Re: kvm "tablet" device burning cpu cycles

[Eric Blake]

[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.

>  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. 
Meanwhile, sufficiently new qemu provides USB device emulation, which is
more efficient than the PCI tablet emulation; although it is not as
apparent whether typical guests support that device driver in their
default install (one of the reasons we default to the older tablet
emulation is that it is likely to have a driver pre-installed on most
guest OSs).  The idea of swapping the default to a USB pointer should be
raised against virt-manager and/or python-virtinst, when installing a
new-enough guest OS with new enough qemu support, while continuing to
provide the compatible fallback of the tablet for older setups.

-- 
Eric Blake   eblake(a)redhat.com    [phone]
Libvirt virtualization library http://libvirt.org