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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 5216FC4320A for ; Tue, 24 Aug 2021 12:51:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3721561357 for ; Tue, 24 Aug 2021 12:51:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236992AbhHXMwf (ORCPT ); Tue, 24 Aug 2021 08:52:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229870AbhHXMwe (ORCPT ); Tue, 24 Aug 2021 08:52:34 -0400 Received: from mail-ej1-x630.google.com (mail-ej1-x630.google.com [IPv6:2a00:1450:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8279EC061757 for ; Tue, 24 Aug 2021 05:51:50 -0700 (PDT) Received: by mail-ej1-x630.google.com with SMTP id u3so44196702ejz.1 for ; Tue, 24 Aug 2021 05:51:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=3N5N1pL9l1Nd9FtRSCryRrWbfA4JEwfbr4ZSZbB62rY=; b=LanEZp11YjG5tA5E7i5vbAFGEEe0FMTAVPvJ0V5MH+frTIZhz029MuFXMSGh4fCDy/ PaT6n+/EiNW9v3X30JjE6qihfC0ku+CrIbXjWER9z7E/aU8TPKJs0HH49Exr02CGNKAZ 8EfG3E2203L0AqX6Y1zl5Yq+Vmg79VsaigsgsRYpTAHEceQcf34KsUio1lOGbGjF86dr MRe6SfPLzEgufV44aqpM3q0TTctw3I0KjoqApMEBx74M0wpN6Hhe7rsR47xKTUxLXt2F po+XkNz1nflA0WI+08shZokmxRZ+3t7sywy3kkd7kQfsYwPvrgX24d8w4yHp7VCkPsiQ LxSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=3N5N1pL9l1Nd9FtRSCryRrWbfA4JEwfbr4ZSZbB62rY=; b=ZakLNM+Srj/MXJYTit63HOZknLBZLmlY1ZJJkhTwPzScRjo5LrTcwgYmXzz3EzM65K jATnLy4T9N7IXng1fFEer2NsWlttuH9CQCXz9HvxJq9CS2bOVH0FnYmNHjrLIBhSyxDo RA9ZCKUZ4HhMimZess70YVLWOFZSs2y5NiMiefC8rXxr383vpOpkkFX+2YKHSWePjAMM 84esAYHWhS4koPwLEfBe3XpTcejIHybUvb71yxIkFI0zjAqZBFa5dFyePDIvgW1S47vQ 3khYXw4FOwF951jGHvuNMTj1QB+bRHu8os4ANj5L0m+23zndMPTdxfWEEpYtAEcF54wW feNQ== X-Gm-Message-State: AOAM532k0Lw97DaOwVv0hMHIzmUdsAINUfPc19rKp4LPHlU3oM/XgtYS mI1yOzgK22vs6pMFibMLfDaw0g== X-Google-Smtp-Source: ABdhPJyqOKi7ldq/YQP/xGJ/+MEH/MacItQp38lS3qa4BfJxoJdGaOEAHcthSPt/W2qPVB+igGuWZw== X-Received: by 2002:a17:906:a14b:: with SMTP id bu11mr41053184ejb.260.1629809509104; Tue, 24 Aug 2021 05:51:49 -0700 (PDT) Received: from [192.168.0.13] ([83.216.184.132]) by smtp.gmail.com with ESMTPSA id d19sm9094628ejj.122.2021.08.24.05.51.48 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Aug 2021 05:51:48 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: BFQ cgroup weights range From: Paolo Valente In-Reply-To: <20210824105626.GA11367@blackbody.suse.cz> Date: Tue, 24 Aug 2021 14:51:47 +0200 Cc: Jens Axboe , linux-block , Jan Kara Content-Transfer-Encoding: quoted-printable Message-Id: References: <20210824105626.GA11367@blackbody.suse.cz> To: =?utf-8?Q?Michal_Koutn=C3=BD?= X-Mailer: Apple Mail (2.3445.104.11) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > Il giorno 24 ago 2021, alle ore 12:56, Michal Koutn=C3=BD = ha scritto: >=20 > Hello. >=20 > The default weight for proportional IO control associated with a = cgroup > is 100 [1]. The minimum allowed weight is 1 [2] and the maximum weight > 1000 [3]. This is a bit inconsistent with general cgroup weight > semantic where def/min =3D=3D max/def (i.e. symmetric adjustments to = both > sides) [4]. >=20 > 1) Is there a reason why the maximum allowed weight is (only) 1000? > (E.g. it won't be possible to ensure 10^4 ratio of proportional > control but 10^3 is achievable.) > 2) Is the default value 100 special or absolute in a sense? (I suspect > it is, the unchangeable weight of root cgroup members. Therefore two > siblings with equal ratios 10:100 and 100:1000 would behave same = only > when there's no interfering IO from the root.) >=20 Hi, BFQ inherited these constants when we forked it from CFQ. I'm ok with increasing max weight to 10000. I only wonder whether this would break some configuration, as the currently maximum weight would not be the maximum weight any longer. =14 Thanks, Paolo > Thanks, > Michal >=20 > [1] = https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/bl= ock/bfq-cgroup.c?h=3Dv5.14-rc7#n513 > [2] = https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/bl= ock/bfq-iosched.h?h=3Dv5.14-rc7#n18 > [3] = https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/bl= ock/bfq-iosched.h?h=3Dv5.14-rc7#n19 > [4] = https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Do= cumentation/admin-guide/cgroup-v2.rst?h=3Dv5.14-rc7#n602