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Btrfs: reduce worker thread spin_lock_irq hold times 

This changes the btrfs worker threads to batch work items
into a local list.  It allows us to pull work items in
large chunks and significantly reduces the number of times we
need to take the worker thread spinlock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2009-08-07 09:27:38 -04:00
parent 4e3f9c5042
commit 4f878e8475
1 changed files with 60 additions and 14 deletions
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74
fs/btrfs/async-thread.c
View File

@ -196,31 +196,73 @@ static int try_worker_shutdown(struct btrfs_worker_thread *worker)
return freeit;
}
static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker,
struct list_head *prio_head,
struct list_head *head)
{
struct btrfs_work *work = NULL;
struct list_head *cur = NULL;
if(!list_empty(prio_head))
cur = prio_head->next;
smp_mb();
if (!list_empty(&worker->prio_pending))
goto refill;
if (!list_empty(head))
cur = head->next;
if (cur)
goto out;
refill:
spin_lock_irq(&worker->lock);
list_splice_tail_init(&worker->prio_pending, prio_head);
list_splice_tail_init(&worker->pending, head);
if (!list_empty(prio_head))
cur = prio_head->next;
else if (!list_empty(head))
cur = head->next;
spin_unlock_irq(&worker->lock);
if (!cur)
goto out_fail;
out:
work = list_entry(cur, struct btrfs_work, list);
out_fail:
return work;
}
/*
* main loop for servicing work items
*/
static int worker_loop(void *arg)
{
struct btrfs_worker_thread *worker = arg;
struct list_head *cur;
struct list_head head;
struct list_head prio_head;
struct btrfs_work *work;
INIT_LIST_HEAD(&head);
INIT_LIST_HEAD(&prio_head);
do {
spin_lock_irq(&worker->lock);
again_locked:
again:
while (1) {
if (!list_empty(&worker->prio_pending))
cur = worker->prio_pending.next;
else if (!list_empty(&worker->pending))
cur = worker->pending.next;
else
work = get_next_work(worker, &prio_head, &head);
if (!work)
break;
work = list_entry(cur, struct btrfs_work, list);
list_del(&work->list);
clear_bit(WORK_QUEUED_BIT, &work->flags);
work->worker = worker;
spin_unlock_irq(&worker->lock);
work->func(work);
@ -233,9 +275,11 @@ again_locked:
check_pending_worker_creates(worker);
spin_lock_irq(&worker->lock);
check_idle_worker(worker);
}
spin_lock_irq(&worker->lock);
check_idle_worker(worker);
if (freezing(current)) {
worker->working = 0;
spin_unlock_irq(&worker->lock);
@ -274,8 +318,10 @@ again_locked:
spin_lock_irq(&worker->lock);
set_current_state(TASK_INTERRUPTIBLE);
if (!list_empty(&worker->pending) ||
!list_empty(&worker->prio_pending))
goto again_locked;
!list_empty(&worker->prio_pending)) {
spin_unlock_irq(&worker->lock);
goto again;
}
/*
* this makes sure we get a wakeup when someone