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

On Mon, Aug 7, 2017 at 3:14 PM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> 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 :-) )

Sure. I can do that in the next version.
Hopefully we can reach the agreement on the code based on this version
so that the next version can be the final version for this patch
series. Hopefully. :)



Meng Xu
PhD Candidate in Computer and Information Science
University of Pennsylvania

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