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
bench_futex_wake_parallel(int argc __maybe_unused,const char ** argv __maybe_unused)16 int 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 
40 struct thread_data {
41 	pthread_t worker;
42 	unsigned int nwoken;
43 	struct timeval runtime;
44 };
45 
46 static unsigned int nwakes = 1;
47 
48 /* all threads will block on the same futex -- hash bucket chaos ;) */
49 static u_int32_t futex = 0;
50 
51 static pthread_t *blocked_worker;
52 static bool done = false;
53 static struct mutex thread_lock;
54 static struct cond thread_parent, thread_worker;
55 static pthread_barrier_t barrier;
56 static struct stats waketime_stats, wakeup_stats;
57 static unsigned int threads_starting;
58 static int futex_flag = 0;
59 
60 static struct bench_futex_parameters params;
61 
62 static 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 
72 static const char * const bench_futex_wake_parallel_usage[] = {
73 	"perf bench futex wake-parallel <options>",
74 	NULL
75 };
76 
waking_workerfn(void * arg)77 static 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 
wakeup_threads(struct thread_data * td)98 static 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 
blocked_workerfn(void * arg __maybe_unused)130 static 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 
block_threads(pthread_t * w,struct perf_cpu_map * cpu)148 static 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 
print_run(struct thread_data * waking_worker,unsigned int run_num)183 static 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 
print_summary(void)207 static 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 
do_run_stats(struct thread_data * waking_worker)224 static 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 
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)235 static void toggle_done(int sig __maybe_unused,
236 			siginfo_t *info __maybe_unused,
237 			void *uc __maybe_unused)
238 {
239 	done = true;
240 }
241 
bench_futex_wake_parallel(int argc,const char ** argv)242 int 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(NULL);
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