From 4f878e8475a465ddbd951e06a23317303f1b5b30 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Fri, 7 Aug 2009 09:27:38 -0400 Subject: [PATCH] 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 --- fs/btrfs/async-thread.c | 74 +++++++++++++++++++++++++++++++++-------- 1 file changed, 60 insertions(+), 14 deletions(-) diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 4b4372df3b6d..6ea5cd0a595f 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -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 @@ static int worker_loop(void *arg) 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 @@ static int worker_loop(void *arg) 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 -- GitLab