From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 30 Jul 2008 10:35:52 +0100 From: Andy Whitcroft Subject: Re: sparcemem or discontig? Message-ID: <20080730093552.GD1369@brain> References: <488F5D5F.9010006@sciatl.com> <1217368281.13228.72.camel@nimitz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1217368281.13228.72.camel@nimitz> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave Hansen Cc: C Michael Sundius , linux-mm@kvack.org, msundius@sundius.com List-ID: On Tue, Jul 29, 2008 at 02:51:21PM -0700, Dave Hansen wrote: > On Tue, 2008-07-29 at 11:11 -0700, C Michael Sundius wrote: > > > > My understanding is that SPARCEMEM is the way of the future, and since > > I don't really have a NUMA machine, maybe sparcemem is more appropriate, > > yes? On the other hand I can't find much info about how it works or how > > to add support for it on an architecture that has here-to-fore not > > supported that option. > > > > Is there anywhere that there is a paper or rfp that describes how the > > spacemem (or discontig) features work (and/or the differences between > > then)? > > I think you're talking about sparsemem. :) > > My opinion is that NUMA and DISCONTIG are too intertwined to be useful > apart from the other. I use sparsemem on my non-NUMA 2 CPU laptop since > it has a 1GB hole. It is *possible* to use DISCONTIG without NUMA, and > I'm sure people use it this way, but I just personally think it is a bit > of a pain. > > Basically, to add sparsemem support for an architecture, you need a > header like these: > > dave@nimitz:~/lse/linux/2.5/linux-2.6.git$ find | grep sparse | xargs > grep -c '^.*$' > ./include/asm-powerpc/sparsemem.h:32 > ./include/asm-x86/sparsemem.h:34 > ./include/asm-sh/sparsemem.h:16 > ./include/asm-mips/sparsemem.h:14 > ./include/asm-ia64/sparsemem.h:20 > ./include/asm-s390/sparsemem.h:18 > ./include/asm-arm/sparsemem.h:10 > > These are generally pretty darn small (the largest is 34 lines). You > also need to tweak some things in your per-arch Kconfig. ARM looks like > a pretty simple use of sparsemem. You might want to start with what > they've done. We tried really, really hard to make it easy to add to > new architectures. > > Feel free to cc me and Andy (cc'd) on the patches that you come up with. > I'd be happy to sanity check them for you. If *you* want to document > the process for the next guy, I'm sure we'd be able to find some spot in > Documentation/ so the next guy has an easier time. :) Always interested in new users of sparsemem. Cc me :). -apw -- 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