xfs: Don't wake the aild once per second

Now that the AIL push algorithm is traversal safe, we don't need a
watchdog function in the xfsaild to catch pushes that fail to make
progress. Remove the watchdog timeout and make pushes purely driven
by demand. This will remove the once-per-second wakeup that is seen
when the filesystem is idle and make laptop power misers happy.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 11 insertions, 8 deletions

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 2ffc570679be..063dfbdca94b 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -237,14 +237,15 @@ out:
 }
 
 /*
- * Function that does the work of pushing on the AIL
+ * xfsaild_push does the work of pushing on the AIL.  Returning a timeout of
+ * zero indicates that the caller should sleep until woken.
  */
 long
 xfsaild_push(
         struct xfs_ail  *ailp,
         xfs_lsn_t       *last_lsn)
 {
-        long            tout = 1000; /* milliseconds */
+        long            tout = 0;
         xfs_lsn_t       last_pushed_lsn = *last_lsn;
         xfs_lsn_t       target =  ailp->xa_target;
         xfs_lsn_t       lsn;
@@ -262,7 +263,7 @@ xfsaild_push(
                  */
                 xfs_trans_ail_cursor_done(ailp, cur);
                 spin_unlock(&ailp->xa_lock);
-                last_pushed_lsn = 0;
+                *last_lsn = 0;
                 return tout;
         }
 
@@ -279,7 +280,6 @@ xfsaild_push(
          * prevents use from spinning when we can't do anything or there is
          * lots of contention on the AIL lists.
          */
-        tout = 10;
         lsn = lip->li_lsn;
         flush_log = stuck = count = 0;
         while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
@@ -376,14 +376,14 @@ xfsaild_push(
 
         if (!count) {
                 /* We're past our target or empty, so idle */
-                tout = 1000;
+                last_pushed_lsn = 0;
         } else if (XFS_LSN_CMP(lsn, target) >= 0) {
                 /*
                  * We reached the target so wait a bit longer for I/O to
                  * complete and remove pushed items from the AIL before we
                  * start the next scan from the start of the AIL.
                  */
-                tout += 20;
+                tout = 50;
                 last_pushed_lsn = 0;
         } else if ((stuck * 100) / count > 90) {
                 /*
@@ -395,11 +395,14 @@ xfsaild_push(
                  * Backoff a bit more to allow some I/O to complete before
                  * continuing from where we were.
                  */
-                tout += 10;
+                tout = 20;
+        } else {
+                /* more to do, but wait a short while before continuing */
+                tout = 10;
         }
         *last_lsn = last_pushed_lsn;
         return tout;
-}       /* xfsaild_push */
+}
 
 
 /*