Hi Kashyap,

Here I want to test and see how much I/O performance could be improved by virtio-blk data plane feature.

Yes, this is a dirty way to enable it :-), You mentioned using newer libvirt, is there parameter similar "x-data-plane=on" in new version libvirt?

Please let know me you if you have better solution.

Regards,

CY.

On Mon, Apr 20, 2015 at 10:51 PM, Kashyap Chamarthy <kchamart@redhat.com> wrote:

On Mon, Apr 20, 2015 at 10:37:13PM +0800, Chengyuan Li wrote:
> Hi,
>
> I tried to enable virtio-blk data plane feature for VMs in my openstack
> environment, the hypervisor is ubuntu 14.04, libvirt 1.2.2

[I haven't tested the virtio-blk data plane myself.]

This libvirt version seems a little old (from March 2014), you might
want to move to a bit newer.

> and QEMU 2.0.
> As nova doesn't support that parameter yet, I did belows
>
> 1. nova boot a VM with raw disk image.
> 2. nova stop the VM.
> 3. run "virsh edit <instance-id>" on the hyprvisor node, and adding below
> into instance xml just before </domain>.

You're modifying the guest definition behind Nova's back, so you get to
keep all the pieces if something breaks. :-)

> However, the <qemu:commandline> part is ignored and not saved after closing
> virsh edit, seems that libvirt rejected these changes. Is there any XML
> syntax error here? Or libvirt doesn't support <qemu:commandline> tag?
>
> <qemu:commandline>
> <qemu:arg value='-set'/>
> <qemu:arg value='device.drive-virtio-disk0.x-data-plane=on'/>
> </qemu:commandline>

--
/kashyap