Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751004AbWBXNg4 (ORCPT ); Fri, 24 Feb 2006 08:36:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751007AbWBXNg4 (ORCPT ); Fri, 24 Feb 2006 08:36:56 -0500 Received: from pat.uio.no ([129.240.130.16]:14293 "EHLO pat.uio.no") by vger.kernel.org with ESMTP id S1750919AbWBXNgz (ORCPT ); Fri, 24 Feb 2006 08:36:55 -0500 Subject: Re: NFS Still broken in 2.6.x? From: Trond Myklebust To: Andrew Morton Cc: bfink@eventmonitor.com, linux-kernel@vger.kernel.org In-Reply-To: <20060224041435.733b4f0d.akpm@osdl.org> References: <43FE1CAD.3050806@eventmonitor.com> <1140734824.7963.38.camel@lade.trondhjem.org> <20060224041435.733b4f0d.akpm@osdl.org> Content-Type: text/plain Date: Fri, 24 Feb 2006 08:36:38 -0500 Message-Id: <1140788198.3615.3.camel@lade.trondhjem.org> Mime-Version: 1.0 X-Mailer: Evolution 2.4.1 Content-Transfer-Encoding: 7bit X-UiO-Spam-info: not spam, SpamAssassin (score=-3.712, required 12, autolearn=disabled, AWL 1.10, FORGED_RCVD_HELO 0.05, RCVD_IN_SORBS_DUL 0.14, UIO_MAIL_IS_INTERNAL -5.00) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1358 Lines: 34 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 Monitor the traffic using tcpdump. Pretty soon you will see the size of the NFS read requests drop from 32k to 4k, which indicates that there is no readahead at all. Cheers, Trond - 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/