Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751124Ab0DEEWh (ORCPT ); Mon, 5 Apr 2010 00:22:37 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:45099 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751011Ab0DEEWb (ORCPT ); Mon, 5 Apr 2010 00:22:31 -0400 Date: Sun, 4 Apr 2010 21:22:22 -0700 From: "Paul E. McKenney" To: Arjan van de Ven Cc: Dominik Brodowski , Alan Stern , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Dmitry Torokhov Subject: Re: A few questions and issues with dynticks, NOHZ and powertop Message-ID: <20100405042222.GD2644@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100403223328.GA4507@comet.dominikbrodowski.net> <20100404163924.GA18428@comet.dominikbrodowski.net> <20100404204725.GC2644@linux.vnet.ibm.com> <20100404233702.GA24102@linux.vnet.ibm.com> <4BB95C85.80205@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BB95C85.80205@linux.intel.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1138 Lines: 24 On Sun, Apr 04, 2010 at 08:44:05PM -0700, Arjan van de Ven wrote: > >And you did mention offlining some CPUs above. The folloiwng patch > >(from Lai Jiangshan) is needed to handle this case. > > btw on x86... don't offline CPUs if you want to save power.. it doesn't. > (at least not during idle.. and when you're busy it might save power, > but it won't save you energy normally) Hmmm... The fact that offlining CPUs doesn't save power could form the basis of an interesting rationalization for my having ignored offlined CPUs in my original patch, I suppose. ;-) So the proper approach is to affinity everything away from the CPUs in question so that they stay in dyntick-idle mode? I must confess that I find this quite counter-intuitive -- and I suspect that I am not the only one who would expect offlined CPUs to drop to the lowest possible power consumption. Thanx, Paul -- 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/