From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q113xK9M186579 for ; Tue, 31 Jan 2012 21:59:20 -0600 Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net [150.101.137.141]) by cuda.sgi.com with ESMTP id lFUVPcYRjPk8ITbQ for ; Tue, 31 Jan 2012 19:59:18 -0800 (PST) Date: Wed, 1 Feb 2012 14:59:15 +1100 From: Dave Chinner Subject: Re: Performance problem - reads slower than writes Message-ID: <20120201035915.GS9090@dastard> References: <20120130220019.GA45782@nsrc.org> <20120131020508.GF9090@dastard> <20120131103126.GA46170@nsrc.org> <20120131145205.GA6607@infradead.org> <20120131215210.GB47420@soundmouse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20120131215210.GB47420@soundmouse.com> 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: Brian Candler Cc: Christoph Hellwig , xfs@oss.sgi.com On Tue, Jan 31, 2012 at 09:52:10PM +0000, Brian Candler wrote: > On Tue, Jan 31, 2012 at 09:52:05AM -0500, Christoph Hellwig wrote: > > You don't just read a single file at a time but multiple ones, don't > > you? > > It's sequential at the moment, although I'll do further tests with the -c > (concurrency) option to bonnie++ > > > Try playing with the following tweaks to get larger I/O to the disk: > > > > a) make sure you use the noop or deadline elevators > > b) increase /sys/block/sdX/queue/max_sectors_kb from its low default > > c) dramatically increase /sys/devices/virtual/bdi/:/read_ahead_kb > > Thank you very much: I will do further tests with these. > > Is the read_ahead_kb knob aware of file boundaries? That is, is there any > risk that if I set it too large it would read useless blocks past the end of > the file? Yes, readahead only occurs within the file, and won't readahead past EOF. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs