Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755484Ab0DEQXm (ORCPT ); Mon, 5 Apr 2010 12:23:42 -0400 Received: from mga07.intel.com ([143.182.124.22]:9575 "EHLO azsmga101.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755173Ab0DEQXh (ORCPT ); Mon, 5 Apr 2010 12:23:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.51,366,1267430400"; d="scan'208";a="262178621" Message-ID: <4BBA0E74.2090803@linux.intel.com> Date: Mon, 05 Apr 2010 09:23:16 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com 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 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> <20100405042222.GD2644@linux.vnet.ibm.com> <4BB9F657.4050901@linux.intel.com> <20100405151401.GA2525@linux.vnet.ibm.com> <4BBA0AC5.1080905@linux.intel.com> <20100405162249.GB2525@linux.vnet.ibm.com> In-Reply-To: <20100405162249.GB2525@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1256 Lines: 27 On 4/5/2010 9:22, Paul E. McKenney wrote: > On Mon, Apr 05, 2010 at 09:07:33AM -0700, Arjan van de Ven wrote: >> On 4/5/2010 8:14, Paul E. McKenney wrote: >>> So the main issue is that for many workloads, it is best to run full bore >>> and get done quickly, thus allowing the entire machine to be powered down? >> >> yep >> >>> If so, it seems likely that there would be some workloads that were sometimes >>> unable to use all the CPUs, in which case shutting down (idling, offlining, >>> dyntick-idling, whatever) the excess CPUs might nevertheless be the right >>> thing to do. >> >> but the point is that the normal scheduler + idle behavior gives you exactly that >> in a natural way ! >> If you don't have enough work (tasks) to keep all cores busy, the others are and stay idle. > > So your earlier objection was not to dyntick-idle as such, but rather > to artificially constraining the scheduler to induce dyntick-idle? my objection was against the notion that offlining cpus helps power/energy ;-) -- 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/