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threadpool: move globals into struct ThreadPool

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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: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-03-07 13:41:45 +01:00
parent 5f3aa1ff47
commit b811203cf2
2 changed files with 109 additions and 79 deletions
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184
thread-pool.c
View File

@ -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 */
/* The following variables are protected by lock. */
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 */
};
static void *worker_thread(void *unused)
/* 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_one(ThreadPool *pool, AioContext *ctx)
{
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);
}
static void thread_pool_init(void)
{
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,
thread_pool_active);
QTAILQ_INIT(&request_list);
new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);
thread_pool_init_one(&global_pool, NULL);
}
block_init(thread_pool_init)

4
trace-events
View File

@ -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