2 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
4 * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
6 * This program is particularly useful for measuring the kernel's futex hash
7 * table/function implementation. In order for it to make sense, use with as
8 * many threads and futexes as possible.
11 /* For the CLR_() macros */
18 #include <linux/compiler.h>
19 #include <linux/kernel.h>
22 #include "../util/stat.h"
23 #include <subcmd/parse-options.h>
30 static unsigned int nthreads = 0;
31 static unsigned int nsecs = 10;
32 /* amount of futexes per thread */
33 static unsigned int nfutexes = 1024;
34 static bool fshared = false, done = false, silent = false;
35 static int futex_flag = 0;
37 struct timeval start, end, runtime;
38 static pthread_mutex_t thread_lock;
39 static unsigned int threads_starting;
40 static struct stats throughput_stats;
41 static pthread_cond_t thread_parent, thread_worker;
50 static const struct option options[] = {
51 OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
52 OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds)"),
53 OPT_UINTEGER('f', "futexes", &nfutexes, "Specify amount of futexes per threads"),
54 OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"),
55 OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"),
59 static const char * const bench_futex_hash_usage[] = {
60 "perf bench futex hash <options>",
64 static void *workerfn(void *arg)
67 struct worker *w = (struct worker *) arg;
69 unsigned long ops = w->ops; /* avoid cacheline bouncing */
71 pthread_mutex_lock(&thread_lock);
73 if (!threads_starting)
74 pthread_cond_signal(&thread_parent);
75 pthread_cond_wait(&thread_worker, &thread_lock);
76 pthread_mutex_unlock(&thread_lock);
79 for (i = 0; i < nfutexes; i++, ops++) {
81 * We want the futex calls to fail in order to stress
82 * the hashing of uaddr and not measure other steps,
83 * such as internal waitqueue handling, thus enlarging
84 * the critical region protected by hb->lock.
86 ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
88 (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
89 warn("Non-expected futex return call");
97 static void toggle_done(int sig __maybe_unused,
98 siginfo_t *info __maybe_unused,
99 void *uc __maybe_unused)
101 /* inform all threads that we're done for the day */
103 gettimeofday(&end, NULL);
104 timersub(&end, &start, &runtime);
107 static void print_summary(void)
109 unsigned long avg = avg_stats(&throughput_stats);
110 double stddev = stddev_stats(&throughput_stats);
112 printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
113 !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
114 (int) runtime.tv_sec);
117 int bench_futex_hash(int argc, const char **argv)
121 struct sigaction act;
122 unsigned int i, ncpus;
123 pthread_attr_t thread_attr;
124 struct worker *worker = NULL;
126 argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
128 usage_with_options(bench_futex_hash_usage, options);
132 ncpus = sysconf(_SC_NPROCESSORS_ONLN);
134 sigfillset(&act.sa_mask);
135 act.sa_sigaction = toggle_done;
136 sigaction(SIGINT, &act, NULL);
138 if (!nthreads) /* default to the number of CPUs */
141 worker = calloc(nthreads, sizeof(*worker));
146 futex_flag = FUTEX_PRIVATE_FLAG;
148 printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
149 getpid(), nthreads, nfutexes, fshared ? "shared":"private", nsecs);
151 init_stats(&throughput_stats);
152 pthread_mutex_init(&thread_lock, NULL);
153 pthread_cond_init(&thread_parent, NULL);
154 pthread_cond_init(&thread_worker, NULL);
156 threads_starting = nthreads;
157 pthread_attr_init(&thread_attr);
158 gettimeofday(&start, NULL);
159 for (i = 0; i < nthreads; i++) {
161 worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
162 if (!worker[i].futex)
166 CPU_SET(i % ncpus, &cpu);
168 ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu);
170 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
172 ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
173 (void *)(struct worker *) &worker[i]);
175 err(EXIT_FAILURE, "pthread_create");
178 pthread_attr_destroy(&thread_attr);
180 pthread_mutex_lock(&thread_lock);
181 while (threads_starting)
182 pthread_cond_wait(&thread_parent, &thread_lock);
183 pthread_cond_broadcast(&thread_worker);
184 pthread_mutex_unlock(&thread_lock);
187 toggle_done(0, NULL, NULL);
189 for (i = 0; i < nthreads; i++) {
190 ret = pthread_join(worker[i].thread, NULL);
192 err(EXIT_FAILURE, "pthread_join");
195 /* cleanup & report results */
196 pthread_cond_destroy(&thread_parent);
197 pthread_cond_destroy(&thread_worker);
198 pthread_mutex_destroy(&thread_lock);
200 for (i = 0; i < nthreads; i++) {
201 unsigned long t = worker[i].ops/runtime.tv_sec;
202 update_stats(&throughput_stats, t);
205 printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
206 worker[i].tid, &worker[i].futex[0], t);
208 printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
209 worker[i].tid, &worker[i].futex[0],
210 &worker[i].futex[nfutexes-1], t);
213 free(worker[i].futex);
221 err(EXIT_FAILURE, "calloc");