CPU Frequency Scaling

[Callum Lerwick]

On Sat, 2006-12-02 at 22:03 -0500, Jon Nettleton wrote:
> The kernel has had the scaling governor modules for a while now and I am
> not sure why Fedora is still relying on the cpuspeed daemon by default.
> If anyone in the know could answer that question I would appreciate it.

On my wife's eMachines m6805, running FC6 x86_64, it boots up with
ondemand enabled automagically. It seems to be built into the kernel?
Its not listed as a module.

On my Athlon 64 3000+ desktop, it doesn't work out of the box. Being a
desktop, the native PowerNow driver doesn't seem to work but ACPI does.
It only has two speeds, 2ghz and 1ghz. I found the cpuspeed demon will
flap up and down by default, as its doesn't tune itself to the actual
speed difference. I shouldn't have to tune *anything*. I dumped it in
favor of loading and enabling ondemand in rc.local, it doesn't seem to
have such flapping problems.

Another point against userspace is the recent crusade against context
switching. A bit ironically, all the userspace polling sends context
switching through the roof. In theory, I don't know how its actually
implemented, but the kernel governor could run alongside and interact
with the kernel scheduler directly, without adding additional context
switching and without icky polling.
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