Re: [Qemu-devel] [PATCH v2 0/3] re-enable balloon stats

[Dietmar Maurer]

> Let me try once more to explain our options and why I think this is series is
> our best choice.
> 
> Basically, we have try options:
> 
> 1. Add stats to query-balloon
> 
> This breaks existing clients, because query-balloon is a synchronous
> command that returns immediately. If we add stats to it (as we did) then it
> will have to wait for the guest to respond, which can take a long time or even
> doesn't happen at all if the guest is paused.

No, there is no need to wait (see my patch).
 
> This broke libvirt, as explained here:
> 
>  https://bugzilla.redhat.com/show_bug.cgi?id=623903

My new patch does not introduce such bug.
 
> 2. Add a new command that just request the stats to be sent (ie. it doesn't
> block), and then get the stats through an event
> 
> This was my last proposal:
> 
>  http://lists.gnu.org/archive/html/qemu-devel/2012-02/msg00983.html
> 
> This sort of worked, but it has two problems. First, events can be lost.
> Second, most failures can't be synchronously reported.
> 
> 3. Add stats through device properties (this series)
> 
> While this isn't perfect, it does solve the issues with previous
> implementations. Besides, it has the advantage of avoiding adding new
> commands and it integrates nicely with the balloon driver, making some
> errors automatically reported (eg. if the balloon is not enabled).

We can have both - see my new patch.