Messages in this thread | | | Date | Tue, 27 May 2008 21:40:25 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8) |
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Lee Schermerhorn wrote: > On Mon, 2008-05-26 at 15:33 -0400, Rik van Riel wrote: >> On Mon, 26 May 2008 23:54:55 +0530 >> Balbir Singh <balbir@linux.vnet.ibm.com> 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.
I have not looked at the patches, but thanks for the heads up. I intend to start looking at it in the spare bandwidth I have.
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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