Re: [Xen-devel] [DOC RFC] Heterogeneous Multi Processing Support in Xen

[Juergen Gross <jgross@xxxxxxxx>]

On 08/12/16 11:27, Dario Faggioli wrote:
> On Thu, 2016-12-08 at 07:12 +0100, Juergen Gross wrote:
>> On 07/12/16 19:29, Dario Faggioli wrote:
>>> ### Phase 2
>>>
>>> Inside Xen, the various schedulers will be modified to deal
>>> internally with
>>> the fact that vCPUs can only run on pCPUs from the class(es) they
>>> are
>>> associated with. This allows for more efficient implementation, and
>>> paves
>>> the way for enabling more intelligent logic (e.g., for minimizing
>>> power
>>> consumption) in *phase 3*.
>>>
>> Any idea how to avoid problems in the schedulers related to vcpus
>> with
>> different weights? 
>>
> Sure: use Credit2! :-P
> 
> And I'm not joking (not entirely, at least), as the alternative is to
> re-engineer significantly the algorithm inside Credit, which I'm not
> sure is doable or worthwhile, especially considering we have
> alternatives.

So you really solved the following problem in credit2?

You have three domains with 2 vcpus each and different weights. Run them
on 3 physical cpus with following pinning:

dom1: pcpu 1 and 2
dom2: pcpu 2 and 3
dom3: pcpu 1 and 3

How do you decide which vcpu to run on which pcpu for how long?


Juergen

> 
>> Remember, weights and pinning don't go well together,
>> that was the main reason for inventing cpupools. You should at least
>> name that problem. 
>>
> Yes, that's true. I will add a paragraph about it.
> 
> 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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