From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Renninger <trenn@suse.de>
Subject: Re: Overall picture of cpufreq..
Date: Sun, 13 Jan 2008 23:54:34 +0100
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To: Saru Addep <saru.dpm@gmail.com>
Cc: cpufreq@lists.linux.org.uk


On Fri, 2008-01-11 at 14:15 -0800, Saru Addep wrote:
> Hi All,
...
> 2) What is the purpose of userspace governor.

You can set the frequency from userspace:
/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
(or similar) pops up when you switch to userspace governor.

The first dynamic cpufreq approaches were done in userspace. You have a
daemon checking every some 100 ms for the CPU load (/proc/stats) and
then decide whether to increase or decrease the freq.

The ondemand governor is doing that in kernel, but has the sideeffect of
not supporting HW (IIRC speedstep-lib, possibly longhaul, powernow-k7
(not sure) and other older ones) that takes too long for switching
frequencies. Then you would still need the userspace governor for
switching.

   Thomas