From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758151AbXHSUd0 (ORCPT ); Sun, 19 Aug 2007 16:33:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757890AbXHSUdJ (ORCPT ); Sun, 19 Aug 2007 16:33:09 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:36513 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758787AbXHSUdE (ORCPT ); Sun, 19 Aug 2007 16:33:04 -0400 From: "Rafael J. Wysocki" To: Jean Delvare Subject: Re: CONFIG_SUSPEND and power consumption Date: Sun, 19 Aug 2007 22:42:43 +0200 User-Agent: KMail/1.9.5 Cc: LKML References: <20070819153259.2c96b904@hyperion.delvare> In-Reply-To: <20070819153259.2c96b904@hyperion.delvare> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200708192242.43819.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Sunday, 19 August 2007 15:32, Jean Delvare wrote: > Hi all, hi Rafael, > > Running kernel 2.6.23-rc3-git1, I noticed yesterday that my CPU (AMD > Sempron 2600+) was running at a much lower temperature when > CONFIG_SUSPEND was enabled. Hm, interesting. > The temperature difference was quite significant, about 6 degrees Celsius at > idle. Measuring the power consumption of my system confirmed that the energy > savings were real: with CONFIG_SUSPEND=n, the system consumes 80 W of power > (idle), while with CONFIG_SUSPEND=y, the system consumes only 69 W (idle)! > Can anyone explain how this works? I can't. > I didn't expect CONFIG_SUSPEND to make any difference before actually > switching the system to standby or suspend state. Yes, that's the expected behavior. > I tried the same trick on two Intel motherboards I use for testing, but > this option didn't seem to make any difference in the power consumption > for these. Do you have CONFIG_HIBERNATION set? If not, please see if setting it instead of CONFIG_SUSPEND leads to the same result on the affected box (ie. running at lower temperatures). Greetings, Rafael