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>
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 4b4372d..6ea5cd0 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -196,31 +196,73 @@
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 @@
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 @@
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