powernowd vs. ondemand governor

[Scott James Remnant]

On Tue, 2009-02-17 at 16:45 +0000, Matt Zimmerman wrote:

> > Furthermore, my understanding is that even if udev could autoload the
> > modules, there's no way to set a policy for which governor to use without
> > running a script exactly like the current powernowd init script.
> 
> Yes, we might need to provide some method to override it, but
> CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND would take care of the default.
> 
I think you're both confusing the governor and the mechanism.

In jaunty, the governor modules are built in to the system; the default
is selected with a kernel option (and probably should be changed to
ondemand).

That would eliminate a whole bunch of complicated stuff in that init
script.


*But* the mechanism still needs to be set.  The right module is detected
by the /usr/share/powernowd/cpufreq-detect.sh script by grepping
information in /proc and /sys.

The very fact it's done by grepping kernel supplied information means
that we're just working around kernel lazyness.  This could be
auto-loaded by the kernel, or it could be auto-loaded by udev if the
kernel supplied enough information.

The fact that these modules seem perfectly able to determine whether
they can be loaded or not really suggests the kernel knows what hardware
they need:

FATAL: Error inserting powernow_k8
(/lib/modules/2.6.28-7-server/kernel/arch/x86/kernel/cpu/cpufreq/powernow-k8.ko): No such device


Hell, at worse, why aren't these all just builtin anyway?  The kernel
seems to know which one to load.

Scott
-- 
Scott James Remnant
scott at canonical.com
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