From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q2SFAnsO113741 for ; Wed, 28 Mar 2012 10:10:54 -0500 Received: from bombadil.infradead.org (173-166-109-252-newengland.hfc.comcastbusiness.net [173.166.109.252]) by cuda.sgi.com with ESMTP id XzcTzTAp5EF1GtAL (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Wed, 28 Mar 2012 08:10:46 -0700 (PDT) Date: Wed, 28 Mar 2012 11:10:41 -0400 From: Christoph Hellwig Subject: Re: [PATCH 00/10] remove xfsbufd Message-ID: <20120328151040.GA2487@infradead.org> References: <20120327164400.967415009@bombadil.infradead.org> <20120328005337.GH3592@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20120328005337.GH3592@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: Christoph Hellwig , xfs@oss.sgi.com 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. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs