From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752440Ab1HKSau (ORCPT ); Thu, 11 Aug 2011 14:30:50 -0400 Received: from merlin.infradead.org ([205.233.59.134]:48687 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339Ab1HKSat convert rfc822-to-8bit (ORCPT ); Thu, 11 Aug 2011 14:30:49 -0400 Subject: Re: [PATCH v2 0/2] new cpumask for hotpluggable CPUs From: Peter Zijlstra To: Mike Turquette Cc: linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, linaro-dev@lists.linaro.org, patches@linaro.org, gregkh@suse.de Date: Thu, 11 Aug 2011 20:30:23 +0200 In-Reply-To: <1313006614-28702-1-git-send-email-mturquette@ti.com> References: <1313006614-28702-1-git-send-email-mturquette@ti.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.2- Message-ID: <1313087423.8491.11.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-08-10 at 13:03 -0700, Mike Turquette wrote: > This patch series introduces a new cpumask which tracks CPUs that > support hotplugging. The purpose of this patch series is to provide a > simple method for kernel code to know which CPUs can be hotplugged and > which ones cannot. Potential users of this code might be a thermal > mitigation technique which uses hotplug to lower temperature, or a power > capping mechanism which uses hotplug to lower power consumption. > > All the of usual cpumask helper functions are created for this new mask. > The second patch in this series simply sets the bit for elligible CPUs > while they are being registered. The cpumask itself is static after > boot and should not change (like the possbile mask). I still most strongly object to people using hotplug for these goals. Why do you need to go through the entire dance of hotplug just to idle a cpu? Hotplug not only idles the cpu but tears down (and rebuilds) an insane amount of resources associated with the cpu. Nacked-by: Peter Zijlstra