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

[Yuanzhen Gu]

Hi Eric,

Thank you very much for your suggestion, it do help.

I enabled libvirt debugging, and saw the log file under /var/log/libvirt/libvirtd.log,

for example, I saw
2014-07-17 20:06:55.992+0000: 4391: debug : qemuProcessHandleResume:575 : Transitioned guest ubuntu out of paused into resumed state

my further question is, is there any way to locate the function call for pause and resume from source code, based on the log info? thanks!

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.

>
>
>  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