Re: [Patch] don't kick ALB in the presence of pinned task

[Ingo Molnar]

* Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:

> Siddha, Suresh B wrote:
> >Jack Steiner brought this issue at my OLS talk.
> >
> >Take a scenario where two tasks are pinned to two HT threads in a physical
> >package. Idle packages in the system will keep kicking migration_thread
> >on the busy package with out any success.
> >
> >We will run into similar scenarios in the presence of CMP/NUMA.
> >
> >Patch appended.
> >
> 
> Hmm, I would have hoped the new "all_pinned" logic should have handled 
> this case properly. [...]

no, active_balance is a different case, not covered by the all_pinned 
logic. This is a HT-special scenario, where busiest->nr_running == 1, 
and we have to do active load-balancing. This does not go through 
move_tasks() and does not set all_pinned. (If nr_running werent 1 we'd 
not have to kick active load-balancing.)

	Ingo
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