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

[Gonglei (Arei)]

Hi, Gerd.

What's your opinion about this issue? Thanks!



Best regards,
-Gonglei


> -----Original Message-----
> From: Gonglei (Arei)
> Sent: Wednesday, March 26, 2014 4:15 PM
> To: 'Gerd Hoffmann'
> Cc: address@hidden; Huangweidong (C)
> Subject: RE: [PATCH] uhci: Lower uhci timer freq when guest is idle
> 
> > -----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