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Re: [Qemu-devel] Rethinking missed tick catchup
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] Rethinking missed tick catchup |
Date: |
Thu, 13 Sep 2012 09:35:18 -0500 |
User-agent: |
Notmuch/0.13.2+93~ged93d79 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Gleb Natapov <address@hidden> writes:
> On Thu, Sep 13, 2012 at 09:06:29AM -0500, Anthony Liguori wrote:
>> "Daniel P. Berrange" <address@hidden> 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.
>> 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.
Regards,
Anthony Liguori
>
>>
>> We know exactly when it's necessary, libvirt would need to guess.
>>
>> Yes, we could generate a QMP event when a large skew was dedicated, but
>> I think this could happen often enough that it would be problematic.
>> Since QEMU is already implementing policy doing timer catchup in the
>> first place, I think we probably should own time catchup policy entirely.
>>
>> Regards,
>>
>> Anthony Liguori
>>
>> >
>> > Regards,
>> > Daniel
>> > --
>> > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/
>> > :|
>> > |: http://libvirt.org -o- http://virt-manager.org
>> > :|
>> > |: http://autobuild.org -o- http://search.cpan.org/~danberr/
>> > :|
>> > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc
>> > :|
>
> --
> Gleb.
- Re: [Qemu-devel] Rethinking missed tick catchup, (continued)
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/16
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/16
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/19
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/19
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] Rethinking missed tick catchup,
Anthony Liguori <=
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Anthony Liguori, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Avi Kivity, 2012/09/13
- Re: [Qemu-devel] Rethinking missed tick catchup, Gleb Natapov, 2012/09/13
Re: [Qemu-devel] Rethinking missed tick catchup, Stefan Weil, 2012/09/12