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

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

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.