Re: [Xen-devel] [PATCH v2 for Xen 4.6 3/4] libxl: enabling XL to set per-VCPU parameters of a domain for RTDS scheduler

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Wed, 2015-06-17 at 13:14 +0100, Ian Campbell wrote:
> On Mon, 2015-06-15 at 12:12 +0200, Dario Faggioli wrote:
> > A parameter is either per-domain or per-vcpu, no matter how the user try
> > to set or get it. In RTDS, all parameters are per-domain now and, with
> > your work, all of them are becoming per-vcpu, and that's ok. But then,
> > per-dom parameters should just no longer exist.
> 
> Are you saying there is going to be no domain wide default for a given
> per-vcpu parameter? 
> 
No, no, there sure is a default, and I certainly would make it domain
wide.

> if that is the case then what happens if I hotplug a new VCPU without
> settings its per-vcpu properties?
> 
Exactly.

> I expected something like.
> 
> domain_params_set (weight=10)
> add vcpu0 (weight will be 10)
> add vcpu1 (weight will be 10)
> vcpu_params_set(0, weight=20)
> add vcpu2 (weight will be 10, from domain wide default)
> 
> If not that then what weight should vcpu2 have at this point?
> 
Absolutely.

What I'm aiming at here is the per-domain API to have a well defined and
valuable behavior, and the one you suggest in your other email (i.e.,
let's return the default) is exactly that! :-)

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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