From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 01968612C4; Tue, 20 Feb 2024 09:42:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708422163; cv=none; b=YHOYGLPOAmOAlEb3NPtbpxGBJkEtoDLit5OMDralDUfcUvhU3ifeDmFDzB/ZsmS7GeUrgKPMd/YGhkfqU9tHSbRHEiDSdw0/P2BMlorJhSeQAlU1Av1OQVT2lXXle2hlDfM8rvDK1oR2dnjegqbOtdNUtf0J7D+LtB5vP0kND+M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708422163; c=relaxed/simple; bh=uDG9cAYKJYSYSHi325nWVNf8kjyRZS47PqKTYPJsUAk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ra2Dm0W1400as/i6CQ6V84DTOvEKkpZLgWVARpZ25UU37dAjV8QLBL3wFDBqINeOoL1zfX5TFT8ZKzhYWunt2a12VFXOKvsADpVwtzIflMWddrYkBL/iIoT8KUIT9nYcqFfCvDz4OaNe1uVU3Aia2CllCUs6z+VkatkH+hcjAEM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=BdasEJXK; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="BdasEJXK" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=5SSkrbrnicB74FPesB7xzBJgVzBnvlkeQP7w3VkDLKU=; b=BdasEJXKfWVY+L9Pc4se7Nr7+o si6UvA4SUbJeKoz3mH4fBTuOvl9XdyYqliKSLK2SFHdARXj1RwEJcvgR3gy1f7IBhYHqDfRjQwJDd o12R+g2RBtd4e3dinT87WSCprqhcv/5SGLLhVw+VbFD0rjMV0TWxKTYhlK9p8AN+DHIfWiKHiT4IQ 5XTpSRCLhBRoSndPrNMqWTVE2Q8rey+Zuoolp8GJiPk4mE9tNK553y2JRMls8xao0oFnFa5Q+vB11 GZ/qAVKNGG9qUeHr1xupgkVtUJgAk80OZwfaBhGiTrhD5C3qN89lQZ7NPnmfCQEWpQja8Eg21uiVN uevkRmhQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rcMe6-0000000E3ir-0atQ; Tue, 20 Feb 2024 09:42:38 +0000 Date: Tue, 20 Feb 2024 01:42:38 -0800 From: Christoph Hellwig To: "zhaoyang.huang" Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Zhaoyang Huang , steve.kang@unisoc.com Subject: Re: [PATCH 2/2] block: adjust CFS request expire time Message-ID: References: <20240220061542.489922-1-zhaoyang.huang@unisoc.com> <20240220061542.489922-2-zhaoyang.huang@unisoc.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240220061542.489922-2-zhaoyang.huang@unisoc.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Feb 20, 2024 at 02:15:42PM +0800, zhaoyang.huang wrote: > From: Zhaoyang Huang > > According to current policy, CFS's may suffer involuntary IO-latency by > being preempted by RT/DL tasks or IRQ since they possess the privilege for > both of CPU and IO scheduler. What is 'current policy', what is CFS, what is RT/DL? What privilege is possessed? > 1. All types of sched class's load(util) are tracked and calculated in the > same way(using a geometric series which known as PELT) > 2. Keep the legacy policy by NOT adjusting rq's position in fifo_list > but only make changes over expire_time. > 3. The fixed expire time(hundreds of ms) is in the same range of cpu > avg_load's account series(the utilization will be decayed to 0.5 in 32ms) What problem does this fix, i.e. what performance number are improved or what other effects does it have? > + * The expire time is adjusted via calculating the proportion of > + * CFS's activation among whole cpu time during last several > + * dazen's ms.Whearas, this would NOT affect the rq's position in > + * fifo_list but only take effect when this rq is checked for its > + * expire time when at head. > */ Please speel check the comment and fix the formatting to have white spaces after sentences and never exceed 80 characters in block comments.