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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 6B21FC433DF for ; Fri, 31 Jul 2020 12:05:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F87A22CAE for ; Fri, 31 Jul 2020 12:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733001AbgGaMFK (ORCPT ); Fri, 31 Jul 2020 08:05:10 -0400 Received: from foss.arm.com ([217.140.110.172]:56192 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732975AbgGaMFI (ORCPT ); Fri, 31 Jul 2020 08:05:08 -0400 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 D918D1FB; Fri, 31 Jul 2020 05:05:07 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id BF1A73F71F; Fri, 31 Jul 2020 05:05:06 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Quentin Perret , mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, morten.rasmussen@arm.com Subject: [PATCH v4 03/10] sched/topology: Propagate SD_ASYM_CPUCAPACITY upwards Date: Fri, 31 Jul 2020 12:54:55 +0100 Message-Id: <20200731115502.12954-4-valentin.schneider@arm.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200731115502.12954-1-valentin.schneider@arm.com> References: <20200731115502.12954-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We currently set this flag *only* on domains whose topology level exactly match the level where we detect asymmetry (as returned by asym_cpu_capacity_level()). This is rather problematic. Say there are two clusters in the system, one with a lone big CPU and the other with a mix of big and LITTLE CPUs (as is allowed by DynamIQ): DIE [ ] MC [ ][ ] 0 1 2 3 4 L L B B B asym_cpu_capacity_level() will figure out that the MC level is the one where all CPUs can see a CPU of max capacity, and we will thus set SD_ASYM_CPUCAPACITY at MC level for all CPUs. That lone big CPU will degenerate its MC domain, since it would be alone in there, and will end up with just a DIE domain. Since the flag was only set at MC, this CPU ends up not seeing any SD with the flag set, which is broken. Rather than clearing dflags at every topology level, clear it before entering the topology level loop. This will properly propagate upwards flags that are set starting from a certain level. Reviewed-by: Quentin Perret Signed-off-by: Valentin Schneider --- kernel/sched/topology.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 865fff3ef20a..42b89668e1e4 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1985,11 +1985,10 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att /* Set up domains for CPUs specified by the cpu_map: */ for_each_cpu(i, cpu_map) { struct sched_domain_topology_level *tl; + int dflags = 0; sd = NULL; for_each_sd_topology(tl) { - int dflags = 0; - if (tl == tl_asym) { dflags |= SD_ASYM_CPUCAPACITY; has_asym = true; -- 2.27.0