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=-10.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 4171BC2D0A3 for ; Mon, 26 Oct 2020 10:15:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB1FA223AC for ; Mon, 26 Oct 2020 10:15:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1769417AbgJZKPR (ORCPT ); Mon, 26 Oct 2020 06:15:17 -0400 Received: from foss.arm.com ([217.140.110.172]:33808 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1768371AbgJZJr3 (ORCPT ); Mon, 26 Oct 2020 05:47:29 -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 629AE30E; Mon, 26 Oct 2020 02:47:28 -0700 (PDT) Received: from [192.168.178.2] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5AFB53F719; Mon, 26 Oct 2020 02:47:27 -0700 (PDT) Subject: Re: [PATCH v3 1/1] sched/uclamp: add SCHED_FLAG_UTIL_CLAMP_RESET flag to reset uclamp To: Yun Hsiang , peterz@infradead.org Cc: linux-kernel@vger.kernel.org, qais.yousef@arm.com, patrick.bellasi@matbug.net References: <20201025073632.720393-1-hsiang023167@gmail.com> From: Dietmar Eggemann Message-ID: <08b7cdda-291c-bdf1-b72d-0a3ef411fcf3@arm.com> Date: Mon, 26 Oct 2020 10:47:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201025073632.720393-1-hsiang023167@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/10/2020 08:36, Yun Hsiang wrote: > If the user wants to stop controlling uclamp and let the task inherit > the value from the group, we need a method to reset. > > Add SCHED_FLAG_UTIL_CLAMP_RESET flag to allow the user to reset uclamp via > sched_setattr syscall. > > The policy is > _CLAMP_RESET => reset both min and max > _CLAMP_RESET | _CLAMP_MIN => reset min value > _CLAMP_RESET | _CLAMP_MAX => reset max value > _CLAMP_RESET | _CLAMP_MIN | _CLAMP_MAX => reset both min and max > > Signed-off-by: Yun Hsiang [...] > @@ -1451,7 +1464,8 @@ static void __setscheduler_uclamp(struct task_struct *p, > struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; > > /* Keep using defined clamps across class changes */ > - if (uc_se->user_defined) > + if (flags != SCHED_FLAG_UTIL_CLAMP_RESET && > + uc_se->user_defined) > continue; With: (1) _CLAMP_RESET => reset both min and max (2) _CLAMP_RESET | _CLAMP_MIN => reset min value (3) _CLAMP_RESET | _CLAMP_MAX => reset max value (4) _CLAMP_RESET | _CLAMP_MIN | _CLAMP_MAX => reset both min and max If you reset an RT task with (1) you don't reset its uclamp.min value. __uclamp_update_util_min_rt_default(p) doesn't know about SCHED_FLAG_UTIL_CLAMP_RESET. It only knows user_defined and will bail early. [...] > - if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) > + if (likely(!flags || flags == SCHED_FLAG_UTIL_CLAMP_RESET)) > return; > > - if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { > + if (flags & SCHED_FLAG_UTIL_CLAMP_MIN) { > + if (reset) { > + clamp_value = __default_uclamp_value(p, UCLAMP_MIN); > + user_defined = false; > + } else { > + clamp_value = attr->sched_util_min; > + user_defined = true; > + } Why do you reset for (1) in the for_each_clamp_id(clamp_id) loop and for (2)-(4) in the if (flags & SCHED_FLAG_UTIL_CLAMP_MXX) condition? You could reset (1)-(4) in the for_each_clamp_id(clamp_id) loop? In this case you wouldn't need __default_uclamp_value(). [...]