1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015 Davidlohr Bueso.
4 *
5 * Block a bunch of threads and let parallel waker threads wakeup an
6 * equal amount of them. The program output reflects the avg latency
7 * for each individual thread to service its share of work. Ultimately
8 * it can be used to measure futex_wake() changes.
9 */
10#include "bench.h"
11#include <linux/compiler.h>
12#include "../util/debug.h"
13#include "../util/mutex.h"
14
15#ifndef HAVE_PTHREAD_BARRIER
16int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
17{
18	pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
19	return 0;
20}
21#else /* HAVE_PTHREAD_BARRIER */
22/* For the CLR_() macros */
23#include <string.h>
24#include <pthread.h>
25
26#include <signal.h>
27#include "../util/stat.h"
28#include <subcmd/parse-options.h>
29#include <linux/kernel.h>
30#include <linux/time64.h>
31#include <errno.h>
32#include "futex.h"
33#include <perf/cpumap.h>
34
35#include <err.h>
36#include <stdlib.h>
37#include <sys/time.h>
38#include <sys/mman.h>
39
40struct thread_data {
41	pthread_t worker;
42	unsigned int nwoken;
43	struct timeval runtime;
44};
45
46static unsigned int nwakes = 1;
47
48/* all threads will block on the same futex -- hash bucket chaos ;) */
49static u_int32_t futex = 0;
50
51static pthread_t *blocked_worker;
52static bool done = false;
53static struct mutex thread_lock;
54static struct cond thread_parent, thread_worker;
55static pthread_barrier_t barrier;
56static struct stats waketime_stats, wakeup_stats;
57static unsigned int threads_starting;
58static int futex_flag = 0;
59
60static struct bench_futex_parameters params;
61
62static const struct option options[] = {
63	OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
64	OPT_UINTEGER('w', "nwakers", &params.nwakes, "Specify amount of waking threads"),
65	OPT_BOOLEAN( 's', "silent",  &params.silent, "Silent mode: do not display data/details"),
66	OPT_BOOLEAN( 'S', "shared",  &params.fshared, "Use shared futexes instead of private ones"),
67	OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
68
69	OPT_END()
70};
71
72static const char * const bench_futex_wake_parallel_usage[] = {
73	"perf bench futex wake-parallel <options>",
74	NULL
75};
76
77static void *waking_workerfn(void *arg)
78{
79	struct thread_data *waker = (struct thread_data *) arg;
80	struct timeval start, end;
81
82	pthread_barrier_wait(&barrier);
83
84	gettimeofday(&start, NULL);
85
86	waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
87	if (waker->nwoken != nwakes)
88		warnx("couldn't wakeup all tasks (%d/%d)",
89		      waker->nwoken, nwakes);
90
91	gettimeofday(&end, NULL);
92	timersub(&end, &start, &waker->runtime);
93
94	pthread_exit(NULL);
95	return NULL;
96}
97
98static void wakeup_threads(struct thread_data *td)
99{
100	unsigned int i;
101	pthread_attr_t thread_attr;
102
103	pthread_attr_init(&thread_attr);
104	pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
105
106	pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
107
108	/* create and block all threads */
109	for (i = 0; i < params.nwakes; i++) {
110		/*
111		 * Thread creation order will impact per-thread latency
112		 * as it will affect the order to acquire the hb spinlock.
113		 * For now let the scheduler decide.
114		 */
115		if (pthread_create(&td[i].worker, &thread_attr,
116				   waking_workerfn, (void *)&td[i]))
117			err(EXIT_FAILURE, "pthread_create");
118	}
119
120	pthread_barrier_wait(&barrier);
121
122	for (i = 0; i < params.nwakes; i++)
123		if (pthread_join(td[i].worker, NULL))
124			err(EXIT_FAILURE, "pthread_join");
125
126	pthread_barrier_destroy(&barrier);
127	pthread_attr_destroy(&thread_attr);
128}
129
130static void *blocked_workerfn(void *arg __maybe_unused)
131{
132	mutex_lock(&thread_lock);
133	threads_starting--;
134	if (!threads_starting)
135		cond_signal(&thread_parent);
136	cond_wait(&thread_worker, &thread_lock);
137	mutex_unlock(&thread_lock);
138
139	while (1) { /* handle spurious wakeups */
140		if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
141			break;
142	}
143
144	pthread_exit(NULL);
145	return NULL;
146}
147
148static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
149{
150	cpu_set_t *cpuset;
151	unsigned int i;
152	int nrcpus = perf_cpu_map__nr(cpu);
153	size_t size;
154
155	threads_starting = params.nthreads;
156
157	cpuset = CPU_ALLOC(nrcpus);
158	BUG_ON(!cpuset);
159	size = CPU_ALLOC_SIZE(nrcpus);
160
161	/* create and block all threads */
162	for (i = 0; i < params.nthreads; i++) {
163		pthread_attr_t thread_attr;
164
165		pthread_attr_init(&thread_attr);
166		CPU_ZERO_S(size, cpuset);
167		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
168
169		if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
170			CPU_FREE(cpuset);
171			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
172		}
173
174		if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
175			CPU_FREE(cpuset);
176			err(EXIT_FAILURE, "pthread_create");
177		}
178		pthread_attr_destroy(&thread_attr);
179	}
180	CPU_FREE(cpuset);
181}
182
183static void print_run(struct thread_data *waking_worker, unsigned int run_num)
184{
185	unsigned int i, wakeup_avg;
186	double waketime_avg, waketime_stddev;
187	struct stats __waketime_stats, __wakeup_stats;
188
189	init_stats(&__wakeup_stats);
190	init_stats(&__waketime_stats);
191
192	for (i = 0; i < params.nwakes; i++) {
193		update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
194		update_stats(&__wakeup_stats, waking_worker[i].nwoken);
195	}
196
197	waketime_avg = avg_stats(&__waketime_stats);
198	waketime_stddev = stddev_stats(&__waketime_stats);
199	wakeup_avg = avg_stats(&__wakeup_stats);
200
201	printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
202	       "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
203	       params.nthreads, waketime_avg / USEC_PER_MSEC,
204	       rel_stddev_stats(waketime_stddev, waketime_avg));
205}
206
207static void print_summary(void)
208{
209	unsigned int wakeup_avg;
210	double waketime_avg, waketime_stddev;
211
212	waketime_avg = avg_stats(&waketime_stats);
213	waketime_stddev = stddev_stats(&waketime_stats);
214	wakeup_avg = avg_stats(&wakeup_stats);
215
216	printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
217	       wakeup_avg,
218	       params.nthreads,
219	       waketime_avg / USEC_PER_MSEC,
220	       rel_stddev_stats(waketime_stddev, waketime_avg));
221}
222
223
224static void do_run_stats(struct thread_data *waking_worker)
225{
226	unsigned int i;
227
228	for (i = 0; i < params.nwakes; i++) {
229		update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
230		update_stats(&wakeup_stats, waking_worker[i].nwoken);
231	}
232
233}
234
235static void toggle_done(int sig __maybe_unused,
236			siginfo_t *info __maybe_unused,
237			void *uc __maybe_unused)
238{
239	done = true;
240}
241
242int bench_futex_wake_parallel(int argc, const char **argv)
243{
244	int ret = 0;
245	unsigned int i, j;
246	struct sigaction act;
247	struct thread_data *waking_worker;
248	struct perf_cpu_map *cpu;
249
250	argc = parse_options(argc, argv, options,
251			     bench_futex_wake_parallel_usage, 0);
252	if (argc) {
253		usage_with_options(bench_futex_wake_parallel_usage, options);
254		exit(EXIT_FAILURE);
255	}
256
257	memset(&act, 0, sizeof(act));
258	sigfillset(&act.sa_mask);
259	act.sa_sigaction = toggle_done;
260	sigaction(SIGINT, &act, NULL);
261
262	if (params.mlockall) {
263		if (mlockall(MCL_CURRENT | MCL_FUTURE))
264			err(EXIT_FAILURE, "mlockall");
265	}
266
267	cpu = perf_cpu_map__new_online_cpus();
268	if (!cpu)
269		err(EXIT_FAILURE, "calloc");
270
271	if (!params.nthreads)
272		params.nthreads = perf_cpu_map__nr(cpu);
273
274	/* some sanity checks */
275	if (params.nwakes > params.nthreads ||
276	    !params.nwakes)
277		params.nwakes = params.nthreads;
278
279	if (params.nthreads % params.nwakes)
280		errx(EXIT_FAILURE, "Must be perfectly divisible");
281	/*
282	 * Each thread will wakeup nwakes tasks in
283	 * a single futex_wait call.
284	 */
285	nwakes = params.nthreads/params.nwakes;
286
287	blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
288	if (!blocked_worker)
289		err(EXIT_FAILURE, "calloc");
290
291	if (!params.fshared)
292		futex_flag = FUTEX_PRIVATE_FLAG;
293
294	printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
295	       "futex %p), %d threads waking up %d at a time.\n\n",
296	       getpid(), params.nthreads, params.fshared ? "shared":"private",
297	       &futex, params.nwakes, nwakes);
298
299	init_stats(&wakeup_stats);
300	init_stats(&waketime_stats);
301
302	mutex_init(&thread_lock);
303	cond_init(&thread_parent);
304	cond_init(&thread_worker);
305
306	for (j = 0; j < bench_repeat && !done; j++) {
307		waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
308		if (!waking_worker)
309			err(EXIT_FAILURE, "calloc");
310
311		/* create, launch & block all threads */
312		block_threads(blocked_worker, cpu);
313
314		/* make sure all threads are already blocked */
315		mutex_lock(&thread_lock);
316		while (threads_starting)
317			cond_wait(&thread_parent, &thread_lock);
318		cond_broadcast(&thread_worker);
319		mutex_unlock(&thread_lock);
320
321		usleep(100000);
322
323		/* Ok, all threads are patiently blocked, start waking folks up */
324		wakeup_threads(waking_worker);
325
326		for (i = 0; i < params.nthreads; i++) {
327			ret = pthread_join(blocked_worker[i], NULL);
328			if (ret)
329				err(EXIT_FAILURE, "pthread_join");
330		}
331
332		do_run_stats(waking_worker);
333		if (!params.silent)
334			print_run(waking_worker, j);
335
336		free(waking_worker);
337	}
338
339	/* cleanup & report results */
340	cond_destroy(&thread_parent);
341	cond_destroy(&thread_worker);
342	mutex_destroy(&thread_lock);
343
344	print_summary();
345
346	free(blocked_worker);
347	perf_cpu_map__put(cpu);
348	return ret;
349}
350#endif /* HAVE_PTHREAD_BARRIER */
351