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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6CD14C05027 for ; Wed, 8 Feb 2023 17:53:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231272AbjBHRxr (ORCPT ); Wed, 8 Feb 2023 12:53:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231182AbjBHRxp (ORCPT ); Wed, 8 Feb 2023 12:53:45 -0500 Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2BAB59E2; Wed, 8 Feb 2023 09:53:44 -0800 (PST) Received: by mail-pl1-f182.google.com with SMTP id k13so20227761plg.0; Wed, 08 Feb 2023 09:53:44 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UHYPrSiTkVKIlfo8HfMdMKbV5juD4qgKqM8oSnLweE8=; b=sQwEsm+G5eaUbb7aY1mSz7DJb8FYCFum2/YVoB4IJIWjliqWRFDlUam0z9NiKPYfl8 1tx0ZjD+WdqUjwWbtzjxx7ER0S2E5GXcsunYeS4CrkWjR9XYMWLqDJ4nEvPJCSNqIvKb gfN6bySy569/MsWsXFEAkVF4qIQST4IGSFtaJH+fsb9We1LUyqwXmJ3fpzv1DjUV6AIa PSgDdeytsXpAHk5wZ2tP94Rpr4UZo8amFj1z7QqvKjnOUKQEtRiAwf74C3i1O99Tgher 6dsKD1+ZmRXMW33Qm45LSgQRcu6PLgAZi8GhupiKbkeyVEY76bLEapaRwoODq13AOYgW mzMw== X-Gm-Message-State: AO0yUKVCqbh/42wON6JxA3liBwlzgya8lCkqcJMjXdGNC+g/UpnwRqxD 1plw+3ptQzc+rGEA/FGB//Y= X-Google-Smtp-Source: AK7set/GrvVfRVcZ26t5iBnwWqMEPtJBrPM9dsurSPWoOG+E6492+ASW9DmosYVxi30oZtwSF3UQFQ== X-Received: by 2002:a17:902:e1c4:b0:195:e92e:c4d3 with SMTP id t4-20020a170902e1c400b00195e92ec4d3mr5589893pla.46.1675878824157; Wed, 08 Feb 2023 09:53:44 -0800 (PST) Received: from ?IPV6:2620:15c:211:201:869f:66a2:40c:445d? ([2620:15c:211:201:869f:66a2:40c:445d]) by smtp.gmail.com with ESMTPSA id u2-20020a170902a60200b001962858f990sm11370358plq.164.2023.02.08.09.53.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Feb 2023 09:53:43 -0800 (PST) Message-ID: <7fcd4c38-ccbe-6411-e424-a57595ad9c0b@acm.org> Date: Wed, 8 Feb 2023 09:53:41 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy Content-Language: en-US To: Jan Kara Cc: Hou Tao , linux-block@vger.kernel.org, Jens Axboe , cgroups@vger.kernel.org, Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, houtao1@huawei.com References: <20230201045227.2203123-1-houtao@huaweicloud.com> <8c068af3-7199-11cf-5c69-a523c7c22d9a@acm.org> <4f7dcb3e-2d5a-cae3-0e1c-a82bcc3d2217@huaweicloud.com> <20230208134345.77bdep3kzp52haxu@quack3> From: Bart Van Assche In-Reply-To: <20230208134345.77bdep3kzp52haxu@quack3> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/8/23 05:43, Jan Kara wrote: > On Fri 03-02-23 11:45:32, Bart Van Assche wrote: >> On 2/2/23 17:48, Hou Tao wrote: >>> I don't get it on how to remove IOPRIO_POL_PROMOTION when calculating the final >>> ioprio for bio. IOPRIO_POL_PROMOTION is not used for IOPRIO_CLASS values but >>> used to determinate on how to calculate the final ioprio for bio: choosing the >>> maximum or minimum between blkcg ioprio and original bio bi_ioprio. >> >> Do the block layer code changes shown below implement the functionality >> that you need? > > Just one question guys: So with my a78418e6a04c ("block: Always initialize > bio IO priority on submit") none-to-rt policy became effectively a noop as > Hou properly noticed. Are we aware of any users that were broken by this? > Shouldn't we rather fix the code so that none-to-rt starts to operate > correctly again? Or maybe change the none-to-rt meaning to be actually > promote-to-rt? > > I have to admit I'm wondering a bit what was the intended usecase behind > the introduction of none-to-rt policy. Can someone elaborate? promote-to-rt > makes some sense to me - we have a priviledged cgroup we want to provide > low latency access to IO but none-to-rt just does not make much sense to > me... Hi Jan, The test results I shared some time ago show that IOPRIO_CLASS_NONE was the default I/O priority two years ago (see also https://lore.kernel.org/linux-block/20210927220328.1410161-5-bvanassche@acm.org/). The none-to-rt policy increases the priority of bio's that have not been assigned an I/O priority to RT. Does this answer your question? Thanks, Bart.