Re: [Qemu-devel] Rethinking missed tick catchup

[Gleb Natapov <gleb@redhat.com>]

On Thu, Sep 13, 2012 at 07:14:08AM -0600, Eric Blake wrote:
> On 09/13/2012 04:49 AM, Gleb Natapov wrote:
> >> They do if you hibernate your laptop.
> >>
> > AFAIK libvirt migrates vm into a file on hibernate. It is better to move to S3
> > (using qemu-ga) instead and migrate to file only if s3 fails.
> 
> On host hibernate, libvirt currently does nothing to the guest.  When
> the host resumes, the guests see a large gap in execution.
> 
> Libvirt would need a hook into host hibernation, to have enough time to
> tell the guests to go into S3 prior to allowing the host to go into S3.
> 
> On host reboot, libvirt currently saves guests to disk using migrate to
> file.  The ideal solution would be to first tell the guest to go into S3
> before migrating to file, but the migration to file STILL must occur,
> because the host is about to reboot and S3 is not persistent.  S3 is a
> better solution than S4, in that S4 requires the guest to have enough
> memory (and if it doesn't cooperate, data is lost), but with S3, even if
> the guest doesn't cooperate, we can still fall back to migration to file
> with the guest only losing time, but not data.
> 
Correct, after S3 libvirt needs to migrate to file. So my AFAIK was
incorrect. Is it possible to hook into host hibernation?

--
			Gleb.