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List:       kde-devel
Subject:    Re: [PATCH] powerdevil-remove-cpufreq.patch
From:       Oswald Buddenhagen <ossi () kde ! org>
Date:       2010-03-08 8:14:53
Message-ID: 20100308081453.GA26095 () ugly ! local
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On Sun, Mar 07, 2010 at 11:57:37PM +0100, Holger Macht wrote:
> Remove all CPU frequency scaling code from powerdevil and the kcm
> module. You should never offer those options to the user because he
> might not understand what the impact is. You only want a dynamic
> frequency algorithm which is the default these days (ondemand
> governor). A good explanation is provided in [1].
> 
i disagree.

i use my laptop as a node in a compile cluster (not a particularly big
one, heh). unlike my desktop, it is not water-cooled, i.e., loud when
under heavy load. so if i want to compile something while, e.g.,
watching a movie, i always set it to "powersave" manually.

the second point is that the ondemand governor doesn't give full
performance. i'm running the node with max 3 concurrent jobs while it
has only one core, so it is pretty much saturated all the time. but i
still see it downclocking. of course this is a bug (hmm, i should
upgrade the kernel on that machine ...), but "being robbed" of an easily
accessible workaround would just suck.

a third datapoint is the wrongness of the assumption that the workload
is fixed and should just be executed as fast as possible. this certainly
isn't so, for example in interactive applications which refesh "as often
as possible" there is always somthing to do. downclocking the cpu is the
only way to conserve power in such a scenario. also, perceived slowness
of the machine has a psychological effect of not demanding too much of
it, i.e., it changes the usage pattern to something more power-friendly.
 
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