From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 0/5] Swapless page migration V2: Overview From: Lee Schermerhorn In-Reply-To: References: <20060413235406.15398.42233.sendpatchset@schroedinger.engr.sgi.com> <20060413170853.0757af41.akpm@osdl.org> Content-Type: text/plain Date: Fri, 14 Apr 2006 10:14:43 -0400 Message-Id: <1145024083.5211.8.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andrew Morton , hugh@veritas.com, linux-kernel , linux-mm@kvack.org, taka@valinux.co.jp, marcelo.tosatti@cyclades.com, kamezawa.hiroyu@jp.fujitsu.com List-ID: 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org