Re: suspend blockers & Android integration

[Arjan van de Ven]

On Thu, 3 Jun 2010 19:26:50 -0700 (PDT)
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> 
> If the system is idle (or almost idle) for long times, I would
> heartily recommend actively shutting down unused cores. Some CPU's
> are hopefully smart enough to not even need that kind of software
> management, but I suspect even the really smart ones might be able to
> take advantage of the kernel saying: "I'm shutting you down, you
> don't have to worry about latency AT ALL, because I'm keeping another
> CPU active to do any real work".

sadly the reality is that "offline" is actually the same as "deepest C
state". At best.

As far as I can see, this is at least true for all Intel and AMD cpus.

And because there's then no power saving (but a performance cost), it's
actually a negative for battery life/total energy.

(lots of experiments inside Intel seem to confirm that, it's not just
theory)





-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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