examples/performance-thread/common/lthread_sched.c

/*
 * SPDX-License-Identifier: BSD-3-Clause
 * Copyright 2015 Intel Corporation.
 * Copyright 2012 Hasan Alayli <halayli@gmail.com>
 */

#define RTE_MEM 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stddef.h>
#include <limits.h>
#include <inttypes.h>
#include <unistd.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sched.h>

#include <rte_prefetch.h>
#include <rte_per_lcore.h>
#include <rte_atomic.h>
#include <rte_atomic_64.h>
#include <rte_log.h>
#include <rte_common.h>
#include <rte_branch_prediction.h>

#include "lthread_api.h"
#include "lthread_int.h"
#include "lthread_sched.h"
#include "lthread_objcache.h"
#include "lthread_timer.h"
#include "lthread_mutex.h"
#include "lthread_cond.h"
#include "lthread_tls.h"
#include "lthread_diag.h"

/*
 * This file implements the lthread scheduler
 * The scheduler is the function lthread_run()
 * This must be run as the main loop of an EAL thread.
 *
 * Currently once a scheduler is created it cannot be destroyed
 * When a scheduler shuts down it is assumed that the application is terminating
 */

static rte_atomic16_t num_schedulers;
static rte_atomic16_t active_schedulers;

/* one scheduler per lcore */
RTE_DEFINE_PER_LCORE(struct lthread_sched *, this_sched) = NULL;

struct lthread_sched *schedcore[LTHREAD_MAX_LCORES];

diag_callback diag_cb;

uint64_t diag_mask;


/* constructor */
RTE_INIT(lthread_sched_ctor)
{
    memset(schedcore, 0, sizeof(schedcore));
    rte_atomic16_init(&num_schedulers);
    rte_atomic16_set(&num_schedulers, 1);
    rte_atomic16_init(&active_schedulers);
    rte_atomic16_set(&active_schedulers, 0);
    diag_cb = NULL;
}


enum sched_alloc_phase {
    SCHED_ALLOC_OK,
    SCHED_ALLOC_QNODE_POOL,
    SCHED_ALLOC_READY_QUEUE,
    SCHED_ALLOC_PREADY_QUEUE,
    SCHED_ALLOC_LTHREAD_CACHE,
    SCHED_ALLOC_STACK_CACHE,
    SCHED_ALLOC_PERLT_CACHE,
    SCHED_ALLOC_TLS_CACHE,
    SCHED_ALLOC_COND_CACHE,
    SCHED_ALLOC_MUTEX_CACHE,
};

static int
_lthread_sched_alloc_resources(struct lthread_sched *new_sched)
{
    int alloc_status;

    do {
        /* Initialize per scheduler queue node pool */
        alloc_status = SCHED_ALLOC_QNODE_POOL;
        new_sched->qnode_pool =
            _qnode_pool_create("qnode pool", LTHREAD_PREALLOC);
        if (new_sched->qnode_pool == NULL)
            break;

        /* Initialize per scheduler local ready queue */
        alloc_status = SCHED_ALLOC_READY_QUEUE;
        new_sched->ready = _lthread_queue_create("ready queue");
        if (new_sched->ready == NULL)
            break;

        /* Initialize per scheduler local peer ready queue */
        alloc_status = SCHED_ALLOC_PREADY_QUEUE;
        new_sched->pready = _lthread_queue_create("pready queue");
        if (new_sched->pready == NULL)
            break;

        /* Initialize per scheduler local free lthread cache */
        alloc_status = SCHED_ALLOC_LTHREAD_CACHE;
        new_sched->lthread_cache =
            _lthread_objcache_create("lthread cache",
                        sizeof(struct lthread),
                        LTHREAD_PREALLOC);
        if (new_sched->lthread_cache == NULL)
            break;

        /* Initialize per scheduler local free stack cache */
        alloc_status = SCHED_ALLOC_STACK_CACHE;
        new_sched->stack_cache =
            _lthread_objcache_create("stack_cache",
                        sizeof(struct lthread_stack),
                        LTHREAD_PREALLOC);
        if (new_sched->stack_cache == NULL)
            break;

        /* Initialize per scheduler local free per lthread data cache */
        alloc_status = SCHED_ALLOC_PERLT_CACHE;
        new_sched->per_lthread_cache =
            _lthread_objcache_create("per_lt cache",
                        RTE_PER_LTHREAD_SECTION_SIZE,
                        LTHREAD_PREALLOC);
        if (new_sched->per_lthread_cache == NULL)
            break;

        /* Initialize per scheduler local free tls cache */
        alloc_status = SCHED_ALLOC_TLS_CACHE;
        new_sched->tls_cache =
            _lthread_objcache_create("TLS cache",
                        sizeof(struct lthread_tls),
                        LTHREAD_PREALLOC);
        if (new_sched->tls_cache == NULL)
            break;

        /* Initialize per scheduler local free cond var cache */
        alloc_status = SCHED_ALLOC_COND_CACHE;
        new_sched->cond_cache =
            _lthread_objcache_create("cond cache",
                        sizeof(struct lthread_cond),
                        LTHREAD_PREALLOC);
        if (new_sched->cond_cache == NULL)
            break;

        /* Initialize per scheduler local free mutex cache */
        alloc_status = SCHED_ALLOC_MUTEX_CACHE;
        new_sched->mutex_cache =
            _lthread_objcache_create("mutex cache",
                        sizeof(struct lthread_mutex),
                        LTHREAD_PREALLOC);
        if (new_sched->mutex_cache == NULL)
            break;

        alloc_status = SCHED_ALLOC_OK;
    } while (0);

    /* roll back on any failure */
    switch (alloc_status) {
    case SCHED_ALLOC_MUTEX_CACHE:
        _lthread_objcache_destroy(new_sched->cond_cache);
        /* fall through */
    case SCHED_ALLOC_COND_CACHE:
        _lthread_objcache_destroy(new_sched->tls_cache);
        /* fall through */
    case SCHED_ALLOC_TLS_CACHE:
        _lthread_objcache_destroy(new_sched->per_lthread_cache);
        /* fall through */
    case SCHED_ALLOC_PERLT_CACHE:
        _lthread_objcache_destroy(new_sched->stack_cache);
        /* fall through */
    case SCHED_ALLOC_STACK_CACHE:
        _lthread_objcache_destroy(new_sched->lthread_cache);
        /* fall through */
    case SCHED_ALLOC_LTHREAD_CACHE:
        _lthread_queue_destroy(new_sched->pready);
        /* fall through */
    case SCHED_ALLOC_PREADY_QUEUE:
        _lthread_queue_destroy(new_sched->ready);
        /* fall through */
    case SCHED_ALLOC_READY_QUEUE:
        _qnode_pool_destroy(new_sched->qnode_pool);
        /* fall through */
    case SCHED_ALLOC_QNODE_POOL:
        /* fall through */
    case SCHED_ALLOC_OK:
        break;
    }
    return alloc_status;
}


/*
 * Create a scheduler on the current lcore
 */
struct lthread_sched *_lthread_sched_create(size_t stack_size)
{
    int status;
    struct lthread_sched *new_sched;
    unsigned lcoreid = rte_lcore_id();

    RTE_ASSERT(stack_size <= LTHREAD_MAX_STACK_SIZE);

    if (stack_size == 0)
        stack_size = LTHREAD_MAX_STACK_SIZE;

    new_sched =
         rte_calloc_socket(NULL, 1, sizeof(struct lthread_sched),
                RTE_CACHE_LINE_SIZE,
                rte_socket_id());
    if (new_sched == NULL) {
        RTE_LOG(CRIT, LTHREAD,
            "Failed to allocate memory for scheduler\n");
        return NULL;
    }

    _lthread_key_pool_init();

    new_sched->stack_size = stack_size;
    new_sched->birth = rte_rdtsc();
    THIS_SCHED = new_sched;

    status = _lthread_sched_alloc_resources(new_sched);
    if (status != SCHED_ALLOC_OK) {
        RTE_LOG(CRIT, LTHREAD,
            "Failed to allocate resources for scheduler code = %d\n",
            status);
        rte_free(new_sched);
        return NULL;
    }

    bzero(&new_sched->ctx, sizeof(struct ctx));

    new_sched->lcore_id = lcoreid;

    schedcore[lcoreid] = new_sched;

    new_sched->run_flag = 1;

    DIAG_EVENT(new_sched, LT_DIAG_SCHED_CREATE, rte_lcore_id(), 0);

    rte_wmb();
    return new_sched;
}

/*
 * Set the number of schedulers in the system
 */
int lthread_num_schedulers_set(int num)
{
    rte_atomic16_set(&num_schedulers, num);
    return (int)rte_atomic16_read(&num_schedulers);
}

/*
 * Return the number of schedulers active
 */
int lthread_active_schedulers(void)
{
    return (int)rte_atomic16_read(&active_schedulers);
}


void lthread_scheduler_shutdown(unsigned lcoreid)
{
    uint64_t coreid = (uint64_t) lcoreid;

    if (coreid < LTHREAD_MAX_LCORES) {
        if (schedcore[coreid] != NULL)
            schedcore[coreid]->run_flag = 0;
    }
}

void lthread_scheduler_shutdown_all(void)
{
    uint64_t i;

    /*
     * give time for all schedulers to have started
     * Note we use sched_yield() rather than pthread_yield() to allow
     * for the possibility of a pthread wrapper on lthread_yield(),
     * something that is not possible unless the scheduler is running.
     */
    while (rte_atomic16_read(&active_schedulers) <
           rte_atomic16_read(&num_schedulers))
        sched_yield();

    for (i = 0; i < LTHREAD_MAX_LCORES; i++) {
        if (schedcore[i] != NULL)
            schedcore[i]->run_flag = 0;
    }
}

/*
 * Resume a suspended lthread
 */
static __rte_always_inline void
_lthread_resume(struct lthread *lt);
static inline void _lthread_resume(struct lthread *lt)
{
    struct lthread_sched *sched = THIS_SCHED;
    struct lthread_stack *s;
    uint64_t state = lt->state;
#if LTHREAD_DIAG
    int init = 0;
#endif

    sched->current_lthread = lt;

    if (state & (BIT(ST_LT_CANCELLED) | BIT(ST_LT_EXITED))) {
        /* if detached we can free the thread now */
        if (state & BIT(ST_LT_DETACH)) {
            _lthread_free(lt);
            sched->current_lthread = NULL;
            return;
        }
    }

    if (state & BIT(ST_LT_INIT)) {
        /* first time this thread has been run */
        /* assign thread to this scheduler */
        lt->sched = THIS_SCHED;

        /* allocate stack */
        s = _stack_alloc();

        lt->stack_container = s;
        _lthread_set_stack(lt, s->stack, s->stack_size);

        /* allocate memory for TLS used by this thread */
        _lthread_tls_alloc(lt);

        lt->state = BIT(ST_LT_READY);
#if LTHREAD_DIAG
        init = 1;
#endif
    }

    DIAG_EVENT(lt, LT_DIAG_LTHREAD_RESUMED, init, lt);

    /* switch to the new thread */
    ctx_switch(&lt->ctx, &sched->ctx);

    /* If posting to a queue that could be read by another lcore
     * we defer the queue write till now to ensure the context has been
     * saved before the other core tries to resume it
     * This applies to blocking on mutex, cond, and to set_affinity
     */
    if (lt->pending_wr_queue != NULL) {
        struct lthread_queue *dest = lt->pending_wr_queue;

        lt->pending_wr_queue = NULL;

        /* queue the current thread to the specified queue */
        _lthread_queue_insert_mp(dest, lt);
    }

    sched->current_lthread = NULL;
}

/*
 * Handle sleep timer expiry
*/
void
_sched_timer_cb(struct rte_timer *tim, void *arg)
{
    struct lthread *lt = (struct lthread *) arg;
    uint64_t state = lt->state;

    DIAG_EVENT(lt, LT_DIAG_LTHREAD_TMR_EXPIRED, &lt->tim, 0);

    rte_timer_stop(tim);

    if (lt->state & BIT(ST_LT_CANCELLED))
        (THIS_SCHED)->nb_blocked_threads--;

    lt->state = state | BIT(ST_LT_EXPIRED);
    _lthread_resume(lt);
    lt->state = state & CLEARBIT(ST_LT_EXPIRED);
}



/*
 * Returns 0 if there is a pending job in scheduler or 1 if done and can exit.
 */
static inline int _lthread_sched_isdone(struct lthread_sched *sched)
{
    return (sched->run_flag == 0) &&
            (_lthread_queue_empty(sched->ready)) &&
            (_lthread_queue_empty(sched->pready)) &&
            (sched->nb_blocked_threads == 0);
}

/*
 * Wait for all schedulers to start
 */
static inline void _lthread_schedulers_sync_start(void)
{
    rte_atomic16_inc(&active_schedulers);

    /* wait for lthread schedulers
     * Note we use sched_yield() rather than pthread_yield() to allow
     * for the possibility of a pthread wrapper on lthread_yield(),
     * something that is not possible unless the scheduler is running.
     */
    while (rte_atomic16_read(&active_schedulers) <
           rte_atomic16_read(&num_schedulers))
        sched_yield();

}

/*
 * Wait for all schedulers to stop
 */
static inline void _lthread_schedulers_sync_stop(void)
{
    rte_atomic16_dec(&active_schedulers);
    rte_atomic16_dec(&num_schedulers);

    /* wait for schedulers
     * Note we use sched_yield() rather than pthread_yield() to allow
     * for the possibility of a pthread wrapper on lthread_yield(),
     * something that is not possible unless the scheduler is running.
     */
    while (rte_atomic16_read(&active_schedulers) > 0)
        sched_yield();

}


/*
 * Run the lthread scheduler
 * This loop is the heart of the system
 */
void lthread_run(void)
{

    struct lthread_sched *sched = THIS_SCHED;
    struct lthread *lt = NULL;

    RTE_LOG(INFO, LTHREAD,
        "starting scheduler %p on lcore %u phys core %u\n",
        sched, rte_lcore_id(),
        rte_lcore_index(rte_lcore_id()));

    /* if more than one, wait for all schedulers to start */
    _lthread_schedulers_sync_start();


    /*
     * This is the main scheduling loop
     * So long as there are tasks in existence we run this loop.
     * We check for:-
     *   expired timers,
     *   the local ready queue,
     *   and the peer ready queue,
     *
     * and resume lthreads ad infinitum.
     */
    while (!_lthread_sched_isdone(sched)) {

        rte_timer_manage();

        lt = _lthread_queue_poll(sched->ready);
        if (lt != NULL)
            _lthread_resume(lt);
        lt = _lthread_queue_poll(sched->pready);
        if (lt != NULL)
            _lthread_resume(lt);
    }


    /* if more than one wait for all schedulers to stop */
    _lthread_schedulers_sync_stop();

    (THIS_SCHED) = NULL;

    RTE_LOG(INFO, LTHREAD,
        "stopping scheduler %p on lcore %u phys core %u\n",
        sched, rte_lcore_id(),
        rte_lcore_index(rte_lcore_id()));
    fflush(stdout);
}

/*
 * Return the scheduler for this lcore
 *
 */
struct lthread_sched *_lthread_sched_get(unsigned int lcore_id)
{
    struct lthread_sched *res = NULL;

    if (lcore_id < LTHREAD_MAX_LCORES)
        res = schedcore[lcore_id];

    return res;
}

/*
 * migrate the current thread to another scheduler running
 * on the specified lcore.
 */
int lthread_set_affinity(unsigned lcoreid)
{
    struct lthread *lt = THIS_LTHREAD;
    struct lthread_sched *dest_sched;

    if (unlikely(lcoreid >= LTHREAD_MAX_LCORES))
        return POSIX_ERRNO(EINVAL);

    DIAG_EVENT(lt, LT_DIAG_LTHREAD_AFFINITY, lcoreid, 0);

    dest_sched = schedcore[lcoreid];

    if (unlikely(dest_sched == NULL))
        return POSIX_ERRNO(EINVAL);

    if (likely(dest_sched != THIS_SCHED)) {
        lt->sched = dest_sched;
        lt->pending_wr_queue = dest_sched->pready;
        _affinitize();
        return 0;
    }
    return 0;
}