Using Info from User Space?

I am also going to add that latency is a big part of this calculation. As you correctly point out, keeping the processing core hotted up reduces latency for new work that is unknown to the scheduler. The finish fast theory is all about latency too, what is the latency of powering up more cores to add capacity versus just running on the cores which are already active, which way will finish first and return to a lower power state the fastest. The schedule can guesstimate this for work it knows about, although interrupt driven work has different properties.