linux-kernel - Re: Power Management framework proposal

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Message-Id: <1185125189.2714.13.camel@laptopd505.fenrus.org>
Date:	Sun, 22 Jul 2007 10:26:28 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	david@...g.hm
Cc:	LKML <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>
Subject: Re: Power Management framework proposal

On Sat, 2007-07-21 at 23:49 -0700, david@...g.hm wrote:

> this approach would allow the transition of ALL drivers to the new mode of 
> operation in one fell swoop, and then adding additional power management 
> features is just adding to the existing list rather then implementing new 
> functions.

I have a concern with this approach though. It seems to assume that
there is one global thing somewhere that sets the system state; in my
experience that is the wrong approach; in fact there is a very definite
evidence that there are many decisions on power that are to be made
local at a high frequency. An example of this is the processor speed;
the ondemand governer does exactly this for the cpus that can switch
speeds fast; it's just impossible to beat such a local, fast decision
with anything on a global scale.

On the other hand, some things (the high level goals and constraints)
are obviously global.

However, your design seems to want to put the low level settings in a
global thing, and that is just a mistake.

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