On Wed, 11 Nov 2009 01:06:14 am Anthony Liguori wrote: > Rusty Russell wrote: > > On Tue, 10 Nov 2009 03:02:06 am Adam Litke wrote: > > > >> A simpler approach is to collect memory statistics in the virtio > >> balloon driver and communicate them to the host via the device config > >> space. > >> > > > > There are two issues I see with this. First, there's an atomicity problem > > since you can't tell when the stats are consistent. > > Actually, config writes always require notification from the guest to > the host. This means the host knows when they config space is changed > so atomicity isn't a problem.
I think you missed my point: the stats are inter-related, so they should be served together. > In fact, if it were a problem, then the balloon driver would be > fundamentally broken because target and actual are stored in the config > space. No, one is written by the host, the other the guest. Still works. > If you recall, we had this discussion originally wrt the balloon driver :-) And I never did get around to the lguest implementation, which would have seen if this really is an issue. > > Second, polling is ugly. > > As opposed to? As opposed to giving the stats whenever asked by the host. > > 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. It does, *if* we don't need accuracy. Otherwise, it seems like we need something else. Cheers, Rusty. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization