From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp09.in.ibm.com (e28smtp09.in.ibm.com [59.145.155.9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp09.in.ibm.com", Issuer "Equifax" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id 13164B6EDE for ; Thu, 6 Aug 2009 23:48:57 +1000 (EST) Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by e28smtp09.in.ibm.com (8.14.3/8.13.1) with ESMTP id n76Dk4AD001178 for ; Thu, 6 Aug 2009 19:16:04 +0530 Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n76DmoNH1892356 for ; Thu, 6 Aug 2009 19:18:50 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id n76DmnQh008168 for ; Thu, 6 Aug 2009 23:48:50 +1000 Date: Thu, 6 Aug 2009 19:18:44 +0530 From: Gautham R Shenoy To: Shaohua Li Subject: Re: [PATCH 0/3] cpu: idle state framework for offline CPUs. Message-ID: <20090806134844.GA19146@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 In-Reply-To: <20090806015855.GA20596@sli10-desk.sh.intel.com> Cc: "Brown, Len" , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "Pallipadi, Venkatesh" , Ingo Molnar , "linuxppc-dev@lists.ozlabs.org" , "Darrick J. Wong" Reply-To: ego@in.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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