From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: Paravirt KVM capabilities Date: Thu, 11 Jan 2007 14:21:36 +1100 Message-ID: <1168485696.19646.250.camel@localhost.localdomain> References: <45A3A642.1030604@qumranet.com> <1168384852.19646.161.camel@localhost.localdomain> <20070110094750.GA934@elte.hu> <45A4BB74.9010102@redhat.com> <20070110101839.GA6444@elte.hu> <45A4C345.5050404@qumranet.com> <20070110105202.GA13412@elte.hu> <1168476120.19646.209.camel@localhost.localdomain> <20070111004957.GA3279@elte.hu> <1168483188.19646.241.camel@localhost.localdomain> <20070111025130.GB21368@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: To: Ingo Molnar In-Reply-To: <20070111025130.GB21368-X9Un+BFzKDI@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 On Thu, 2007-01-11 at 03:51 +0100, Ingo Molnar wrote: > * Rusty Russell wrote: > > > > > Err no, this isn't true. See Documentation/lhype.txt or various blog > > > > entries on the subject 8) Both Xen and lhype get native syscall speeds > > > > (within measurement error). > > > > > > i was talking about 64-bit. (we dont really design for 32-bit anymore.) > [...] > > > > > I know that lhype uses Xen's ring 1 trick, but that's a 32-bit-only > > > thing. Also, can SYSENTER trap from guest userspace ring 3 into guest > > > kernelspace ring 1 on lhype? > > > > As I understand it, sysenter has to go to ring 0, and the reflection > > cost is way greater than the saving. > > so how can both "Xen and lhype get native syscall speeds (within > measurement error)", if it cannot use SYSENTER (it has to use int > $0x80), while a HVM kernel can? Sorry, my mistake. I was measuring with a statically linked binary, which didn't use SYSENTER even when available 8( I've fixed virtbench now, and reflects this correctly. "syscalls almost as fast as poorly-implemented native syscalls"? Rusty. ------------------------------------------------------------------------- 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