From: Alex Elder <aelder@sgi.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 2/4] xfs: do not discard alloc btree blocks
Date: Thu, 19 May 2011 16:54:29 -0500 [thread overview]
Message-ID: <1305842069.2825.88.camel@doink> (raw)
In-Reply-To: <20110504190011.319521066@bombadil.infradead.org>
On Wed, 2011-05-04 at 14:55 -0400, Christoph Hellwig wrote:
> Blocks for the allocation btree are allocated from and release to
> the AGFL, and thus frequently reused. Even worse we do not have
> an easy way to avoid using an AGFL block when it is discarded due
> to the simple FILO list of free blocks, and thus can frequently
> stall on blocks that are currently undergoing a discard.
>
> Add a flag to the busy extent tracking structure to skip the discard for
> allocation btree blocks. In normal operation these blocks are reused
> frequently enough that there is no need to discard them anyway, but
> if they spill over to the allocation btree as part of a balance we
> "leak" blocks that we would otherwise discard. We could fix this
> by adding another flag and keeping these block in the rbtree even
> after they aren't busy any more so that we could discard them when
> they migrate out of the AGFL. Given that this would cause significant
> overhead I don't think it's worthwile for now.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
This one looks good. (If you add support for discard
with nodelaylog it will need to be updated.)
Reviewed-by: Alex Elder <aelder@sgi.com>
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next prev parent reply other threads:[~2011-05-19 21:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 18:55 [PATCH 0/4] online discard support V3 Christoph Hellwig
2011-05-04 18:55 ` [PATCH 1/4] xfs: add online discard support Christoph Hellwig
2011-05-19 21:53 ` Alex Elder
2011-05-20 10:24 ` Christoph Hellwig
2011-05-20 11:43 ` Lukas Czerner
2011-05-20 13:57 ` Alex Elder
2011-05-20 13:40 ` Alex Elder
2011-05-20 13:45 ` [PATCH 1/4 v2] " Christoph Hellwig
2011-05-20 15:42 ` Alex Elder
2011-05-04 18:55 ` [PATCH 2/4] xfs: do not discard alloc btree blocks Christoph Hellwig
2011-05-19 21:54 ` Alex Elder [this message]
2011-05-04 18:55 ` [PATCH 3/4] xfs: add a reference count to the CIL context Christoph Hellwig
2011-05-19 21:54 ` Alex Elder
2011-05-20 10:25 ` Christoph Hellwig
2011-05-04 18:55 ` [PATCH 4/4] xfs: make discard operations asynchronous Christoph Hellwig
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