From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f180.google.com (mail-pf1-f180.google.com [209.85.210.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2CFCE2D0C9D for ; Mon, 25 Aug 2025 09:51:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756115474; cv=none; b=eWCxlV6rUerfnMmz07xmzV+Ws5SHH/KCdH27LoVVd+TrCJQTPfpVvEUBU1jphCNlM2dt6MuGHw1QoBGO3JOhL2zoHxV1EMr1AbRZCqzZ8qAWmTekIIxZbb1NVMh7O8e9e74/RhB3WwD30CVcqer35XayNcK+Qa/9NaWt3KxD2fA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756115474; c=relaxed/simple; bh=B8eCYEono40PCIy16xmaC4Aox2ZtXZbrtkZF8FCENiM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m0t93ZT6LkmXf0E9D7MJ6VhgN8R5kB0keuCunN24l1Q1ksyHY3dO+vOQmZ9ujvLOf37m9bmsjt5xv4SQmBO9chKQ1fh6UzdC/AtMG6q9omFLLuhtDyhC+Lg/7EM8n/CXkxylNVObcyXspT/+05NSckF319Yy12G4zmfZqZioHl4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=E1YSSVrl; arc=none smtp.client-ip=209.85.210.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="E1YSSVrl" Received: by mail-pf1-f180.google.com with SMTP id d2e1a72fcca58-770530175b2so897786b3a.3 for ; Mon, 25 Aug 2025 02:51:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1756115472; x=1756720272; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=91s1cIGRQAxrumxrJ8ni6aEx18e/r1sz4gPLC81PIgY=; b=E1YSSVrl8O1J/DGQWQkRBjERagRt0CuIMoYZFNRkgUW2Y9BQf3qFeYQRmUqFSaHT6O bFkk/QetwGsQXg8DKAjBdYNpQycSlMQ2De0vvYOVRfRu7Gv9HyNMwtWlMXH66KFoyevZ F9um6xbXyAkHdC9p3Mx1m10vpMTfmoz+3BohjFROf2HSDHY+3Daqr+kLdTE22bhx95V9 ExkFTB8d+eEmMphg+c5cjrbHv8aTtiC2dRztLHWxEnQcLWk/yX+zGK/MGq1BIlkkosYt THlG0bmrm8+pEKSmXcfNTCapzIo3fsPZfN67EeBEs+qkUjj6aOV7wQmd8EOwyEFnVRpo Edxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756115472; x=1756720272; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=91s1cIGRQAxrumxrJ8ni6aEx18e/r1sz4gPLC81PIgY=; b=XKOenuvHWM0FAvmmQII+BNPSi2kH+IqqSljqNQZ8rE9LAEla/5bDdcfWP3tEMywa3x dcSAWprQgrCS5wrQ/eKmDQ+lmRRXjFdkPJiAgSl1FMH69zMTcNda1Q8Vs4b7p7Au9vou 28lmMcQe/W4xKd2Uvf+RMnw1omW6qnK6cHuCZpTKWJ5QSguaKyhDgOcl0m2xVD/sIoeZ pPRZfw/624DbC5I2EtQJex1m1J7P45ZkqfawqKDVjciNbaEcFns6PRaGL8ISlV4cTkC+ +qo1jQwff3vfjmvve6iddWLlo1BvpTjsOsMgVkhXjmbfthQvn47+trmi1lk6f0REFT5F 57iA== X-Forwarded-Encrypted: i=1; AJvYcCX20essYBFbiVwB3Ws1Zs8wPZNoy52LOe5rTRXEVxkah8W9enTKJa3weC06g/r5v87EsGXkmDxE@vger.kernel.org X-Gm-Message-State: AOJu0YyS53fLJXWEpFuOCbXtdqN+BB9fmFQpYjAm9OBOh/gF0gUOJ/go ACU0bNbNlEwDchT3dlpgFcR/xvjK2j3Hq84eLSP3cOVGFhInPCCGYVVhFsJbNOrfVQ== X-Gm-Gg: ASbGnctB3XLN2Pt7RSYZFh5+3wlAb2No0uV8eipbAkfGVRKZZUj6K5slUnyeU+jTNVb JGQh6Hpti4AQAF0xdbKcgf9+sOKKS5xobiNXjjDw7SokkPpp0N+iAo4HWkJYXybRsp6ki5bIDJp wVocTawwI8ha2Ak0barqRA+dLCguItnOE1oScyfamVzamdnFc0fO2xdqTfeVLWAWlOyjZMKkW3k VjKkuBPE24Iql23G3pob6gukyFIsh/169+9+uLCnt3rbtfa99u9F9Wpyvgewa+m0g5n6K8ejwUE w02E//9VQ9MaOXAaelN/7RLoF6Bir+33+VpdWmHGkgpP4JKyf7u/ZyspBfv2yahqtlFueci4OlP Ge8B9VPhgs/iAAfbdMzNGK9xtk8M2NJEVQhp5ncx5QEFuH2I= X-Google-Smtp-Source: AGHT+IFKmShdsyMlmj4cT5JRWT7LwYbqWBv7GzkGKLvpKSJg5ombkdXo91DBer2NpWN+oCdJY5Gk/A== X-Received: by 2002:a05:6a00:2288:b0:770:3064:78fa with SMTP id d2e1a72fcca58-77030647984mr14107031b3a.2.1756115472294; Mon, 25 Aug 2025 02:51:12 -0700 (PDT) Received: from bytedance ([61.213.176.56]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-770b5bed408sm3213674b3a.18.2025.08.25.02.51.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Aug 2025 02:51:11 -0700 (PDT) Date: Mon, 25 Aug 2025 17:50:56 +0800 From: Aaron Lu To: xupengbo Cc: bsegall@google.com, cgroups@vger.kernel.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, mgorman@suse.de, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, vincent.guittot@linaro.org, vschneid@redhat.com Subject: Re: [PATCH v2] sched/fair: Fix unfairness caused by stalled tg_load_avg_contrib when the last task migrates out. Message-ID: <20250825095056.GA87@bytedance> References: <20250806071848.GA629@bytedance> <20250806083810.27678-1-xupengbo@oppo.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250806083810.27678-1-xupengbo@oppo.com> Hi xupengbo, On Wed, Aug 06, 2025 at 04:38:10PM +0800, xupengbo wrote: ... ... > > It actually becomes: > if (cfs_rq->tg_load_avg_contrib > 0) > if cfs_rq->tg_load_avg_contrib == 0 , it will be false. As it is an unsigned > long, this condition is equivalent to : > if (cfs_rq->tg_load_avg_contrib) I suppose we have reached a conclusion that the right fix is to add a check of cfs_rq->tg_load_avg_contrib in cfs_rq_is_decayed()? Something like below: diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index af33d107d8034..3ebcb683063f0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4056,6 +4056,9 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) if (child_cfs_rq_on_list(cfs_rq)) return false; + if (cfs_rq->tg_load_avg_contrib) + return false; + return true; } If you also agree, can you send an updated patch to fix this problem? Thanks.