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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 143A3C48BE5 for ; Tue, 22 Jun 2021 10:14:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F42096109E for ; Tue, 22 Jun 2021 10:14:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229853AbhFVKQw (ORCPT ); Tue, 22 Jun 2021 06:16:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:38006 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229674AbhFVKQv (ORCPT ); Tue, 22 Jun 2021 06:16:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 190266109E; Tue, 22 Jun 2021 10:14:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1624356874; bh=cMy6BBj1ibQ2XrT7h06HDmFSBOdtVkwQnDCm39eQh2U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cfXGRgJ7YCVRmoA5dMcNPixzJVbFk61JDKbEVwwzcZz2CyhjCAUD9xtEn8Rt4LjyL R6s9tSxAqW+mCo/eoBDpsc43MfgErstbtFc1j51eXSv+CVf4SLUMFuB+MayqgHeJiC b/p/+oCuAmxBTlhC5PlFXNr1sBpHHiy5Z/9hcsDo= Date: Tue, 22 Jun 2021 12:14:31 +0200 From: Greg Kroah-Hartman To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Odin Ugedal , Vincent Guittot , Sasha Levin Subject: Re: [PATCH 5.10 095/146] sched/fair: Correctly insert cfs_rqs to list on unthrottle Message-ID: References: <20210621154911.244649123@linuxfoundation.org> <20210621154917.185551238@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 21, 2021 at 06:57:58PM +0200, Peter Zijlstra wrote: > On Mon, Jun 21, 2021 at 06:15:25PM +0200, Greg Kroah-Hartman wrote: > > From: Odin Ugedal > > > > [ Upstream commit a7b359fc6a37faaf472125867c8dc5a068c90982 ] > > > > Fix an issue where fairness is decreased since cfs_rq's can end up not > > being decayed properly. For two sibling control groups with the same > > priority, this can often lead to a load ratio of 99/1 (!!). > > > > This happens because when a cfs_rq is throttled, all the descendant > > cfs_rq's will be removed from the leaf list. When they initial cfs_rq > > is unthrottled, it will currently only re add descendant cfs_rq's if > > they have one or more entities enqueued. This is not a perfect > > heuristic. > > > > Instead, we insert all cfs_rq's that contain one or more enqueued > > entities, or it its load is not completely decayed. > > > > Can often lead to situations like this for equally weighted control > > groups: > > > > $ ps u -C stress > > USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND > > root 10009 88.8 0.0 3676 100 pts/1 R+ 11:04 0:13 stress --cpu 1 > > root 10023 3.0 0.0 3676 104 pts/1 R+ 11:04 0:00 stress --cpu 1 > > > > Fixes: 31bc6aeaab1d ("sched/fair: Optimize update_blocked_averages()") > > [vingo: !SMP build fix] > > Signed-off-by: Odin Ugedal > > Signed-off-by: Peter Zijlstra (Intel) > > Reviewed-by: Vincent Guittot > > Link: https://lore.kernel.org/r/20210612112815.61678-1-odin@uged.al > > Signed-off-by: Sasha Levin > > This one is currently known to cause some LTP fail, fixes are being > discussed, please hold off for now. Now dropped from all queues, thanks. greg k-h