Btrfs: Allow worker threads to exit when idle
The Btrfs worker threads don't currently die off after they have been idle for a while, leading to a lot of threads sitting around doing nothing for each mount. Also, they are unable to start atomically (from end_io hanlders). This commit reworks the worker threads so they can be started from end_io handlers (just setting a flag that asks for a thread to be added at a later date) and so they can exit if they have been idle for a long time. Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
parent
ceab36edd3
commit
9042846bc7
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@ -48,6 +48,9 @@ struct btrfs_worker_thread {
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/* number of things on the pending list */
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atomic_t num_pending;
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/* reference counter for this struct */
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atomic_t refs;
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unsigned long sequence;
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/* protects the pending list. */
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@ -93,6 +96,31 @@ static void check_busy_worker(struct btrfs_worker_thread *worker)
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}
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}
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static void check_pending_worker_creates(struct btrfs_worker_thread *worker)
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{
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struct btrfs_workers *workers = worker->workers;
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unsigned long flags;
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rmb();
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if (!workers->atomic_start_pending)
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return;
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spin_lock_irqsave(&workers->lock, flags);
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if (!workers->atomic_start_pending)
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goto out;
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workers->atomic_start_pending = 0;
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if (workers->num_workers >= workers->max_workers)
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goto out;
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spin_unlock_irqrestore(&workers->lock, flags);
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btrfs_start_workers(workers, 1);
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return;
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out:
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spin_unlock_irqrestore(&workers->lock, flags);
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}
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static noinline int run_ordered_completions(struct btrfs_workers *workers,
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struct btrfs_work *work)
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{
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@ -140,6 +168,36 @@ static noinline int run_ordered_completions(struct btrfs_workers *workers,
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return 0;
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}
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static void put_worker(struct btrfs_worker_thread *worker)
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{
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if (atomic_dec_and_test(&worker->refs))
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kfree(worker);
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}
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static int try_worker_shutdown(struct btrfs_worker_thread *worker)
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{
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int freeit = 0;
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spin_lock_irq(&worker->lock);
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spin_lock_irq(&worker->workers->lock);
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if (worker->workers->num_workers > 1 &&
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worker->idle &&
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!worker->working &&
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!list_empty(&worker->worker_list) &&
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list_empty(&worker->prio_pending) &&
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list_empty(&worker->pending)) {
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freeit = 1;
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list_del_init(&worker->worker_list);
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worker->workers->num_workers--;
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}
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spin_unlock_irq(&worker->workers->lock);
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spin_unlock_irq(&worker->lock);
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if (freeit)
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put_worker(worker);
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return freeit;
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}
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/*
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* main loop for servicing work items
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*/
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@ -175,6 +233,8 @@ again_locked:
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*/
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run_ordered_completions(worker->workers, work);
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check_pending_worker_creates(worker);
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spin_lock_irq(&worker->lock);
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check_idle_worker(worker);
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}
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@ -226,8 +286,13 @@ again_locked:
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worker->working = 0;
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spin_unlock_irq(&worker->lock);
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if (!kthread_should_stop())
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schedule();
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if (!kthread_should_stop()) {
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schedule_timeout(HZ * 120);
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if (!worker->working &&
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try_worker_shutdown(worker)) {
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return 0;
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}
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}
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}
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__set_current_state(TASK_RUNNING);
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}
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@ -242,16 +307,30 @@ int btrfs_stop_workers(struct btrfs_workers *workers)
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{
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struct list_head *cur;
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struct btrfs_worker_thread *worker;
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int can_stop;
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spin_lock_irq(&workers->lock);
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list_splice_init(&workers->idle_list, &workers->worker_list);
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while (!list_empty(&workers->worker_list)) {
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cur = workers->worker_list.next;
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worker = list_entry(cur, struct btrfs_worker_thread,
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worker_list);
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kthread_stop(worker->task);
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list_del(&worker->worker_list);
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kfree(worker);
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atomic_inc(&worker->refs);
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workers->num_workers -= 1;
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if (!list_empty(&worker->worker_list)) {
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list_del_init(&worker->worker_list);
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put_worker(worker);
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can_stop = 1;
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} else
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can_stop = 0;
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spin_unlock_irq(&workers->lock);
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if (can_stop)
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kthread_stop(worker->task);
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spin_lock_irq(&workers->lock);
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put_worker(worker);
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}
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spin_unlock_irq(&workers->lock);
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return 0;
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}
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@ -270,6 +349,8 @@ void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max)
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workers->idle_thresh = 32;
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workers->name = name;
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workers->ordered = 0;
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workers->atomic_start_pending = 0;
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workers->atomic_worker_start = 0;
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}
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/*
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@ -294,6 +375,7 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
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INIT_LIST_HEAD(&worker->worker_list);
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spin_lock_init(&worker->lock);
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atomic_set(&worker->num_pending, 0);
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atomic_set(&worker->refs, 1);
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worker->workers = workers;
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worker->task = kthread_run(worker_loop, worker,
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"btrfs-%s-%d", workers->name,
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@ -303,7 +385,6 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
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kfree(worker);
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goto fail;
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}
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spin_lock_irq(&workers->lock);
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list_add_tail(&worker->worker_list, &workers->idle_list);
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worker->idle = 1;
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@ -367,6 +448,7 @@ static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers)
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{
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struct btrfs_worker_thread *worker;
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unsigned long flags;
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struct list_head *fallback;
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again:
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spin_lock_irqsave(&workers->lock, flags);
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@ -376,19 +458,10 @@ again:
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if (!worker) {
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spin_lock_irqsave(&workers->lock, flags);
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if (workers->num_workers >= workers->max_workers) {
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struct list_head *fallback = NULL;
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/*
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* we have failed to find any workers, just
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* return the force one
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*/
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if (!list_empty(&workers->worker_list))
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fallback = workers->worker_list.next;
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if (!list_empty(&workers->idle_list))
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fallback = workers->idle_list.next;
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BUG_ON(!fallback);
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worker = list_entry(fallback,
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struct btrfs_worker_thread, worker_list);
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spin_unlock_irqrestore(&workers->lock, flags);
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goto fallback;
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} else if (workers->atomic_worker_start) {
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workers->atomic_start_pending = 1;
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goto fallback;
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} else {
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spin_unlock_irqrestore(&workers->lock, flags);
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/* we're below the limit, start another worker */
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@ -397,6 +470,22 @@ again:
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}
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}
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return worker;
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fallback:
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fallback = NULL;
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/*
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* we have failed to find any workers, just
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* return the first one we can find.
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*/
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if (!list_empty(&workers->worker_list))
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fallback = workers->worker_list.next;
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if (!list_empty(&workers->idle_list))
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fallback = workers->idle_list.next;
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BUG_ON(!fallback);
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worker = list_entry(fallback,
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struct btrfs_worker_thread, worker_list);
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spin_unlock_irqrestore(&workers->lock, flags);
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return worker;
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}
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/*
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@ -435,9 +524,9 @@ int btrfs_requeue_work(struct btrfs_work *work)
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worker->working = 1;
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}
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spin_unlock_irqrestore(&worker->lock, flags);
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if (wake)
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wake_up_process(worker->task);
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spin_unlock_irqrestore(&worker->lock, flags);
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out:
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return 0;
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@ -492,10 +581,10 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
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wake = 1;
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worker->working = 1;
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spin_unlock_irqrestore(&worker->lock, flags);
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if (wake)
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wake_up_process(worker->task);
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spin_unlock_irqrestore(&worker->lock, flags);
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out:
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return 0;
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}
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@ -73,6 +73,15 @@ struct btrfs_workers {
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/* force completions in the order they were queued */
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int ordered;
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/* more workers required, but in an interrupt handler */
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int atomic_start_pending;
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/*
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* are we allowed to sleep while starting workers or are we required
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* to start them at a later time?
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*/
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int atomic_worker_start;
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/* list with all the work threads. The workers on the idle thread
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* may be actively servicing jobs, but they haven't yet hit the
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* idle thresh limit above.
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@ -1682,7 +1682,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
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err = -EINVAL;
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goto fail_iput;
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}
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printk("thread pool is %d\n", fs_info->thread_pool_size);
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/*
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* we need to start all the end_io workers up front because the
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* queue work function gets called at interrupt time, and so it
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@ -1727,20 +1727,22 @@ struct btrfs_root *open_ctree(struct super_block *sb,
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fs_info->endio_workers.idle_thresh = 4;
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fs_info->endio_meta_workers.idle_thresh = 4;
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fs_info->endio_write_workers.idle_thresh = 64;
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fs_info->endio_meta_write_workers.idle_thresh = 64;
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fs_info->endio_write_workers.idle_thresh = 2;
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fs_info->endio_meta_write_workers.idle_thresh = 2;
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fs_info->endio_workers.atomic_worker_start = 1;
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fs_info->endio_meta_workers.atomic_worker_start = 1;
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fs_info->endio_write_workers.atomic_worker_start = 1;
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fs_info->endio_meta_write_workers.atomic_worker_start = 1;
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btrfs_start_workers(&fs_info->workers, 1);
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btrfs_start_workers(&fs_info->submit_workers, 1);
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btrfs_start_workers(&fs_info->delalloc_workers, 1);
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btrfs_start_workers(&fs_info->fixup_workers, 1);
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btrfs_start_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
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btrfs_start_workers(&fs_info->endio_meta_workers,
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fs_info->thread_pool_size);
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btrfs_start_workers(&fs_info->endio_meta_write_workers,
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fs_info->thread_pool_size);
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btrfs_start_workers(&fs_info->endio_write_workers,
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fs_info->thread_pool_size);
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btrfs_start_workers(&fs_info->endio_workers, 1);
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btrfs_start_workers(&fs_info->endio_meta_workers, 1);
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btrfs_start_workers(&fs_info->endio_meta_write_workers, 1);
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btrfs_start_workers(&fs_info->endio_write_workers, 1);
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fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
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fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
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