/*
 * 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.
 */

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

#include <signal.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 "bench.h"
#include "futex.h"

#include <err.h>
#include <stdlib.h>
#include <sys/time.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, silent = false, fshared = false;
static unsigned int nblocked_threads = 0, nwaking_threads = 0;
static pthread_mutex_t thread_lock;
static pthread_cond_t thread_parent, thread_worker;
static struct stats waketime_stats, wakeup_stats;
static unsigned int ncpus, threads_starting;
static int futex_flag = 0;

static const struct option options[] = {
        OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"),
        OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"),
        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_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;

        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, pthread_attr_t thread_attr)
{
        unsigned int i;

        pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);

        /* create and block all threads */
        for (i = 0; i < nwaking_threads; 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");
        }

        for (i = 0; i < nwaking_threads; i++)
                if (pthread_join(td[i].worker, NULL))
                        err(EXIT_FAILURE, "pthread_join");
}

static void *blocked_workerfn(void *arg __maybe_unused)
{
        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);

        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, pthread_attr_t thread_attr)
{
        cpu_set_t cpu;
        unsigned int i;

        threads_starting = nblocked_threads;

        /* create and block all threads */
        for (i = 0; i < nblocked_threads; i++) {
                CPU_ZERO(&cpu);
                CPU_SET(i % ncpus, &cpu);

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

                if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL))
                        err(EXIT_FAILURE, "pthread_create");
        }
}

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 < nwaking_threads; 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,
               nblocked_threads, 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,
               nblocked_threads,
               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 < nwaking_threads; 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,
                              const char *prefix __maybe_unused)
{
        int ret = 0;
        unsigned int i, j;
        struct sigaction act;
        pthread_attr_t thread_attr;
        struct thread_data *waking_worker;

        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);
        }

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

        ncpus = sysconf(_SC_NPROCESSORS_ONLN);
        if (!nblocked_threads)
                nblocked_threads = ncpus;

        /* some sanity checks */
        if (nwaking_threads > nblocked_threads || !nwaking_threads)
                nwaking_threads = nblocked_threads;

        if (nblocked_threads % nwaking_threads)
                errx(EXIT_FAILURE, "Must be perfectly divisible");
        /*
         * Each thread will wakeup nwakes tasks in
         * a single futex_wait call.
         */
        nwakes = nblocked_threads/nwaking_threads;

        blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker));
        if (!blocked_worker)
                err(EXIT_FAILURE, "calloc");

        if (!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(), nblocked_threads, fshared ? "shared":"private",
               &futex, nwaking_threads, nwakes);

        init_stats(&wakeup_stats);
        init_stats(&waketime_stats);

        pthread_attr_init(&thread_attr);
        pthread_mutex_init(&thread_lock, NULL);
        pthread_cond_init(&thread_parent, NULL);
        pthread_cond_init(&thread_worker, NULL);

        for (j = 0; j < bench_repeat && !done; j++) {
                waking_worker = calloc(nwaking_threads, sizeof(*waking_worker));
                if (!waking_worker)
                        err(EXIT_FAILURE, "calloc");

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

                /* make sure all threads are already blocked */
                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);

                usleep(100000);

                /* Ok, all threads are patiently blocked, start waking folks up */
                wakeup_threads(waking_worker, thread_attr);

                for (i = 0; i < nblocked_threads; i++) {
                        ret = pthread_join(blocked_worker[i], NULL);
                        if (ret)
                                err(EXIT_FAILURE, "pthread_join");
                }

                do_run_stats(waking_worker);
                if (!silent)
                        print_run(waking_worker, j);

                free(waking_worker);
        }

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

        print_summary();

        free(blocked_worker);
        return ret;
}