From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758438AbYE0PyJ (ORCPT ); Tue, 27 May 2008 11:54:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757081AbYE0Px4 (ORCPT ); Tue, 27 May 2008 11:53:56 -0400 Received: from g4t0015.houston.hp.com ([15.201.24.18]:5873 "EHLO g4t0015.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756394AbYE0Pxz (ORCPT ); Tue, 27 May 2008 11:53:55 -0400 Subject: Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8) From: Lee Schermerhorn To: Rik van Riel Cc: balbir@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, Andrew Morton , Kosaki Motohiro In-Reply-To: <20080526153318.29edc0b2@bree.surriel.com> References: <20080523195506.084894989@redhat.com> <483B0077.7000207@linux.vnet.ibm.com> <20080526153318.29edc0b2@bree.surriel.com> Content-Type: text/plain Organization: HP/OSLO Date: Tue, 27 May 2008 11:54:02 -0400 Message-Id: <1211903642.7283.16.camel@lts-notebook> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2008-05-26 at 15:33 -0400, Rik van Riel wrote: > On Mon, 26 May 2008 23:54:55 +0530 > Balbir Singh wrote: > > > Rik van Riel wrote: > > > On large memory systems, the VM can spend way too much time scanning > > > through pages that it cannot (or should not) evict from memory. Not > > > only does it use up CPU time, but it also provokes lock contention > > > and can leave large systems under memory presure in a catatonic state. > > > > Hi, Rik, > > > > This patchset looks good (I did a brief scan). I'll go ahead and play with it? > > What is a good memory size to test the patches on (to see improvements). > > The larger, the better. One known problem with the current upstream > VM is large numbers of anonymous pages, or a mix of mlocked and anon > pages. > > Once the system needs to swap something out, every single anon page > will have the referenced bit set and the system needs to do lots of > scanning before it can evict the first page. This scanning causes > multiple CPUs to pile up and things slow down exponentially and/or > catastrophically :) > > Unfortunately the largest system I have access to on a regular basis > has "only" 16GB of RAM :( > > I am also making 2.6.25 based kernel RPMs available with the split LRU > patch set, at http://people.redhat.com/riel/splitvm/ > > The most recently posted patches are newer, though... > I tested Rik's previous patch set with my noreclaim/mlock patches over the long weekend on 32GB systems--one ia64 [16cpu x 4 nodes] and one x86_64 [8 core x 4 nodes] on 26-rc2-mm1. A fairly heavy stress load ran for 92-93 hours on each system w/o error. Stats tracked throughout, no leaked pages, ... Since Balbir is starting to look at this, I need to ask about interaction with the memory controller. It is currently unaware of the noreclaim list. I'm not sure what will happen if/when the memory controller tries to reclaim a page that system has moved to the noreclaim list. Something we'll need to address. It's on my list, but I won't get to it for a couple of weeks. Lee