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 3E0C5C3F2D1 for ; Mon, 2 Mar 2020 13:27:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 122E02086A for ; Mon, 2 Mar 2020 13:27:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728043AbgCBN1u (ORCPT ); Mon, 2 Mar 2020 08:27:50 -0500 Received: from foss.arm.com ([217.140.110.172]:60918 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728022AbgCBN1q (ORCPT ); Mon, 2 Mar 2020 08:27:46 -0500 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 B51F111FB; Mon, 2 Mar 2020 05:27:45 -0800 (PST) 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 4BEED3F534; Mon, 2 Mar 2020 05:27:44 -0800 (PST) From: Qais Yousef To: Ingo Molnar , Peter Zijlstra , Steven Rostedt , Dietmar Eggemann , Pavan Kondeti Cc: Juri Lelli , Vincent Guittot , Ben Segall , Mel Gorman , linux-kernel@vger.kernel.org, Qais Yousef Subject: [PATCH v3 6/6] sched/rt: Fix pushing unfit tasks to a better CPU Date: Mon, 2 Mar 2020 13:27:21 +0000 Message-Id: <20200302132721.8353-7-qais.yousef@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200302132721.8353-1-qais.yousef@arm.com> References: <20200302132721.8353-1-qais.yousef@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a task was running on unfit CPU we could ignore migrating if the priority level of the new fitting CPU is the *same* as the unfit one. Add an extra check to select_task_rq_rt() to allow the push in case: * p->prio == new_cpu.highest_priority * task_fits(p, new_cpu) Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware") Signed-off-by: Qais Yousef --- kernel/sched/rt.c | 41 ++++++++++++++++++++++++++++------------- 1 file changed, 28 insertions(+), 13 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ce230bec6847..8aaa442e4867 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1474,20 +1474,35 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags) if (test || !rt_task_fits_capacity(p, cpu)) { int target = find_lowest_rq(p); - /* - * Bail out if we were forcing a migration to find a better - * fitting CPU but our search failed. - */ - if (!test && target != -1 && !rt_task_fits_capacity(p, target)) - goto out_unlock; + if (target != -1) { + bool fit_target = rt_task_fits_capacity(p, target); - /* - * Don't bother moving it if the destination CPU is - * not running a lower priority task. - */ - if (target != -1 && - p->prio < cpu_rq(target)->rt.highest_prio.curr) - cpu = target; + /* + * Bail out if we were forcing a migration to find a + * better fitting CPU but our search failed. + */ + if (!test && !fit_target) + goto out_unlock; + + /* + * Don't bother moving it if the destination CPU is + * not running a lower priority task. + */ + if (p->prio < cpu_rq(target)->rt.highest_prio.curr) { + + cpu = target; + + } else if (p->prio == cpu_rq(target)->rt.highest_prio.curr) { + + /* + * If the priority is the same and the new CPU + * is a better fit, then move, otherwise don't + * bother here either. + */ + if (fit_target) + cpu = target; + } + } } out_unlock: -- 2.17.1