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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 4ED0DC47259 for ; Fri, 1 May 2020 16:12:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A74E216FD for ; Fri, 1 May 2020 16:12:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730153AbgEAQMN (ORCPT ); Fri, 1 May 2020 12:12:13 -0400 Received: from foss.arm.com ([217.140.110.172]:43348 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730082AbgEAQMM (ORCPT ); Fri, 1 May 2020 12:12:12 -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 A474C31B; Fri, 1 May 2020 09:12:11 -0700 (PDT) Received: from [192.168.0.7] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 362503F85E; Fri, 1 May 2020 09:12:09 -0700 (PDT) Subject: Re: [PATCH v2 5/6] sched/deadline: Make DL capacity-aware To: Pavan Kondeti Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Steven Rostedt , Luca Abeni , Daniel Bristot de Oliveira , Wei Wang , Quentin Perret , Alessio Balsini , Patrick Bellasi , Morten Rasmussen , Valentin Schneider , Qais Yousef , linux-kernel@vger.kernel.org References: <20200427083709.30262-1-dietmar.eggemann@arm.com> <20200427083709.30262-6-dietmar.eggemann@arm.com> <20200430131036.GE19464@codeaurora.org> From: Dietmar Eggemann Message-ID: Date: Fri, 1 May 2020 18:12:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200430131036.GE19464@codeaurora.org> 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 30/04/2020 15:10, Pavan Kondeti wrote: > On Mon, Apr 27, 2020 at 10:37:08AM +0200, Dietmar Eggemann wrote: >> From: Luca Abeni [...] >> @@ -1653,10 +1654,19 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags) >> * other hand, if it has a shorter deadline, we >> * try to make it stay here, it might be important. >> */ >> - if (unlikely(dl_task(curr)) && >> - (curr->nr_cpus_allowed < 2 || >> - !dl_entity_preempt(&p->dl, &curr->dl)) && >> - (p->nr_cpus_allowed > 1)) { >> + select_rq = unlikely(dl_task(curr)) && >> + (curr->nr_cpus_allowed < 2 || >> + !dl_entity_preempt(&p->dl, &curr->dl)) && >> + p->nr_cpus_allowed > 1; >> + >> + /* >> + * Take the capacity of the CPU into account to >> + * ensure it fits the requirement of the task. >> + */ >> + if (static_branch_unlikely(&sched_asym_cpucapacity)) >> + select_rq |= !dl_task_fits_capacity(p, cpu); >> + >> + if (select_rq) { >> int target = find_later_rq(p); > > I see that find_later_rq() checks if the previous CPU is part of > later_mask and returns it immediately. So we don't migrate the > task in the case where there previous CPU can't fit the task and > there are no idle CPUs on which the task can fit. LGTM. Hope I understand you here. I don't think that [patch 6/6] provides this already. In case 'later_mask' has no fitting CPUs, 'max_cpu' is set in the otherwise empty 'later_mask'. But 'max_cpu' is not necessary task_cpu(p). Example on Juno [L b b L L L] with thread0-0 (big task) cpudl_find [thread0-0 2117] orig later_mask=0,3-4 later_mask=0 find_later_rq [thread0-0 2117] task_cpu=2 later_mask=0 A tweak could be added favor task_cpu(p) in case it is amongst the CPUs with the maximum capacity in cpudl_find() for the !fit case. [...] >> +/* >> + * Verify the fitness of task @p to run on @cpu taking into account the >> + * CPU original capacity and the runtime/deadline ratio of the task. >> + * >> + * The function will return true if the CPU original capacity of the >> + * @cpu scaled by SCHED_CAPACITY_SCALE >= runtime/deadline ratio of the >> + * task and false otherwise. >> + */ >> +static inline bool dl_task_fits_capacity(struct task_struct *p, int cpu) >> +{ >> + unsigned long cap = arch_scale_cpu_capacity(cpu); >> + >> + return cap_scale(p->dl.dl_deadline, cap) >= p->dl.dl_runtime; >> +} >> + > > This is same as > > return p->dl.dl_bw >> (BW_SHIFT - SCHED_CAPACITY_SHIFT) <= cap > > Correct? If yes, would it be better to use this? We could use sched_dl_entity::dl_density (dl_runtime / dl_deadline) but then I would have to export BW_SHIFT.