Messages in this thread | | | Date | Tue, 10 Nov 2009 08:58:27 -0600 | From | Anthony Liguori <> | Subject | Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver |
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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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