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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 2C842C43603 for ; Thu, 5 Dec 2019 09:24:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5F7C24651 for ; Thu, 5 Dec 2019 09:24:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729088AbfLEJYr (ORCPT ); Thu, 5 Dec 2019 04:24:47 -0500 Received: from foss.arm.com ([217.140.110.172]:55140 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726239AbfLEJYq (ORCPT ); Thu, 5 Dec 2019 04:24:46 -0500 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 B9D6A328; Thu, 5 Dec 2019 01:24:45 -0800 (PST) Received: from [192.168.0.9] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2A00F3F68E; Thu, 5 Dec 2019 01:24:43 -0800 (PST) Subject: Re: [RFC 0/3] Introduce per-task latency_tolerance for scheduler hints To: Parth Shah , linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, patrick.bellasi@matbug.net, valentin.schneider@arm.com, qais.yousef@arm.com, pavel@ucw.cz, dhaval.giani@oracle.com, qperret@qperret.net, David.Laight@ACULAB.COM, morten.rasmussen@arm.com, pjt@google.com, tj@kernel.org, viresh.kumar@linaro.org, rafael.j.wysocki@intel.com, daniel.lezcano@linaro.org References: <20191125094618.30298-1-parth@linux.ibm.com> From: Dietmar Eggemann Message-ID: <450fc7e2-49d5-d809-281f-7d9a99d3e530@arm.com> Date: Thu, 5 Dec 2019 10:24:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 MIME-Version: 1.0 In-Reply-To: <20191125094618.30298-1-parth@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/11/2019 10:46, Parth Shah wrote: > This patch series is based on the discussion started as the "Usecases for > the per-task latency-nice attribute"[1] > > This patch series introduces a new per-task attribute latency_tolerance to > provide the scheduler hints about the latency requirements of the task. I forgot but is there a chance to have this as a per-taskgroup attribute as well? > Latency_tolerance is a ranged attribute of a task with the value ranging > from [-20, 19] both inclusive which makes it align with the task nice > value. > > The value should provide scheduler hints about the relative latency > requirements of tasks, meaning the task with "latency_tolerance = -20" > should have lower latency than compared to those tasks with higher values. > Similarly a task with "latency_tolerance = 19" can have higher latency and > hence such tasks may bot care much about the latency numbers. > > The default value is set to 0. The usecases defined in [1] can use this > range of [-20, 19] for latency_tolerance for the specific purpose. This > patch does not define any use cases for such attribute so that any change > in naming or range does not affect much to the other (future) patches using > this. The actual use of latency_tolerance during task wakeup and > load-balancing is yet to be coded for each of those usecases. This can definitely be useful for Android/EAS by replacing the current proprietary solution in android-google-common android-5.4: commit 760b82c9b88d ("ANDROID: sched/fair: Bias EAS placement for latency") commit c28f9d3945f1 ("ANDROID: sched/core: Add a latency-sensitive flag to uclamp") which links to usercase 6 (EAS) in [1].