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Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the ball
From: |
Rusty Russell |
Subject: |
Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver |
Date: |
Wed, 11 Nov 2009 10:29:13 +1030 |
User-agent: |
KMail/1.12.2 (Linux/2.6.31-14-generic; KDE/4.3.2; i686; ; ) |
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.
- [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2), Adam Litke, 2009/11/09
- [Qemu-devel] virtio: Add memory statistics reporting to the balloon driver, Adam Litke, 2009/11/09
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Rusty Russell, 2009/11/09
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Anthony Liguori, 2009/11/10
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Avi Kivity, 2009/11/10
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Anthony Liguori, 2009/11/10
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Jamie Lokier, 2009/11/11
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Daniel P. Berrange, 2009/11/11
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Adam Litke, 2009/11/11
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Avi Kivity, 2009/11/11
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver,
Rusty Russell <=
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Anthony Liguori, 2009/11/10
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Rusty Russell, 2009/11/10
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Anthony Liguori, 2009/11/10
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Rusty Russell, 2009/11/10
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Adam Litke, 2009/11/11
- [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, Rusty Russell, 2009/11/11
Re: [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2), Jamie Lokier, 2009/11/09