// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2013 Davidlohr Bueso <[email protected]>
*
* futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time.
*
* This program is particularly useful to measure the latency of nthread wakeups
* in non-error situations: all waiters are queued and all wake calls wakeup
* one or more tasks, and thus the waitqueue is never empty.
*/
/* 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>
/* all threads will block on the same futex */
static u_int32_t futex1 = 0;
static pthread_t *worker;
static bool done = false;
static struct mutex thread_lock;
static struct cond thread_parent, thread_worker;
static struct stats waketime_stats, wakeup_stats;
static unsigned int threads_starting;
static int futex_flag = 0;
static struct bench_futex_parameters params = {
/*
* How many wakeups to do at a time.
* Default to 1 in order to make the kernel work more.
*/
.nwakes = 1,
};
static const struct option options[] = {
OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake at once"),
OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
OPT_END()
};
static const char * const bench_futex_wake_usage[] = {
"perf bench futex wake <options>",
NULL
};
static void *workerfn(void *arg __maybe_unused)
{
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 (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
break;
}
pthread_exit(NULL);
return NULL;
}
static void print_summary(void)
{
double waketime_avg = avg_stats(&waketime_stats);
double waketime_stddev = stddev_stats(&waketime_stats);
unsigned int wakeup_avg = avg_stats(&wakeup_stats);
printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
wakeup_avg,
params.nthreads,
waketime_avg / USEC_PER_MSEC,
rel_stddev_stats(waketime_stddev, waketime_avg));
}
static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
{
cpu_set_t *cpuset;
unsigned int i;
size_t size;
int nrcpus = cpu__max_cpu().cpu;
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++) {
pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
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");
}
pthread_attr_destroy(&thread_attr);
}
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_wake(int argc, const char **argv)
{
int ret = 0;
unsigned int i, j;
struct sigaction act;
struct perf_cpu_map *cpu;
argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
if (argc) {
usage_with_options(bench_futex_wake_usage, options);
exit(EXIT_FAILURE);
}
cpu = perf_cpu_map__new_online_cpus();
if (!cpu)
err(EXIT_FAILURE, "calloc");
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;
printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
"waking up %d at a time.\n\n",
getpid(), params.nthreads, params.fshared ? "shared":"private",
&futex1, params.nwakes);
init_stats(&wakeup_stats);
init_stats(&waketime_stats);
mutex_init(&thread_lock);
cond_init(&thread_parent);
cond_init(&thread_worker);
for (j = 0; j < bench_repeat && !done; j++) {
unsigned int nwoken = 0;
struct timeval start, end, runtime;
/* create, launch & block all threads */
block_threads(worker, 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 waking folks up */
gettimeofday(&start, NULL);
while (nwoken != params.nthreads)
nwoken += futex_wake(&futex1,
params.nwakes, futex_flag);
gettimeofday(&end, NULL);
timersub(&end, &start, &runtime);
update_stats(&wakeup_stats, nwoken);
update_stats(&waketime_stats, runtime.tv_usec);
if (!params.silent) {
printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
j + 1, nwoken, params.nthreads,
runtime.tv_usec / (double)USEC_PER_MSEC);
}
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);
print_summary();
free(worker);
perf_cpu_map__put(cpu);
return ret;
}
Codebase Browser
linux