Messages in this thread | | | Date | Thu, 29 May 2008 14:47:43 +0200 | From | Carsten Otte <> | Subject | Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8) |
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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. > > Against 2.6.26-rc2-mm1 > > This patch series improves VM scalability by: > > 1) putting filesystem backed, swap backed and non-reclaimable pages > onto their own LRUs, so the system only scans the pages that it > can/should evict from memory > > 2) switching to SEQ replacement for the anonymous LRUs, so the > number of pages that need to be scanned when the system > starts swapping is bound to a reasonable number > > 3) keeping non-reclaimable pages off the LRU completely, so the > VM does not waste CPU time scanning them. Currently only > ramfs and SHM_LOCKED pages are kept on the noreclaim list, > mlock()ed VMAs will be added later I think I've run into #2 with kvm on s390 lately. I've tried a large setup with 200 guests running WebSphere. The guest memory is stored in anonymous pages, all guests are started up from a script so everything is dirty initially. I use 200gig swap with 45 gig main memory for the scenario. Everything runs perfect except when vmscan is triggered for the first time: it starts to writeback, and the whole system freezes until it has paged out the 15gig in the inactive list. From there on, everything runs smooth again with a constant swap rate. I'd like to try your patchset to see how that behave in this scenario. Do you have a version that applies against current git, 2.6.26-rc3 or similar?
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