Btrfs: Wait for kernel threads to make progress during async submission
Before this change, btrfs would use a bdi congestion function to make
sure there weren't too many pending async checksum work items.
This change makes the process creating async work items wait instead,
leading to fewer congestion returns from the bdi. This improves
pdflush background_writeout scanning.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 5f2f5a8..958cd8b 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -48,6 +48,7 @@
/* number of things on the pending list */
atomic_t num_pending;
+ unsigned long sequence;
/* protects the pending list. */
spinlock_t lock;
@@ -197,6 +198,7 @@
spin_lock_irq(&workers->lock);
list_add_tail(&worker->worker_list, &workers->idle_list);
+ worker->idle = 1;
workers->num_workers++;
spin_unlock_irq(&workers->lock);
}
@@ -238,7 +240,10 @@
*/
next = workers->worker_list.next;
worker = list_entry(next, struct btrfs_worker_thread, worker_list);
- list_move_tail(next, &workers->worker_list);
+ atomic_inc(&worker->num_pending);
+ worker->sequence++;
+ if (worker->sequence % 4 == 0)
+ list_move_tail(next, &workers->worker_list);
return worker;
}