From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sat, 23 Sep 2006 09:35:26 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id k8NGZDaG015916 for ; Sat, 23 Sep 2006 09:35:16 -0700 Received: from sandeen.net (sandeen.net [209.173.210.139]) by cuda.sgi.com (Spam Firewall) with ESMTP id 6B835D10E74F for ; Sat, 23 Sep 2006 09:34:35 -0700 (PDT) Message-ID: <4515620F.5010607@sandeen.net> Date: Sat, 23 Sep 2006 11:34:23 -0500 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: largeio mount and performance impact References: <55EF1E5D5804A542A6CA37E446DDC206655888@mapibe17.exchange.xchg> In-Reply-To: <55EF1E5D5804A542A6CA37E446DDC206655888@mapibe17.exchange.xchg> 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: Sebastian Brings Cc: xfs@oss.sgi.com Sebastian Brings wrote: > In a different thread I read about the largeio mount option for XFS. Now > I wonder if the problems I recently ran in have been caused by this. > > After a system uprgade from sles9 sp2 to sp3 one app started > misbehaving. Before the upgrade it used 15% CPU, after the upgrade it > was 90+% and the performance dropped by about 50%. The app is writing a > wave audio file, and for every 3840 bytes of audio samples it appends, > it updates the RIFF header of the file. All of this was done using the > buffered fopen/fwrite/... C library functions. > An strace showed that seeking to the beginning of the file also > triggered a 12MiB read(2) call, and seeking to the end, for example to > 13MiB, translated to a seek(2) to offset 1mib and a read(2) of 12 MiB. > > Initiall I assumed something very strange had happened to the C lib > defaults. Otoh 12MiB is the swidth of the filesystem, so I assume that > the C lib got the 12 MiB optimal IO size from XFS and therefore behaved > as described above. Could that be? Unless you specify the largeio mount option, I don't -think- any of this is exposed. What does stat -c %o say? Did this strace behavior change from sp2 to sp3? -Eric