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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 2AB32C433FC for ; Mon, 20 Jul 2020 16:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08FD820773 for ; Mon, 20 Jul 2020 16:23:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595262209; bh=9fcM8UNcJIVaRWwp8+SdABCME/wG7n29B/fICmrFgRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0/EWMeu7wDtwPIChqGpEZZVzhotHSghPMQsfqGYI+yZdQKdGpqpWJ6E6iVzfNbavI rW6+1Zm8101cVJk6mIIXBLxjO0VSIhp9b+lhvfprI+X/dgHT04y5a60/q+JA6GBJxS c16x0SS55R17xvy+pZvKf3opiM24C/YxMUtzTvzg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388738AbgGTQX2 (ORCPT ); Mon, 20 Jul 2020 12:23:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:41196 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732644AbgGTQFf (ORCPT ); Mon, 20 Jul 2020 12:05:35 -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 26B5A2064B; Mon, 20 Jul 2020 16:05:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595261134; bh=9fcM8UNcJIVaRWwp8+SdABCME/wG7n29B/fICmrFgRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uao4MNRY0FK3yurvQKkMp0eNXoRFUkIY0SOCu9aaS1EJ0QKBc+z2DZpkKm6glRxV4 TZ+htyWveymbDOjNwcmQwhPabI2chlXkis4s5aqfYaMcy2eOW6S6KrniBtA8e7u8oE Kx4U7Dy4Nc37JuJDC5gRqdI2Ye4/q1yUEkU7giWE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Guittot , "Peter Zijlstra (Intel)" , Valentin Schneider , Dietmar Eggemann Subject: [PATCH 5.4 203/215] sched/fair: handle case of task_h_load() returning 0 Date: Mon, 20 Jul 2020 17:38:05 +0200 Message-Id: <20200720152829.823407143@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152820.122442056@linuxfoundation.org> References: <20200720152820.122442056@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 commit 01cfcde9c26d8555f0e6e9aea9d6049f87683998 upstream. task_h_load() can return 0 in some situations like running stress-ng mmapfork, which forks thousands of threads, in a sched group on a 224 cores system. The load balance doesn't handle this correctly because env->imbalance never decreases and it will stop pulling tasks only after reaching loop_max, which can be equal to the number of running tasks of the cfs. Make sure that imbalance will be decreased by at least 1. misfit task is the other feature that doesn't handle correctly such situation although it's probably more difficult to face the problem because of the smaller number of CPUs and running tasks on heterogenous system. We can't simply ensure that task_h_load() returns at least one because it would imply to handle underflow in other places. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Reviewed-by: Dietmar Eggemann Tested-by: Dietmar Eggemann Cc: # v4.4+ Link: https://lkml.kernel.org/r/20200710152426.16981-1-vincent.guittot@linaro.org Signed-off-by: Greg Kroah-Hartman --- kernel/sched/fair.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3824,7 +3824,11 @@ static inline void update_misfit_status( return; } - rq->misfit_task_load = task_h_load(p); + /* + * Make sure that misfit_task_load will not be null even if + * task_h_load() returns 0. + */ + rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1); } #else /* CONFIG_SMP */ @@ -7407,7 +7411,15 @@ static int detach_tasks(struct lb_env *e if (!can_migrate_task(p, env)) goto next; - load = task_h_load(p); + /* + * Depending of the number of CPUs and tasks and the + * cgroup hierarchy, task_h_load() can return a null + * value. Make sure that env->imbalance decreases + * otherwise detach_tasks() will stop only after + * detaching up to loop_max tasks. + */ + load = max_t(unsigned long, task_h_load(p), 1); + if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) goto next;