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