From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM architecture docs Date: Tue, 04 Mar 2008 17:08:49 +0200 Message-ID: <47CD6601.5050907@qumranet.com> References: <47CC1E91.7050207@sintesi80.it> <47CC421F.5070003@qumranet.com> <47CD0769.6020104@qumranet.com> <47CD14B6.9010908@qumranet.com> <90eb1dc70803040617j3590c52bj3d77a327143bda5f@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net To: Javier Guerra Return-path: In-Reply-To: <90eb1dc70803040617j3590c52bj3d77a327143bda5f@mail.gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Javier Guerra wrote: > On 3/4/08, Avi Kivity wrote: > >> apply to kvm guests. With mmu notifiers, the trend will grow even stronger. >> > > could you (or anybody) elaborate on that? the mmu-related threads show > lots of progress, but it's way (way) out of my league. > > AFAICT, it's about the infrastructure to later write drivers (virtio?) > to DMA-heavy hardware (IB, RDMA, etc). am i wrong? or is it > something more complete (like a ready to use driver)? > > mmu notifiers provide a way for the core Linux memory management code to propagate changes in how Linux views a process' memory map to external memory management units that are also interested in that memory map. These changes include things like swapping, page migration, changes to memory protection, defragmentation, and copy-on-write. In this context, kvm appears as a dma capable memory controller, like RDMA NICs or GPUs. For kvm, this is important as it allows all those features to be used transparently with guests. - swapping allows you to overcommit memory - page migration allows optimization of memory placement within the host in response to changing workloads - defragmentation will allow (if/when it is merged into Linux) more widespread use of large pages, which improve performance - copy-on-write allows sharing identical pages of memory among guests, increasing guest density -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/