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

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

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On Thu, 2016-12-08 at 07:12 +0100, Juergen Gross wrote:
> On 07/12/16 19:29, Dario Faggioli wrote:
> > 
> > Setting and getting the CPU class of a vCPU will happen via two new
> > hypercalls:
> > 
> > * `XEN_DOMCTL_setvcpuclass`
> > * `XEN_DOMCTL_setvcpuclass`
> 
> XEN_DOMCTL_getvcpuclass
> 
Oops, thanks.

> > ### 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.

> 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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