Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752084AbYCJLHj (ORCPT ); Mon, 10 Mar 2008 07:07:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751271AbYCJLHa (ORCPT ); Mon, 10 Mar 2008 07:07:30 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:47594 "EHLO gprs189-60.eurotel.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751212AbYCJLH3 (ORCPT ); Mon, 10 Mar 2008 07:07:29 -0400 Date: Mon, 10 Mar 2008 11:00:08 +0100 From: Pavel Machek To: Pierre Ossman Cc: LKML , linux-pm@lists.linux-foundation.org, "Pallipadi, Venkatesh" , Dave Jones , Andi Kleen , Alan Stern , Adam Belay , Lee Revell Subject: Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors Message-ID: <20080310100008.GA9520@elf.ucw.cz> References: <20080303231033.GB15255@one.firstfloor.org> <20080304040048.GA31562@codemonkey.org.uk> <20080304071423.0e6b71c1@mjolnir.drzeus.cx> <20080304181924.70aaf8c1@mjolnir.drzeus.cx> <924EFEDD5F540B4284297C4DC59F3DEEA77031@orsmsx423.amr.corp.intel.com> <20080305070201.0d16cd40@mjolnir.drzeus.cx> <20080305094023.6486ebdf@mjolnir.drzeus.cx> <20080306092730.4412d085@mjolnir.drzeus.cx> <20080309151659.63d54f38@mjolnir.drzeus.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080309151659.63d54f38@mjolnir.drzeus.cx> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1235 Lines: 31 On Sun 2008-03-09 15:16:59, Pierre Ossman wrote: > I'm beginning to think this is a lost cause. I've tried several variants, all without satisfactory results. > > In case anyone else has any more ideas, I'll detail what I've found influences the noise: > > 1. C state > > This is the big one. There is no noise as long as C3 is avoided (processor.max_cstate). > > 2. uhci_hcd driver > > USB is somehow involved in this problem. Unloading the uhci_hcd driver almost entirely kills the noise on a 1000 HZ NO_HZ kernel. On a 100 HZ, no NO_HZ kernel, the effect is very small, but still there. USB keeps processor out of C3 in many cases. > 4. Battery and AC > > The noise increases with the battery present and also when the AC supply is removed. > On battery, some machines swap C3 for "secret" C4, which is slower but saves power. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/