From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17900.60167.418766.280544@cargo.ozlabs.ibm.com> Date: Tue, 6 Mar 2007 15:16:07 +1100 From: Paul Mackerras Subject: Re: The performance and behaviour of the anti-fragmentation related patches In-Reply-To: References: <20070301101249.GA29351@skynet.ie> <20070301160915.6da876c5.akpm@linux-foundation.org> <45E7835A.8000908@in.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Balbir Singh , Andrew Morton , Mel Gorman , npiggin@suse.de, clameter@engr.sgi.com, mingo@elte.hu, jschopp@austin.ibm.com, arjan@infradead.org, mbligh@mbligh.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Linus Torvalds writes: > The point being that in the guests, hotunplug is almost useless (for > bigger ranges), and we're much better off just telling the virtualization > hosts on a per-page level whether we care about a page or not, than to > worry about fragmentation. We don't have that luxury on IBM System p machines, where the hypervisor manages memory in much larger units than a page. Typically the size of memory block that the hypervisor uses to manage memory is 16MB or more -- which makes sense from the point of view that if the hypervisor had to manage individual pages, it would end up adding a lot more overhead than it does. Paul. -- 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