Re: [Qemu-devel] [PATCH] uhci: Lower uhci timer freq when guest is idle

[Gonglei (Arei)]

> -----Original Message-----
> From: Gerd Hoffmann [mailto:address@hidden
> Sent: Wednesday, March 26, 2014 3:59 PM
> To: Gonglei (Arei)
> Cc: address@hidden; Huangweidong (C)
> Subject: Re: [PATCH] uhci: Lower uhci timer freq when guest is idle
> 
> On Mi, 2014-03-26 at 11:57 +0800, address@hidden wrote:
> > From: Gonglei <address@hidden>
> >
> > UHCI emulation polls the device at a freq of 1000HZ, which consumes
> > 12~13% CPU even though a Windows guest is completely idle when the guest
> > was configed usb1.1 tablet devcie. This solution counts accumulated NAK
> > packets. when it reaches to 64, then the guest is supposed to be idle
> > and the freq is lowered to 10HZ.
> >
> > This patch has been tested on Win7/WinXP/Win2008 guests, that reduces
> > the CPU consume from 12~13% to 6~7%.
> 
> Which qemu version did you test with?  
I tested it with the latest qemu upstream mainline.

BTW, I encountered the windows guest boot up failed problem which I have 
reported.

>With any 2.0 release candidate
> windows guests should suspend the usb-tablet.  And possibly stop all usb
> polling done by the uhci controller in case the tables is the only
> device connected.
Yeah, if there is no device attached uhci controller, I think we can reduce the 
freq,
otherwise the CPU consume is waste.

Best regards,
-Gonglei