Re: [RFT] IRQ sharing for assigned devices - method selection

[Avi Kivity <avi@redhat.com>]

On 01/07/2011 09:03 PM, Jan Kiszka wrote:
> >>
> >>  So, if you have a good high-bandwidth test case at hand, I would
> >>  appreciate if you could give this a try and report your findings. Does
> >>  switching from exclusive to shared IRQ mode decrease the throughput or
> >>  increase the host load? Is there a difference to current kvm?
> >
> >  I think any sufficiently high bandwidth device will be using MSI and or
> >  NAPI, so I wouldn't expect we're going to see much change there.
>
> That's also why I'm no longer sure it's worth to worry about irq_disable
> vs. PCI disable. Anyone who cares about performance in a large
> pass-through scenario will try to use MSI-capable hardware anyway (or
> was so far unable to use tons of legacy IRQ driven devices due to IRQ
> conflicts).

PCI disable is probably only ridiculously slow with cf8/cfc config space 
access, and significantly faster (though still slow) with mmconfig.  
Needs to be taken into account as well.

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