From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: A testing for KVM Date: Wed, 13 Jun 2007 13:58:36 +0300 Message-ID: <466FCDDC.3060400@qumranet.com> References: <10EA09EFD8728347A513008B6B0DA77A0198452F@pdsmsx411.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: "Dong, Eddie" Return-path: In-Reply-To: <10EA09EFD8728347A513008B6B0DA77A0198452F-wq7ZOvIWXbNpB2pF5aRoyrfspsVTdybXVpNB7YpNyf8@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 Dong, Eddie wrote: >> We found that using an hrtimer enabled host with >> CONFIG_HZ=1000 improves >> things. However I don't think that it's as accurate as 7 >> seconds in 20 >> minutes (that's better than 1% accuracy), so probably more work is >> needed in qemu to correct time drift. >> >> > Time virtualization for HVM is always a headache, no simple way can > provide > accurate source :-( > Per current KVM time virtualization policy, drop of jiffies or redundant > jiffies > may happen frequently. There is some code in kvm's qemu to track dropped ticks and reinject them. The code is disabled because it doesn't work well. > BTW, even in Xen, we are not satisfied with the > time > virtualization especially for TSC timer. > I don't think tsc can be virtualized well. It's too fast. > Some modification in guest Linux side is really needed, maybe somebody > can bring this issue to virtualization mini summit? > Linux already has support for paravirtualized time, we just need to use it. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/