Re: About vcpu wakeup and runq tickling in credit

[Dario Faggioli <raistlin@linux.it>]

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On Thu, 2012-11-15 at 12:18 +0000, George Dunlap wrote:
> > So, in the vcpu-affinity case, if pcpu 3 get tickled, when it peeks at
> > pcpu 13's runq for work to steal it does not find anything suitable and
> > give up, leaving d51v1 in the runq even if there are idle pcpus on which
> > it could run, which is already bad.
> > In the node-affinity case, pcpu 3 will actually manage in stealing d51v1
> > and running it, even if there are idle pcpus with which it has
> > node-affinity, and thus defeating most of the benefits of the whole NUMA
> > aware scheduling thing (at least for some workloads).
> 
> Maybe what we should do is do the wake-up based on who is likely to run 
> on the current cpu: i.e., if "current" is likely to be pre-empted, look 
> at idlers based on "current"'s mask; if "new" is likely to be put on the 
> queue, look at idlers based on "new"'s mask.
> 
EhEh, if you check  the whole thread, you'll find evidence that I
thought this to be a good idea from the very beginning. I've already a
patch for that, just let me see if numbers (with and without NUMA
scheduling) are aligned with impressions and then I'll send everything
together.

Thanks for your time,
Dario

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


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