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_2 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 8F4F8C2D0EA for ; Wed, 8 Apr 2020 14:30:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B45C20780 for ; Wed, 8 Apr 2020 14:30:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728799AbgDHOax (ORCPT ); Wed, 8 Apr 2020 10:30:53 -0400 Received: from mail.santannapisa.it ([193.205.80.98]:18167 "EHLO mail.santannapisa.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726774AbgDHOax (ORCPT ); Wed, 8 Apr 2020 10:30:53 -0400 X-Greylist: delayed 3600 seconds by postgrey-1.27 at vger.kernel.org; Wed, 08 Apr 2020 10:30:52 EDT Received: from [151.41.75.232] (account l.abeni@santannapisa.it HELO nowhere) by santannapisa.it (CommuniGate Pro SMTP 6.1.11) with ESMTPSA id 147238791; Wed, 08 Apr 2020 15:30:48 +0200 Date: Wed, 8 Apr 2020 15:30:32 +0200 From: luca abeni To: Valentin Schneider Cc: 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 , Qais Yousef , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities Message-ID: <20200408153032.447e098d@nowhere> In-Reply-To: References: <20200408095012.3819-1-dietmar.eggemann@arm.com> <20200408095012.3819-3-dietmar.eggemann@arm.com> Organization: Scuola Superiore S.Anna X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Luca