From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: paravirtual drivers? Date: Fri, 13 Apr 2007 17:27:32 +0200 Message-ID: <461FA164.1090703@wpkg.org> References: <461DFE2E.3020805@wpkg.org> <461E3C65.5080207@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Anthony Liguori Return-path: In-Reply-To: <461E3C65.5080207-rdkfGonbjUSkNkDKm+mE6A@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 Anthony Liguori schrieb: (...) > 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). How does one enable SCSI emulation? "qemu-system-x86_64 -h" gives no hints about SCSI (at least in KVM-18); similarly, I didn't find anything in the archive or in the wiki. Certainly, there is a kvm-18/qemu/hw/scsi-disk.c file, so it's like the feature is there... Is it possible to boot a guest from a "SCSI-emulated" device? -- Tomasz Chmielewski http://wpkg.org ------------------------------------------------------------------------- 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