_usec/1e3);
177 /* everybody should be blocked on futex2, wake'em up */
178 nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG);
179 if (nthreads != nrequeued)
180 warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);
182 for (i = 0; i < nthreads; i++) {
183 ret = pthread_join(worker[i], NULL);
185 err(EXIT_FAILURE, "pthread_join");
190 /* cleanup & report results */
191 pthread_cond_destroy(&thread_parent);
192 pthread_cond_destroy(&thread_worker);
193 pthread_mutex_destroy(&thread_lock);
194 pthread_attr_destroy(&thread_attr);
201 usage_with_options(bench_futex_requeue_usage, options);