Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751591Ab2FRNGP (ORCPT ); Mon, 18 Jun 2012 09:06:15 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:45547 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751016Ab2FRNGN convert rfc822-to-8bit (ORCPT ); Mon, 18 Jun 2012 09:06:13 -0400 MIME-Version: 1.0 X-Originating-IP: [87.66.96.49] In-Reply-To: <4FDF255E.3080402@linaro.org> References: <4FDEE98D.7010802@linaro.org> <4FDF16DB.6080004@linux.vnet.ibm.com> <4FDF209E.7070803@linaro.org> <20120618125327.GB32111@tbergstrom-lnx.Nvidia.com> <4FDF255E.3080402@linaro.org> Date: Mon, 18 Jun 2012 15:06:12 +0200 Message-ID: Subject: Re: cpuidle future and improvements From: Jean Pihet To: Daniel Lezcano Cc: Peter De Schrijver , 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" 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: 4309 Lines: 102 Hi Daniel, On Mon, Jun 18, 2012 at 2:55 PM, Daniel Lezcano wrote: > 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 That makes sense, especially if you can refactor _and_ add new functionality at the same time. >>>> 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. Do you mean by keeping the parameters in the cpuidle_driver struct and not calling the new API? That looks great. >>> >>> 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. Nice! The new tree needs to be as close as possible to mainline though. Do you have plans for that? Do not hesitate to ask for help on OMAPs! Regards, Jean >> >> 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/ -- 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/