Re: KVM usability

Avi Kivity
2010-03-07T11:36:40Z

On 03/02/2010 11:34 AM, Jernej Simončič wrote:
> On Tuesday, March 2, 2010, 9:21:18, Chris Webb wrote:
>
>
>> I remember about a year ago, someone asserting on the list that -usbdevice
>> tablet was very CPU intensive even when not in use, and should be avoided if
>> mouse support wasn't needed, e.g. on non-graphical VMs. Was that actually a
>> significant hit, and is it still true today?
>>
> It would appear that this is still the case, at least on slower hosts
> - on Atom Z530 (1,6GHz), the XP VM uses ~30% CPU when idle with
> -usbdevice tablet, but only ~4% without it. However, on a faster host
> (Core2 Quad 2,66GHz), there's practically no difference (Vista x64 VM
> uses ~1% CPU when idle regardless of -usbdevice tablet).
>

Looks like the tablet is set to 100 Hz polling rate. We may be able to
get away with 30 Hz or even less (ep_bInterval, in ms, in hw/usb-wacom.c).

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