From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 1/2] xfs: block allocation work needs to be kswapd aware
Date: Tue, 27 May 2014 03:38:29 -0700 [thread overview]
Message-ID: <20140527103829.GA1440@infradead.org> (raw)
In-Reply-To: <1401143214-9181-2-git-send-email-david@fromorbit.com>
On Tue, May 27, 2014 at 08:26:53AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Upon memory pressure, kswapd calls xfs_vm_writepage() from
> shrink_page_list(). This can result in delayed allocation occurring
> and that gets deferred to the the allocation workqueue.
>
> The allocation then runs outside kswapd context, which means if it
> needs memory (and it does to demand page metadata from disk) it can
> block in shrink_inactive_list() waiting for IO congestion. These
> blocking waits are normally avoiding in kswapd context, so under
> memory pressure writeback from kswapd can be arbitrarily delayed by
> memory reclaim.
>
> To avoid this, pass the kswapd context to the allocation being done
> by the workqueue, so that memory reclaim understands correctly that
> the work is being done for kswapd and therefore it is not blocked
> and does not delay memory reclaim.
>
> To avoid issues with int->char conversion of flag fields (as noticed
> in v1 of this patch) convert the flag fields in the struct
> xfs_bmalloca to bool types. pahole indicates these variables are
> still single byte variables, so no extra space is consumed by this
> change.
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
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next prev parent reply other threads:[~2014-05-27 10:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-26 22:26 [PATCH 0/2] xfs: regression fixes Dave Chinner
2014-05-26 22:26 ` [PATCH 1/2] xfs: block allocation work needs to be kswapd aware Dave Chinner
2014-05-27 10:38 ` Christoph Hellwig [this message]
2014-05-26 22:26 ` [PATCH 2/2] xfs: xfs_readsb needs to check for magic numbers Dave Chinner
2014-05-27 10:40 ` Christoph Hellwig
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