Messages in this thread | | | Subject | Re: [PATCH 0/5] Swapless page migration V2: Overview | From | Lee Schermerhorn <> | Date | Fri, 14 Apr 2006 10:14:43 -0400 |
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On Thu, 2006-04-13 at 17:27 -0700, Christoph Lameter wrote: > On Thu, 13 Apr 2006, Andrew Morton wrote: > > > > Currently page migration is depending on the ability to assign swap entries > > > to pages. However, those entries will only be to identify anonymous pages. > > > Page migration will not work without swap although swap space is never > > > really used. > > > > That strikes me as a fairly minor limitation? > > Some people want never ever to use swap. Systems that have no swap defined > will currently not be able to migrate pages. Its kind of difficult to > comprehend that you need to have swap for migration, but then its not > going to be used. > > > > The patchset will allow later patches to enable migration of VM_LOCKED vmas, > > > the ability to exempt vmas from page migration, and allow the implementation > > > of a another userland migration API for handling batches of pages. > > > > These seem like more important justifications. Would you agree with that > > judgement? > > The swapless thing is the most important for us because many of our > customers do not have swap setup. Then follow the above > features then the efficiency consideration.
I do have the migration cache working against 17-rc1-mm2. I tried to address Christoph's prior comments. I just haven't posted yet, as I was working the migrate-on-fault/auto-migration series. If one accepts lazy migration, then the migration cache becomes more important because anon pages can/will stay in the swap cache until the page is finally freed [or maybe gets evicted from the swap cache?].
The migration cache still uses the swap infrastructure, so must configure SWAP. But, no swap devices need be configured. Should address that particular concern w/o major surgery to the existing migration code.
Let me know if I should repost the patches. Meanwhile, they're available at: http://free.linux.hp.com/~lts/Patches/PageMigration/ [which seems temporarily, I hope, unavailable]. Look for the migcache tarball.
Lee
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