Re: [Qemu-devel] High CPU use of -usbdevice tablet (was Re: KVM usability)

Paul Brook
2010-04-04T21:03:10Z

> > The USB HID devices implement the SET_IDLE command, so the polling
> > interval will have no real effect on performance.
>
> On a Linux guest (F12), I see 125 USB interrupts per second with no
> mouse movement, so something is broken (on the guest or host).

Turns out to be a a bug in the UHCI emulation. It should only raise an
interrupt if the transfer actually completes (i.e. the active bit is set to
zero). Fixed by 5bd2c0d7.

I was testing with an OHCI controller, which does not have this bug.

Paul