Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932681AbZJGLsF (ORCPT ); Wed, 7 Oct 2009 07:48:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758978AbZJGLsE (ORCPT ); Wed, 7 Oct 2009 07:48:04 -0400 Received: from e28smtp09.in.ibm.com ([59.145.155.9]:55613 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758948AbZJGLsC (ORCPT ); Wed, 7 Oct 2009 07:48:02 -0400 Date: Wed, 7 Oct 2009 17:17:20 +0530 From: Balbir Singh To: Vaidyanathan Srinivasan Cc: Peter Zijlstra , Arjan van de Ven , arun@linux.vnet.ibm.com, Joel Schopp , Benjamin Herrenschmidt , Paul Mackerras , Ingo Molnar , Dipankar Sarma , Gautham R Shenoy , Venkatesh Pallipadi , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org Subject: Re: [v7 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power management code in x86, cleanup drivers/cpuidle/cpuidle.c and introduce cpuidle to POWER. Message-ID: <20091007114719.GH6818@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20091006152421.GA7278@linux.vnet.ibm.com> <20091006163521.GA10425@linux.vnet.ibm.com> <1254852279.17055.2.camel@laptop> <20091007112648.GC7646@dirshya.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20091007112648.GC7646@dirshya.in.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2042 Lines: 49 * Vaidy [2009-10-07 16:56:48]: > * Peter Zijlstra [2009-10-06 20:04:39]: > > > On Tue, 2009-10-06 at 22:05 +0530, Arun R Bharadwaj wrote: > > > > > Also, the per-cpu nature of registration/unregistration of cpuidle > > > has been maintained as ACPI needs this. > > > > Right, so can't we ditch that and have acpi default to the lowest common > > C-state and warn when various cpus report different C-states? > > Hi Peter, > > As Arjan mentioned previously, the per-cpu registration has to stay > for x86 for now due to legacy ACPI compatibility. Breaking that may > break lot of existing users and we do not have a clean fallback > method. > > As far as powerpc is concerned, we can work with a single global > registration. However we would like to have the same interface across > different archs. > > With the new re-factoring (v7), Arun has killed most of the list > traversal and linking between various cpu's cpuidle_driver structures. > Now we have a per-cpu stack of registered devices and we lookup the > structs using online cpumasks. The cpuidle_driver structure has list > of idle routing pointers (struct cpuidle_state) and rest of it is > statistics that needs to be maintained at a per-cpu level anyway. All > that is duplicated here is the array of idle routines (struct > cpuidle_state) on each cpu. > > The objective of the refactoring is to have a single common idle > routine management framework (remove pm_idle) and we have it done > through cpuidle registration framework. We can incrementally remove > the per-cpu registration later easily by splitting the cpuidle_driver > structure. > Yes, incremental refactoring makes the most sense from the do not break as you refactor point of view. -- Balbir -- 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/