Re: [PATCH] powerdevil-remove-cpufreq.patch

[Sebastian Kügler <sebas@xxxxxxx>]

On Monday 08 March 2010 17:15:18 Martin Sandsmark wrote:
> On Monday 8. March 2010 13.39.16 Sebastian Kügler wrote:
> > If the ondemand governor doesn't scale up when more CPU cycles would be
> > needed, that's a kernel bug and shouldn't be papered over by UI options
> > in PowerDevil. For the downscaling, that is bogus anyway since doing the
> > work as quickly as possible and going back to sleep to save power is
> > more efficient than doing the work slower and thus keeping the CPU awake
> > longer.
> 
> You're ignoring the fact that increasing CPU frequency also increases the
> heat  generated, and at least here it then leads to the fan firing up,
> bringing down battery time rather drastically.

Not sure how much your fan eats, but it's a rule of thumb that doing a task on 
the CPU very fast and then sleeping for as long as possible is way more efficient 
than spreading the work over a longer period of time, working a little less hard.

Basically, the difference between a sleeping CPU and an active CPU is huge, while 
the difference between a fully active CPU and a throttled one is nearly linear 
(not an order of magnitude different, in any event).

Thermal management is a valid reason, though in most cases cleaning out the 
system fan will give you both, longer battery life *and* a more silent system. :)
-- 
sebas

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