Re: [patch] Remove the per cpu tick skew

From: Arjan van de Ven
Date: Fri Jul 30 2010 - 09:57:32 EST

On Fri, 30 Jul 2010 17:27:04 +1000
Nick Piggin <npiggin@xxxxxxx> wrote:
> > Nowadays, with the tickless kernel, this contention no longer
> > happens since time keeping and updating are done differently. In
> > addition, this skew is actually hurting power consumption in a
> > measurable way on many-core systems.
> Question, how much of a win is it? What does it do that tickless
> idle does not, can you explain?

tickless idle works great if you're really almost idle

if there's "some work but not fully busy" this still matters

this is not about 'a few milliwatts', but on a server in our labs
(sorry, no hardware details in public) this effect is in the "several
dozen Watts" range.

Arjan van de Ven Intel Open Source Technology Centre
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