Btrfs: Worker thread optimizations
This changes the worker thread pool to maintain a list of idle threads,
avoiding a complex search for a good thread to wake up.
Threads have two states:
idle - we try to reuse the last thread used in hopes of improving the batching
ratios
busy - each time a new work item is added to a busy task, the task is
rotated to the end of the line.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h
index 52fc9da..3436ff89 100644
--- a/fs/btrfs/async-thread.h
+++ b/fs/btrfs/async-thread.h
@@ -60,11 +60,12 @@
/* 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;