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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C0223C43467 for ; Thu, 8 Oct 2020 10:14:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74DC921D43 for ; Thu, 8 Oct 2020 10:14:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729423AbgJHKOh (ORCPT ); Thu, 8 Oct 2020 06:14:37 -0400 Received: from foss.arm.com ([217.140.110.172]:48508 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729341AbgJHKOh (ORCPT ); Thu, 8 Oct 2020 06:14:37 -0400 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 38C9631B; Thu, 8 Oct 2020 03:14:36 -0700 (PDT) Received: from localhost (unknown [10.1.199.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CE4CD3F70D; Thu, 8 Oct 2020 03:14:35 -0700 (PDT) Date: Thu, 8 Oct 2020 11:14:34 +0100 From: Ionela Voinescu To: Lukasz Luba Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, daniel.lezcano@linaro.org, amitk@kernel.org, Dietmar.Eggemann@arm.com Subject: Re: [PATCH 2/2] thermal: power allocator: estimate sustainable power only once Message-ID: <20201008101434.GA23491@arm.com> References: <20201002122416.13659-1-lukasz.luba@arm.com> <20201002122416.13659-3-lukasz.luba@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201002122416.13659-3-lukasz.luba@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Lukasz, On Friday 02 Oct 2020 at 13:24:16 (+0100), Lukasz Luba wrote: > The sustainable power value might come from the Device Tree or can be > estimated in run time. There is no need to estimate every time when the > governor is called and temperature is high. Instead, store the estimated > value and make it available via standard sysfs interface so it can be > checked from the user-space. > > Signed-off-by: Lukasz Luba > --- > drivers/thermal/gov_power_allocator.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c > index f69fafe486a5..dd59085f38f5 100644 > --- a/drivers/thermal/gov_power_allocator.c > +++ b/drivers/thermal/gov_power_allocator.c > @@ -204,6 +204,8 @@ static u32 pid_controller(struct thermal_zone_device *tz, > estimate_pid_constants(tz, sustainable_power, > params->trip_switch_on, control_temp, > true); > + /* Do the estimation only once and make available in sysfs */ > + tz->tzp->sustainable_power = sustainable_power; After looking over the code, it does seems mostly useless to do the estimation every time the controller kicks in. But I have two comments in this regard: - The estimation is dependent on the temperature we control for which can be changed from sysfs. While I don't see that as a big worry, (sustainable power is an estimation anyway), it might be worth a more detailed comment on why we don't expect this to be a problem, or what we expect the consequences of computing sustainable power only once could be. - In the function comment for estimate_pid_constants() there is a mention of sustainable power: """ * Sustainable power is provided in case it was estimated. The * estimated sustainable_power should not be stored in the * thermal_zone_parameters so it has to be passed explicitly to this * function. """ If we are going to compute the sustainable power estimation only once, this comment should be removed, the estimated value should be added to the trip point parameters before estimate_pid_constants(), and the sustainable_power argument should be removed. Otherwise we end up with conflicting information in the code. Regards, Ionela. > } > > err = control_temp - tz->temperature; > -- > 2.17.1 >