From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o4JNPGAk162911 for ; Wed, 19 May 2010 18:25:16 -0500 Received: from mail.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 298D61411EAD for ; Wed, 19 May 2010 16:27:34 -0700 (PDT) Received: from mail.internode.on.net (bld-mail16.adl2.internode.on.net [150.101.137.101]) by cuda.sgi.com with ESMTP id XuRBrEf4l3B6C1Rb for ; Wed, 19 May 2010 16:27:34 -0700 (PDT) Date: Thu, 20 May 2010 09:27:31 +1000 From: Dave Chinner Subject: Re: XFS on 2.6.26: reading the first 4K of a large file takes ages Message-ID: <20100519232731.GR8120@dastard> References: <8239xojfco.fsf@mid.bfk.de> <20100519114826.GA18224@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100519114826.GA18224@infradead.org> 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: Christoph Hellwig Cc: xfs@oss.sgi.com, Florian Weimer On Wed, May 19, 2010 at 07:48:26AM -0400, Christoph Hellwig wrote: > On Wed, May 19, 2010 at 11:33:27AM +0000, Florian Weimer wrote: > > We've got a couple of rather large files, and with a cold cache, > > reading the first 4K bytes of the file (e.g., just running > > "head --bytes 4096" on it) takes ages, up to several minutes, > > sometimes triggering the hang check timer. > > > > I wonder if XFS reads the whole extent information into RAM when the > > file is opened. Is this the case, at least on 2.6.26? Has this > > changed in later versions, perhaps? > > Yes, XFS always reads in the extent map, and no this hasn't changed > recently. And demand paging the in-memory information is hard. It's on a to-do list somewhere 'round here.... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs