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 04F97C2BA1A for ; Wed, 8 Apr 2020 14:23:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D50F320787 for ; Wed, 8 Apr 2020 14:23:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728742AbgDHOXU (ORCPT ); Wed, 8 Apr 2020 10:23:20 -0400 Received: from foss.arm.com ([217.140.110.172]:39236 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727070AbgDHOXT (ORCPT ); Wed, 8 Apr 2020 10:23:19 -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 98F3D30E; Wed, 8 Apr 2020 07:23:18 -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 9E25F3F68F; Wed, 8 Apr 2020 07:23:16 -0700 (PDT) Date: Wed, 8 Apr 2020 15:23:14 +0100 From: Qais Yousef To: luca abeni Cc: Valentin Schneider , Dietmar Eggemann , 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: <20200408142313.j6yfv6s3i5pzs5wv@e107158-lin.cambridge.arm.com> References: <20200408095012.3819-1-dietmar.eggemann@arm.com> <20200408095012.3819-3-dietmar.eggemann@arm.com> <20200408153032.447e098d@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200408153032.447e098d@nowhere> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/08/20 15:30, luca abeni wrote: > Hi Valentin, > > On Wed, 08 Apr 2020 11:42:14 +0100 > Valentin Schneider wrote: > > > On 08/04/20 10:50, Dietmar Eggemann wrote: > > > +++ b/kernel/sched/sched.h > > > @@ -304,11 +304,14 @@ void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, > > > int cpus) __dl_update(dl_b, -((s32)tsk_bw / cpus)); > > > } > > > > > > +static inline unsigned long rd_capacity(int cpu); > > > + > > > static inline > > > -bool __dl_overflow(struct dl_bw *dl_b, int cpus, u64 old_bw, u64 > > > new_bw) +bool __dl_overflow(struct dl_bw *dl_b, int cpu, u64 > > > old_bw, u64 new_bw) { > > > return dl_b->bw != -1 && > > > - dl_b->bw * cpus < dl_b->total_bw - old_bw + new_bw; > > > + cap_scale(dl_b->bw, rd_capacity(cpu)) < > > > + dl_b->total_bw - old_bw + new_bw; > > > } > > > > > > > I don't think this is strictly equivalent to what we have now for the > > SMP case. 'cpus' used to come from dl_bw_cpus(), which is an ugly way > > of writing > > > > cpumask_weight(rd->span AND cpu_active_mask); > > > > The rd->cpu_capacity_orig field you added gets set once per domain > > rebuild, so it also happens in sched_cpu_(de)activate() but is > > separate from touching cpu_active_mask. AFAICT this mean we can > > observe a CPU as !active but still see its capacity_orig accounted in > > a root_domain. > > Sorry, I suspect this is my fault, because the bug comes from my > original patch. > When I wrote the original code, I believed that when a CPU is > deactivated it is also removed from its root domain. > > I now see that I was wrong. Shouldn't rd->online be equivalent to (rd->span & cpu-active_mask)? -- Qais Yousef