RE: [PATCH][2.5.32] CPU frequency and voltage scaling (0/4)

From: Linus Torvalds (torvalds@transmeta.com)
Date: Wed Aug 28 2002 - 15:46:11 EST


On Wed, 28 Aug 2002, Grover, Andrew wrote:
>
> Well TMTA CPUs would seem to be easy, because all this is done behind the
> OS's back, right?

Yes. However, I certainly wouldn't mind having the same interfaces as
everybody else to set things like "aggressive" vs "powersave". Transmeta
does all the actual _work_ behind the OS's back, but you can still tell
the CPU what policy to take, and what frequency limits to use.

> Let's talk about CPUs in which the OS has to control processor performance.
> The way I see it, there are a bunch of inputs that are going to determine
> CPU speed & voltage: user preference, workload, and thermals.

Absolutely.

> Any workload analysis has to be in the kernel.

...with user mode input (ie user mode can know a lot of high-level stuff
that the kernel _doesn't_ know). So the kernel does potentially need user
input on policy.

                Linus

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