From: Dave Chinner Subject: Re: high latency NFS Date: Mon, 4 Aug 2008 10:32:06 +1000 Message-ID: <20080804003206.GB6119@disturbed> References: <200807241311.31457.shuey@purdue.edu> <20080730192110.GA17061@fieldses.org> <4890DFC7.3020309@cse.unsw.edu.au> <200807302235.50068.shuey@purdue.edu> <20080731031512.GA26203@fieldses.org> <18577.25513.494821.481623@notabene.brown> <20080801072320.GE6201@disturbed> <20080801191559.GI7764@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Neil Brown , Michael Shuey , Shehjar Tikoo , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, rees@citi.umich.edu, aglo@citi.umich.edu To: "J. Bruce Fields" Return-path: Received: from ipmail01.adl6.internode.on.net ([203.16.214.146]:57402 "EHLO ipmail01.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752030AbYHDAcM (ORCPT ); Sun, 3 Aug 2008 20:32:12 -0400 In-Reply-To: <20080801191559.GI7764@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Aug 01, 2008 at 03:15:59PM -0400, J. Bruce Fields wrote: > On Fri, Aug 01, 2008 at 05:23:20PM +1000, Dave Chinner wrote: > > On Thu, Jul 31, 2008 at 05:03:05PM +1000, Neil Brown wrote: > > > You might want to track the max length of the request queue too and > > > start more threads if the queue is long, to allow a quick ramp-up. > > > > Right, but even request queue depth is not a good indicator. You > > need to leep track of how many NFSDs are actually doing useful > > work. That is, if you've got an NFSD on the CPU that is hitting > > the cache and not blocking, you don't need more NFSDs to handle > > that load because they can't do any more work than the NFSD > > that is currently running is. > > > > i.e. take the solution that Greg banks used for the CPU scheduler > > overload issue (limiting the number of nfsds woken but not yet on > > the CPU), > > I don't remember that, or wasn't watching when it happened.... Do you > have a pointer? Ah, I thought that had been sent to mainline because it was mentioned in his LCA talk at the start of the year. Slides 65-67 here: http://mirror.linux.org.au/pub/linux.conf.au/2007/video/talks/41.pdf Cheers, Dave. -- Dave Chinner david@fromorbit.com