From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: Re-design the architecture of Xen Date: Tue, 24 May 2011 10:24:18 -0400 Message-ID: <20110524142418.GF10926@dumpdata.com> References: <1306150777633-4418793.post@n5.nabble.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <1306150777633-4418793.post@n5.nabble.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: henanwxr Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Mon, May 23, 2011 at 04:39:37AM -0700, henanwxr wrote: > http://xen.1045712.n5.nabble.com/file/n4418793/6.bmp We have researched > virtualization for several years, with the reference of Xen, we have de= sign > a new VMM architecture called Cooperative model VMM=EF=BC=8Cand have im= plemented a > prototype system. > We present its principle and part of details here. >=20 >=20 > Part1 motivation >=20 >=20 > B. Domain0 problems > Domain0 has several features:=20 Features or disadvantages? > =EF=81=AC Running modified operating system.=20 What does 'modified' mean? > =EF=81=AC Running on processor with privilege level 1=20 > =EF=81=AC Running in a form of virtual machine > =EF=81=AC Single system managing hardware Right, but that does not have to be the case.. > These features of Domain0 bring the following issues: > 1) tight coupling > >From a performance point of view, the coordination of Domain0 and VMM = (such > as: hypercall), event channel and IO ring can improve virtualization > efficiency, which, however, requires more modification of guest operati= ng > system. Also, VMM needs to provide the corresponding interface. The tig= ht I am still lost what you mean by 'more modification' ? > coupling formed between Domain0 and VMM results that VMM implementation= s > must take third-party system characteristics into account, design is la= ck of such as? > independence and flexibility.=20 > 2) privilege level switch > Domain0 is running on the processor with privilege level 1, context swi= tch Not neccesarily. > from the VMM to Domain0 will trigger processor privilege level switches= . If > operation of this type is more frequent (such as IO request operation f= or a > virtual machine), it will result in larger processor overhead, impactin= g the I think you are referring to sysctl. That can be eliminated by having a 32-bit OS. > performance of virtual machine. > 3) overhead of management > Operating as a virtual machine, Domain0 needs VMM to provide appropriat= e > virtual machine managing interface, such as: creation, resource allocat= ion, > scheduling, and destruction, etc., the resulting administrative overhea= d. > Domain0, as the main provider of device access, its function is relativ= ely > fixed and administrative overhead should be avoided to reduce the burde= n on > VMM.=20 So.. remove the administration from Dom0. But why? What are the=20 disadvantages of doing this in Dom0? > 4) scheduling Delay=20 > Domain0 and other virtual machines take part in VMM scheduling, due to > scheduling rotation characteristics, Domain0 can not guarantee timely > delivery of services, which results a number of related issues. First, = after > VMM receive IO request from virtual machine, Domain0 could not be > immediately notice, only asynchronous notice way which similar to soft > interrupt can be used, and Domian0 will test and process it when runnin= g. > Second, device model of Domain0 is provided by Qemu, which is running a= s a > process of guest OS. When Domain0 is not running, Qemu can not handle I= O > requests from virtual machine, resulting in delay of processing IO requ= ests. If you are using legacy hardware in QEMU - sure. But nowadays every Linux distro has drivers to use the PV drivers which omit QEMU. Also they are available under Windows (even WHQL certified ones). Furtheremore the stub-domains eliminate this. Anyhow, I stopped reading after this..