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SubjectRe: Rescheduling interrupts

* Matt Mackall <mpm@selenic.com> wrote:

> > amarokapp does wake up threads every 20 microseconds - that could
> > explain it. It's probably Xorg running on one core, amarokapp on the
> > other core. That's already 100 reschedules/sec.
>
> That suggests we want an "anti-load-balancing" heuristic when CPU
> usage is very low. Migrating everything onto one core when we're close
> to idle will save power and probably reduce latencies.

that would probably be the case if it's multiple sockets - but for
multiple cores exactly the opposite is true: the sooner _both_ cores
finish processing, the deeper power use the CPU can reach. So effective
and immediate spreading of workloads amongst multiple cores - especially
with shared L2 caches where the cost of migration is low, helps power
consumption. (and it obviously helps latencies and bandwith)

Ingo


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