On 02/02/2012 11:16 PM, Nikola Ciprich wrote:
> Hello everybody,
>
> I'm a bit confused regarding windows guests and PIO.. some time ago, I was 
> trying
> to find out, why one of my windows guests was running terribly slow.
> After checking the trace-cmd output, Avi stated that windows were using PIO 
> instead
> of DMA, after changing that, windows indeed got a lot faster. I didn't check  
> traces
>  after that, but I'm now testing host with two windows 2003 guests, and 
> checking the
> trac-cmd output, I see a lot of kvm_pio calls.
> While windows don't seem to be running particularly slow, they're not 
> especially
> fast either, and I'm wandering whether this could be related. But checking IDE
> bus in guests, they seem to be using DMA which confuses me...
> so my questions is, what are the kvm_pio operations I see in traces, and how 
> can
> I tell what is OK and what is wrong, regarding disks DMA/PIO?
> If somebody could shed some light on this for me, I'd be very grateful...

Not all PIO operations are DMA.  Provide a trace and we can look.

-- 
error compiling committee.c: too many arguments to function

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