xref: /openbmc/linux/tools/perf/bench/futex-hash.c (revision de2bdb3d)
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 <pthread.h>
13 
14 #include <errno.h>
15 #include <signal.h>
16 #include <stdlib.h>
17 #include <linux/compiler.h>
18 #include <linux/kernel.h>
19 #include <sys/time.h>
20 
21 #include "../util/stat.h"
22 #include <subcmd/parse-options.h>
23 #include "bench.h"
24 #include "futex.h"
25 
26 #include <err.h>
27 #include <sys/time.h>
28 
29 static unsigned int nthreads = 0;
30 static unsigned int nsecs    = 10;
31 /* amount of futexes per thread */
32 static unsigned int nfutexes = 1024;
33 static bool fshared = false, done = false, silent = false;
34 static int futex_flag = 0;
35 
36 struct timeval start, end, runtime;
37 static pthread_mutex_t thread_lock;
38 static unsigned int threads_starting;
39 static struct stats throughput_stats;
40 static pthread_cond_t thread_parent, thread_worker;
41 
42 struct worker {
43 	int tid;
44 	u_int32_t *futex;
45 	pthread_t thread;
46 	unsigned long ops;
47 };
48 
49 static const struct option options[] = {
50 	OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
51 	OPT_UINTEGER('r', "runtime", &nsecs,    "Specify runtime (in seconds)"),
52 	OPT_UINTEGER('f', "futexes", &nfutexes, "Specify amount of futexes per threads"),
53 	OPT_BOOLEAN( 's', "silent",  &silent,   "Silent mode: do not display data/details"),
54 	OPT_BOOLEAN( 'S', "shared",  &fshared,  "Use shared futexes instead of private ones"),
55 	OPT_END()
56 };
57 
58 static const char * const bench_futex_hash_usage[] = {
59 	"perf bench futex hash <options>",
60 	NULL
61 };
62 
63 static void *workerfn(void *arg)
64 {
65 	int ret;
66 	unsigned int i;
67 	struct worker *w = (struct worker *) arg;
68 
69 	pthread_mutex_lock(&thread_lock);
70 	threads_starting--;
71 	if (!threads_starting)
72 		pthread_cond_signal(&thread_parent);
73 	pthread_cond_wait(&thread_worker, &thread_lock);
74 	pthread_mutex_unlock(&thread_lock);
75 
76 	do {
77 		for (i = 0; i < nfutexes; i++, w->ops++) {
78 			/*
79 			 * We want the futex calls to fail in order to stress
80 			 * the hashing of uaddr and not measure other steps,
81 			 * such as internal waitqueue handling, thus enlarging
82 			 * the critical region protected by hb->lock.
83 			 */
84 			ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
85 			if (!silent &&
86 			    (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
87 				warn("Non-expected futex return call");
88 		}
89 	}  while (!done);
90 
91 	return NULL;
92 }
93 
94 static void toggle_done(int sig __maybe_unused,
95 			siginfo_t *info __maybe_unused,
96 			void *uc __maybe_unused)
97 {
98 	/* inform all threads that we're done for the day */
99 	done = true;
100 	gettimeofday(&end, NULL);
101 	timersub(&end, &start, &runtime);
102 }
103 
104 static void print_summary(void)
105 {
106 	unsigned long avg = avg_stats(&throughput_stats);
107 	double stddev = stddev_stats(&throughput_stats);
108 
109 	printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
110 	       !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
111 	       (int) runtime.tv_sec);
112 }
113 
114 int bench_futex_hash(int argc, const char **argv,
115 		     const char *prefix __maybe_unused)
116 {
117 	int ret = 0;
118 	cpu_set_t cpu;
119 	struct sigaction act;
120 	unsigned int i, ncpus;
121 	pthread_attr_t thread_attr;
122 	struct worker *worker = NULL;
123 
124 	argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
125 	if (argc) {
126 		usage_with_options(bench_futex_hash_usage, options);
127 		exit(EXIT_FAILURE);
128 	}
129 
130 	ncpus = sysconf(_SC_NPROCESSORS_ONLN);
131 
132 	sigfillset(&act.sa_mask);
133 	act.sa_sigaction = toggle_done;
134 	sigaction(SIGINT, &act, NULL);
135 
136 	if (!nthreads) /* default to the number of CPUs */
137 		nthreads = ncpus;
138 
139 	worker = calloc(nthreads, sizeof(*worker));
140 	if (!worker)
141 		goto errmem;
142 
143 	if (!fshared)
144 		futex_flag = FUTEX_PRIVATE_FLAG;
145 
146 	printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
147 	       getpid(), nthreads, nfutexes, fshared ? "shared":"private", nsecs);
148 
149 	init_stats(&throughput_stats);
150 	pthread_mutex_init(&thread_lock, NULL);
151 	pthread_cond_init(&thread_parent, NULL);
152 	pthread_cond_init(&thread_worker, NULL);
153 
154 	threads_starting = nthreads;
155 	pthread_attr_init(&thread_attr);
156 	gettimeofday(&start, NULL);
157 	for (i = 0; i < nthreads; i++) {
158 		worker[i].tid = i;
159 		worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
160 		if (!worker[i].futex)
161 			goto errmem;
162 
163 		CPU_ZERO(&cpu);
164 		CPU_SET(i % ncpus, &cpu);
165 
166 		ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu);
167 		if (ret)
168 			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
169 
170 		ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
171 				     (void *)(struct worker *) &worker[i]);
172 		if (ret)
173 			err(EXIT_FAILURE, "pthread_create");
174 
175 	}
176 	pthread_attr_destroy(&thread_attr);
177 
178 	pthread_mutex_lock(&thread_lock);
179 	while (threads_starting)
180 		pthread_cond_wait(&thread_parent, &thread_lock);
181 	pthread_cond_broadcast(&thread_worker);
182 	pthread_mutex_unlock(&thread_lock);
183 
184 	sleep(nsecs);
185 	toggle_done(0, NULL, NULL);
186 
187 	for (i = 0; i < nthreads; i++) {
188 		ret = pthread_join(worker[i].thread, NULL);
189 		if (ret)
190 			err(EXIT_FAILURE, "pthread_join");
191 	}
192 
193 	/* cleanup & report results */
194 	pthread_cond_destroy(&thread_parent);
195 	pthread_cond_destroy(&thread_worker);
196 	pthread_mutex_destroy(&thread_lock);
197 
198 	for (i = 0; i < nthreads; i++) {
199 		unsigned long t = worker[i].ops/runtime.tv_sec;
200 		update_stats(&throughput_stats, t);
201 		if (!silent) {
202 			if (nfutexes == 1)
203 				printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
204 				       worker[i].tid, &worker[i].futex[0], t);
205 			else
206 				printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
207 				       worker[i].tid, &worker[i].futex[0],
208 				       &worker[i].futex[nfutexes-1], t);
209 		}
210 
211 		free(worker[i].futex);
212 	}
213 
214 	print_summary();
215 
216 	free(worker);
217 	return ret;
218 errmem:
219 	err(EXIT_FAILURE, "calloc");
220 }
221