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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 23DB6C4743C for ; Mon, 21 Jun 2021 10:39:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A74561153 for ; Mon, 21 Jun 2021 10:39:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230377AbhFUKlg (ORCPT ); Mon, 21 Jun 2021 06:41:36 -0400 Received: from foss.arm.com ([217.140.110.172]:60452 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230075AbhFUKlb (ORCPT ); Mon, 21 Jun 2021 06:41:31 -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 BDEA3ED1; Mon, 21 Jun 2021 03:39:17 -0700 (PDT) Received: from e120877-lin.cambridge.arm.com (e120877-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 8890D3F718; Mon, 21 Jun 2021 03:39:16 -0700 (PDT) From: Vincent Donnefort To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com Cc: vincent.guittot@linaro.org, dietmar.eggemann@arm.com, valentin.schneider@arm.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org, Vincent Donnefort Subject: [PATCH v2 2/2] sched/rt: Fix Deadline utilization tracking during policy change Date: Mon, 21 Jun 2021 11:37:52 +0100 Message-Id: <1624271872-211872-3-git-send-email-vincent.donnefort@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1624271872-211872-1-git-send-email-vincent.donnefort@arm.com> References: <1624271872-211872-1-git-send-email-vincent.donnefort@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org DL keeps track of the utilization on a per-rq basis with the structure avg_dl. This utilization is updated during task_tick_dl(), put_prev_task_dl() and set_next_task_dl(). However, when the current running task changes its policy, set_next_task_dl() which would usually take care of updating the utilization when the rq starts running DL tasks, will not see a such change, leaving the avg_dl structure outdated. When that very same task will be dequeued later, put_prev_task_dl() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the DL utilization signal. The signal would eventually recover from this issue after few ms. Even if no DL tasks are run, avg_dl is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_dl, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to DL. Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking") Signed-off-by: Vincent Donnefort Reviewed-by: Vincent Guittot diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 3829c5a..915227a 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2497,6 +2497,8 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) check_preempt_curr_dl(rq, p, 0); else resched_curr(rq); + } else { + update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0); } } -- 2.7.4