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[2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id q11-20020a05620a024b00b007811c90b7fbsi17595652qkn.587.2023.12.29.03.03.22 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Dec 2023 03:03:22 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-13053-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel+bounces-13053-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-13053-linux.lists.archive=gmail.com@vger.kernel.org" Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id A5AF81C22311 for ; Fri, 29 Dec 2023 11:03:22 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id F28B410A3B; Fri, 29 Dec 2023 11:03:15 +0000 (UTC) X-Original-To: linux-kernel@vger.kernel.org Received: from mail115-171.sinamail.sina.com.cn (mail115-171.sinamail.sina.com.cn [218.30.115.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D42CD10A25 for ; Fri, 29 Dec 2023 11:03:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([113.88.48.91]) by sina.com (172.16.235.25) with ESMTP id 658EA744000068AB; Fri, 29 Dec 2023 19:02:31 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 54383334210437 X-SMAIL-UIID: 36E1B2CE68CB4074B6B6069F7C8FF0C1-20231229-190231-1 From: Hillf Danton To: Qais Yousef Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Pierre Gondois , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched/fair: Check a task has a fitting cpu when updating misfit Date: Fri, 29 Dec 2023 19:02:18 +0800 Message-Id: <20231229110218.1928-1-hdanton@sina.com> In-Reply-To: <20231212154056.626978-1-qyousef@layalina.io> References: <20231212154056.626978-1-qyousef@layalina.io> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On 12/12/23 16:40 Qais Yousef > > If a misfit task is affined to a subset of the possible cpus, we need to > verify that one of these cpus can fit it. Otherwise the load balancer > code will continuously trigger needlessly leading the balance_interval > to increase in return and eventually end up with a situation where real > imbalances take a long time to address because of this impossible > imbalance situation. > > This can happen in Android world where it's common for background tasks > to be restricted to little cores. What sense could you make by forcing a pill down through Peter's throat to fix the insane userspace behavior that blindly drives load balance mad by binding background tasks to littles cores? Is eevdf failing to handle your background tasks?