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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08E36C4321E for ; Fri, 7 Sep 2018 00:15:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1D2E2075B for ; Fri, 7 Sep 2018 00:15:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B1D2E2075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727834AbeIGEw6 (ORCPT ); Fri, 7 Sep 2018 00:52:58 -0400 Received: from foss.arm.com ([217.140.101.70]:52460 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726618AbeIGEw6 (ORCPT ); Fri, 7 Sep 2018 00:52:58 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 461B07A9; Thu, 6 Sep 2018 17:14:58 -0700 (PDT) Received: from [10.103.100.29] (unknown [10.103.100.29]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B0D7F3F557; Thu, 6 Sep 2018 17:14:57 -0700 (PDT) Subject: Re: [PATCH v6 04/14] PM / EM: Expose the Energy Model in sysfs To: Quentin Perret Cc: peterz@infradead.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@codeaurora.org, skannan@codeaurora.org, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org References: <20180820094420.26590-1-quentin.perret@arm.com> <20180820094420.26590-5-quentin.perret@arm.com> <20180906140914.noe3yz7xrb4g5sf4@queper01-lin> From: Dietmar Eggemann Message-ID: Date: Thu, 6 Sep 2018 17:14:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906140914.noe3yz7xrb4g5sf4@queper01-lin> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/06/2018 07:09 AM, Quentin Perret wrote: > Hi Dietmar, > > On Wednesday 05 Sep 2018 at 23:56:43 (-0700), Dietmar Eggemann wrote: >> On 08/20/2018 02:44 AM, Quentin Perret wrote: >>> Expose the Energy Model (read-only) of all performance domains in sysfs >>> for convenience. To do so, add a kobject to the CPU subsystem under the >>> umbrella of which a kobject for each performance domain is attached. >>> >>> The resulting hierarchy is as follows for a platform with two >>> performance domains for example: >>> >>> /sys/devices/system/cpu/energy_model >>> ├── pd0 >>> │   ├── cost >>> │   ├── cpus >>> │   ├── frequency >>> │   └── power >> >> cpus (cpumask of the perf domain), frequency (OPP's of the perf domain) and >> power (values at those OPP's) are somehow easy to grasp, cost is definitely >> not. >> >> You have this nice description in em_pd_energy() what cost actually is. >> IMHO, might be worth repeating this at least in the patch header here. > > Hmm, this patch introduces the sysfs interface, not the 'cost' field > itself. As long as 'cost' is documented in the patch that introduces it > we should be good no ? I mean this patch header tells you _where_ the > fields of the structure are exposed. _What_ the structure is all about > is a different story. Mmmh, so maybe a EAS related documentation file explaining this interface as well, which can be introduced later is the solution here? I'm just not 100% convinced that those cost values are self-explanatory like the other three items: root@h960:~# ls /sys/devices/system/cpu/energy_model/pd0/ cost cpus frequency power root@h960:~# cat /sys/devices/system/cpu/energy_model/pd0/* 96 129 163 201 245 0-3 533000 999000 1402000 1709000 1844000 28 70 124 187 245 > But yeah, in any case, a reminder shouldn't hurt I guess, if you really > want one :-) Nothing which should hold this patch-set back though.