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From: "Darrick J. Wong" <djwong@kernel.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	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, 2 Feb 2021 12:51:56 -0800	[thread overview]
Message-ID: <20210202205156.GU7193@magnolia> (raw)
In-Reply-To: <20181112210839.GM19305@dastard>

On Tue, Nov 13, 2018 at 08:08:39AM +1100, Dave Chinner wrote:
> 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.

FWIW I've been running this patch in my development kernels as part of
exercising realtime reflink with rextsize > 1.  So far I haven't seen
any particularly adverse effects.

--D

> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com

  reply	other threads:[~2021-02-02 20:52 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
2021-02-02 20:51       ` Darrick J. Wong [this message]
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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