Re: [Qemu-devel] Rethinking missed tick catchup

[Eric Blake]

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.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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