From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: RE: yanked share, round 2 Date: Sat, 14 Jan 2006 14:34:11 +1100 Message-ID: <1137209651.22193.20.camel@localhost.localdomain> References: <44BDAFB888F59F408FAE3CC35AB4704102C66D7D@orsmsx409> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <44BDAFB888F59F408FAE3CC35AB4704102C66D7D@orsmsx409> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "King, Steven R" Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On Fri, 2006-01-13 at 15:02 -0800, King, Steven R wrote: > How about combining both ideas: In order to map N pages from Xen's > share pool, a DomU must provide N pages back to the pool. When a DomU > unmaps (or crashes), it gets N pages back. OK, early last year I hacked up a prototype implementation, which I'm now bringing up-to-date with the modern Xen code, and some new simplifications I'm toying with. It's certainly a simple model to never have domains share their own pages, and the hypervisor provide a DMA-like mechanism between domains to allow bulk transfer. This would then page-swap if appropriate. It makes drivers nice and simple, and avoids problems with starvation et. al. Earlier results suggested it is competitive on benchmarks, too, but it needs real testing under various loads. Noone here should be surprised though, that I regard the simplicity of the scheme as the most important factor. Cheers! Rusty. -- ccontrol: http://ozlabs.org/~rusty/ccontrol