From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 18 Oct 2005 10:16:42 -0200 From: Marcelo Tosatti Subject: Re: [PATCH 0/2] Page migration via Swap V2: Overview Message-ID: <20051018121642.GA13963@logos.cnet> References: <20051018004932.3191.30603.sendpatchset@schroedinger.engr.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051018004932.3191.30603.sendpatchset@schroedinger.engr.sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: akpm@osdl.org, linux-mm@kvack.org, ak@suse.de, lhms-devel@lists.sourceforge.net List-ID: On Mon, Oct 17, 2005 at 05:49:32PM -0700, Christoph Lameter wrote: > In a NUMA system it is often beneficial to be able to move the memory > in use by a process to different nodes in order to enhance performance. > Currently Linux simply does not support this facility. > > Page migration is also useful for other purposes: > > 1. Memory hotplug. Migrating processes off a memory node that is going > to be disconnected. > > 2. Remapping of bad pages. These could be detected through soft ECC errors > and other mechanisms. > > Work on page migration has been done in the context of the memory hotplug project > (see https://lists.sourceforge.net/lists/listinfo/lhms-devel). Ray Bryant > hs also posted a series of manual page migration patchsets. However, the patches > are complex, and may have impacts on the VM in various places, there are unresolved > issues regarding memory placement during direct migration and thus the functionality > may not be available for some time. Is there a description of the unresolved issues you mention somewhere? Having a duplicate implementation is somewhat disappointing - why not fix the problems with real page migration? > This patchset was done in awareness of the work done there and realizes page > migration via swap. Pages are not directly moved to their target > location but simply swapped out. If the application touches the page later then > a new page is allocated in the desired location. > > The advantage of page based swapping is that the necessary changes to the kernel > are minimal. With a fully functional but minimal page migration capability we > will be able to enhance low level code and higher level APIs at the same time. > This will hopefully decrease the time needed to get the code for direct page > migration working and into the kernel trees. Why would that be the case? -- 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