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=-9.8 required=3.0 tests=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 90A24C2D0EA for ; Wed, 8 Apr 2020 09:50:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DF5920753 for ; Wed, 8 Apr 2020 09:50:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728001AbgDHJuk (ORCPT ); Wed, 8 Apr 2020 05:50:40 -0400 Received: from foss.arm.com ([217.140.110.172]:36354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725932AbgDHJui (ORCPT ); Wed, 8 Apr 2020 05:50:38 -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 2CE8811D4; Wed, 8 Apr 2020 02:50:38 -0700 (PDT) Received: from macbook.arm.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 4D7B23F73D; Wed, 8 Apr 2020 02:50:35 -0700 (PDT) From: Dietmar Eggemann To: Ingo Molnar , Peter Zijlstra , Juri Lelli Cc: Vincent Guittot , Steven Rostedt , Luca Abeni , Daniel Bristot de Oliveira , Wei Wang , Quentin Perret , Alessio Balsini , Pavan Kondeti , Patrick Bellasi , Morten Rasmussen , Valentin Schneider , Qais Yousef , linux-kernel@vger.kernel.org Subject: [PATCH 4/4] sched/deadline: Implement fallback mechanism for !fit case Date: Wed, 8 Apr 2020 11:50:12 +0200 Message-Id: <20200408095012.3819-5-dietmar.eggemann@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200408095012.3819-1-dietmar.eggemann@arm.com> References: <20200408095012.3819-1-dietmar.eggemann@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Luca Abeni When a task has a runtime that cannot be served within the scheduling deadline by any of the idle CPU (later_mask) the task is doomed to miss its deadline. This can happen since the SCHED_DEADLINE admission control guarantees only bounded tardiness and not the hard respect of all deadlines. In this case try to select the idle CPU with the largest CPU capacity to minimize tardiness. Signed-off-by: Luca Abeni Signed-off-by: Dietmar Eggemann --- kernel/sched/cpudeadline.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 8630f2a40a3f..8525d73e3de4 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -121,19 +121,30 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, if (later_mask && cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) { - int cpu; + unsigned long cap, max_cap = 0; + int cpu, max_cpu = -1; if (!static_branch_unlikely(&sched_asym_cpucapacity)) return 1; /* Ensure the capacity of the CPUs fits the task. */ for_each_cpu(cpu, later_mask) { - if (!dl_task_fits_capacity(p, cpu)) + if (!dl_task_fits_capacity(p, cpu)) { cpumask_clear_cpu(cpu, later_mask); + + cap = arch_scale_cpu_capacity(cpu); + + if (cap > max_cap) { + max_cap = cap; + max_cpu = cpu; + } + } } - if (!cpumask_empty(later_mask)) - return 1; + if (cpumask_empty(later_mask)) + cpumask_set_cpu(max_cpu, later_mask); + + return 1; } else { int best_cpu = cpudl_maximum(cp); -- 2.17.1