xref: /linux/tools/perf/bench/futex-hash.c (revision c411ed854584a71b0e86ac3019b60e4789d88086)
1 /*
2  * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
3  *
4  * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
5  *
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.
9  */
10 
11 /* For the CLR_() macros */
12 #include <string.h>
13 #include <pthread.h>
14 
15 #include <errno.h>
16 #include <signal.h>
17 #include <stdlib.h>
18 #include <linux/compiler.h>
19 #include <linux/kernel.h>
20 #include <sys/time.h>
21 
22 #include "../util/stat.h"
23 #include <subcmd/parse-options.h>
24 #include "bench.h"
25 #include "futex.h"
26 
27 #include <err.h>
28 #include <sys/time.h>
29 
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;
36 
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;
42 
43 struct worker {
44 	int tid;
45 	u_int32_t *futex;
46 	pthread_t thread;
47 	unsigned long ops;
48 };
49 
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"),
56 	OPT_END()
57 };
58 
59 static const char * const bench_futex_hash_usage[] = {
60 	"perf bench futex hash <options>",
61 	NULL
62 };
63 
64 static void *workerfn(void *arg)
65 {
66 	int ret;
67 	struct worker *w = (struct worker *) arg;
68 	unsigned int i;
69 	unsigned long ops = w->ops; /* avoid cacheline bouncing */
70 
71 	pthread_mutex_lock(&thread_lock);
72 	threads_starting--;
73 	if (!threads_starting)
74 		pthread_cond_signal(&thread_parent);
75 	pthread_cond_wait(&thread_worker, &thread_lock);
76 	pthread_mutex_unlock(&thread_lock);
77 
78 	do {
79 		for (i = 0; i < nfutexes; i++, ops++) {
80 			/*
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.
85 			 */
86 			ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
87 			if (!silent &&
88 			    (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
89 				warn("Non-expected futex return call");
90 		}
91 	}  while (!done);
92 
93 	w->ops = ops;
94 	return NULL;
95 }
96 
97 static void toggle_done(int sig __maybe_unused,
98 			siginfo_t *info __maybe_unused,
99 			void *uc __maybe_unused)
100 {
101 	/* inform all threads that we're done for the day */
102 	done = true;
103 	gettimeofday(&end, NULL);
104 	timersub(&end, &start, &runtime);
105 }
106 
107 static void print_summary(void)
108 {
109 	unsigned long avg = avg_stats(&throughput_stats);
110 	double stddev = stddev_stats(&throughput_stats);
111 
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);
115 }
116 
117 int bench_futex_hash(int argc, const char **argv)
118 {
119 	int ret = 0;
120 	cpu_set_t cpu;
121 	struct sigaction act;
122 	unsigned int i, ncpus;
123 	pthread_attr_t thread_attr;
124 	struct worker *worker = NULL;
125 
126 	argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
127 	if (argc) {
128 		usage_with_options(bench_futex_hash_usage, options);
129 		exit(EXIT_FAILURE);
130 	}
131 
132 	ncpus = sysconf(_SC_NPROCESSORS_ONLN);
133 
134 	sigfillset(&act.sa_mask);
135 	act.sa_sigaction = toggle_done;
136 	sigaction(SIGINT, &act, NULL);
137 
138 	if (!nthreads) /* default to the number of CPUs */
139 		nthreads = ncpus;
140 
141 	worker = calloc(nthreads, sizeof(*worker));
142 	if (!worker)
143 		goto errmem;
144 
145 	if (!fshared)
146 		futex_flag = FUTEX_PRIVATE_FLAG;
147 
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);
150 
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);
155 
156 	threads_starting = nthreads;
157 	pthread_attr_init(&thread_attr);
158 	gettimeofday(&start, NULL);
159 	for (i = 0; i < nthreads; i++) {
160 		worker[i].tid = i;
161 		worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
162 		if (!worker[i].futex)
163 			goto errmem;
164 
165 		CPU_ZERO(&cpu);
166 		CPU_SET(i % ncpus, &cpu);
167 
168 		ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu);
169 		if (ret)
170 			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
171 
172 		ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
173 				     (void *)(struct worker *) &worker[i]);
174 		if (ret)
175 			err(EXIT_FAILURE, "pthread_create");
176 
177 	}
178 	pthread_attr_destroy(&thread_attr);
179 
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);
185 
186 	sleep(nsecs);
187 	toggle_done(0, NULL, NULL);
188 
189 	for (i = 0; i < nthreads; i++) {
190 		ret = pthread_join(worker[i].thread, NULL);
191 		if (ret)
192 			err(EXIT_FAILURE, "pthread_join");
193 	}
194 
195 	/* cleanup & report results */
196 	pthread_cond_destroy(&thread_parent);
197 	pthread_cond_destroy(&thread_worker);
198 	pthread_mutex_destroy(&thread_lock);
199 
200 	for (i = 0; i < nthreads; i++) {
201 		unsigned long t = worker[i].ops/runtime.tv_sec;
202 		update_stats(&throughput_stats, t);
203 		if (!silent) {
204 			if (nfutexes == 1)
205 				printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
206 				       worker[i].tid, &worker[i].futex[0], t);
207 			else
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);
211 		}
212 
213 		free(worker[i].futex);
214 	}
215 
216 	print_summary();
217 
218 	free(worker);
219 	return ret;
220 errmem:
221 	err(EXIT_FAILURE, "calloc");
222 }
223