Re: [RFC] [PATCH] cpufreq: allow full selection of default governors

Dominik Brodowski
2007-04-27T01:54:13Z

On Tue, Apr 24, 2007 at 08:03:27PM -0400, Dave Jones wrote:
> On Tue, Apr 24, 2007 at 03:05:36PM -0700, Nish Aravamudan wrote:
> > On 4/24/07, Dave Jones <davej@redhat.com> wrote:
> > > On Tue, Apr 24, 2007 at 09:03:23PM +0000, William Heimbigner wrote:
> > > > The following patches should allow selection of conservative, powersave, and
> > > > ondemand in the kernel configuration.
> > >
> > > This has been rejected several times already.
> > > Ondemand and conservative isn't a viable governor for all cpufreq
> > > implementations (ie, ones with high switching latencies).
> >
> > This piques my curiosity -- some governors don't work with some
> > cpufreq implementations. Are those implementations in the kernel or in
> > userspace? If in the kernel, then perhaps there should be some
> > dependency expressed there in Kconfig between cpufreq implementation
> > and the available governors
>
> it can't be solved that easily. powernow-k8 for example is fine to
> use with ondemand on newer systems, where the latency is low.
> On older models however, it isn't.
>
> > > Also, see the
> > > comment in the Kconfig a few lines above where you are adding this.
> >
> > Are these governors unfixable? If
>
> tbh, I've forgotten the original issues that caused the comment
> to be placed there. Dominik ?

Not unfixable, but: cpufreq is currently[*] built around the assumption that
at least one governor is correctly initialized or can be brought to work
when a CPU is registered with the cpufreq core.

Dominik

[*] That is, the last time I looked at it ;)