From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LqRXs-0003Wc-T8 for qemu-devel@nongnu.org; Sun, 05 Apr 2009 08:33:52 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LqRXo-0003Ut-K2 for qemu-devel@nongnu.org; Sun, 05 Apr 2009 08:33:52 -0400 Received: from [199.232.76.173] (port=40582 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LqRXo-0003Un-F7 for qemu-devel@nongnu.org; Sun, 05 Apr 2009 08:33:48 -0400 Received: from mx2.redhat.com ([66.187.237.31]:45997) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LqRXo-0006K0-1f for qemu-devel@nongnu.org; Sun, 05 Apr 2009 08:33:48 -0400 Message-ID: <49D8A527.3080204@redhat.com> Date: Sun, 05 Apr 2009 15:33:43 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 00/10] xen: pv domain support. References: <1238621982-18333-1-git-send-email-kraxel@redhat.com> <1238706878.5426.1.camel@Quad> <49D6708D.4000601@redhat.com> <88ADCEFD-E057-4264-8447-9E53A661B35D@suse.de> <49D87044.3030406@redhat.com> <803692EA-B562-4D41-A809-7EF552180B8F@suse.de> <49D8980D.1070000@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: qemu-devel , xen-devel@lists.xensource.com, Gerd Hoffmann , Laurent Vivier Alexander Graf wrote: >>> >>> 1) Migration path. If you could already use KVM on a Xen host, you >>> could have Xen PV guests and KVM guests in parallel, easing >>> migration to KVM for customers. >> >> I like this, of course, but we have a path through Xenner. Maybe >> this (kvm-on-xen) path will be easier to take. > > Oh, I thought Xenner was semi on hold? Is it still actively developed? > I thought Gerd's main goal for now was to get qemu-dm into upstream > qemu for now. I understood that Xenner is the next thing on the list. >> With npt/ept pv performance might be higher running under kvm+xenner >> than with software-only Xen by letting the guest kernel access >> pagetables directly. Though Gerd had some issues with 64-bit guests >> IIRC, which is a pity since it's there that the pv performance hit is >> greatest. > > Well that might be true, but I'm not fully convinced yet :-). Either > way with "current" hardware (pre-Nehalem, pre-Barcelona) PV is still > faster. Right, but every day this is becoming less important. > Also, FWIW IO performance on PV Xen is still way superior to KVM. > Please correct me if I stand wrong there. We still have some work some work to do on virtio, but bandwidth should be comparable. And it has nothing to do with pv-vs-fv. -- error compiling committee.c: too many arguments to function