Re: Status of X86_P4_CLOCKMOD?

[Dominik Brodowski <linux@dominikbrodowski.net>]

On Tue, Feb 28, 2006 at 03:26:32PM -0600, Matt Mackall wrote:
> > So even if the battery lasts longer, you don't have anything of it, 'cause
> > the CPU can even compute _less_ in this longer time-span. Remember that
> > idling doesn't count...
> 
> Which is different from other power-saving modes how? If it means I
> can read my email longer on the plane, it's a power-saving mode.

But you can't... [*]

> > > In short, power usage and heat production are _the same thing_.
> > 
> > Yes and no. The heat production is more levelled if you use throttling, so
> > the temperature achieved is lesser, which might cause fans not having to
> > start or air conditioning having less work to do.
> 
> The time scale for heat propagation is enough slower than throttling
> that I'd expect this difference to amount to approximately nil.

For short-term load spikes, yes. If your server has a task which takes up
one hour at full time, and the temp reaches 45° C then, but you have nothing
else for it to do overnight, then it does might sense to throttle it to
50%, which will mean two hours, but only 40° C.

	Dominik


[*] unless the idling algorithm is broken and does not enter C2-type idle
states.