From patchwork Mon Mar 1 16:10:47 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 389900 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=-18.8 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, 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 13CDDC4332B for ; Mon, 1 Mar 2021 17:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD42265328 for ; Mon, 1 Mar 2021 17:42:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234875AbhCARmM (ORCPT ); Mon, 1 Mar 2021 12:42:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:54078 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238500AbhCARdg (ORCPT ); Mon, 1 Mar 2021 12:33:36 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id ECF26650AB; Mon, 1 Mar 2021 16:53:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614617608; bh=xdwfSV7ZBz4TERZnDslXSd0AhoF7MXiDomkSzH4L09I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=euuo6RneKTkzeft2fFWXeTJOUso5UAqlWL+m90zTyLnJibIC5XE4nLcJX19MtzeSK Y9vByGxibioszZjBd+/0Ab6qQrNg005QfSv0/xdRRkTka4FJW/Jq9/9ZE6bHeD6Yf4 LRcRSHgBq9C9fwZu56OoE1HRw5LZB/OljAi86+R0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qais Yousef , "Peter Zijlstra (Intel)" , Quentin Perret , Valentin Schneider , Sasha Levin Subject: [PATCH 5.4 103/340] sched/eas: Dont update misfit status if the task is pinned Date: Mon, 1 Mar 2021 17:10:47 +0100 Message-Id: <20210301161053.397919838@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161048.294656001@linuxfoundation.org> References: <20210301161048.294656001@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qais Yousef [ Upstream commit 0ae78eec8aa64e645866e75005162603a77a0f49 ] If the task is pinned to a cpu, setting the misfit status means that we'll unnecessarily continuously attempt to migrate the task but fail. This continuous failure will cause the balance_interval to increase to a high value, and eventually cause unnecessary significant delays in balancing the system when real imbalance happens. Caught while testing uclamp where rt-app calibration loop was pinned to cpu 0, shortly after which we spawn another task with high util_clamp value. The task was failing to migrate after over 40ms of runtime due to balance_interval unnecessary expanded to a very high value from the calibration loop. Not done here, but it could be useful to extend the check for pinning to verify that the affinity of the task has a cpu that fits. We could end up in a similar situation otherwise. Fixes: 3b1baa6496e6 ("sched/fair: Add 'group_misfit_task' load-balance type") Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Quentin Perret Acked-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210119120755.2425264-1-qais.yousef@arm.com Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3dd7c10d6a582..611adca1e6d0c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3814,7 +3814,7 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) if (!static_branch_unlikely(&sched_asym_cpucapacity)) return; - if (!p) { + if (!p || p->nr_cpus_allowed == 1) { rq->misfit_task_load = 0; return; }