Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to theballoon driver

[Anthony Liguori]

Avi Kivity wrote:
> On 11/10/2009 04:36 PM, Anthony Liguori wrote:
> > > A stats vq might solve this more cleanly?
> >
> > actual and target are both really just stats.  Had we implemented 
> > those with a vq, I'd be inclined to agree with you but since they're 
> > implemented in the config space, it seems natural to extend the 
> > config space with other stats.
>
> There is in fact a difference; actual and target are very rarely 
> updated, while the stats are updated very often.  Using a vq means a 
> constant number of exits per batch instead of one exit per statistic.  
> If the vq is host-driven, it also allows the host to control the 
> update frequency dynamically (i.e. stop polling when there is no 
> memory pressure).

I'm not terribly opposed to using a vq for this.  I would expect the 
stat update interval to be rather long (10s probably) but a vq works 
just as well.

--
Regards,

Anthony Liguori

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