From: Jeff Garzik Subject: Re: read-ahead in NFS server Date: Thu, 27 Dec 2007 10:07:38 -0500 Message-ID: <4773BFBA.70709@garzik.org> References: <47730F2F.3080900@garzik.org> <47739288.7000308@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Cc: linux-kernel@vger.kernel.org, NFS list To: saeed bishara Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:59923 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751934AbXL0PHl (ORCPT ); Thu, 27 Dec 2007 10:07:41 -0500 In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: saeed bishara wrote: >>>> Are you using TCP? Are you using NFSv4, or an older version? >>> I'm using NFSv3/UDP. >> IMO, you definitely want TCP and NFSv4. Much better network behavior, >> with some of the silly UDP limits (plus greatly improved caching >> behavior, due to v4 delegations). > the clients of my system going to be embedded system with low > performance cpus and I need UDP as it needs less cpu power. I bet TCP + fewer revalidations + greater local pagecache activity uses less cpu power than UDP + revalidations + rx/tx network activity >>> when I run local dd with bs=4K, I can see that the average IO size is >>> more than 300KB. >> Read-ahead is easier in NFSv4, because the client probably has the file >> delegated locally, and has far less need to constantly revalidate file >> mapping(s). > I'll check that. > but what about the server side? why the issued IO's are only as twice > as the size of the NFS requests? No idea. I bet the source code can tell you :) Jeff