futex-lock-pi.c

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// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015 Davidlohr Bueso.
 */

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

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

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

struct worker {
    int tid;
    u_int32_t *futex;
    pthread_t thread;
    unsigned long ops;
};

static u_int32_t global_futex = 0;
static struct worker *worker;
static unsigned int nsecs = 10;
static bool silent = false, multi = false;
static bool done = false, fshared = false;
static unsigned int nthreads = 0;
static int futex_flag = 0;
struct timeval start, end, runtime;
static pthread_mutex_t thread_lock;
static unsigned int threads_starting;
static struct stats throughput_stats;
static pthread_cond_t thread_parent, thread_worker;

static const struct option options[] = {
    OPT_UINTEGER('t', "threads",  &nthreads, "Specify amount of threads"),
    OPT_UINTEGER('r', "runtime", &nsecs,     "Specify runtime (in seconds)"),
    OPT_BOOLEAN( 'M', "multi",   &multi,     "Use multiple futexes"),
    OPT_BOOLEAN( 's', "silent",  &silent,    "Silent mode: do not display data/details"),
    OPT_BOOLEAN( 'S', "shared",  &fshared,   "Use shared futexes instead of private ones"),
    OPT_END()
};

static const char * const bench_futex_lock_pi_usage[] = {
    "perf bench futex lock-pi <options>",
    NULL
};

static void print_summary(void)
{
    unsigned long avg = avg_stats(&throughput_stats);
    double stddev = stddev_stats(&throughput_stats);

    printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
           !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
           (int) runtime.tv_sec);
}

static void toggle_done(int sig __maybe_unused,
            siginfo_t *info __maybe_unused,
            void *uc __maybe_unused)
{
    /* inform all threads that we're done for the day */
    done = true;
    gettimeofday(&end, NULL);
    timersub(&end, &start, &runtime);
}

static void *workerfn(void *arg)
{
    struct worker *w = (struct worker *) arg;
    unsigned long ops = w->ops;

    pthread_mutex_lock(&thread_lock);
    threads_starting--;
    if (!threads_starting)
        pthread_cond_signal(&thread_parent);
    pthread_cond_wait(&thread_worker, &thread_lock);
    pthread_mutex_unlock(&thread_lock);

    do {
        int ret;
    again:
        ret = futex_lock_pi(w->futex, NULL, futex_flag);

        if (ret) { /* handle lock acquisition */
            if (!silent)
                warn("thread %d: Could not lock pi-lock for %p (%d)",
                     w->tid, w->futex, ret);
            if (done)
                break;

            goto again;
        }

        usleep(1);
        ret = futex_unlock_pi(w->futex, futex_flag);
        if (ret && !silent)
            warn("thread %d: Could not unlock pi-lock for %p (%d)",
                 w->tid, w->futex, ret);
        ops++; /* account for thread's share of work */
    }  while (!done);

    w->ops = ops;
    return NULL;
}

static void create_threads(struct worker *w, pthread_attr_t thread_attr,
               struct cpu_map *cpu)
{
    cpu_set_t cpuset;
    unsigned int i;

    threads_starting = nthreads;

    for (i = 0; i < nthreads; i++) {
        worker[i].tid = i;

        if (multi) {
            worker[i].futex = calloc(1, sizeof(u_int32_t));
            if (!worker[i].futex)
                err(EXIT_FAILURE, "calloc");
        } else
            worker[i].futex = &global_futex;

        CPU_ZERO(&cpuset);
        CPU_SET(cpu->map[i % cpu->nr], &cpuset);

        if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset))
            err(EXIT_FAILURE, "pthread_attr_setaffinity_np");

        if (pthread_create(&w[i].thread, &thread_attr, workerfn, &worker[i]))
            err(EXIT_FAILURE, "pthread_create");
    }
}

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

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

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

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

    if (!nthreads)
        nthreads = cpu->nr;

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

    if (!fshared)
        futex_flag = FUTEX_PRIVATE_FLAG;

    printf("Run summary [PID %d]: %d threads doing pi lock/unlock pairing for %d secs.\n\n",
           getpid(), nthreads, nsecs);

    init_stats(&throughput_stats);
    pthread_mutex_init(&thread_lock, NULL);
    pthread_cond_init(&thread_parent, NULL);
    pthread_cond_init(&thread_worker, NULL);

    threads_starting = nthreads;
    pthread_attr_init(&thread_attr);
    gettimeofday(&start, NULL);

    create_threads(worker, thread_attr, cpu);
    pthread_attr_destroy(&thread_attr);

    pthread_mutex_lock(&thread_lock);
    while (threads_starting)
        pthread_cond_wait(&thread_parent, &thread_lock);
    pthread_cond_broadcast(&thread_worker);
    pthread_mutex_unlock(&thread_lock);

    sleep(nsecs);
    toggle_done(0, NULL, NULL);

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

    /* cleanup & report results */
    pthread_cond_destroy(&thread_parent);
    pthread_cond_destroy(&thread_worker);
    pthread_mutex_destroy(&thread_lock);

    for (i = 0; i < nthreads; i++) {
        unsigned long t = worker[i].ops/runtime.tv_sec;

        update_stats(&throughput_stats, t);
        if (!silent)
            printf("[thread %3d] futex: %p [ %ld ops/sec ]\n",
                   worker[i].tid, worker[i].futex, t);

        if (multi)
            free(worker[i].futex);
    }

    print_summary();

    free(worker);
    return ret;
err:
    usage_with_options(bench_futex_lock_pi_usage, options);
    exit(EXIT_FAILURE);
}