Messages in this thread | | | Date | Wed, 28 May 2008 17:19:34 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8) |
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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... >
Rik,
I've run into a case where with the splitvm patches the memory controller immediately OOMs a task in the cgroup on exceeding it's limit. I am going to try and find the root cause for it.
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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