From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904AbZHFNsy (ORCPT ); Thu, 6 Aug 2009 09:48:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755870AbZHFNsx (ORCPT ); Thu, 6 Aug 2009 09:48:53 -0400 Received: from e28smtp03.in.ibm.com ([59.145.155.3]:46397 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755855AbZHFNsx (ORCPT ); Thu, 6 Aug 2009 09:48:53 -0400 Date: Thu, 6 Aug 2009 19:18:44 +0530 From: Gautham R Shenoy To: Shaohua Li Cc: Joel Schopp , "Brown, Len" , Peter Zijlstra , Balbir Singh , "Pallipadi, Venkatesh" , Benjamin Herrenschmidt , Ingo Molnar , Vaidyanathan Srinivasan , Dipankar Sarma , "Darrick J. Wong" , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 0/3] cpu: idle state framework for offline CPUs. Message-ID: <20090806134844.GA19146@in.ibm.com> Reply-To: ego@in.ibm.com References: <20090805142311.553.78286.stgit@sofia.in.ibm.com> <20090806015855.GA20596@sli10-desk.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090806015855.GA20596@sli10-desk.sh.intel.com> 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 Hi Shaohua, On Thu, Aug 06, 2009 at 09:58:55AM +0800, Shaohua Li wrote: > Hi, > > On Wed, Aug 05, 2009 at 10:25:53PM +0800, Gautham R Shenoy wrote: > > In this patch-series, we propose to extend the CPU-Hotplug infrastructure > > and allow the system administrator to choose the desired state the CPU should > > go to when it is offlined. We think this approach addresses the concerns about > > determinism as well as transparency, since CPU-Hotplug already provides > > notification mechanism which the userspace can listen to for any change > > in the configuration and correspondingly readjust any previously set > > cpu-affinities. > Peter dislikes any approach (including cpuhotplug) which breaks userspace policy, > even userspace can get a notification. I think Peter's problem was more to do with the kernel offlining the CPUs behind the scenes, right ? We don't do that in this patch series. The option to offline the CPUs is very much with the admin. The patch-series only provides the interface that helps the admin choose the state the CPU must reside in when it goes offline. > > > Also, approaches such as [1] can make use of this > > extended infrastructure instead of putting the CPU to an arbitrary C-state > > when it is offlined, thereby providing the system administrator a rope to hang > > himself with should he feel the need to do so. > I didn't see the reason why administrator needs to know which state offline cpu > should stay. Don't know about powerpc side, but in x86 side, it appears deepest > C-state is already preferred. We can still provide a sane default value based on what states are available and what the BIOS limits us to. Thus we can still use the idle-state-offline patch that Venki posted sometime ago, right ? > > Thanks, > Shaohua -- Thanks and Regards gautham