diff options
| -rw-r--r-- | fs/btrfs/async-thread.c | 100 | ||||
| -rw-r--r-- | fs/btrfs/async-thread.h | 7 |
2 files changed, 73 insertions, 34 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 8b9e2cf50606..8d4cc4679d51 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -34,6 +34,9 @@ * One of these is allocated per thread. */ struct btrfs_worker_thread { + /* pool we belong to */ + struct btrfs_workers *workers; + /* list of struct btrfs_work that are waiting for service */ struct list_head pending; @@ -51,9 +54,45 @@ struct btrfs_worker_thread { /* set to non-zero when this thread is already awake and kicking */ int working; + + /* are we currently idle */ + int idle; }; /* + * helper function to move a thread onto the idle list after it + * has finished some requests. + */ +static void check_idle_worker(struct btrfs_worker_thread *worker) +{ + if (!worker->idle && atomic_read(&worker->num_pending) < + worker->workers->idle_thresh / 2) { + unsigned long flags; + spin_lock_irqsave(&worker->workers->lock, flags); + worker->idle = 1; + list_move(&worker->worker_list, &worker->workers->idle_list); + spin_unlock_irqrestore(&worker->workers->lock, flags); + } +} + +/* + * helper function to move a thread off the idle list after new + * pending work is added. + */ +static void check_busy_worker(struct btrfs_worker_thread *worker) +{ + if (worker->idle && atomic_read(&worker->num_pending) >= + worker->workers->idle_thresh) { + unsigned long flags; + spin_lock_irqsave(&worker->workers->lock, flags); + worker->idle = 0; + list_move_tail(&worker->worker_list, + &worker->workers->worker_list); + spin_unlock_irqrestore(&worker->workers->lock, flags); + } +} + +/* * main loop for servicing work items */ static int worker_loop(void *arg) @@ -76,6 +115,7 @@ static int worker_loop(void *arg) atomic_dec(&worker->num_pending); spin_lock_irq(&worker->lock); + check_idle_worker(worker); } worker->working = 0; if (freezing(current)) { @@ -98,6 +138,7 @@ int btrfs_stop_workers(struct btrfs_workers *workers) struct list_head *cur; struct btrfs_worker_thread *worker; + list_splice_init(&workers->idle_list, &workers->worker_list); while(!list_empty(&workers->worker_list)) { cur = workers->worker_list.next; worker = list_entry(cur, struct btrfs_worker_thread, @@ -116,9 +157,10 @@ void btrfs_init_workers(struct btrfs_workers *workers, int max) { workers->num_workers = 0; INIT_LIST_HEAD(&workers->worker_list); - workers->last = NULL; + INIT_LIST_HEAD(&workers->idle_list); spin_lock_init(&workers->lock); workers->max_workers = max; + workers->idle_thresh = 64; } /* @@ -143,14 +185,14 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) spin_lock_init(&worker->lock); atomic_set(&worker->num_pending, 0); worker->task = kthread_run(worker_loop, worker, "btrfs"); + worker->workers = workers; if (IS_ERR(worker->task)) { ret = PTR_ERR(worker->task); goto fail; } spin_lock_irq(&workers->lock); - list_add_tail(&worker->worker_list, &workers->worker_list); - workers->last = worker; + list_add_tail(&worker->worker_list, &workers->idle_list); workers->num_workers++; spin_unlock_irq(&workers->lock); } @@ -169,42 +211,30 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) { struct btrfs_worker_thread *worker; struct list_head *next; - struct list_head *start; int enforce_min = workers->num_workers < workers->max_workers; - /* start with the last thread if it isn't busy */ - worker = workers->last; - if (atomic_read(&worker->num_pending) < 64) - goto done; - - next = worker->worker_list.next; - start = &worker->worker_list; - /* - * check all the workers for someone that is bored. FIXME, do - * something smart here + * if we find an idle thread, don't move it to the end of the + * idle list. This improves the chance that the next submission + * will reuse the same thread, and maybe catch it while it is still + * working */ - while(next != start) { - if (next == &workers->worker_list) { - next = workers->worker_list.next; - continue; - } + if (!list_empty(&workers->idle_list)) { + next = workers->idle_list.next; worker = list_entry(next, struct btrfs_worker_thread, worker_list); - if (atomic_read(&worker->num_pending) < 64 || !enforce_min) - goto done; - next = next->next; + return worker; } + if (enforce_min || list_empty(&workers->worker_list)) + return NULL; + /* - * nobody was bored, if we're already at the max thread count, - * use the last thread + * if we pick a busy task, move the task to the end of the list. + * hopefully this will keep things somewhat evenly balanced */ - if (!enforce_min || atomic_read(&workers->last->num_pending) < 64) { - return workers->last; - } - return NULL; -done: - workers->last = worker; + next = workers->worker_list.next; + worker = list_entry(next, struct btrfs_worker_thread, worker_list); + list_move_tail(next, &workers->worker_list); return worker; } @@ -221,11 +251,17 @@ again: if (!worker) { spin_lock_irqsave(&workers->lock, flags); if (workers->num_workers >= workers->max_workers) { + struct list_head *fallback = NULL; /* * we have failed to find any workers, just * return the force one */ - worker = list_entry(workers->worker_list.next, + if (!list_empty(&workers->worker_list)) + fallback = workers->worker_list.next; + if (!list_empty(&workers->idle_list)) + fallback = workers->idle_list.next; + BUG_ON(!fallback); + worker = list_entry(fallback, struct btrfs_worker_thread, worker_list); spin_unlock_irqrestore(&workers->lock, flags); } else { @@ -254,6 +290,7 @@ int btrfs_requeue_work(struct btrfs_work *work) spin_lock_irqsave(&worker->lock, flags); atomic_inc(&worker->num_pending); list_add_tail(&work->list, &worker->pending); + check_busy_worker(worker); spin_unlock_irqrestore(&worker->lock, flags); out: return 0; @@ -276,6 +313,7 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) spin_lock_irqsave(&worker->lock, flags); atomic_inc(&worker->num_pending); + check_busy_worker(worker); list_add_tail(&work->list, &worker->pending); /* diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h index 52fc9da0f9e7..3436ff897597 100644 --- a/fs/btrfs/async-thread.h +++ b/fs/btrfs/async-thread.h @@ -60,11 +60,12 @@ struct btrfs_workers { /* max number of workers allowed. changed by btrfs_start_workers */ int max_workers; + /* once a worker has this many requests or fewer, it is idle */ + int idle_thresh; + /* list with all the work threads */ struct list_head worker_list; - - /* the last worker thread to have something queued */ - struct btrfs_worker_thread *last; + struct list_head idle_list; /* lock for finding the next worker thread to queue on */ spinlock_t lock; |