powernowd vs. ondemand governor

Steve Langasek steve.langasek at ubuntu.com
Mon Feb 16 21:20:21 GMT 2009

On Mon, Feb 16, 2009 at 02:58:01PM +0000, Matt Zimmerman wrote:
> We currently ship powernowd in the desktop seed, its main purpose being to
> load cpufreq modules set up the kernel's CPU frequency scaling governor.  If
> (and only if) that fails, it starts up powernowd instead.  I'm not sure on
> which platforms that's still needed, if any.

> Is this still an appropriate default?  Aren't the necessary modules loaded
> automatically now?  Would it be a better idea to set the default to ondemand
> in the kernel and drop powernowd altogether?

None of the cpufreq modules (under
/lib/modules/$kvers/kernel/arch/x86/kernel/cpu/cpufreq/) have any module
aliases, so I don't think they get loaded except via the powernowd init
script.  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.

As for platforms where it's needed, I have one system (an older AMD64) that
doesn't work with any of the platform cpufreq modules, so powernowd is the
only option there.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org

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