From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46952) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ScE3r-0006oY-Hc for qemu-devel@nongnu.org; Wed, 06 Jun 2012 07:06:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ScE3l-0005F7-9X for qemu-devel@nongnu.org; Wed, 06 Jun 2012 07:05:59 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:37142) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ScE3l-0005Ev-3L for qemu-devel@nongnu.org; Wed, 06 Jun 2012 07:05:53 -0400 Received: by pbbro12 with SMTP id ro12so9563133pbb.4 for ; Wed, 06 Jun 2012 04:05:51 -0700 (PDT) Message-ID: <4FCF3988.5020107@codemonkey.ws> Date: Wed, 06 Jun 2012 19:05:44 +0800 From: Anthony Liguori MIME-Version: 1.0 References: <1338875386-21051-1-git-send-email-yhalperi@redhat.com> <4FCDF49E.6090006@codemonkey.ws> <4FCE067E.5030903@redhat.com> <4FCF1E70.3030703@redhat.com> <4FCF214D.8060001@codemonkey.ws> <20120606105447.GF16572@garlic.tlv.redhat.com> In-Reply-To: <20120606105447.GF16572@garlic.tlv.redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 0/5] asynchronous migration state change handlers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yonit Halperin , Gerd Hoffmann , aliguori@us.ibm.com, qemu-devel@nongnu.org On 06/06/2012 06:54 PM, Alon Levy wrote: > On Wed, Jun 06, 2012 at 05:22:21PM +0800, Anthony Liguori wrote: >> On 06/06/2012 05:10 PM, Yonit Halperin wrote: >> Spice client migration has nothing to do with guest migration. Trying to > > I don't understand this POV. If it were a VNC connection instead of a > Spice one would it make a difference? Of course, I would say yes if it was VNC. Because the only possibly way I could disagree with something Spice related is because I'm biased against it. Give me the benefit of the doubt at least. More importantly, try to stop and think about what I'm saying before you assume the anti-Spice brigade is coming in to rain on your parade. > If there is an active VNC client > then it is there as a result of a user choosing to use it, so it should > be treated as part of the user experience and not as something external. > The experience from ignoring this and choosing to treat the remote > console as an unrelated part is bound to be suboptimal. Guest migration affects correctness! If the Spice client is slow (even due to network lag) in responding to your flush message, you will disrupt the guest and potentially drop network connections and/or cause lockup detectors to trigger. Migrating the Spice client is a UI feature. It has absolutely no affect no the workloads that are running in the guest. Impacting migration *correctness* in order to support a UI feature is unacceptable especially when there are ways to achieve the same results without having any impact on correctness. We have had a simple rule with migration in QEMU. Nothing gets to impact downtime with migration. No device gets magic hooks or anything like that. Go read the TPM threads if you want to see another example of this. Regards, Anthony Liguori