Re: [fedora-virt] kvm "tablet" device burning cpu cycles
On 12/07/2011 10:20 AM, Daniel P. Berrange wrote:
On Tue, Dec 06, 2011 at 04:33:43PM -0700, Eric Blake wrote:
> [redirecting to the fedora virt list]
>
> On 12/06/2011 03:36 PM, Dennis Jacobfeuerborn wrote:
>> Hi,
>> I noticed that when you install a virtual system with virt-manager it
>> always installs a tablet device by default.
>> The problem is that this device consumes 10% of cpu resources of the host
>> according to "top" which should probably be considered a bug.
>
> The poor behavior of a tablet device should be raised against the qemu
> team, to see if it can be made more efficient.
This is a long standing problem, but it shouldn't be taking anywhree
near 10% of CPU.
If using SPICE with the SPICE guest agent installed there is a parvirt
mouse available, avoiding the need for the USB tablet.
I did some more testing today and also installed a Fedora 16 VM. Here I
don't see the big overhead and an idle guest is also idle on the host so it
seems this is an issue with the driver on the guest side. While I tried
SPICE I didn't play with the guest agent yet. When using SPICE I switch the
display device from VNC to SPICE and let virt-manager add an additional
channel device (it asks me if it should do so). Is it sufficient to install
spice-vdagent in the guest to make use of the client mouse mode?
>
>> What is worse is that removing the tablet also means no mouse pointer
>> showing up in a centos 6 guest which means you are pretty much forced to
>> use the tablet device.
That shouldn't be the case. If you boot the guest with no USB tablet
present, X should auto-detect the PS2 mouse and use that. You would
only have trouble if either hot-unpluging the USB tablet, or if you
have hardcoded its use in /etc/X11/xorg.conf
I experimented a bit and I only see this:
1) when I use "qxl" as video model
2) when I keep the graphical console open in virt-manager after booting
When I close the window and reopen it again the mouse pointer is there and
when I use "cirrus" as model the problem doesn't happen at all.
Regards,
Dennis