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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 36AF9C11D3D for ; Thu, 27 Feb 2020 16:28:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0950724677 for ; Thu, 27 Feb 2020 16:28:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730028AbgB0Q2F (ORCPT ); Thu, 27 Feb 2020 11:28:05 -0500 Received: from foss.arm.com ([217.140.110.172]:54360 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729263AbgB0Q2E (ORCPT ); Thu, 27 Feb 2020 11:28:04 -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 2DCD61FB; Thu, 27 Feb 2020 08:28:04 -0800 (PST) Received: from [10.0.8.126] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7C6DF3F7B4; Thu, 27 Feb 2020 08:28:02 -0800 (PST) Subject: Re: [PATCH 1/2] sched/topology: Don't enable EAS on SMT systems To: Quentin Perret , Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peter Zijlstra , Ingo Molnar , Vincent Guittot , morten.rasmussen@arm.com, Catalin Marinas , Will Deacon , Mark Rutland , kernel-team@android.com References: <20200226164118.6405-1-valentin.schneider@arm.com> <20200226164118.6405-2-valentin.schneider@arm.com> <20200227130001.GA107011@google.com> From: Dietmar Eggemann Message-ID: <7ce12aa2-1925-f991-a85f-5bd81ba668fb@arm.com> Date: Thu, 27 Feb 2020 16:28:01 +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: <20200227130001.GA107011@google.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 27.02.20 13:00, Quentin Perret wrote: > On Wednesday 26 Feb 2020 at 16:41:17 (+0000), Valentin Schneider wrote: >> EAS already requires asymmetric CPU capacities to be enabled, and mixing >> this with SMT is an aberration, but better be safe than sorry. >> >> Signed-off-by: Valentin Schneider > > Acked-by: Quentin Perret > > Thanks, > Quentin > >> --- >> kernel/sched/topology.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c >> index 00911884b7e7..76cd0a370b9a 100644 >> --- a/kernel/sched/topology.c >> +++ b/kernel/sched/topology.c >> @@ -360,6 +360,10 @@ static bool build_perf_domains(const struct cpumask *cpu_map) >> goto free; >> } >> >> + /* EAS definitely does *not* handle SMT */ >> + if (sched_smt_active()) Can you add a pr_warn() and use the current comment as the warning message? Since we have one for !Asym CPU capacity and !schedutil. >> + goto free; >> + [...] There is this 'EAS can be used ...' list of currently 4 items in the build_perf_domains() function header. You could include 'X. No SMT support' there. ;-)