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