Re: [Qemu-devel] [PATCH v2 0/3] Event notifications for balloon driver

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 21 May 2012 17:59:50 +0100
"Daniel P. Berrange" <berrange@redhat.com> wrote:

> This series is a followup to 2 previously posted patches
> 
>  * BALLOON_CHANGE QMP event:
>    http://lists.nongnu.org/archive/html/qemu-devel/2012-05/msg02215.html
> 
>  * query-events QMP command: 
>    http://lists.nongnu.org/archive/html/qemu-devel/2012-05/msg02255.html
> 
> Changes since v1:
> 
>  - Use a static array of strings for QMP event ID -> string conversion
>  - Add BALLOON_CHANGE to qmp-events.txt
> 
> There is also a new patch in this series, which introduces the ability
> todo simple rate limiting of stateless monitor events. With the ballooning
> of a 1.8 GB guest, down to 0.9 GB this reduced the number of events
> emitted from ~50 down to just 4, spread across a 4 second time window.

How would that be with a 1TB guest?

One way of solving this would be to move the policy to the mngt app. that is,
we could have a qmp-event-set-rate-limit command that could be allowed to
be run while in negotiation mode (ie. before qmp_capabilities is executed).

But I'm honestly not sure if rate limit is the best solution for this problem...
How can several events spread in several seconds be useful to libvirt?

IMO, the best would be to have a way to know when the balloon driver is done
servicing a balloon request.

Amit, is this possible?