From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A33CEC7EE29 for ; Tue, 30 May 2023 10:33:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231529AbjE3Kdk (ORCPT ); Tue, 30 May 2023 06:33:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231514AbjE3Kdb (ORCPT ); Tue, 30 May 2023 06:33:31 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A02BE125; Tue, 30 May 2023 03:33:27 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A3C71AB6; Tue, 30 May 2023 03:34:12 -0700 (PDT) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 244CE3F67D; Tue, 30 May 2023 03:33:25 -0700 (PDT) Message-ID: <0968c915-0344-b08f-7117-5b1ff6b126fd@arm.com> Date: Tue, 30 May 2023 12:33:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 14/17] Documentation: EM: Add a new section about the design Content-Language: en-US To: Lukasz Luba , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rafael@kernel.org Cc: rui.zhang@intel.com, amit.kucheria@verdurent.com, amit.kachhap@gmail.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, len.brown@intel.com, pavel@ucw.cz, Pierre.Gondois@arm.com, ionela.voinescu@arm.com, rostedt@goodmis.org, mhiramat@kernel.org References: <20230512095743.3393563-1-lukasz.luba@arm.com> <20230512095743.3393563-15-lukasz.luba@arm.com> From: Dietmar Eggemann In-Reply-To: <20230512095743.3393563-15-lukasz.luba@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/05/2023 11:57, Lukasz Luba wrote: > Add a new section 'Design' which covers the information about Energy > Model. It contains the design decisions, describes models and how they > reflect the reality. Add description of the basic const. EM. Change the > other section IDs. I would vote for coalescing the 4 doc patches into 1. > > Signed-off-by: Lukasz Luba > --- > Documentation/power/energy-model.rst | 36 +++++++++++++++++++++------- > 1 file changed, 27 insertions(+), 9 deletions(-) > > diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst > index ef341be2882b..e97c7f18d8bd 100644 > --- a/Documentation/power/energy-model.rst > +++ b/Documentation/power/energy-model.rst > @@ -72,16 +72,34 @@ required to have the same micro-architecture. CPUs in different performance > domains can have different micro-architectures. > > > -2. Core APIs > +2. Design > +----------------- > + > +2.1 Basic EM > +^^^^^^^^^^^^ Can we make sure that people get the relation between 'basic' and 'default' easier? It should be obvious that `pd->default_table->state` refers to this `basic (const.) EM. Using the same identifier always helps in this situation. > + > +The basic EM is built around const. power information for each performance > +state. This model can be derived based on power measurements of the device > +e.g. CPU while running some benchmark. The benchmark might be integer heavy > +or floating point computation with a data set fitting into the CPU cache or > +registers. Bare in mind that this model might not be covering all possible > +workloads running on CPUs. Thus, please run a few different benchmarks and > +verify with some real workloads your power model values. The power variation > +due to the workload instruction mix and data set is not modeled. > +Also static power which can change during runtime due to variation of SOC > +temperature is not modeled in EM. > + > + > +3. Core APIs > ------------ > > -2.1 Config options > +3.1 Config options > ^^^^^^^^^^^^^^^^^^ > > CONFIG_ENERGY_MODEL must be enabled to use the EM framework. > > > -2.2 Registration of performance domains > +3.2 Registration of performance domains > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Registration of 'advanced' EM > @@ -110,8 +128,8 @@ The last argument 'microwatts' is important to set with correct value. Kernel > subsystems which use EM might rely on this flag to check if all EM devices use > the same scale. If there are different scales, these subsystems might decide > to return warning/error, stop working or panic. > -See Section 3. for an example of driver implementing this > -callback, or Section 2.4 for further documentation on this API > +See Section 4. for an example of driver implementing this > +callback, or Section 3.4 for further documentation on this API > > Registration of EM using DT > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > @@ -156,7 +174,7 @@ The EM which is registered using this method might not reflect correctly the > physics of a real device, e.g. when static power (leakage) is important. > > > -2.3 Accessing performance domains > +3.3 Accessing performance domains > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > There are two API functions which provide the access to the energy model: > @@ -175,10 +193,10 @@ CPUfreq governor is in use in case of CPU device. Currently this calculation is > not provided for other type of devices. > > More details about the above APIs can be found in ```` > -or in Section 2.4 > +or in Section 3.4 > > > -2.4 Description details of this API > +3.4 Description details of this API > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > .. kernel-doc:: include/linux/energy_model.h > :internal: > @@ -187,7 +205,7 @@ or in Section 2.4 > :export: > > > -3. Example driver > +4. Example driver > ----------------- > > The CPUFreq framework supports dedicated callback for registering