Re: [Qemu-devel] pause and restore function before and after QEMU Live Snapshot

[Yuanzhen Gu]

Thank you very much, Eric!

So do you mean, if I turn on libvirt debugging to trace QMP/agent commands, I can find the pause and thaw functions in the source code, is it right ?

and is there any way that I freeze and thaw outside guest agent via command line?   or profiling tools suggest for freeze and thaw in guest agent? thanks a lot!

Best,

Yuanzhen

On Wed, Jul 16, 2014 at 5:18 PM, Eric Blake <address@hidden> wrote:

On 07/16/2014 03:13 PM, Yuanzhen Gu wrote:
> Hi folks,
>
>
> I am going to make a patch, and need to find the pause and thaw(restore)
> function before and after taking Live QEMU Snapshot respectively.

Libvirt has the ability to do just that, when taking external disk-only
snapshots.  You can turn on libvirt debugging to trace what QMP/agent
commands are sent during the overall snapshot operation.

    So do you mean, if I turn on libvirt debugging to trace QMP/agent commands, I can find the pause and thaw functions in the source code, is it right ?

>
>
>  Basically, I'm using # (qemu) snapshot_blkdev <blockX>
> <snapshot-file><format> taking snapshot,
> http://wiki.qemu.org/Features/Snapshots    my profile tool didn't work when
> giving command inside QMP.
>
>
>  Does anyone know how to find the pause (freeze) and restore(thaw) function
> before and after taking snapshot? Or anyway using snapshot_blkdev command
> outside QEMU console? Thanks a lot in advance!

You have to coordinate multiple commands: freeze to the guest agent,
then snapshot to QMP, then thaw to the guest agent.

--
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org