Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751066AbWBXOWV (ORCPT ); Fri, 24 Feb 2006 09:22:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751068AbWBXOWV (ORCPT ); Fri, 24 Feb 2006 09:22:21 -0500 Received: from rs27.luxsci.com ([66.216.127.24]:17879 "EHLO rs27.luxsci.com") by vger.kernel.org with ESMTP id S1751064AbWBXOWU (ORCPT ); Fri, 24 Feb 2006 09:22:20 -0500 Message-ID: <43FF16B7.9060407@eventmonitor.com> Date: Fri, 24 Feb 2006 09:22:47 -0500 From: Bryan Fink User-Agent: Mozilla Thunderbird 1.0.7 (X11/20050923) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Trond Myklebust CC: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: NFS Still broken in 2.6.x? References: <43FE1CAD.3050806@eventmonitor.com> <1140734824.7963.38.camel@lade.trondhjem.org> <20060224041435.733b4f0d.akpm@osdl.org> <1140788198.3615.3.camel@lade.trondhjem.org> In-Reply-To: <1140788198.3615.3.camel@lade.trondhjem.org> 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 Content-Length: 2119 Lines: 54 Trond Myklebust wrote: >On Fri, 2006-02-24 at 04:14 -0800, Andrew Morton wrote: > > >>Trond Myklebust wrote: >> >> >>>On Thu, 2006-02-23 at 15:35 -0500, Bryan Fink wrote: >>> > Hi All. I'm running into a bit of trouble with NFS on 2.6. I see that >>> > at least Trond thought, mid-January, that "The readahead algorithm has >>> > been broken in 2.6.x for at least the past 6 months." ( >>> > http://www.ussg.iu.edu/hypermail/linux/kernel/0601.2/0559.html) Anyone >>> > know if that has been fixed? >>> >>> No it hasn't been fixed. ...and no, this is not a problem that only >>> affects NFS: it just happens to give a more noticeable performance >>> impact due to the larger latency of NFS over a 100Mbps link. >>> >>> >>iirc, last time we went round this loop Ram and I were unable to reproduce it. >> >>Does anyone have a testcase? >> >> > >Yes. A dead simple one > >run iozone in sequential read mode on a tcp link w/ rsize == 32k > > I'm sure Trond's testcase is much more useful, but for reference, I thought I'd add that I've been doing my testing with a simple "dd if=/nfsmount/file of=/dev/null bs=32k". /nfsmount/file is usually 2.5-3 GB, which makes the difference between NFS servers long enough that I feel safe throwing a "time" in front of the whole command. That is, the difference is nowhere near millisecond resolution (it's nearer a minute), so I like to start the test and then walk away to do other things. Interesting that it's not an NFS-only bug. I assumed it was when I logged into each server so I could run "dd if=file of=/dev/null bs=32k" locally. When I did that, both servers gave roughly the same speed. Sorry I left this bit out of my first email. I assume this example only illustrates how opaque the code around this problem truly is. Thanks very much for the help. -Bryan - 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/