Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751907Ab2FRM4H (ORCPT ); Mon, 18 Jun 2012 08:56:07 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:62353 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751018Ab2FRM4E (ORCPT ); Mon, 18 Jun 2012 08:56:04 -0400 Message-ID: <4FDF255E.3080402@linaro.org> Date: Mon, 18 Jun 2012 14:55:58 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Peter De Schrijver CC: Deepthi Dharwar , "linux-acpi@vger.kernel.org" , "linux-pm@lists.linux-foundation.org" , Lists Linaro-dev , Linux Kernel Mailing List , Amit Kucheria , "lenb@kernel.org" , Andrew Morton , Linus Torvalds , Colin Cross , Rob Lee , "rjw@sisk.pl" , Kevin Hilman , "linux-next@vger.kernel.org" Subject: Re: cpuidle future and improvements References: <4FDEE98D.7010802@linaro.org> <4FDF16DB.6080004@linux.vnet.ibm.com> <4FDF209E.7070803@linaro.org> <20120618125327.GB32111@tbergstrom-lnx.Nvidia.com> In-Reply-To: <20120618125327.GB32111@tbergstrom-lnx.Nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3508 Lines: 81 On 06/18/2012 02:53 PM, Peter De Schrijver wrote: > On Mon, Jun 18, 2012 at 02:35:42PM +0200, Daniel Lezcano wrote: >> On 06/18/2012 01:54 PM, Deepthi Dharwar wrote: >>> On 06/18/2012 02:10 PM, Daniel Lezcano wrote: >>> >>>> >>>> Dear all, >>>> >>>> A few weeks ago, Peter De Schrijver proposed a patch [1] to allow per >>>> cpu latencies. We had a discussion about this patchset because it >>>> reverse the modifications Deepthi did some months ago [2] and we may >>>> want to provide a different implementation. >>>> >>>> The Linaro Connect [3] event bring us the opportunity to meet people >>>> involved in the power management and the cpuidle area for different SoC. >>>> >>>> With the Tegra3 and big.LITTLE architecture, making per cpu latencies >>>> for cpuidle is vital. >>>> >>>> Also, the SoC vendors would like to have the ability to tune their cpu >>>> latencies through the device tree. >>>> >>>> We agreed in the following steps: >>>> >>>> 1. factor out / cleanup the cpuidle code as much as possible >>>> 2. better sharing of code amongst SoC idle drivers by moving common bits >>>> to core code >>>> 3. make the cpuidle_state structure contain only data >>>> 4. add a API to register latencies per cpu >>> >>> On huge systems especially servers, doing a cpuidle registration on a >>> per-cpu basis creates a big overhead. >>> So global registration was introduced in the first place. >>> >>> Why not have it as a configurable option or so ? >>> Architectures having uniform cpuidle state parameters can continue to >>> use global registration, else have an api to register latencies per cpu >>> as proposed. We can definitely work to see the best way to implement it. >> >> Absolutely, this is one reason I think adding a function: >> >> cpuidle_register_latencies(int cpu, struct cpuidle_latencies); >> >> makes sense if it is used only for cpus with different latencies. >> The other architecture will be kept untouched. >> >> IMHO, before adding more functionalities to cpuidle, we should cleanup >> and consolidate the code. For example, there is a dependency between >> acpi_idle and intel_idle which can be resolved with the notifiers, or >> there is intel specific code in cpuidle.c and cpuidle.h, cpu_relax is >> also introduced to cpuidle which is related to x86 not the cpuidle core, >> etc ... >> >> Cleanup the code will help to move the different bits from the arch >> specific code to the core code and reduce the impact of the core's >> modifications. That should let a common pattern to emerge and will >> facilitate the modifications in the future (per cpu latencies is one of >> them). >> >> That will be a lot of changes and this is why I proposed to put in place >> a cpuidle-next tree in order to consolidate all the cpuidle >> modifications people is willing to see upstream and provide better testing. > > Sounds like a good idea. Do you have something like that already? Yes but I need to cleanup the tree before. http://git.linaro.org/gitweb?p=people/dlezcano/linux-next.git;a=summary -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/