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 58B6AC2BA19 for ; Tue, 14 Apr 2020 15:41:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37E16206D5 for ; Tue, 14 Apr 2020 15:41:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440772AbgDNPlm (ORCPT ); Tue, 14 Apr 2020 11:41:42 -0400 Received: from foss.arm.com ([217.140.110.172]:58718 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2440742AbgDNPlZ (ORCPT ); Tue, 14 Apr 2020 11:41:25 -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 33EC830E; Tue, 14 Apr 2020 08:41:24 -0700 (PDT) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.195.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2F5483F73D; Tue, 14 Apr 2020 08:41:22 -0700 (PDT) Date: Tue, 14 Apr 2020 16:41:19 +0100 From: Qais Yousef To: Valentin Schneider Cc: Dietmar Eggemann , luca abeni , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Steven Rostedt , Daniel Bristot de Oliveira , Wei Wang , Quentin Perret , Alessio Balsini , Pavan Kondeti , Patrick Bellasi , Morten Rasmussen , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities Message-ID: <20200414154119.sffnwggqdibdwpp7@e107158-lin.cambridge.arm.com> References: <20200408095012.3819-1-dietmar.eggemann@arm.com> <20200408095012.3819-3-dietmar.eggemann@arm.com> <20200408153032.447e098d@nowhere> <31620965-e1e7-6854-ad46-8192ee4b41af@arm.com> <20200414114032.wigdlnegism6qqns@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/14/20 15:29, Valentin Schneider wrote: > > On 14/04/20 12:40, Qais Yousef wrote: > > > > I haven't followed this discussion closely, so I could be missing something > > here. > > > > In sched_cpu_dying() we call set_rq_offline() which clears the cpu in > > rq->rd->online. > > > > So the way I read the code > > > > rd->online = cpumask_and(rd->span, cpu_active_mask) > > > > But I could have easily missed some detail. > > > > sched_cpu_dying() is wayyyy below sched_cpu_deactivate(). This doesn't help > at all for the dl_cpu_busy() check in sched_cpu_deactivate(). It'd makes more sense to introduce rd->active then rather than a PERCPU global variable IMHO. > > > Regardless, it seems to me that DL is working around something not right in the > > definition of rd->span or using the wrong variable. > > > > What DL is doing now is fine, it only needs to be aligned with the active > mask (which it is). We're making things a bit trickier by adding capacity > values into the mix. I'm still worried that others might be affected by a similar problem. Will dig deeper next week when I'm back from hols. Thanks -- Qais Yousef