Re: [RFCv3 PATCH 33/48] sched: Energy-aware wake-up task placement

[Peter Zijlstra]

On Tue, Mar 24, 2015 at 03:42:42PM +0000, Morten Rasmussen wrote:
> Right, I agree that we should preferably do the normal thing for U ~= 1.
> We can restructure the wake-up path to follow that pattern, but we need
> to know U beforehand to choose the right path. U isn't just
> get_cpu_usage(prev_cpu) but some broader view of the of the cpu
> utilizations. For example, prev_cpu might be full, but everyone else is
> idle so we still want to try to do an energy aware wake-up on some other
> cpu. U could be the minium utilization of all cpus in prev_cpu's
> sd_llc, which is somewhat similar to what energy_aware_wake_cpu() does.

Yeah, or a setting in the root domain set by the regular periodic load
balancer; that already grew some mojo to determine this in a patch I
recently commented on.

> I guess energy_aware_wake_cpu() could be refactored to call
> select_idle_sibling() if it find U ~= 1?

Sure yeah, that's not the hard part I think.
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