Re: [PATCH RFC v1] xen:rtds: towards work conserving RTDS

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Mon, 2017-08-07 at 14:27 -0400, Meng Xu wrote:
> On Mon, Aug 7, 2017 at 1:35 PM, Dario Faggioli
> 
> > Is this wanted or expected?
> 
> It is wanted.
> 
> A VCPU i that has already got budget_i * priority_level_i time has
> higher priority than another VCPU j that got budget_j *
> priority_level_j time, where priority_level_j > priority_level_i.
> 
> For the unreserved resource, a VCPU will gets roughly budget/period
> proportional unreserved CPU time.
> 
> 
> > Basically, if I'm not wrong, this means that the actual priority,
> > during the extratime phase, is some combination of deadline and
> > budget
> > (which would make me think to utilization)... is this the case?
> 
> Yes.
> The higher utilization a VCPU has, the more extra time it will get in
> the extratime phase.
> 
> > 
> > I don't care much about the actual schedule during the extratime
> > phase,
> > in the sense that it doesn't have to be anything too complicated or
> > super advanced... but I at least would like:
> > - to know how it works, and hence what to expect,
> > - for it to be roughly fair.
> 
> The unreserved resource is proportionally allocated to VCPUs roughly
> based on VCPU's budget/period.
> 
Right. Then this deserves both:
- a quick mention in the changelog
- a little bit more detailed explanation in a comment close to one of 
  the place where the policy is enacted (or at the top of the file, 
  or, well, somewhere :-) )

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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