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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 2B544C07E9C for ; Mon, 12 Jul 2021 06:22:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1404261176 for ; Mon, 12 Jul 2021 06:22:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234501AbhGLGYq (ORCPT ); Mon, 12 Jul 2021 02:24:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:39102 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235014AbhGLGY0 (ORCPT ); Mon, 12 Jul 2021 02:24:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BE03D61185; Mon, 12 Jul 2021 06:20:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626070857; bh=VdU5if/H3h+GWxk3WVaJSJnSIav16mMlfhXKIH2qt40=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mZmGzhM1pvyTnI2wb3Bl7vQptBJ/C7nPZdoTGK+uaTM2mrfv8PaOQin1sSFisK4G0 rUapk/YoPdfIPMQJ5zRJDoHkTJ/FTT/SJ5/pb1MlIAPFaX9fZv1G9GEmBt4tNZ/iEV TKYRbijfZFovKNOnUdtXaPWZjTQeYGOo6Ci+kYg0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Donnefort , "Peter Zijlstra (Intel)" , Vincent Guittot , Sasha Levin Subject: [PATCH 5.4 171/348] sched/rt: Fix Deadline utilization tracking during policy change Date: Mon, 12 Jul 2021 08:09:15 +0200 Message-Id: <20210712060723.545687840@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060659.886176320@linuxfoundation.org> References: <20210712060659.886176320@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vincent Donnefort [ Upstream commit d7d607096ae6d378b4e92d49946d22739c047d4c ] 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 Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com Signed-off-by: Sasha Levin --- kernel/sched/deadline.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 4ce8c11e5e4a..3cf776d5bce8 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2392,6 +2392,8 @@ 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); } } -- 2.30.2