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 D8283C2BA1A for ; Wed, 8 Apr 2020 09:50:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8CB220753 for ; Wed, 8 Apr 2020 09:50:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727990AbgDHJuh (ORCPT ); Wed, 8 Apr 2020 05:50:37 -0400 Received: from foss.arm.com ([217.140.110.172]:36330 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725932AbgDHJuf (ORCPT ); Wed, 8 Apr 2020 05:50:35 -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 F38C4106F; Wed, 8 Apr 2020 02:50:34 -0700 (PDT) Received: from macbook.arm.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 209993F73D; Wed, 8 Apr 2020 02:50:31 -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 3/4] sched/deadline: Make DL capacity-aware Date: Wed, 8 Apr 2020 11:50:11 +0200 Message-Id: <20200408095012.3819-4-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 The current SCHED_DEADLINE (DL) scheduler uses a global EDF scheduling algorithm w/o considering CPU capacity or task utilization. This works well on homogeneous systems where DL tasks are guaranteed to have a bounded tardiness but presents issues on heterogeneous systems. A DL task can migrate to a CPU which does not have enough CPU capacity to correctly serve the task (e.g. a task w/ 70ms runtime and 100ms period on a CPU w/ 512 capacity). Add the DL fitness function dl_task_fits_capacity() for DL admission control on heterogeneous systems. A task fits onto a CPU if: CPU original capacity / 1024 >= task runtime / task deadline Use this function on heterogeneous systems to try to find a CPU which meets this criterion during task wakeup, push and offline migration. On homogeneous systems the original behavior of the DL admission control should be retained. Signed-off-by: Luca Abeni Signed-off-by: Dietmar Eggemann --- kernel/sched/cpudeadline.c | 14 +++++++++++++- kernel/sched/deadline.c | 18 ++++++++++++++---- kernel/sched/sched.h | 15 +++++++++++++++ 3 files changed, 42 insertions(+), 5 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 5cc4012572ec..8630f2a40a3f 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -121,7 +121,19 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, if (later_mask && cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) { - return 1; + int cpu; + + 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)) + cpumask_clear_cpu(cpu, later_mask); + } + + if (!cpumask_empty(later_mask)) + return 1; } else { int best_cpu = cpudl_maximum(cp); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 53b34a95e29e..e10adf1e3c27 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1604,6 +1604,7 @@ static int select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags) { struct task_struct *curr; + bool select_rq; struct rq *rq; if (sd_flag != SD_BALANCE_WAKE) @@ -1623,10 +1624,19 @@ 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; + + /* + * We take into account the capacity of the CPU 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); if (target != -1 && diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 6cbdf7a342a6..598b58c68639 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -306,6 +306,21 @@ void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, int cpus) static inline unsigned long rd_capacity(int cpu); +/* + * 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; +} + static inline bool __dl_overflow(struct dl_bw *dl_b, int cpu, u64 old_bw, u64 new_bw) { -- 2.17.1