futex-hash.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
  4 *
  5 * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
  6 *
  7 * This program is particularly useful for measuring the kernel's futex hash
  8 * table/function implementation. In order for it to make sense, use with as
  9 * many threads and futexes as possible.
 10 */
 11
 12/* For the CLR_() macros */
 13#include <string.h>
 14#include <pthread.h>
 15
 16#include <errno.h>
 17#include <signal.h>
 18#include <stdlib.h>
 19#include <linux/compiler.h>
 20#include <linux/kernel.h>
 21#include <linux/zalloc.h>
 22#include <sys/time.h>
 23#include <sys/mman.h>
 24#include <sys/prctl.h>
 25#include <perf/cpumap.h>
 26
 27#include "../util/mutex.h"
 28#include "../util/stat.h"
 29#include <subcmd/parse-options.h>
 30#include "bench.h"
 31#include "futex.h"
 32
 33#include <err.h>
 34
 35static bool done = false;
 36static int futex_flag = 0;
 37
 38struct timeval bench__start, bench__end, bench__runtime;
 39static struct mutex thread_lock;
 40static unsigned int threads_starting;
 41static struct stats throughput_stats;
 42static struct cond thread_parent, thread_worker;
 43
 44struct worker {
 45	int tid;
 46	u_int32_t *futex;
 47	pthread_t thread;
 48	unsigned long ops;
 49};
 50
 51static struct bench_futex_parameters params = {
 52	.nfutexes = 1024,
 53	.runtime  = 10,
 54	.nbuckets = -1,
 55};
 56
 57static const struct option options[] = {
 58	OPT_INTEGER( 'b', "buckets", &params.nbuckets, "Specify amount of hash buckets"),
 59	OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
 60	OPT_UINTEGER('r', "runtime", &params.runtime, "Specify runtime (in seconds)"),
 61	OPT_UINTEGER('f', "futexes", &params.nfutexes, "Specify amount of futexes per threads"),
 62	OPT_BOOLEAN( 's', "silent",  &params.silent, "Silent mode: do not display data/details"),
 63	OPT_BOOLEAN( 'S', "shared",  &params.fshared, "Use shared futexes instead of private ones"),
 64	OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
 65	OPT_END()
 66};
 67
 68static const char * const bench_futex_hash_usage[] = {
 69	"perf bench futex hash <options>",
 70	NULL
 71};
 72
 73static void *workerfn(void *arg)
 74{
 75	int ret;
 76	struct worker *w = (struct worker *) arg;
 77	unsigned int i;
 78	unsigned long ops = w->ops; /* avoid cacheline bouncing */
 79
 80	mutex_lock(&thread_lock);
 81	threads_starting--;
 82	if (!threads_starting)
 83		cond_signal(&thread_parent);
 84	cond_wait(&thread_worker, &thread_lock);
 85	mutex_unlock(&thread_lock);
 86
 87	do {
 88		for (i = 0; i < params.nfutexes; i++, ops++) {
 89			/*
 90			 * We want the futex calls to fail in order to stress
 91			 * the hashing of uaddr and not measure other steps,
 92			 * such as internal waitqueue handling, thus enlarging
 93			 * the critical region protected by hb->lock.
 94			 */
 95			ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
 96			if (!params.silent &&
 97			    (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
 98				warn("Non-expected futex return call");
 99		}
100	}  while (!done);
101
102	w->ops = ops;
103	return NULL;
104}
105
106static void toggle_done(int sig __maybe_unused,
107			siginfo_t *info __maybe_unused,
108			void *uc __maybe_unused)
109{
110	/* inform all threads that we're done for the day */
111	done = true;
112	gettimeofday(&bench__end, NULL);
113	timersub(&bench__end, &bench__start, &bench__runtime);
114}
115
116static void print_summary(void)
117{
118	unsigned long avg = avg_stats(&throughput_stats);
119	double stddev = stddev_stats(&throughput_stats);
120
121	printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
122	       !params.silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
123	       (int)bench__runtime.tv_sec);
124	futex_print_nbuckets(&params);
125}
126
127int bench_futex_hash(int argc, const char **argv)
128{
129	int ret = 0;
130	cpu_set_t *cpuset;
131	struct sigaction act;
132	unsigned int i;
133	pthread_attr_t thread_attr;
134	struct worker *worker = NULL;
135	struct perf_cpu_map *cpu;
136	int nrcpus;
137	size_t size;
138
139	argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
140	if (argc) {
141		usage_with_options(bench_futex_hash_usage, options);
142		exit(EXIT_FAILURE);
143	}
144
145	cpu = perf_cpu_map__new_online_cpus();
146	if (!cpu)
147		goto errmem;
148
149	memset(&act, 0, sizeof(act));
150	sigfillset(&act.sa_mask);
151	act.sa_sigaction = toggle_done;
152	sigaction(SIGINT, &act, NULL);
153
154	if (params.mlockall) {
155		if (mlockall(MCL_CURRENT | MCL_FUTURE))
156			err(EXIT_FAILURE, "mlockall");
157	}
158
159	if (!params.nthreads) /* default to the number of CPUs */
160		params.nthreads = perf_cpu_map__nr(cpu);
161
162	worker = calloc(params.nthreads, sizeof(*worker));
163	if (!worker)
164		goto errmem;
165
166	if (!params.fshared)
167		futex_flag = FUTEX_PRIVATE_FLAG;
168	futex_set_nbuckets_param(&params);
169
170	printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
171	       getpid(), params.nthreads, params.nfutexes, params.fshared ? "shared":"private", params.runtime);
172
173	init_stats(&throughput_stats);
174	mutex_init(&thread_lock);
175	cond_init(&thread_parent);
176	cond_init(&thread_worker);
177
178	threads_starting = params.nthreads;
179	pthread_attr_init(&thread_attr);
180	gettimeofday(&bench__start, NULL);
181
182	nrcpus = cpu__max_cpu().cpu;
183	cpuset = CPU_ALLOC(nrcpus);
184	BUG_ON(!cpuset);
185	size = CPU_ALLOC_SIZE(nrcpus);
186
187	for (i = 0; i < params.nthreads; i++) {
188		worker[i].tid = i;
189		worker[i].futex = calloc(params.nfutexes, sizeof(*worker[i].futex));
190		if (!worker[i].futex)
191			goto errmem;
192
193		CPU_ZERO_S(size, cpuset);
194
195		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
196		ret = pthread_attr_setaffinity_np(&thread_attr, size, cpuset);
197		if (ret) {
198			CPU_FREE(cpuset);
199			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
200		}
201		ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
202				     (void *)(struct worker *) &worker[i]);
203		if (ret) {
204			CPU_FREE(cpuset);
205			err(EXIT_FAILURE, "pthread_create");
206		}
207
208	}
209	CPU_FREE(cpuset);
210	pthread_attr_destroy(&thread_attr);
211
212	mutex_lock(&thread_lock);
213	while (threads_starting)
214		cond_wait(&thread_parent, &thread_lock);
215	cond_broadcast(&thread_worker);
216	mutex_unlock(&thread_lock);
217
218	sleep(params.runtime);
219	toggle_done(0, NULL, NULL);
220
221	for (i = 0; i < params.nthreads; i++) {
222		ret = pthread_join(worker[i].thread, NULL);
223		if (ret)
224			err(EXIT_FAILURE, "pthread_join");
225	}
226
227	/* cleanup & report results */
228	cond_destroy(&thread_parent);
229	cond_destroy(&thread_worker);
230	mutex_destroy(&thread_lock);
231
232	for (i = 0; i < params.nthreads; i++) {
233		unsigned long t = bench__runtime.tv_sec > 0 ?
234			worker[i].ops / bench__runtime.tv_sec : 0;
235		update_stats(&throughput_stats, t);
236		if (!params.silent) {
237			if (params.nfutexes == 1)
238				printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
239				       worker[i].tid, &worker[i].futex[0], t);
240			else
241				printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
242				       worker[i].tid, &worker[i].futex[0],
243				       &worker[i].futex[params.nfutexes-1], t);
244		}
245
246		zfree(&worker[i].futex);
247	}
248
249	print_summary();
250
251	free(worker);
252	free(cpu);
253	return ret;
254errmem:
255	err(EXIT_FAILURE, "calloc");
256}