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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 33969C4743C for ; Wed, 23 Jun 2021 08:19:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EEBD60724 for ; Wed, 23 Jun 2021 08:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230392AbhFWIV7 (ORCPT ); Wed, 23 Jun 2021 04:21:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230391AbhFWIVk (ORCPT ); Wed, 23 Jun 2021 04:21:40 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60D96C061766; Wed, 23 Jun 2021 01:19:23 -0700 (PDT) Date: Wed, 23 Jun 2021 08:19:20 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1624436361; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=B517Cxk53bPhx0ZH7YJQ/2Tbc2ga10Zno7Gp1uYPWkM=; b=q8R84NQzYMyuSk4Mwyuh6iwA281OO1V/xJLg2oaq8kywIDwK8RWSV/LbT6m+hrFzJIJPZe PXFEEPIUQJ3izLxsfoYAhrwH0FYMskRx1FFde9Wpg4FZ/NkyYtlCIwm9to3/8dzGO2oPbh 53eJ3jUuzvBNJHTYdi3wyvPIuhvgG69xinb5kTmlZtA9LM0/khXNzyioiIN7HEb9Z5vzaV 5X1j7comimUqonFohnkJYiZmx1Q1dkAUj4DOPMKSFsDwfp7ML+N480j7gSwWiJy5l+0nvN RdrbzlDtja27V+w4BJAwyMUzu0tuo951nJMeUGF8X5ZMDV4X8568gwvL4OFV1A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1624436361; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=B517Cxk53bPhx0ZH7YJQ/2Tbc2ga10Zno7Gp1uYPWkM=; b=SF/uHc4H2he/fgczUn9BPewgbY2awZrbTrYHet39eRijc2juRfpRXJzwGlwF3XSl4nSAbo CAgn7qHSfYLN6aCQ== From: "tip-bot2 for Vincent Donnefort" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/rt: Fix RT utilization tracking during policy change Cc: Vincent Donnefort , "Peter Zijlstra (Intel)" , Vincent Guittot , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1624271872-211872-2-git-send-email-vincent.donnefort@arm.com> References: <1624271872-211872-2-git-send-email-vincent.donnefort@arm.com> MIME-Version: 1.0 Message-ID: <162443636097.395.8556355025777632399.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: fecfcbc288e9f4923f40fd23ca78a6acdc7fdf6c Gitweb: https://git.kernel.org/tip/fecfcbc288e9f4923f40fd23ca78a6acdc7fdf6c Author: Vincent Donnefort AuthorDate: Mon, 21 Jun 2021 11:37:51 +01:00 Committer: Peter Zijlstra CommitterDate: Tue, 22 Jun 2021 16:41:59 +02:00 sched/rt: Fix RT utilization tracking during policy change RT keeps track of the utilization on a per-rq basis with the structure avg_rt. This utilization is updated during task_tick_rt(), put_prev_task_rt() and set_next_task_rt(). However, when the current running task changes its policy, set_next_task_rt() which would usually take care of updating the utilization when the rq starts running RT tasks, will not see a such change, leaving the avg_rt structure outdated. When that very same task will be dequeued later, put_prev_task_rt() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the RT utilization signal. The signal would eventually recover from this issue after few ms. Even if no RT tasks are run, avg_rt is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_rt, 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 RT. Fixes: 371bf427 ("sched/rt: Add rt_rq utilization tracking") Signed-off-by: Vincent Donnefort Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Link: https://lore.kernel.org/r/1624271872-211872-2-git-send-email-vincent.donnefort@arm.com --- kernel/sched/rt.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index a525447..3daf42a 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2341,13 +2341,20 @@ void __init init_sched_rt_class(void) static void switched_to_rt(struct rq *rq, struct task_struct *p) { /* - * If we are already running, then there's nothing - * that needs to be done. But if we are not running - * we may need to preempt the current running task. - * If that current running task is also an RT task + * If we are running, update the avg_rt tracking, as the running time + * will now on be accounted into the latter. + */ + if (task_current(rq, p)) { + update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0); + return; + } + + /* + * If we are not running we may need to preempt the current + * running task. If that current running task is also an RT task * then see if we can move to another run queue. */ - if (task_on_rq_queued(p) && rq->curr != p) { + if (task_on_rq_queued(p)) { #ifdef CONFIG_SMP if (p->nr_cpus_allowed > 1 && rq->rt.overloaded) rt_queue_push_tasks(rq);