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

From: Paul Brook
Subject: Re: [Qemu-devel] High CPU use of -usbdevice tablet (was Re: KVM usability)
Date: Sun, 4 Apr 2010 22:03:05 +0100
User-agent: KMail/1.12.4 (Linux/2.6.33-2-amd64; KDE/4.3.4; x86_64; ; )

> > 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.


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