From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762578AbXGWWYQ (ORCPT ); Mon, 23 Jul 2007 18:24:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751965AbXGWWYF (ORCPT ); Mon, 23 Jul 2007 18:24:05 -0400 Received: from gate.crashing.org ([63.228.1.57]:58215 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751716AbXGWWYD (ORCPT ); Mon, 23 Jul 2007 18:24:03 -0400 Subject: Re: Power Management framework proposal From: Benjamin Herrenschmidt To: Arjan van de Ven Cc: david@lang.hm, LKML , linux-pm In-Reply-To: <1185125189.2714.13.camel@laptopd505.fenrus.org> References: <1185125189.2714.13.camel@laptopd505.fenrus.org> Content-Type: text/plain Date: Tue, 24 Jul 2007 08:23:25 +1000 Message-Id: <1185229405.5439.148.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2007-07-22 at 10:26 -0700, Arjan van de Ven wrote: > On Sat, 2007-07-21 at 23:49 -0700, david@lang.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. I think we need a set of constraints that trickle down the power tree and limit what a given driver can do locally. Ben.