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From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 01/16] xfs: drop ->writepage completely
Date: Tue, 13 Nov 2018 08:08:39 +1100	[thread overview]
Message-ID: <20181112210839.GM19305@dastard> (raw)
In-Reply-To: <20181109151239.GD9153@infradead.org>

On Fri, Nov 09, 2018 at 07:12:39AM -0800, Christoph Hellwig wrote:
> [adding linux-mm to the CC list]
> 
> On Wed, Nov 07, 2018 at 05:31:12PM +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > ->writepage is only used in one place - single page writeback from
> > memory reclaim. We only allow such writeback from kswapd, not from
> > direct memory reclaim, and so it is rarely used. When it comes from
> > kswapd, it is effectively random dirty page shoot-down, which is
> > horrible for IO patterns. We will already have background writeback
> > trying to clean all the dirty pages in memory as efficiently as
> > possible, so having kswapd interrupt our well formed IO stream only
> > slows things down. So get rid of xfs_vm_writepage() completely.
> 
> Interesting.  IFF we can pull this off it would simplify a lot of
> things, so I'm generally in favor of it.

Over the past few days of hammeringon this, the only thing I've
noticed is that page reclaim hangs up less, but it's also putting a
bit more pressure on the shrinkers. Filesystem intensive workloads
that drive the machine into reclaim via the page cache seem to hit
breakdown conditions slightly earlier and the impact is that the
shrinkers are run harder. Mostly I see this as the XFS buffer cache
having a much harder time keeping a working set active.

However, while the workloads hit the working set cache, writeback
performance does seem to be slightly higher. It is, however, being
offset by the deeper lows that come from the cache being turned
over.

So there's a bit of rebalancing to be done here as a followup, but
I've been unable to drive the system into unexepected OOM kills or
other bad behaviour as a result of removing ->writepage.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2018-11-12 21:08 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-07  6:31 [RFC PATCH 00/16] xfs: Block size > PAGE_SIZE support Dave Chinner
2018-11-07  6:31 ` [PATCH 01/16] xfs: drop ->writepage completely Dave Chinner
2018-11-09 15:12   ` Christoph Hellwig
2018-11-12 21:08     ` Dave Chinner [this message]
2021-02-02 20:51       ` Darrick J. Wong
2018-11-07  6:31 ` [PATCH 02/16] xfs: move writepage context warnings to writepages Dave Chinner
2018-11-07  6:31 ` [PATCH 03/16] xfs: finobt AG reserves don't consider last AG can be a runt Dave Chinner
2018-11-07 16:55   ` Darrick J. Wong
2018-11-09  0:21     ` Dave Chinner
2018-11-07  6:31 ` [PATCH 04/16] xfs: extent shifting doesn't fully invalidate page cache Dave Chinner
2018-11-07  6:31 ` [PATCH 05/16] iomap: sub-block dio needs to zeroout beyond EOF Dave Chinner
2018-11-09 15:15   ` Christoph Hellwig
2018-11-07  6:31 ` [PATCH 06/16] iomap: support block size > page size for direct IO Dave Chinner
2018-11-08 11:28   ` Nikolay Borisov
2018-11-09 15:18   ` Christoph Hellwig
2018-11-11  1:12     ` Dave Chinner
2018-11-07  6:31 ` [PATCH 07/16] iomap: prepare buffered IO paths for block size > page size Dave Chinner
2018-11-09 15:19   ` Christoph Hellwig
2018-11-11  1:15     ` Dave Chinner
2018-11-07  6:31 ` [PATCH 08/16] iomap: mode iomap_zero_range and friends Dave Chinner
2018-11-09 15:19   ` Christoph Hellwig
2018-11-07  6:31 ` [PATCH 09/16] iomap: introduce zero-around functionality Dave Chinner
2018-11-07  6:31 ` [PATCH 10/16] iomap: enable zero-around for iomap_zero_range() Dave Chinner
2018-11-07  6:31 ` [PATCH 11/16] iomap: Don't mark partial pages zeroing uptodate for zero-around Dave Chinner
2018-11-07  6:31 ` [PATCH 12/16] iomap: zero-around in iomap_page_mkwrite Dave Chinner
2018-11-07  6:31 ` [PATCH 13/16] xfs: add zero-around controls to iomap Dave Chinner
2018-11-07  6:31 ` [PATCH 14/16] xfs: align writepages to large block sizes Dave Chinner
2018-11-09 15:22   ` Christoph Hellwig
2018-11-11  1:20     ` Dave Chinner
2018-11-11 16:32       ` Christoph Hellwig
2018-11-14 14:19   ` Brian Foster
2018-11-14 21:18     ` Dave Chinner
2018-11-15 12:55       ` Brian Foster
2018-11-16  6:19         ` Dave Chinner
2018-11-16 13:29           ` Brian Foster
2018-11-19  1:14             ` Dave Chinner
2018-11-07  6:31 ` [PATCH 15/16] xfs: expose block size in stat Dave Chinner
2018-11-07  6:31 ` [PATCH 16/16] xfs: enable block size larger than page size support Dave Chinner
2018-11-07 17:14 ` [RFC PATCH 00/16] xfs: Block size > PAGE_SIZE support Darrick J. Wong
2018-11-07 22:04   ` Dave Chinner
2018-11-08  1:38     ` Darrick J. Wong
2018-11-08  9:04       ` Dave Chinner
2018-11-08 22:17         ` Darrick J. Wong
2018-11-08 22:22           ` Dave Chinner

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