Re: just an observation about USB

[Paolo Bonzini <pbonzini@redhat.com>]

On 14/10/2015 21:39, Eric S. Johansson wrote:
>  update from the  NaturallySpeaking in a VM project.
> 
>  don't remember what I told you before but, yes I can now send keystroke
> events generated by speech recognition in the Windows guest into the
> Linux input queue. I can also extract information from the Linux side,
> and have it modify the grammar on the Windows side. The result of 
> activating that grammar  is that I can execute code on either side  in
> response to speech recognition commands. it's fragile as all hell but
> I'm the only one using it so far. :-)

That's awesome!  What was the problem?

> Latency is a bit longer than I like. USB and network connections break
> every time I come out of suspend part at least I don't have to use
> Windows all the time.
> 
>  One thing is puzzling though. Windows, in idle, consume something like
> 15 to 20% CPU according to top. I turn on NaturallySpeaking, the
> utilization climbs to him roughly 30 to 40%. I turn on the microphone
> and utilization jumps up to 80-110%.  In other words, it takes up a
> whole core.

USB is really expensive because it's all done through polling.  Do that
in hardware, and your computer is a bit hotter; do that in software
(that's what VMs do) and your computer doubles as a frying pan.

If you have USB3 drivers in Windows, you can try using a USB3
controller.  But it's probably going to waste a lot of processing power
too, because USB audio uses a lot of small packets, making it basically
the worst case.

Paolo