From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:51806) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCAiL-0006EE-4V for qemu-devel@nongnu.org; Thu, 13 Sep 2012 10:48:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TCAiG-0007Iy-C5 for qemu-devel@nongnu.org; Thu, 13 Sep 2012 10:48:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7676) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCAiG-0007Ir-2S for qemu-devel@nongnu.org; Thu, 13 Sep 2012 10:48:16 -0400 Date: Thu, 13 Sep 2012 17:48:11 +0300 From: Gleb Natapov Message-ID: <20120913144811.GL20907@redhat.com> References: <87pq5r5otp.fsf@codemonkey.ws> <20120912151549.GT20907@redhat.com> <87y5kfrtne.fsf@codemonkey.ws> <20120913104940.GA20907@redhat.com> <5051DC20.4090204@redhat.com> <20120913132804.GO7767@redhat.com> <87r4q6xbiy.fsf@codemonkey.ws> <20120913142228.GK20907@redhat.com> <87boha7zyx.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87boha7zyx.fsf@codemonkey.ws> Subject: Re: [Qemu-devel] Rethinking missed tick catchup List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel@nongnu.org, Jan Kiszka , Michael Roth , Luiz Capitulino , Avi Kivity , Paolo Bonzini , Eric Blake On Thu, Sep 13, 2012 at 09:35:18AM -0500, Anthony Liguori wrote: > Gleb Natapov writes: > > > On Thu, Sep 13, 2012 at 09:06:29AM -0500, Anthony Liguori wrote: > >> "Daniel P. Berrange" writes: > >> > >> I think it's better for QEMU to talk to qemu-ga. We can tell when a large > >> period of time has passed in QEMU because we'll accumulate a large > >> number of missed ticks. > >> > > With RTC configured to use vm clock we will not. > > Not for host suspend. For stop and live migration, we stop vm_clock. > But QEMU isn't aware of host suspend so vm_clock cannot be stopped. > Hmm, true. What about hooking into suspend and doing vmstop during suspend. > >> This could happen because of stop, host suspend, live migration to a > >> file, etc. > >> > >> It's much easier for us to call into qemu-ga to do the time correction > >> whenever this event occurs than to try and have libvirt figure out when > >> it's necessary. > > And if guest does not have qemu-ga what is better inject interrupts like > > crazy for next 2 minutes or leave guest with incorrect time? > > Yes, at least that's fixable by the end-user. QEMU consuming 100% CPU > for a prolonged period of time isn't fixable. > You mean yes to "leave guest with incorrect time"? QEMU will still consume 100% of cpu for some time calling qemu_timer callback millions times. timedrift code is not the right level to fix that. -- Gleb.