Commit b811203c authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

threadpool: move globals into struct ThreadPool 



Move global variables into a struct so multiple thread pools can be
supported in the future.

This patch does not change thread-pool.h interfaces.  There is still a
global thread pool and it is not yet possible to create/destroy
individual thread pools.  Moving the variables into a struct first makes
later patches easier to review.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5f3aa1ff

thread-pool.c

+110 −80
Original line number Diff line number Diff line
@@ -24,7 +24,9 @@ 
#include "qemu/event_notifier.h"

#include "block/thread-pool.h"



static void do_spawn_thread(void);

typedef struct ThreadPool ThreadPool;



static void do_spawn_thread(ThreadPool *pool);



typedef struct ThreadPoolElement ThreadPoolElement;
@@ -37,6 +39,7 @@ enum ThreadState { 


struct ThreadPoolElement {

    BlockDriverAIOCB common;

    ThreadPool *pool;

    ThreadPoolFunc *func;

    void *arg;
@@ -54,49 +57,56 @@ struct ThreadPoolElement { 
    QLIST_ENTRY(ThreadPoolElement) all;

};



static EventNotifier notifier;

static QemuMutex lock;

static QemuCond check_cancel;

static QemuSemaphore sem;

static int max_threads = 64;

static QEMUBH *new_thread_bh;

struct ThreadPool {

    EventNotifier notifier;

    QemuMutex lock;

    QemuCond check_cancel;

    QemuSemaphore sem;

    int max_threads;

    QEMUBH *new_thread_bh;



/* The following variables are protected by the global mutex.  */

static QLIST_HEAD(, ThreadPoolElement) head;

    /* The following variables are only accessed from one AioContext. */

    QLIST_HEAD(, ThreadPoolElement) head;



    /* The following variables are protected by lock.  */

static QTAILQ_HEAD(, ThreadPoolElement) request_list;

static int cur_threads;

static int idle_threads;

static int new_threads;     /* backlog of threads we need to create */

static int pending_threads; /* threads created but not running yet */

static int pending_cancellations; /* whether we need a cond_broadcast */



static void *worker_thread(void *unused)

    QTAILQ_HEAD(, ThreadPoolElement) request_list;

    int cur_threads;

    int idle_threads;

    int new_threads;     /* backlog of threads we need to create */

    int pending_threads; /* threads created but not running yet */

    int pending_cancellations; /* whether we need a cond_broadcast */

};



/* Currently there is only one thread pool instance. */

static ThreadPool global_pool;



static void *worker_thread(void *opaque)

{

    qemu_mutex_lock(&lock);

    pending_threads--;

    do_spawn_thread();

    ThreadPool *pool = opaque;



    qemu_mutex_lock(&pool->lock);

    pool->pending_threads--;

    do_spawn_thread(pool);



    while (1) {

        ThreadPoolElement *req;

        int ret;



        do {

            idle_threads++;

            qemu_mutex_unlock(&lock);

            ret = qemu_sem_timedwait(&sem, 10000);

            qemu_mutex_lock(&lock);

            idle_threads--;

        } while (ret == -1 && !QTAILQ_EMPTY(&request_list));

            pool->idle_threads++;

            qemu_mutex_unlock(&pool->lock);

            ret = qemu_sem_timedwait(&pool->sem, 10000);

            qemu_mutex_lock(&pool->lock);

            pool->idle_threads--;

        } while (ret == -1 && !QTAILQ_EMPTY(&pool->request_list));

        if (ret == -1) {

            break;

        }



        req = QTAILQ_FIRST(&request_list);

        QTAILQ_REMOVE(&request_list, req, reqs);

        req = QTAILQ_FIRST(&pool->request_list);

        QTAILQ_REMOVE(&pool->request_list, req, reqs);

        req->state = THREAD_ACTIVE;

        qemu_mutex_unlock(&lock);

        qemu_mutex_unlock(&pool->lock);



        ret = req->func(req->arg);
@@ -105,45 +115,47 @@ static void *worker_thread(void *unused) 
        smp_wmb();

        req->state = THREAD_DONE;



        qemu_mutex_lock(&lock);

        if (pending_cancellations) {

            qemu_cond_broadcast(&check_cancel);

        qemu_mutex_lock(&pool->lock);

        if (pool->pending_cancellations) {

            qemu_cond_broadcast(&pool->check_cancel);

        }



        event_notifier_set(&notifier);

        event_notifier_set(&pool->notifier);

    }



    cur_threads--;

    qemu_mutex_unlock(&lock);

    pool->cur_threads--;

    qemu_mutex_unlock(&pool->lock);

    return NULL;

}



static void do_spawn_thread(void)

static void do_spawn_thread(ThreadPool *pool)

{

    QemuThread t;



    /* Runs with lock taken.  */

    if (!new_threads) {

    if (!pool->new_threads) {

        return;

    }



    new_threads--;

    pending_threads++;

    pool->new_threads--;

    pool->pending_threads++;



    qemu_thread_create(&t, worker_thread, NULL, QEMU_THREAD_DETACHED);

    qemu_thread_create(&t, worker_thread, pool, QEMU_THREAD_DETACHED);

}



static void spawn_thread_bh_fn(void *opaque)

{

    qemu_mutex_lock(&lock);

    do_spawn_thread();

    qemu_mutex_unlock(&lock);

    ThreadPool *pool = opaque;



    qemu_mutex_lock(&pool->lock);

    do_spawn_thread(pool);

    qemu_mutex_unlock(&pool->lock);

}



static void spawn_thread(void)

static void spawn_thread(ThreadPool *pool)

{

    cur_threads++;

    new_threads++;

    pool->cur_threads++;

    pool->new_threads++;

    /* If there are threads being created, they will spawn new workers, so

     * we don't spend time creating many threads in a loop holding a mutex or

     * starving the current vcpu.
@@ -151,23 +163,25 @@ static void spawn_thread(void) 
     * If there are no idle threads, ask the main thread to create one, so we

     * inherit the correct affinity instead of the vcpu affinity.

     */

    if (!pending_threads) {

        qemu_bh_schedule(new_thread_bh);

    if (!pool->pending_threads) {

        qemu_bh_schedule(pool->new_thread_bh);

    }

}



static void event_notifier_ready(EventNotifier *notifier)

{

    ThreadPool *pool = container_of(notifier, ThreadPool, notifier);

    ThreadPoolElement *elem, *next;



    event_notifier_test_and_clear(notifier);

restart:

    QLIST_FOREACH_SAFE(elem, &head, all, next) {

    QLIST_FOREACH_SAFE(elem, &pool->head, all, next) {

        if (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {

            continue;

        }

        if (elem->state == THREAD_DONE) {

            trace_thread_pool_complete(elem, elem->common.opaque, elem->ret);

            trace_thread_pool_complete(pool, elem, elem->common.opaque,

                                       elem->ret);

        }

        if (elem->state == THREAD_DONE && elem->common.cb) {

            QLIST_REMOVE(elem, all);
@@ -186,34 +200,36 @@ restart: 


static int thread_pool_active(EventNotifier *notifier)

{

    return !QLIST_EMPTY(&head);

    ThreadPool *pool = container_of(notifier, ThreadPool, notifier);

    return !QLIST_EMPTY(&pool->head);

}



static void thread_pool_cancel(BlockDriverAIOCB *acb)

{

    ThreadPoolElement *elem = (ThreadPoolElement *)acb;

    ThreadPool *pool = elem->pool;



    trace_thread_pool_cancel(elem, elem->common.opaque);



    qemu_mutex_lock(&lock);

    qemu_mutex_lock(&pool->lock);

    if (elem->state == THREAD_QUEUED &&

        /* No thread has yet started working on elem. we can try to "steal"

         * the item from the worker if we can get a signal from the

         * semaphore.  Because this is non-blocking, we can do it with

         * the lock taken and ensure that elem will remain THREAD_QUEUED.

         */

        qemu_sem_timedwait(&sem, 0) == 0) {

        QTAILQ_REMOVE(&request_list, elem, reqs);

        qemu_sem_timedwait(&pool->sem, 0) == 0) {

        QTAILQ_REMOVE(&pool->request_list, elem, reqs);

        elem->state = THREAD_CANCELED;

        event_notifier_set(&notifier);

        event_notifier_set(&pool->notifier);

    } else {

        pending_cancellations++;

        pool->pending_cancellations++;

        while (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {

            qemu_cond_wait(&check_cancel, &lock);

            qemu_cond_wait(&pool->check_cancel, &pool->lock);

        }

        pending_cancellations--;

        pool->pending_cancellations--;

    }

    qemu_mutex_unlock(&lock);

    qemu_mutex_unlock(&pool->lock);

}



static const AIOCBInfo thread_pool_aiocb_info = {
@@ -224,24 +240,26 @@ static const AIOCBInfo thread_pool_aiocb_info = { 
BlockDriverAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,

        BlockDriverCompletionFunc *cb, void *opaque)

{

    ThreadPool *pool = &global_pool;

    ThreadPoolElement *req;



    req = qemu_aio_get(&thread_pool_aiocb_info, NULL, cb, opaque);

    req->func = func;

    req->arg = arg;

    req->state = THREAD_QUEUED;

    req->pool = pool;



    QLIST_INSERT_HEAD(&head, req, all);

    QLIST_INSERT_HEAD(&pool->head, req, all);



    trace_thread_pool_submit(req, arg);

    trace_thread_pool_submit(pool, req, arg);



    qemu_mutex_lock(&lock);

    if (idle_threads == 0 && cur_threads < max_threads) {

        spawn_thread();

    qemu_mutex_lock(&pool->lock);

    if (pool->idle_threads == 0 && pool->cur_threads < pool->max_threads) {

        spawn_thread(pool);

    }

    QTAILQ_INSERT_TAIL(&request_list, req, reqs);

    qemu_mutex_unlock(&lock);

    qemu_sem_post(&sem);

    QTAILQ_INSERT_TAIL(&pool->request_list, req, reqs);

    qemu_mutex_unlock(&pool->lock);

    qemu_sem_post(&pool->sem);

    return &req->common;

}
@@ -272,18 +290,30 @@ void thread_pool_submit(ThreadPoolFunc *func, void *arg) 
    thread_pool_submit_aio(func, arg, NULL, NULL);

}



static void thread_pool_init(void)

static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)

{

    QLIST_INIT(&head);

    event_notifier_init(&notifier, false);

    qemu_mutex_init(&lock);

    qemu_cond_init(&check_cancel);

    qemu_sem_init(&sem, 0);

    qemu_aio_set_event_notifier(&notifier, event_notifier_ready,

    if (!ctx) {

        ctx = qemu_get_aio_context();

    }



    memset(pool, 0, sizeof(*pool));

    event_notifier_init(&pool->notifier, false);

    qemu_mutex_init(&pool->lock);

    qemu_cond_init(&pool->check_cancel);

    qemu_sem_init(&pool->sem, 0);

    pool->max_threads = 64;

    pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);



    QLIST_INIT(&pool->head);

    QTAILQ_INIT(&pool->request_list);



    aio_set_event_notifier(ctx, &pool->notifier, event_notifier_ready,

                           thread_pool_active);

}



    QTAILQ_INIT(&request_list);

    new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);

static void thread_pool_init(void)

{

    thread_pool_init_one(&global_pool, NULL);

}



block_init(thread_pool_init)

trace-events

+2 −2
Original line number Diff line number Diff line
@@ -115,8 +115,8 @@ virtio_blk_data_plane_complete_request(void *s, unsigned int head, int ret) "dat 
vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"



# thread-pool.c

thread_pool_submit(void *req, void *opaque) "req %p opaque %p"

thread_pool_complete(void *req, void *opaque, int ret) "req %p opaque %p ret %d"

thread_pool_submit(void *pool, void *req, void *opaque) "pool %p req %p opaque %p"

thread_pool_complete(void *pool, void *req, void *opaque, int ret) "pool %p req %p opaque %p ret %d"

thread_pool_cancel(void *req, void *opaque) "req %p opaque %p"



# posix-aio-compat.c