From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by bilbo.ozlabs.org (Postfix) with ESMTP id 7E908B7087 for ; Thu, 6 Aug 2009 12:08:56 +1000 (EST) Date: Thu, 6 Aug 2009 09:58:55 +0800 From: Shaohua Li To: Gautham R Shenoy Subject: Re: [PATCH 0/3] cpu: idle state framework for offline CPUs. Message-ID: <20090806015855.GA20596@sli10-desk.sh.intel.com> References: <20090805142311.553.78286.stgit@sofia.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20090805142311.553.78286.stgit@sofia.in.ibm.com> Cc: "Brown, Len" , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "Pallipadi, Venkatesh" , Ingo Molnar , "linuxppc-dev@lists.ozlabs.org" , "Darrick J. Wong" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. > 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. Thanks, Shaohua