From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: paravirtual drivers? Date: Thu, 12 Apr 2007 09:04:21 -0500 Message-ID: <461E3C65.5080207@codemonkey.ws> References: <461DFE2E.3020805@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Tomasz Chmielewski Return-path: In-Reply-To: <461DFE2E.3020805-Nem3ZqsbT/g@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Tomasz Chmielewski wrote: > As I understand, fully virtualized KVM guests (on Intel VT or AMD-V) can > perform with near native speeds only when it comes to the CPU - because > the things like network or block device are basically emulated. > > > Among many changes, KVM in 2.6.21 has "Initial paravirtualization > support, which has much faster performance", and is based on KVM-15. > > > At least two PV drivers are needed: > - network > - block device > I don't believe a PV block driver is actually necessary. Disk devices are actually quite slow (unless you have a large array). With a few small changes (bump MMU cache up to 1024 and actually enable the aio subsystem), SCSI emulation does as well as Xen's PV block driver (about 210 mb/sec whereas native is around 250 mb/sec). There's a lot of room to optimize the SCSI emulation too since there are a number of copies in that path. The SCSI emulation is a lot like what one would design in a PV driver. It supports multiple outstanding requests and doesn't require a whole lot of exits to submit a request (it uses scripts). Regards, Anthony Liguori > > What is the state of these PV drivers now? Is it usable on Linux now? > > Are Windows PV drivers planned, too? If yes, who is going to take the > lead here (Qumranet, community, not decided yet etc.?). > > > > ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV