diff mbox series

xfs: revert AIL TASK_KILLABLE threshold

Message ID 20240805184622.GB623936@frogsfrogsfrogs (mailing list archive)
State New
Headers show
Series xfs: revert AIL TASK_KILLABLE threshold | expand

Commit Message

Darrick J. Wong Aug. 5, 2024, 6:46 p.m. UTC 
From: Darrick J. Wong <djwong@kernel.org>

In commit ce46e893b6762, we changed the behavior of the AIL thread to
set its own task state to KILLABLE whenever the timeout value is
nonzero.  Unfortunately, this missed the fact that xfsaild_push will
return 50ms (aka a longish sleep) when we reach the push target or the
AIL becomes empty, so xfsaild goes to sleep for a long period of time in
uninterruptible D state.

This results in artificially high load averages because KILLABLE
processes are UNINTERRUPTIBLE, which contributes to load average even
though the AIL is asleep waiting for someone to interrupt it.  It's not
blocked on IOs or anything, but people scrap ps for processes that look
like they're stuck in D state, so restore the previous threshold.

Fixes: ce46e893b6762 ("xfs: AIL doesn't need manual pushing")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_trans_ail.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Aug. 6, 2024, 1:07 p.m. UTC | #1 
Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 0fafcc9f3dbe..8ede9d099d1f 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -644,7 +644,12 @@  xfsaild(
 	set_freezable();
 
 	while (1) {
-		if (tout)
+		/*
+		 * Long waits of 50ms or more occur when we've run out of items
+		 * to push, so we only want uninterruptible state if we're
+		 * actually blocked on something.
+		 */
+		if (tout && tout <= 20)
 			set_current_state(TASK_KILLABLE|TASK_FREEZABLE);
 		else
 			set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);