From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Tue, 05 Jun 2007 16:08:58 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id l55N8qWt006311 for ; Tue, 5 Jun 2007 16:08:54 -0700 Message-ID: <4665ED89.4090202@sgi.com> Date: Wed, 06 Jun 2007 09:11:05 +1000 From: Vlad Apostolov MIME-Version: 1.0 Subject: Re: Reducing memory requirements for high extent xfs files References: <200705301649.l4UGnckA027406@oss.sgi.com> <20070530225516.GB85884050@sgi.com> <4665E276.9020406@agami.com> In-Reply-To: <4665E276.9020406@agami.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Michael Nishimoto Cc: David Chinner , Michael Nishimoto , xfs@oss.sgi.com Michael Nishimoto wrote: > > > David Chinner wrote: >> On Wed, May 30, 2007 at 09:49:38AM -0700, Michael Nishimoto wrote: >> > Hello, >> > >> > Has anyone done any work or had thoughts on changes required >> > to reduce the total memory footprint of high extent xfs files? >> >> We changed the way we do memory allocation to avoid needing >> large contiguous chunks of memory a bit over a year ago; >> that solved the main OOM problem we were getting reported >> with highly fragmented files. >> >> > Obviously, it is important to reduce fragmentation as files >> > are generated and to regularly defrag files, but both of these >> > alternatives are not complete solutions. >> > >> > To reduce memory consumption, xfs could bring in extents >> > from disk as needed (or just before needed) and could free >> > up mappings when certain extent ranges have not been recently >> > accessed. A solution should become more aggressive about >> > reclaiming extent mapping memory as free memory becomes limited. >> >> Yes, it could, but that's a pretty major overhaul of the extent >> interface which currently assumes everywhere that the entire >> extent tree is in core. >> >> Can you describe the problem you are seeing that leads you to >> ask this question? What's the problem you need to solve? >> >> Cheers, >> >> Dave. >> -- >> Dave Chinner >> Principal Engineer >> SGI Australian Software Group > > I realize that this work won't be trivial which is why I asked if anyone > has thought about all relevant issues. > > When using NFS over XFS, slowly growing files (can be ascii log files) > tend to fragment quite a bit. One system had several hundred files > which required more than one page to store the extents. Quite a few > files had extent counts greater than 10k, and one file had 120k extents. > Besides the memory consumption, latency to return the first byte of the > file can get noticeable. > > Michael > Hi Michael, You could use XFS_XFLAG_EXTSIZE and XFS_XFLAG_RTINHERIT flags to set extent hint size, which would reduce the file fragmentation in this scenario. Please check xfcntl man page for more details. Regards, Vlad / /