From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp03.in.ibm.com (e28smtp03.in.ibm.com [59.145.155.3]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp03.in.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id E73D5B7B9D for ; Wed, 7 Oct 2009 22:26:58 +1100 (EST) Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by e28smtp03.in.ibm.com (8.14.3/8.13.1) with ESMTP id n97BQrnQ032001 for ; Wed, 7 Oct 2009 16:56:53 +0530 Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n97BQqk62101248 for ; Wed, 7 Oct 2009 16:56:53 +0530 Received: from d28av01.in.ibm.com (loopback [127.0.0.1]) by d28av01.in.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id n97BQpkH026681 for ; Wed, 7 Oct 2009 16:56:52 +0530 Date: Wed, 7 Oct 2009 16:56:48 +0530 From: Vaidyanathan Srinivasan To: Peter Zijlstra , Arjan van de Ven 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: <20091007112648.GC7646@dirshya.in.ibm.com> References: <20091006152421.GA7278@linux.vnet.ibm.com> <20091006163521.GA10425@linux.vnet.ibm.com> <1254852279.17055.2.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <1254852279.17055.2.camel@laptop> Cc: linux-arch@vger.kernel.org, Gautham R Shenoy , Venkatesh Pallipadi , linux-kernel@vger.kernel.org, Paul Mackerras , arun@linux.vnet.ibm.com, Ingo Molnar , linuxppc-dev@lists.ozlabs.org Reply-To: svaidy@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , * 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. --Vaidy