Re: So, what's the status on the recent patches here?

Pavel Machek
2006-09-03T22:41:32Z

On Sun 2006-09-03 17:31:02, Scott E. Preece wrote:
> | From: Pavel Machek<pavel@ucw.cz>
> | Cc: <amit.kucheria@nokia.com>, <linux-pm@lists.osdl.org>
> | User-Agent: Mutt/1.5.11+cvs20060126
> |
> | On Sun 2006-09-03 16:21:34, Scott E. Preece wrote:
> | > | From: Pavel Machek<pavel@ucw.cz>
> | > some reason, in your perception, why definition of operating points
> | > really needs to be in the kernel? Definition of the operating points,
> | > as opposed to changing from one OP to another, shouldn't have any timing
> | > issues, so why isn't a privileged user-space manager a reasonable
> | > approach?
> |
> | For one thing, is not powerop needed for boot? You need to boot in
> | some operating point after all :-).
> ---
>
> In the implementation we use, the initial OP is set by the boot
> loader. Our kernel power management driver is a module. The assumption
> is that booting involves a lot of processing and it makes sense to just
> use the highest OP anyway. That makes sense in our environment, but I
> wouldn't recommend our version as a general solution, anyway.

That's actually regression; cpufreq saves power even while booting.

> | > As noted previously, OPs bundle together more than just the
> | > frequency. Those of us supporting the OP model believe that you can't
> | > intelligently change CPU frequency in isolation and you can't change
> | > some of those parameters independently, because only certain
> | > combinations work.
> |
> | That's okay. User gives you combination he wants, and you select "next
> | higher" working operating point.
> ---
>
> Hmm. I need to think about that. I guess the OP abstraction *could* be
> entirely inside the user-space policy manager, with the kernel exposing
> individual interfaces for every parameter that the policy manager would
> need to adjust. However, that means that the whole mess has to be at
> user level (kernel just implements simple knobs for individual
> parameters), because the dependency management between the parameters
> would only be known at user level, and means a relatively bulky kernel
> interface, since it would expose more things at the interface.

That would work for me.

But my idea was actually opposite: expose individual knobs to
userspace, and then select some operating point (inside kernel) that
satisfies given knobs.

> On the other hand, that complexity has to be somewhere, so maybe that
> would be OK. As I said, I need to think about it...

Looking forward for new interface proposal ;-).

Pavel
--
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