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_PASS,USER_AGENT_MUTT 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 40F3DC43143 for ; Fri, 22 Jun 2018 08:22:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E0CFB23E71 for ; Fri, 22 Jun 2018 08:22:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0CFB23E71 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751527AbeFVIW2 (ORCPT ); Fri, 22 Jun 2018 04:22:28 -0400 Received: from foss.arm.com ([217.140.101.70]:59608 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750934AbeFVIW0 (ORCPT ); Fri, 22 Jun 2018 04:22:26 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E8E921435; Fri, 22 Jun 2018 01:22:25 -0700 (PDT) Received: from e108498-lin.cambridge.arm.com (e108498-lin.cambridge.arm.com [10.1.211.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 704AE3F58F; Fri, 22 Jun 2018 01:22:24 -0700 (PDT) Date: Fri, 22 Jun 2018 09:22:22 +0100 From: Quentin Perret To: Morten Rasmussen Cc: peterz@infradead.org, mingo@redhat.com, valentin.schneider@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, gaku.inami.xh@renesas.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 1/9] sched: Add static_key for asymmetric cpu capacity optimizations Message-ID: <20180622082222.GD23168@e108498-lin.cambridge.arm.com> References: <1529485549-5191-1-git-send-email-morten.rasmussen@arm.com> <1529485549-5191-2-git-send-email-morten.rasmussen@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1529485549-5191-2-git-send-email-morten.rasmussen@arm.com> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Morten, On Wednesday 20 Jun 2018 at 10:05:41 (+0100), Morten Rasmussen wrote: > +static void update_asym_cpucapacity(int cpu) > +{ > + int enable = false; > + > + rcu_read_lock(); > + if (lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY)) > + enable = true; > + rcu_read_unlock(); > + > + if (enable) { > + /* This expects to be hotplug-safe */ > + static_branch_enable_cpuslocked(&sched_asym_cpucapacity); > + } > +} What would happen if you hotplugged an entire cluster ? You'd loose the SD_ASYM_CPUCAPACITY flag but keep the static key is that right ? Should we care ? And also, Peter mentioned an issue with the EAS patches with multiple root_domains. Does that apply here as well ? What if you had a configuration with big and little CPUs in different root_domains for ex? Should we disable the static key in the above cases ? Thanks, Quentin