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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 AFF5CC4CED1 for ; Thu, 3 Oct 2019 16:08:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83B0C222CC for ; Thu, 3 Oct 2019 16:08:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570118938; bh=lQFsJo/ifnDFbQ6bmQ5/++QOotlYuVYGBuf+IwxkEQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=iX55+7XIf1MXWRjq9zrVCC5WLgdzM+61wSCfj0a2sd06vMoh045aiOE3Ehs94h77K 2cwsi6TQIB8wClkvJgNPjaqhGrQ0+uZ5e49ZjDveAnjQJRNZ8fBOG8BInNJsghuDoR UUbnKcfsqo9nBMIwH8oUz74xdFduLXKHauN7mRQc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733305AbfJCQI5 (ORCPT ); Thu, 3 Oct 2019 12:08:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:57296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733288AbfJCQIx (ORCPT ); Thu, 3 Oct 2019 12:08:53 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B781207FF; Thu, 3 Oct 2019 16:08:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570118932; bh=lQFsJo/ifnDFbQ6bmQ5/++QOotlYuVYGBuf+IwxkEQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SThtAwg2p9/wB/zC16wsdM5cys4DdgcRf9/BzCzq47d0pAgRh0OrHmIv2x9CxO3ZE VOq+VbjpFawfDuARFGQmEyInq3zDNNA6QeP3gV3tN90u84M6186NVJ00/jpr9qIzvG Ov2fprcdVKdNMIiE0d++BWCUfDOQ8Zz9LstN/Jhg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Guittot , "Peter Zijlstra (Intel)" , Linus Torvalds , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH 4.14 063/185] sched/fair: Fix imbalance due to CPU affinity Date: Thu, 3 Oct 2019 17:52:21 +0200 Message-Id: <20191003154451.628695736@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154437.541662648@linuxfoundation.org> References: <20191003154437.541662648@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vincent Guittot [ Upstream commit f6cad8df6b30a5d2bbbd2e698f74b4cafb9fb82b ] The load_balance() has a dedicated mecanism to detect when an imbalance is due to CPU affinity and must be handled at parent level. In this case, the imbalance field of the parent's sched_group is set. The description of sg_imbalanced() gives a typical example of two groups of 4 CPUs each and 4 tasks each with a cpumask covering 1 CPU of the first group and 3 CPUs of the second group. Something like: { 0 1 2 3 } { 4 5 6 7 } * * * * But the load_balance fails to fix this UC on my octo cores system made of 2 clusters of quad cores. Whereas the load_balance is able to detect that the imbalanced is due to CPU affinity, it fails to fix it because the imbalance field is cleared before letting parent level a chance to run. In fact, when the imbalance is detected, the load_balance reruns without the CPU with pinned tasks. But there is no other running tasks in the situation described above and everything looks balanced this time so the imbalance field is immediately cleared. The imbalance field should not be cleared if there is no other task to move when the imbalance is detected. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/1561996022-28829-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c298d47888ed8..808db3566ddbc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8359,9 +8359,10 @@ static int load_balance(int this_cpu, struct rq *this_rq, out_balanced: /* * We reach balance although we may have faced some affinity - * constraints. Clear the imbalance flag if it was set. + * constraints. Clear the imbalance flag only if other tasks got + * a chance to move and fix the imbalance. */ - if (sd_parent) { + if (sd_parent && !(env.flags & LBF_ALL_PINNED)) { int *group_imbalance = &sd_parent->groups->sgc->imbalance; if (*group_imbalance) -- 2.20.1