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, 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 3773BC636CB for ; Thu, 15 Jul 2021 19:02:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 218C6613F3 for ; Thu, 15 Jul 2021 19:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241804AbhGOTFX (ORCPT ); Thu, 15 Jul 2021 15:05:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:38158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242400AbhGOTDk (ORCPT ); Thu, 15 Jul 2021 15:03:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C6D2B613D7; Thu, 15 Jul 2021 18:59:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626375579; bh=qkBu6LtwSHW6e9gJ6y7H1ZaKH79w7EKUPovML+t5HBQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lkuBn3fGf2zFK3zEHgRDuE2jHSrJd5LyAmNaWo6vtEHwrMYagSCgcO9V15aEdOqSk tUzfpfP6lG7v8vetacGXifuZX8D0r6paZqYKBY2MVNfDMl+RD/IM47rhpSsGfPwsiS X/3WzHju2KgJ3xUvlvDuRtwzy6amSBlM269cwBxI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sachin Sant , Naresh Kamboju , Odin Ugedal , "Peter Zijlstra (Intel)" , Vincent Guittot , Sasha Levin Subject: [PATCH 5.12 146/242] sched/fair: Ensure _sum and _avg values stay consistent Date: Thu, 15 Jul 2021 20:38:28 +0200 Message-Id: <20210715182618.902752060@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210715182551.731989182@linuxfoundation.org> References: <20210715182551.731989182@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: Odin Ugedal [ Upstream commit 1c35b07e6d3986474e5635be566e7bc79d97c64d ] The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant Reported-by: Naresh Kamboju Signed-off-by: Odin Ugedal Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Tested-by: Sachin Sant Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 20ac5dff9a0c..572f312cc803 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3665,15 +3665,15 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) r = removed_load; sub_positive(&sa->load_avg, r); - sub_positive(&sa->load_sum, r * divider); + sa->load_sum = sa->load_avg * divider; r = removed_util; sub_positive(&sa->util_avg, r); - sub_positive(&sa->util_sum, r * divider); + sa->util_sum = sa->util_avg * divider; r = removed_runnable; sub_positive(&sa->runnable_avg, r); - sub_positive(&sa->runnable_sum, r * divider); + sa->runnable_sum = sa->runnable_avg * divider; /* * removed_runnable is the unweighted version of removed_load so we -- 2.30.2