Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter

[Hans de Goede]

Hi,

On 05/17/2011 05:02 PM, Gerd Hoffmann wrote:
> Hi,
>
> > (And by the way, where are the focused patches for each, especially the
> > last one - nuking the 8kHz code?
>
> It's squashed in, like everything else.
>
> > We know that it worked on linux and
> > that printers, scanners and storage devices worked ok (mostly).
>
> 8 kHz is insane.
>
> I looked closely while trying to make 8 kHz a runtime option instead of a 
> compile time option, then decided to drop it altogether as it is totally 
> pointless. qemu simply can't handle that wakeup rate. It maxed out at ~3 kHz 
> wakeups in my tests. And it burns tons of CPU time.
>
> I also don't see what it would buy us. We can wakeup with 1 kHz rate (maybe 
> even lower), then emulate 8 (or more) microframes each time.

Agreed, I had a hack in my local tree (which I dropped when preparing things 
for Gerd to pull) which lowered the wakeup
rate for UHCI to 200 and then process 5 frames at a time, this worked fine, 
including redirection of real usb 1 devices,
including usb 1 webcam and audio devices. I would actually like to discuss 
making the wakeup rate for
the UHCI controller lower, maybe together with some mechanism for (emulated) 
input devices to force a wake-up
sooner, so as to not add 4 ms of input latency.

Regards,

Hans