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

[Gerd Hoffmann <kraxel@redhat.com>]

   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.

Throughput issues (guess this is the reason to try 8kHz wakeups) need to 
be addressed by modeling data pipes in the usb system instead of playing 
ping-pong between EHCI and USB device emulation for each single usb 
packet, at 8 kHz.

I see the ehci merge just as very first step.  USB 2.0 (and 3.0) support 
in qemu still has a loooooooong way to go.

cheers,
   Gerd