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 1EC22C35641 for ; Fri, 21 Feb 2020 09:04:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1B48206E2 for ; Fri, 21 Feb 2020 09:04:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727277AbgBUJE4 (ORCPT ); Fri, 21 Feb 2020 04:04:56 -0500 Received: from mx2.suse.de ([195.135.220.15]:36002 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727025AbgBUJEy (ORCPT ); Fri, 21 Feb 2020 04:04:54 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 6BB1DAD08; Fri, 21 Feb 2020 09:04:52 +0000 (UTC) Date: Fri, 21 Feb 2020 09:04:48 +0000 From: Mel Gorman To: Valentin Schneider Cc: Vincent Guittot , Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , linux-kernel , Phil Auld , Parth Shah , Hillf Danton Subject: Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal Message-ID: <20200221090448.GQ3420@suse.de> References: <20200214152729.6059-5-vincent.guittot@linaro.org> <20200219125513.8953-1-vincent.guittot@linaro.org> <9fe822fc-c311-2b97-ae14-b9269dd99f1e@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 20, 2020 at 04:11:18PM +0000, Valentin Schneider wrote: > 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. > So, what is the way forward here? Should this patch be modified now, a patch be placed on top or go with what we have for the moment that works for symmetric CPUs and deal with the asym case later? I do not have any asym systems at all so I've no means of checking whether there is a problem or not. -- Mel Gorman SUSE Labs