[PATCH] xfs: remove unecessary AIL push wakeups

[PATCH] xfs: remove unecessary AIL push wakeups

[JiSheng Zhang]

In commit 0030807c66("xfs: revert to using a kthread for AIL pushing"),
AIL pushing is revert back to use a kthread. But unfortunately, it
introduced a regression: there are unnecessary AIL push wakeups during
idle, ~20 wakeups/s. This change remove the wakeups by reverting a bit
more: set "tout" value as zero during idle.

Signed-off-by: JiSheng Zhang <jszhang3@mail.ustc.edu.cn>
---
 fs/xfs/xfs_trans_ail.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index ed9252b..2014387 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -508,7 +508,7 @@ out_done:
 		ailp->xa_last_pushed_lsn = 0;
 		ailp->xa_log_flush = 0;
 
-		tout = 50;
+		tout = 0;
 	} else if (XFS_LSN_CMP(lsn, target) >= 0) {
 		/*
 		 * We reached the target so wait a bit longer for I/O to
-- 
1.7.8.3

Re: [PATCH] xfs: remove unecessary AIL push wakeups

[Christoph Hellwig]

On Fri, Jan 13, 2012 at 01:30:28AM +0800, JiSheng Zhang wrote:
> 
> In commit 0030807c66("xfs: revert to using a kthread for AIL pushing"),
> AIL pushing is revert back to use a kthread. But unfortunately, it
> introduced a regression: there are unnecessary AIL push wakeups during
> idle, ~20 wakeups/s. This change remove the wakeups by reverting a bit
> more: set "tout" value as zero during idle.
> 
> Signed-off-by: JiSheng Zhang <jszhang3@mail.ustc.edu.cn>

Looks fine, although I'm a bit worried that I don't have the setup to
reproduce the issue that the patch addressed any more and we might
regress here.