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Re: [PATCH 4/4] xfs: convert xfsbufd to use a workqueue

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/4] xfs: convert xfsbufd to use a workqueue
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Wed, 21 Sep 2011 07:26:24 -0400
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20110921062539.GN15688@dastard>
References: <1314341497-23910-1-git-send-email-david@xxxxxxxxxxxxx> <1314341497-23910-5-git-send-email-david@xxxxxxxxxxxxx> <20110826082515.GD3551@xxxxxxxxxxxxx> <20110921062539.GN15688@dastard>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Sep 21, 2011 at 04:25:39PM +1000, Dave Chinner wrote:
> Which is precisely what I want here - to wait for all the delwri
> buffers that were promoted to be submitted before continuing
> onwards.  This makes the scanning algorithm self throttling -
> instead of simply pushing the buffers to the delwri queue and
> kicking a background thread and hoping it can flush buffers faster
> than we can promote them from the AIL, it explicitly pushes the
> delwri buffers before the next round of AIL scanning. The ensures we
> start timely IO on the buffers and don't simple continue to scan the
> AIL while we wait for the background thread to send them off to
> disk and complete.

I didn't say I'm against it.  The important bit is that such changes
in behaviour get documented in the patch description, including
a rationale like the on in this mail.

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