// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2013 Davidlohr Bueso <[email protected]>
*
* 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", ¶ms.nthreads, "Specify amount of threads"),
OPT_UINTEGER('q', "nrequeue", ¶ms.nrequeue, "Specify amount of threads to requeue 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_BOOLEAN( 'B', "broadcast", ¶ms.broadcast, "Requeue all threads at once"),
OPT_BOOLEAN( 'p', "pi", ¶ms.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, struct perf_cpu_map *cpu)
{
cpu_set_t *cpuset;
unsigned int i;
int nrcpus = cpu__max_cpu().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++) {
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_requeue(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_requeue_usage, 0);
if (argc)
goto err;
cpu = perf_cpu_map__new_online_cpus();
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);
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, 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);
print_summary();
free(worker);
perf_cpu_map__put(cpu);
return ret;
err:
usage_with_options(bench_futex_requeue_usage, options);
exit(EXIT_FAILURE);
}
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