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=-2.3 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 63FB4C11D05 for ; Thu, 20 Feb 2020 16:11:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4315220658 for ; Thu, 20 Feb 2020 16:11:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728598AbgBTQLc (ORCPT ); Thu, 20 Feb 2020 11:11:32 -0500 Received: from foss.arm.com ([217.140.110.172]:45702 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728523AbgBTQLb (ORCPT ); Thu, 20 Feb 2020 11:11:31 -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 216BB31B; Thu, 20 Feb 2020 08:11:31 -0800 (PST) Received: from [10.0.2.15] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1B0A73F6CF; Thu, 20 Feb 2020 08:11:28 -0800 (PST) Subject: Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal To: Vincent Guittot Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , linux-kernel , Phil Auld , Parth Shah , Hillf Danton References: <20200214152729.6059-5-vincent.guittot@linaro.org> <20200219125513.8953-1-vincent.guittot@linaro.org> <9fe822fc-c311-2b97-ae14-b9269dd99f1e@arm.com> From: Valentin Schneider Message-ID: Date: Thu, 20 Feb 2020 16:11:18 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: 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 20/02/2020 14:36, Vincent Guittot wrote: > I agree that setting by default to SCHED_CAPACITY_SCALE is too much > for little core. > The problem for little core can be fixed by using the cpu capacity instead > So that's indeed better for big.LITTLE & co. Any reason however for not aligning with the initialization of util_avg ? With the default MC imbalance_pct (117), it takes 875 utilization to make a single CPU group (with 1024 capacity) overloaded (group_is_overloaded()). For a completely idle CPU, that means forking at least 3 tasks (512 + 256 + 128 util_avg) With your change, it only takes 2 tasks. I know I'm being nitpicky here, but I feel like those should be aligned, unless we have a proper argument against it - in which case this should also appear in the changelog with so far only mentions issues with util_avg migration, not the fork time initialization. > @@ -796,6 +794,8 @@ void post_init_entity_util_avg(struct task_struct *p) > } > } > > + sa->runnable_avg = cpu_scale; > + > if (p->sched_class != &fair_sched_class) { > /* > * For !fair tasks do: >> >>> sa->load_avg = scale_load_down(se->load.weight); >>> + } >>> >>> /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ >>> }