Re: [Qemu-devel] [PATCH 6/6] usb-tablet: Allow connecting to ehci

[Erik Rull <erik.rull@rdsoftware.de>]

Hi Gerd, hi Hans,

is my assumption correct that if I check out and compile this version from 
GIT master that the usb-tablet device is automatically routed to ehci 
without changing anything else in the qemu call arguments? (And the 
performance enhancement takes place automatically)
If not - what has to be changed to get it working?

Best regards,

Erik



Gerd Hoffmann wrote:
> From: Hans de Goede <hdegoede@redhat.com>
>
> Our ehci code has is capable of significantly lowering the wakeup rate
> for the hcd emulation while the device is idle. It is possible to add
> similar code ot the uhci emulation, but that simply is not there atm,
> and there is no reason why a (virtual) usb-tablet can not be a USB-2 device.
>
> Making usb-hid devices connect to the emulated ehci controller instead
> of the emulated uhci controller on vms which have both lowers the cpuload
> for a fully idle vm from 20% to 2-3% (on my laptop).
>
> An alternative implementation to using a property to select the tablet
> type, would be simply making it a new device type, ie usb-tablet2, but the
> downside of that is that this will require libvirt changes to be available
> through libvirt at all, and then management tools changes to become the
> default for new vms, where as using a property will automatically get
> any pc-1.3 type vms the lower cpuload.
>
> [ kraxel: adapt compat property for post-1.3 merge ]
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>
> tablet compat fixup
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>