// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015 Davidlohr Bueso.
*
* Block a bunch of threads and let parallel waker threads wakeup an
* equal amount of them. The program output reflects the avg latency
* for each individual thread to service its share of work. Ultimately
* it can be used to measure futex_wake() changes.
*/
#include "bench.h"
#include <linux/compiler.h>
#include "../util/debug.h"
#include "../util/mutex.h"
#ifndef HAVE_PTHREAD_BARRIER
int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
{
pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
return 0;
}
#else /* HAVE_PTHREAD_BARRIER */
/* For the CLR_() macros */
#include <string.h>
#include <pthread.h>
#include <signal.h>
#include "../util/stat.h"
#include <subcmd/parse-options.h>
#include <linux/kernel.h>
#include <linux/time64.h>
#include <errno.h>
#include "futex.h"
#include <perf/cpumap.h>
#include <err.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/mman.h>
struct thread_data {
pthread_t worker;
unsigned int nwoken;
struct timeval runtime;
};
static unsigned int nwakes = 1;
/* all threads will block on the same futex -- hash bucket chaos ;) */
static u_int32_t futex = 0;
static pthread_t *blocked_worker;
static bool done = false;
static struct mutex thread_lock;
static struct cond thread_parent, thread_worker;
static pthread_barrier_t barrier;
static struct stats waketime_stats, wakeup_stats;
static unsigned int threads_starting;
static int futex_flag = 0;
static struct bench_futex_parameters params;
static const struct option options[] = {
OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
OPT_UINTEGER('w', "nwakers", ¶ms.nwakes, "Specify amount of waking threads"),
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_parallel_usage[] = {
"perf bench futex wake-parallel <options>",
NULL
};
static void *waking_workerfn(void *arg)
{
struct thread_data *waker = (struct thread_data *) arg;
struct timeval start, end;
pthread_barrier_wait(&barrier);
gettimeofday(&start, NULL);
waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
if (waker->nwoken != nwakes)
warnx("couldn't wakeup all tasks (%d/%d)",
waker->nwoken, nwakes);
gettimeofday(&end, NULL);
timersub(&end, &start, &waker->runtime);
pthread_exit(NULL);
return NULL;
}
static void wakeup_threads(struct thread_data *td)
{
unsigned int i;
pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
/* create and block all threads */
for (i = 0; i < params.nwakes; i++) {
/*
* Thread creation order will impact per-thread latency
* as it will affect the order to acquire the hb spinlock.
* For now let the scheduler decide.
*/
if (pthread_create(&td[i].worker, &thread_attr,
waking_workerfn, (void *)&td[i]))
err(EXIT_FAILURE, "pthread_create");
}
pthread_barrier_wait(&barrier);
for (i = 0; i < params.nwakes; i++)
if (pthread_join(td[i].worker, NULL))
err(EXIT_FAILURE, "pthread_join");
pthread_barrier_destroy(&barrier);
pthread_attr_destroy(&thread_attr);
}
static void *blocked_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) { /* handle spurious wakeups */
if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
break;
}
pthread_exit(NULL);
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, blocked_workerfn, NULL)) {
CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_create");
}
pthread_attr_destroy(&thread_attr);
}
CPU_FREE(cpuset);
}
static void print_run(struct thread_data *waking_worker, unsigned int run_num)
{
unsigned int i, wakeup_avg;
double waketime_avg, waketime_stddev;
struct stats __waketime_stats, __wakeup_stats;
init_stats(&__wakeup_stats);
init_stats(&__waketime_stats);
for (i = 0; i < params.nwakes; i++) {
update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
update_stats(&__wakeup_stats, waking_worker[i].nwoken);
}
waketime_avg = avg_stats(&__waketime_stats);
waketime_stddev = stddev_stats(&__waketime_stats);
wakeup_avg = avg_stats(&__wakeup_stats);
printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
"in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
params.nthreads, waketime_avg / USEC_PER_MSEC,
rel_stddev_stats(waketime_stddev, waketime_avg));
}
static void print_summary(void)
{
unsigned int wakeup_avg;
double waketime_avg, waketime_stddev;
waketime_avg = avg_stats(&waketime_stats);
waketime_stddev = stddev_stats(&waketime_stats);
wakeup_avg = avg_stats(&wakeup_stats);
printf("Avg per-thread latency (waking %d/%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 do_run_stats(struct thread_data *waking_worker)
{
unsigned int i;
for (i = 0; i < params.nwakes; i++) {
update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
update_stats(&wakeup_stats, waking_worker[i].nwoken);
}
}
static void toggle_done(int sig __maybe_unused,
siginfo_t *info __maybe_unused,
void *uc __maybe_unused)
{
done = true;
}
int bench_futex_wake_parallel(int argc, const char **argv)
{
int ret = 0;
unsigned int i, j;
struct sigaction act;
struct thread_data *waking_worker;
struct perf_cpu_map *cpu;
argc = parse_options(argc, argv, options,
bench_futex_wake_parallel_usage, 0);
if (argc) {
usage_with_options(bench_futex_wake_parallel_usage, options);
exit(EXIT_FAILURE);
}
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");
}
cpu = perf_cpu_map__new_online_cpus();
if (!cpu)
err(EXIT_FAILURE, "calloc");
if (!params.nthreads)
params.nthreads = perf_cpu_map__nr(cpu);
/* some sanity checks */
if (params.nwakes > params.nthreads ||
!params.nwakes)
params.nwakes = params.nthreads;
if (params.nthreads % params.nwakes)
errx(EXIT_FAILURE, "Must be perfectly divisible");
/*
* Each thread will wakeup nwakes tasks in
* a single futex_wait call.
*/
nwakes = params.nthreads/params.nwakes;
blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
if (!blocked_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), %d threads waking up %d at a time.\n\n",
getpid(), params.nthreads, params.fshared ? "shared":"private",
&futex, params.nwakes, 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++) {
waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
if (!waking_worker)
err(EXIT_FAILURE, "calloc");
/* create, launch & block all threads */
block_threads(blocked_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(200000);
/* Ok, all threads are patiently blocked, start waking folks up */
wakeup_threads(waking_worker);
for (i = 0; i < params.nthreads; i++) {
ret = pthread_join(blocked_worker[i], NULL);
if (ret)
err(EXIT_FAILURE, "pthread_join");
}
do_run_stats(waking_worker);
if (!params.silent)
print_run(waking_worker, j);
free(waking_worker);
}
/* cleanup & report results */
cond_destroy(&thread_parent);
cond_destroy(&thread_worker);
mutex_destroy(&thread_lock);
print_summary();
free(blocked_worker);
perf_cpu_map__put(cpu);
return ret;
}
#endif /* HAVE_PTHREAD_BARRIER */
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