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[Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon
From: |
Rusty Russell |
Subject: |
[Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver |
Date: |
Wed, 11 Nov 2009 13:13:23 +1030 |
User-agent: |
KMail/1.12.2 (Linux/2.6.31-14-generic; KDE/4.3.2; i686; ; ) |
On Wed, 11 Nov 2009 10:37:56 am Anthony Liguori wrote:
> Rusty Russell wrote:
> > You register an outbuf at initialization time. The host hands it back when
> > it wants you to refill it with stats.
>
> That's strangely backwards. Guest send a stat buffer that's filled out,
> host acks it when it wants another. That doesn't seem bizarre to you?
Yep! But that's a limitation of our brains, not the infrastructure ;)
Think of the stats as an infinite stream of data. Read from it at your
leisure. This is how, for example, console output works.
> > But the universe is remarkably indifferent to what we want. Is it actually
> > sufficient or are we going to regret our laziness?
>
> It's not laziness, it's consistency. How is actual different than free
> memory or any other stat?
Because it's a COLLECTION of stats. For example, swap in should be < swap
out. Now, the current Linux implementation of all_vm_events() is non-atomic
anyway, so maybe we can just document this as best-effort. I'm saying that
if it *is* a problem, I think we need a vq.
But it raises the question: what stats are generally useful cross-OS? Should
we be supplying numbers like "unused" (free) "instantly discardable" (ie.
clean), "discardable to disk" (ie. file-backed), "discardable to swap"
(ie. swap-backed) and "unswappable" instead?
(I just made those up, of course, but it seems like that would give a fair
indication of real memory pressure in any OS).
Thanks,
Rusty.
- Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver, (continued)
- 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, 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, Anthony Liguori, 2009/11/10
- [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, 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
Re: [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2), Jamie Lokier, 2009/11/09