xfs: reduce the number of AIL push wakeups (e677d0f9) · Commits · 戴 / test

The xfaild often tries to rest to wait for congestion to pass of for IO to complete, but is regularly woken in tail-pushing situations. In severe cases, the xfsaild is getting woken tens of thousands of times a second. Reduce the number needless wakeups by only waking the xfsaild if the new target is larger than the old one. Further make short sleeps uninterruptible as they occur when the xfsaild has decided it needs to back off to allow some IO to complete and being woken early is counter-productive. Signed-off-by:

Dave Chinner <dchinner@redhat.com> Reviewed-by:

Christoph Hellwig <hch@lst.de>

fs/xfs/linux-2.6/xfs_super.c

+16 −4

Original line number	Diff line number	Diff line
		@@ -834,9 +834,12 @@ xfsaild_wakeup(
		struct xfs_ail *ailp,
		xfs_lsn_t threshold_lsn)
		{
		/* only ever move the target forwards */
		if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0) {
		ailp->xa_target = threshold_lsn;
		wake_up_process(ailp->xa_task);
		}
		}

		STATIC int
		xfsaild(
		@@ -847,7 +850,16 @@ xfsaild(
		long tout = 0; /* milliseconds */

		while (!kthread_should_stop()) {
		schedule_timeout_interruptible(tout ?
		/*
		* for short sleeps indicating congestion, don't allow us to
		* get woken early. Otherwise all we do is bang on the AIL lock
		* without making progress.
		*/
		if (tout && tout <= 20)
		__set_current_state(TASK_KILLABLE);
		else
		__set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(tout ?
		msecs_to_jiffies(tout) : MAX_SCHEDULE_TIMEOUT);

		/* swsusp */

Admin message