tools/perf/bench/futex-requeue.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
  *
  * futex-requeue: Block a bunch of threads on futex1 and requeue them
  *                on futex2, N at a time.
  *
  * This program is particularly useful to measure the latency of nthread
  * requeues without waking up any tasks (in the non-pi case) -- thus
  * mimicking a regular futex_wait.
  */

 /* For the CLR_() macros */
 #include <string.h>
 #include <pthread.h>

 #include <signal.h>
 #include "../util/mutex.h"
 #include "../util/stat.h"
 #include <subcmd/parse-options.h>
 #include <linux/compiler.h>
 #include <linux/kernel.h>
 #include <linux/time64.h>
 #include <errno.h>
 #include <perf/cpumap.h>
 #include "bench.h"
 #include "futex.h"

 #include <err.h>
 #include <stdlib.h>
 #include <sys/time.h>
 #include <sys/mman.h>

 static u_int32_t futex1 = 0, futex2 = 0;

 static pthread_t *worker;
 static bool done = false;
 static struct mutex thread_lock;
 static struct cond thread_parent, thread_worker;
 static struct stats requeuetime_stats, requeued_stats;
 static unsigned int threads_starting;
 static int futex_flag = 0;

 static struct bench_futex_parameters params = {
 	/*
 	 * How many tasks to requeue at a time.
 	 * Default to 1 in order to make the kernel work more.
 	 */
 	.nrequeue = 1,
 };

 static const struct option options[] = {
 	OPT_UINTEGER('t', "threads",  &params.nthreads, "Specify amount of threads"),
 	OPT_UINTEGER('q', "nrequeue", &params.nrequeue, "Specify amount of threads to requeue at once"),
 	OPT_BOOLEAN( 's', "silent",   &params.silent, "Silent mode: do not display data/details"),
 	OPT_BOOLEAN( 'S', "shared",   &params.fshared, "Use shared futexes instead of private ones"),
 	OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
 	OPT_BOOLEAN( 'B', "broadcast", &params.broadcast, "Requeue all threads at once"),
 	OPT_BOOLEAN( 'p', "pi", &params.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),

 	OPT_END()
 };

 static const char * const bench_futex_requeue_usage[] = {
 	"perf bench futex requeue <options>",
 	NULL
 };

 static void print_summary(void)
 {
 	double requeuetime_avg = avg_stats(&requeuetime_stats);
 	double requeuetime_stddev = stddev_stats(&requeuetime_stats);
 	unsigned int requeued_avg = avg_stats(&requeued_stats);

 	printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
 	       requeued_avg,
 	       params.nthreads,
 	       requeuetime_avg / USEC_PER_MSEC,
 	       rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
 }

 static void *workerfn(void *arg __maybe_unused)
 {
 	int ret;

 	mutex_lock(&thread_lock);
 	threads_starting--;
 	if (!threads_starting)
 		cond_signal(&thread_parent);
 	cond_wait(&thread_worker, &thread_lock);
 	mutex_unlock(&thread_lock);

 	while (1) {
 		if (!params.pi) {
 			ret = futex_wait(&futex1, 0, NULL, futex_flag);
 			if (!ret)
 				break;

 			if (ret && errno != EAGAIN) {
 				if (!params.silent)
 					warnx("futex_wait");
 				break;
 			}
 		} else {
 			ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
 						    NULL, futex_flag);
 			if (!ret) {
 				/* got the lock at futex2 */
 				futex_unlock_pi(&futex2, futex_flag);
 				break;
 			}

 			if (ret && errno != EAGAIN) {
 				if (!params.silent)
 					warnx("futex_wait_requeue_pi");
 				break;
 			}
 		}
 	}

 	return NULL;
 }

 static void block_threads(pthread_t *w,
 			  pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
 {
 	cpu_set_t *cpuset;
 	unsigned int i;
 	int nrcpus = perf_cpu_map__nr(cpu);
 	size_t size;

 	threads_starting = params.nthreads;

 	cpuset = CPU_ALLOC(nrcpus);
 	BUG_ON(!cpuset);
 	size = CPU_ALLOC_SIZE(nrcpus);

 	/* create and block all threads */
 	for (i = 0; i < params.nthreads; i++) {
 		CPU_ZERO_S(size, cpuset);
 		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);

 		if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
 			CPU_FREE(cpuset);
 			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
 		}

 		if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
 			CPU_FREE(cpuset);
 			err(EXIT_FAILURE, "pthread_create");
 		}
 	}
 	CPU_FREE(cpuset);
 }

 static void toggle_done(int sig __maybe_unused,
 			siginfo_t *info __maybe_unused,
 			void *uc __maybe_unused)
 {
 	done = true;
 }

 int bench_futex_requeue(int argc, const char **argv)
 {
 	int ret = 0;
 	unsigned int i, j;
 	struct sigaction act;
 	pthread_attr_t thread_attr;
 	struct perf_cpu_map *cpu;

 	argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
 	if (argc)
 		goto err;

 	cpu = perf_cpu_map__new(NULL);
 	if (!cpu)
 		err(EXIT_FAILURE, "cpu_map__new");

 	memset(&act, 0, sizeof(act));
 	sigfillset(&act.sa_mask);
 	act.sa_sigaction = toggle_done;
 	sigaction(SIGINT, &act, NULL);

 	if (params.mlockall) {
 		if (mlockall(MCL_CURRENT | MCL_FUTURE))
 			err(EXIT_FAILURE, "mlockall");
 	}

 	if (!params.nthreads)
 		params.nthreads = perf_cpu_map__nr(cpu);

 	worker = calloc(params.nthreads, sizeof(*worker));
 	if (!worker)
 		err(EXIT_FAILURE, "calloc");

 	if (!params.fshared)
 		futex_flag = FUTEX_PRIVATE_FLAG;

 	if (params.nrequeue > params.nthreads)
 		params.nrequeue = params.nthreads;

 	if (params.broadcast)
 		params.nrequeue = params.nthreads;

 	printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
 	       "%d at a time.\n\n",  getpid(), params.nthreads,
 	       params.fshared ? "shared":"private", &futex1,
 	       params.pi ? "PI ": "", &futex2, params.nrequeue);

 	init_stats(&requeued_stats);
 	init_stats(&requeuetime_stats);
 	pthread_attr_init(&thread_attr);
 	mutex_init(&thread_lock);
 	cond_init(&thread_parent);
 	cond_init(&thread_worker);

 	for (j = 0; j < bench_repeat && !done; j++) {
 		unsigned int nrequeued = 0, wakeups = 0;
 		struct timeval start, end, runtime;

 		/* create, launch & block all threads */
 		block_threads(worker, thread_attr, cpu);

 		/* make sure all threads are already blocked */
 		mutex_lock(&thread_lock);
 		while (threads_starting)
 			cond_wait(&thread_parent, &thread_lock);
 		cond_broadcast(&thread_worker);
 		mutex_unlock(&thread_lock);

 		usleep(100000);

 		/* Ok, all threads are patiently blocked, start requeueing */
 		gettimeofday(&start, NULL);
 		while (nrequeued < params.nthreads) {
 			int r;

 			/*
 			 * For the regular non-pi case, do not wakeup any tasks
 			 * blocked on futex1, allowing us to really measure
 			 * futex_wait functionality. For the PI case the first
 			 * waiter is always awoken.
 			 */
 			if (!params.pi) {
 				r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
 						      params.nrequeue,
 						      futex_flag);
 			} else {
 				r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
 							 params.nrequeue,
 							 futex_flag);
 				wakeups++; /* assume no error */
 			}

 			if (r < 0)
 				err(EXIT_FAILURE, "couldn't requeue from %p to %p",
 				    &futex1, &futex2);

 			nrequeued += r;
 		}

 		gettimeofday(&end, NULL);
 		timersub(&end, &start, &runtime);

 		update_stats(&requeued_stats, nrequeued);
 		update_stats(&requeuetime_stats, runtime.tv_usec);

 		if (!params.silent) {
 			if (!params.pi)
 				printf("[Run %d]: Requeued %d of %d threads in "
 				       "%.4f ms\n", j + 1, nrequeued,
 				       params.nthreads,
 				       runtime.tv_usec / (double)USEC_PER_MSEC);
 			else {
 				nrequeued -= wakeups;
 				printf("[Run %d]: Awoke and Requeued (%d+%d) of "
 				       "%d threads in %.4f ms\n",
 				       j + 1, wakeups, nrequeued,
 				       params.nthreads,
 				       runtime.tv_usec / (double)USEC_PER_MSEC);
 			}

 		}

 		if (!params.pi) {
 			/* everybody should be blocked on futex2, wake'em up */
 			nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
 			if (params.nthreads != nrequeued)
 				warnx("couldn't wakeup all tasks (%d/%d)",
 				      nrequeued, params.nthreads);
 		}

 		for (i = 0; i < params.nthreads; i++) {
 			ret = pthread_join(worker[i], NULL);
 			if (ret)
 				err(EXIT_FAILURE, "pthread_join");
 		}
 	}

 	/* cleanup & report results */
 	cond_destroy(&thread_parent);
 	cond_destroy(&thread_worker);
 	mutex_destroy(&thread_lock);
 	pthread_attr_destroy(&thread_attr);

 	print_summary();

 	free(worker);
 	perf_cpu_map__put(cpu);
 	return ret;
 err:
 	usage_with_options(bench_futex_requeue_usage, options);
 	exit(EXIT_FAILURE);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
	*
	* futex-requeue: Block a bunch of threads on futex1 and requeue them
	* on futex2, N at a time.
	*
	* This program is particularly useful to measure the latency of nthread
	* requeues without waking up any tasks (in the non-pi case) -- thus
	* mimicking a regular futex_wait.
	*/

	/* For the CLR_() macros */
	#include <string.h>
	#include <pthread.h>

	#include <signal.h>
	#include "../util/mutex.h"
	#include "../util/stat.h"
	#include <subcmd/parse-options.h>
	#include <linux/compiler.h>
	#include <linux/kernel.h>
	#include <linux/time64.h>
	#include <errno.h>
	#include <perf/cpumap.h>
	#include "bench.h"
	#include "futex.h"

	#include <err.h>
	#include <stdlib.h>
	#include <sys/time.h>
	#include <sys/mman.h>

	static u_int32_t futex1 = 0, futex2 = 0;

	static pthread_t *worker;
	static bool done = false;
	static struct mutex thread_lock;
	static struct cond thread_parent, thread_worker;
	static struct stats requeuetime_stats, requeued_stats;
	static unsigned int threads_starting;
	static int futex_flag = 0;

	static struct bench_futex_parameters params = {
	/*
	* How many tasks to requeue at a time.
	* Default to 1 in order to make the kernel work more.
	*/
	.nrequeue = 1,
	};

	static const struct option options[] = {
	OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
	OPT_UINTEGER('q', "nrequeue", &params.nrequeue, "Specify amount of threads to requeue at once"),
	OPT_BOOLEAN( 's', "silent", &params.silent, "Silent mode: do not display data/details"),
	OPT_BOOLEAN( 'S', "shared", &params.fshared, "Use shared futexes instead of private ones"),
	OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
	OPT_BOOLEAN( 'B', "broadcast", &params.broadcast, "Requeue all threads at once"),
	OPT_BOOLEAN( 'p', "pi", &params.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),

	OPT_END()
	};

	static const char * const bench_futex_requeue_usage[] = {
	"perf bench futex requeue <options>",
	NULL
	};

	static void print_summary(void)
	{
	double requeuetime_avg = avg_stats(&requeuetime_stats);
	double requeuetime_stddev = stddev_stats(&requeuetime_stats);
	unsigned int requeued_avg = avg_stats(&requeued_stats);

	printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
	requeued_avg,
	params.nthreads,
	requeuetime_avg / USEC_PER_MSEC,
	rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
	}

	static void workerfn(void arg __maybe_unused)
	{
	int ret;

	mutex_lock(&thread_lock);
	threads_starting--;
	if (!threads_starting)
	cond_signal(&thread_parent);
	cond_wait(&thread_worker, &thread_lock);
	mutex_unlock(&thread_lock);

	while (1) {
	if (!params.pi) {
	ret = futex_wait(&futex1, 0, NULL, futex_flag);
	if (!ret)
	break;

	if (ret && errno != EAGAIN) {
	if (!params.silent)
	warnx("futex_wait");
	break;
	}
	} else {
	ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
	NULL, futex_flag);
	if (!ret) {
	/* got the lock at futex2 */
	futex_unlock_pi(&futex2, futex_flag);
	break;
	}

	if (ret && errno != EAGAIN) {
	if (!params.silent)
	warnx("futex_wait_requeue_pi");
	break;
	}
	}
	}

	return NULL;
	}

	static void block_threads(pthread_t *w,
	pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
	{
	cpu_set_t *cpuset;
	unsigned int i;
	int nrcpus = perf_cpu_map__nr(cpu);
	size_t size;

	threads_starting = params.nthreads;

	cpuset = CPU_ALLOC(nrcpus);
	BUG_ON(!cpuset);
	size = CPU_ALLOC_SIZE(nrcpus);

	/* create and block all threads */
	for (i = 0; i < params.nthreads; i++) {
	CPU_ZERO_S(size, cpuset);
	CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);

	if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
	CPU_FREE(cpuset);
	err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
	}

	if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
	CPU_FREE(cpuset);
	err(EXIT_FAILURE, "pthread_create");
	}
	}
	CPU_FREE(cpuset);
	}

	static void toggle_done(int sig __maybe_unused,
	siginfo_t *info __maybe_unused,
	void *uc __maybe_unused)
	{
	done = true;
	}

	int bench_futex_requeue(int argc, const char **argv)
	{
	int ret = 0;
	unsigned int i, j;
	struct sigaction act;
	pthread_attr_t thread_attr;
	struct perf_cpu_map *cpu;

	argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
	if (argc)
	goto err;

	cpu = perf_cpu_map__new(NULL);
	if (!cpu)
	err(EXIT_FAILURE, "cpu_map__new");

	memset(&act, 0, sizeof(act));
	sigfillset(&act.sa_mask);
	act.sa_sigaction = toggle_done;
	sigaction(SIGINT, &act, NULL);

	if (params.mlockall) {
	if (mlockall(MCL_CURRENT \| MCL_FUTURE))
	err(EXIT_FAILURE, "mlockall");
	}

	if (!params.nthreads)
	params.nthreads = perf_cpu_map__nr(cpu);

	worker = calloc(params.nthreads, sizeof(*worker));
	if (!worker)
	err(EXIT_FAILURE, "calloc");

	if (!params.fshared)
	futex_flag = FUTEX_PRIVATE_FLAG;

	if (params.nrequeue > params.nthreads)
	params.nrequeue = params.nthreads;

	if (params.broadcast)
	params.nrequeue = params.nthreads;

	printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
	"%d at a time.\n\n", getpid(), params.nthreads,
	params.fshared ? "shared":"private", &futex1,
	params.pi ? "PI ": "", &futex2, params.nrequeue);

	init_stats(&requeued_stats);
	init_stats(&requeuetime_stats);
	pthread_attr_init(&thread_attr);
	mutex_init(&thread_lock);
	cond_init(&thread_parent);
	cond_init(&thread_worker);

	for (j = 0; j < bench_repeat && !done; j++) {
	unsigned int nrequeued = 0, wakeups = 0;
	struct timeval start, end, runtime;

	/* create, launch & block all threads */
	block_threads(worker, thread_attr, cpu);

	/* make sure all threads are already blocked */
	mutex_lock(&thread_lock);
	while (threads_starting)
	cond_wait(&thread_parent, &thread_lock);
	cond_broadcast(&thread_worker);
	mutex_unlock(&thread_lock);

	usleep(100000);

	/* Ok, all threads are patiently blocked, start requeueing */
	gettimeofday(&start, NULL);
	while (nrequeued < params.nthreads) {
	int r;

	/*
	* For the regular non-pi case, do not wakeup any tasks
	* blocked on futex1, allowing us to really measure
	* futex_wait functionality. For the PI case the first
	* waiter is always awoken.
	*/
	if (!params.pi) {
	r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
	params.nrequeue,
	futex_flag);
	} else {
	r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
	params.nrequeue,
	futex_flag);
	wakeups++; /* assume no error */
	}

	if (r < 0)
	err(EXIT_FAILURE, "couldn't requeue from %p to %p",
	&futex1, &futex2);

	nrequeued += r;
	}

	gettimeofday(&end, NULL);
	timersub(&end, &start, &runtime);

	update_stats(&requeued_stats, nrequeued);
	update_stats(&requeuetime_stats, runtime.tv_usec);

	if (!params.silent) {
	if (!params.pi)
	printf("[Run %d]: Requeued %d of %d threads in "
	"%.4f ms\n", j + 1, nrequeued,
	params.nthreads,
	runtime.tv_usec / (double)USEC_PER_MSEC);
	else {
	nrequeued -= wakeups;
	printf("[Run %d]: Awoke and Requeued (%d+%d) of "
	"%d threads in %.4f ms\n",
	j + 1, wakeups, nrequeued,
	params.nthreads,
	runtime.tv_usec / (double)USEC_PER_MSEC);
	}

	}

	if (!params.pi) {
	/* everybody should be blocked on futex2, wake'em up */
	nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
	if (params.nthreads != nrequeued)
	warnx("couldn't wakeup all tasks (%d/%d)",
	nrequeued, params.nthreads);
	}

	for (i = 0; i < params.nthreads; i++) {
	ret = pthread_join(worker[i], NULL);
	if (ret)
	err(EXIT_FAILURE, "pthread_join");
	}
	}

	/* cleanup & report results */
	cond_destroy(&thread_parent);
	cond_destroy(&thread_worker);
	mutex_destroy(&thread_lock);
	pthread_attr_destroy(&thread_attr);

	print_summary();

	free(worker);
	perf_cpu_map__put(cpu);
	return ret;
	err:
	usage_with_options(bench_futex_requeue_usage, options);
	exit(EXIT_FAILURE);
	}