From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: handle negative wbc->nr_to_write during sync writeback
Date: Mon, 23 Aug 2010 09:28:29 -0400 [thread overview]
Message-ID: <20100823132829.GB15918@infradead.org> (raw)
In-Reply-To: <1282565437-13880-1-git-send-email-david@fromorbit.com>
On Mon, Aug 23, 2010 at 10:10:37PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> During data integrity (WB_SYNC_ALL) writeback, wbc->nr_to_write will
> go negative on inodes with more than 1024 dirty pages due to
> implementation details of write_cache_pages(). Currently XFS will
> abort page clustering in writeback once nr_to_write drops below
> zero, and so for data integrity writeback we will do very
> inefficient page at a time allocation and IO submission for inodes
> with large numbers of dirty pages.
>
> Fix this by only aborting the page clustering code when
> wbc->nr_to_write is negative and the sync mode is WB_SYNC_NONE.
Looks okay, but I wonder why if we should remove the check entirely.
We're clustering inside the same extent, and we already have a cap
for the extent size. That means the additional I/O basically is for
free and we really shouldn't let the writeback code restrict us here.
Reviewed-by: Christoph Hellwig <hch@lst.de>
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prev parent reply other threads:[~2010-08-23 13:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-23 12:10 [PATCH] xfs: handle negative wbc->nr_to_write during sync writeback Dave Chinner
2010-08-23 13:28 ` Christoph Hellwig [this message]
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