From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760760AbXGVR2b (ORCPT ); Sun, 22 Jul 2007 13:28:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755530AbXGVR2V (ORCPT ); Sun, 22 Jul 2007 13:28:21 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:42193 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755100AbXGVR2U (ORCPT ); Sun, 22 Jul 2007 13:28:20 -0400 Subject: Re: Power Management framework proposal From: Arjan van de Ven To: david@lang.hm Cc: LKML , linux-pm In-Reply-To: References: Content-Type: text/plain Organization: Intel International BV Date: Sun, 22 Jul 2007 10:26:28 -0700 Message-Id: <1185125189.2714.13.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.10.3 (2.10.3-1.fc7) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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. However, your design seems to want to put the low level settings in a global thing, and that is just a mistake.