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,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 BFE1DC433E0 for ; Thu, 4 Feb 2021 15:11:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8096A64F43 for ; Thu, 4 Feb 2021 15:11:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236977AbhBDPLL (ORCPT ); Thu, 4 Feb 2021 10:11:11 -0500 Received: from foss.arm.com ([217.140.110.172]:59756 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237015AbhBDO6A (ORCPT ); Thu, 4 Feb 2021 09:58:00 -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 1988511D4; Thu, 4 Feb 2021 06:57:08 -0800 (PST) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 18A773F718; Thu, 4 Feb 2021 06:57:05 -0800 (PST) Subject: Re: [PATCH 5/8] sched/fair: Make check_misfit_status() only compare dynamic capacities To: Valentin Schneider , Qais Yousef Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Vincent Guittot , Morten Rasmussen , Quentin Perret , Pavan Kondeti , Rik van Riel References: <20210128183141.28097-1-valentin.schneider@arm.com> <20210128183141.28097-6-valentin.schneider@arm.com> <20210203151546.rwkbdjxc2vgiodvx@e107158-lin> From: Dietmar Eggemann Message-ID: <1c4c5ff0-f29e-3f08-7ba0-6173bda888cd@arm.com> Date: Thu, 4 Feb 2021 15:57:00 +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: 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 04/02/2021 12:34, Valentin Schneider wrote: > On 04/02/21 11:49, Dietmar Eggemann wrote: >> On 03/02/2021 16:15, Qais Yousef wrote: >>> On 01/28/21 18:31, Valentin Schneider wrote: [...] > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 21bd71f58c06..ea7f0155e268 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1482,6 +1482,33 @@ DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing); > DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity); > extern struct static_key_false sched_asym_cpucapacity; > > +/* > + * Note that the static key is system-wide, but the visibility of > + * SD_ASYM_CPUCAPACITY isn't. Thus the static key being enabled does not > + * imply all CPUs can see asymmetry. > + * > + * Consider an asymmetric CPU capacity system such as: > + * > + * MC [ ] > + * 0 1 2 3 4 5 > + * L L L L B B > + * > + * w/ arch_scale_cpu_capacity(L) < arch_scale_cpu_capacity(B) > + * > + * By default, booting this system will enable the sched_asym_cpucapacity > + * static key, and all CPUs will see SD_ASYM_CPUCAPACITY set at their MC > + * sched_domain. > + * > + * Further consider exclusive cpusets creating a "symmetric island": > + * > + * MC [ ][ ] > + * 0 1 2 3 4 5 > + * L L L L B B > + * > + * Again, booting this will enable the static key, but CPUs 0-1 will *not* have > + * SD_ASYM_CPUCAPACITY set in any of their sched_domain. This is the intending s/intending/intended > + * behaviour, as CPUs 0-1 should be treated as a regular, isolated SMP system. > + */ LGTM.