From patchwork Fri Oct 16 09:40:17 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arun Bharadwaj X-Patchwork-Id: 36183 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from bilbo.ozlabs.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 2620FB7EED for ; Fri, 16 Oct 2009 20:40:36 +1100 (EST) Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com [202.81.31.141]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp08.au.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 3B899B7BB0 for ; Fri, 16 Oct 2009 20:40:29 +1100 (EST) Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [202.81.31.245]) by e23smtp08.au.ibm.com (8.14.3/8.13.1) with ESMTP id n9GKTKh0002317 for ; Sat, 17 Oct 2009 07:29:20 +1100 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n9G9eRoh1147036 for ; Fri, 16 Oct 2009 20:40:27 +1100 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id n9G9eNTQ016898 for ; Fri, 16 Oct 2009 20:40:26 +1100 Received: from linux.vnet.ibm.com (Crystal-Planet.in.ibm.com [9.124.35.22]) by d23av01.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVin) with ESMTP id n9G9eHRo016616 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Fri, 16 Oct 2009 20:40:20 +1100 Date: Fri, 16 Oct 2009 15:10:17 +0530 From: Arun R Bharadwaj To: Peter Zijlstra , Benjamin Herrenschmidt , Ingo Molnar , Vaidyanathan Srinivasan , Dipankar Sarma , Balbir Singh , Andi Kleen , Arun Bharadwaj Subject: [v9 PATCH 1/9]: cpuidle: Design documentation patch Message-ID: <20091016094017.GC27350@linux.vnet.ibm.com> References: <20091016093850.GB27350@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20091016093850.GB27350@linux.vnet.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Cc: linux-arch@vger.kernel.org, linux-acpi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.12 Precedence: list Reply-To: arun@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org * Arun R Bharadwaj [2009-10-16 15:08:50]: This patch adds a little information about the redesigned cpuidle infrastructure in Documentation/cpuidle/core.txt Signed-off-by: Arun R Bharadwaj --- Documentation/cpuidle/core.txt | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) Index: linux.trees.git/Documentation/cpuidle/core.txt =================================================================== --- linux.trees.git.orig/Documentation/cpuidle/core.txt +++ linux.trees.git/Documentation/cpuidle/core.txt @@ -21,3 +21,38 @@ which can be used to switch governors at is meant for developer testing only. In normal usage, kernel picks the best governor based on governor ratings. SEE ALSO: sysfs.txt in this directory. + +Design: + +Cpuidle allows for registration of multiple sets of idle routines. +The latest registered set is used by cpuidle governors as the current +active set to choose the right idle state. This set is managed as a +list and each time the newly registered set is added to the head of the +list and made the current active set. + +An example of how this would work on x86 is shown below. + +----------------- ----------------- +| | | | +| choose b/w | mwait is chosen | mwait | +| mwait, poll, |-------------------------------------> |(current active| +| default, c1e | register to cpuidle | set) | +| | with mwait as the idle routine | | +----------------- ----------------- + + +----------------- ----------------- +| | | c1, c2, c3 | +| ACPI | register to cpuidle | (current) | +| discovery |-------------------------------------> |---------------| +| | with c1, c2, c3 | mwait | +| | as set of idle routines | | +----------------- ----------------- + +With this mechanism, a module can register and unregister its set of +idle routines at run time in a clean manner. + +The main idle routine called inside cpu_idle() of every arch is defined in +driver/cpuidle/cpuidle.c which would in turn call the idle routine selected +by the governor. If the CONFIG_CPU_IDLE is disabled, the arch needs to +provide an alternate definition for cpuidle_idle_call().