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Re: [PATCH 1/4] xfs: do not update xa_last_pushed_lsn for locked items

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/4] xfs: do not update xa_last_pushed_lsn for locked items
From: Alex Elder <aelder@xxxxxxx>
Date: Fri, 7 Oct 2011 17:18:05 -0500
Cc: <xfs@xxxxxxxxxxx>, Stefan Priebe <s.priebe@xxxxxxxxxxxx>
In-reply-to: <20111006183549.399127499@xxxxxxxxxxxxxxxxxxxxxx>
References: <20111006183257.036884724@xxxxxxxxxxxxxxxxxxxxxx> <20111006183549.399127499@xxxxxxxxxxxxxxxxxxxxxx>
Reply-to: <aelder@xxxxxxx>
On Thu, 2011-10-06 at 14:32 -0400, Christoph Hellwig wrote:
> If an item was locked we should not update xa_last_pushed_lsn and thus skip
> it when restarting the AIL scan as we need to be able to lock and write it
> out as soon as possible.  Otherwise heavy lock contention might starve AIL
> pushing too easily, especially given the larger backoff once we moved
> xa_last_pushed_lsn all the way to the target lsn.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reported-by: Stefan Priebe <s.priebe@xxxxxxxxxxxx>
> Tested-by: Stefan Priebe <s.priebe@xxxxxxxxxxxx>

I remember wondering about that one line during review, but
I believe I reasoned something about the "already being
reflushed or relogged" made it the right thing to do.

Your explanation makes sense though (but what do I know,
the original code seemed OK too...).

Reviewed-by: Alex Elder <aelder@xxxxxxx>


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