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From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>, xfs@oss.sgi.com
Subject: Re: [PATCH 00/10] remove xfsbufd
Date: Wed, 28 Mar 2012 11:10:41 -0400	[thread overview]
Message-ID: <20120328151040.GA2487@infradead.org> (raw)
In-Reply-To: <20120328005337.GH3592@dastard>

On Wed, Mar 28, 2012 at 11:53:37AM +1100, Dave Chinner wrote:
> in IO patterns and performance under heavy load here with this
> patch set. it doesn't however, reduce the buffer cache lookups all
> that much on such workloads - about 10% at most - as most of the
> lookups are common from the directory and inode buffer
> modifications. Here's a sample profile:

10% might not be extremly huge, but it's pretty significant.

> This shows that 50% of the lookups from the directory code, 25% from
> the inode btree lookups, 12% from mapping inodes, and 10% from
> reading the AGI buffer during inode allocation. 
> 
> You know, I suspect that we could avoid almost all those AGI buffer
> lookups by moving to a similar in-core log and flush technique that
> the inodes use. We've already got all the information in the struct
> xfs_perag - rearranging it to have a "in-core on disk" structures
> for the AGI, AGF and AGFL would make a lot of the "select an AG"
> code much simpler than having to read and modify the AG buffers
> directly. It might even be possible to do such a change without
> needing to change the on-disk journal format for them...
> 
> I think I'll put that on my list of stuff to do - right next to
> in-core unlinked inode lists....

Sounds fine.  A simple short-term fix might be to simply pin a reference
to the AGI buffers and add a pointer from struct xfs_perag to them.

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  reply	other threads:[~2012-03-28 15:10 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-27 16:44 [PATCH 00/10] remove xfsbufd Christoph Hellwig
2012-03-27 16:44 ` [PATCH 01/10] xfs: remove log item from AIL in xfs_qm_dqflush after a shutdown Christoph Hellwig
2012-03-27 18:17   ` Mark Tinguely
2012-04-13  9:36   ` Dave Chinner
2012-03-27 16:44 ` [PATCH 02/10] xfs: remove log item from AIL in xfs_iflush " Christoph Hellwig
2012-04-13  9:37   ` Dave Chinner
2012-03-27 16:44 ` [PATCH 03/10] xfs: allow assigning the tail lsn with the AIL lock held Christoph Hellwig
2012-03-27 18:18   ` Mark Tinguely
2012-04-13  9:42   ` Dave Chinner
2012-03-27 16:44 ` [PATCH 04/10] xfs: implement freezing by emptying the AIL Christoph Hellwig
2012-04-13 10:04   ` Dave Chinner
2012-04-16 13:33   ` Mark Tinguely
2012-04-16 13:47   ` Mark Tinguely
2012-04-16 23:54     ` Dave Chinner
2012-04-17  4:20       ` Dave Chinner
2012-04-17  8:26         ` Dave Chinner
2012-04-18 13:13           ` Mark Tinguely
2012-04-18 18:14             ` Ben Myers
2012-04-18 17:53           ` Mark Tinguely
2012-03-27 16:44 ` [PATCH 05/10] xfs: do flush inodes from background inode reclaim Christoph Hellwig
2012-04-13 10:14   ` Dave Chinner
2012-04-16 19:25   ` Mark Tinguely
2012-03-27 16:44 ` [PATCH 06/10] xfs: do not write the buffer from xfs_iflush Christoph Hellwig
2012-04-13 10:31   ` Dave Chinner
2012-04-18 13:33   ` Mark Tinguely
2012-03-27 16:44 ` [PATCH 07/10] xfs: do not write the buffer from xfs_qm_dqflush Christoph Hellwig
2012-04-13 10:33   ` Dave Chinner
2012-04-18 21:11   ` Mark Tinguely
2012-03-27 16:44 ` [PATCH 08/10] xfs: do not add buffers to the delwri queue until pushed Christoph Hellwig
2012-04-13 10:35   ` Dave Chinner
2012-04-18 21:11   ` Mark Tinguely
2012-03-27 16:44 ` [PATCH 09/10] xfs: on-stack delayed write buffer lists Christoph Hellwig
2012-04-13 11:37   ` Dave Chinner
2012-04-20 18:19   ` Mark Tinguely
2012-04-21  0:42     ` Dave Chinner
2012-04-23  1:57       ` Dave Chinner
2012-03-27 16:44 ` [PATCH 10/10] xfs: remove some obsolete comments in xfs_trans_ail.c Christoph Hellwig
2012-04-13 11:37   ` Dave Chinner
2012-03-28  0:53 ` [PATCH 00/10] remove xfsbufd Dave Chinner
2012-03-28 15:10   ` Christoph Hellwig [this message]
2012-03-29  0:52     ` Dave Chinner
2012-03-29 19:38       ` Christoph Hellwig

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