Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932462AbWEWXSY (ORCPT ); Tue, 23 May 2006 19:18:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932463AbWEWXSY (ORCPT ); Tue, 23 May 2006 19:18:24 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:36826 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S932462AbWEWXSY (ORCPT ); Tue, 23 May 2006 19:18:24 -0400 Date: Wed, 24 May 2006 09:17:41 +1000 From: Nathan Scott To: Jan Engelhardt Cc: xfs@oss.sgi.com, linux-kernel@vger.kernel.org Subject: Re: XFS write speed drop Message-ID: <20060524091741.D267844@wobbly.melbourne.sgi.com> References: <20060522105326.A212600@wobbly.melbourne.sgi.com> <20060523084309.A239136@wobbly.melbourne.sgi.com> <20060524082218.A267844@wobbly.melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20060524082218.A267844@wobbly.melbourne.sgi.com>; from nathans@sgi.com on Wed, May 24, 2006 at 08:22:19AM +1000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1775 Lines: 42 On Wed, May 24, 2006 at 08:22:19AM +1000, Nathan Scott wrote: > On Tue, May 23, 2006 at 03:23:31PM +0200, Jan Engelhardt wrote: > > >> CASE 1: Copying from one disk to another > > >> ======================================== > > >> Copying a compiled 2.6.17-rc4 tree; 306907 KB in 28566 files in 2090 > > >> directories. > > > > > >OK, we can call this a metadata intensive workload - lots of small > > >files, lots of creates. Barriers will hurt the most here, as we'd > > >already have been log I/O bound most likely, and I'd expect barriers > > >to only slow that further. > > > > > Yes and the most important thing is that someone made -o barrier the > > default and did not notice. Someone else? :-D > > Not sure what you're trying to say here. Yes, barriers are on > by default now if the hardware supports them, yes, they will > slow things down relative to write-cache-without-barriers, and > yes we all knew that ... its not the case that someone "did not > notice" or forgot about something. There is no doubt that this > is the right thing to be doing by default - there's no way that > I can tell from inside XFS in the kernel that you have a UPS. ;) Oh, I realised I've slightly misread your mail, you said... | I do not actually need barriers (or an UPS, to poke on another thread), | because power failures are rather rare in Germany. Hmm, even harder for us to detect at runtime, in the kernel, that you're in Germany. :) Power failures aren't the only thing to cause crashes, however. cheers. -- Nathan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/