From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261153AbTFZNEf (ORCPT ); Thu, 26 Jun 2003 09:04:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261188AbTFZNEf (ORCPT ); Thu, 26 Jun 2003 09:04:35 -0400 Received: from static-ctb-210-9-247-235.webone.com.au ([210.9.247.235]:28942 "EHLO chimp.local.net") by vger.kernel.org with ESMTP id S261153AbTFZNEd (ORCPT ); Thu, 26 Jun 2003 09:04:33 -0400 Message-ID: <3EFAF290.9020904@cyberone.com.au> Date: Thu, 26 Jun 2003 23:18:08 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3.1) Gecko/20030527 Debian/1.3.1-2 X-Accept-Language: en MIME-Version: 1.0 To: Nick Piggin CC: Chris Mason , Andrea Arcangeli , Marc-Christian Petersen , Jens Axboe , Marcelo Tosatti , Georg Nikodym , lkml , Matthias Mueller Subject: Re: [PATCH] io stalls References: <1055296630.23697.195.camel@tiny.suse.com> <20030611021030.GQ26270@dualathlon.random> <1055353360.23697.235.camel@tiny.suse.com> <20030611181217.GX26270@dualathlon.random> <1055356032.24111.240.camel@tiny.suse.com> <20030611183503.GY26270@dualathlon.random> <3EE7D1AA.30701@cyberone.com.au> <20030612012951.GG1500@dualathlon.random> <1055384547.24111.322.camel@tiny.suse.com> <3EE7E876.80808@cyberone.com.au> <20030612024608.GE1415@dualathlon.random> <1056567822.10097.133.camel@tiny.suse.com> <3EFA8920.8050509@cyberone.com.au> <1056628116.20899.28.camel@tiny.suse.com> <3EFAEF71.1080109@cyberone.com.au> In-Reply-To: <3EFAEF71.1080109@cyberone.com.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin wrote: snip > > Yeah, something like that. I think that in a queue full situation, > the processes are wanting to submit more than 1 request though. So > the better thoughput you can achieve by batching translates to > better effective throughput. Read my recent debate with Andrea ^^^^^^^^^^ Err, latency snip > > No, the numbers (batch # requests, batch time) are not highly scientific. > Simply when a process wakes up, we'll let them submit a small burst of > requests before they go back to sleep. by this, I mean that its not a big problem that we don't know how many requests a process wants to submit. snip > > The changes do seem to be a critical fix due to the starvation issue, > but I'm worried that they take a big step back in performance under > high disk load. I found my FIFO mechanism to be unacceptably slow for > 2.5. BTW. sorry for the lack of better benchmark numbers. I couldn't find good ones lying around. I found uniprocessor tiobench to be quite helpful at queue_nr_requests * 0.5, 2 threads to measure different types of overloadedness. Also, I didn't see much gain in read performance in my testing - probably due to AS. I expect 2.4 and 2.5 non AS read performance to show bigger improvements from batching (ie. regressions).