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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 367DAC433F5 for ; Wed, 15 Sep 2021 07:37:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1AC0060F4C for ; Wed, 15 Sep 2021 07:37:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236482AbhIOHiX (ORCPT ); Wed, 15 Sep 2021 03:38:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231425AbhIOHiV (ORCPT ); Wed, 15 Sep 2021 03:38:21 -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 94103C061575 for ; Wed, 15 Sep 2021 00:37:02 -0700 (PDT) Received: by mail-ej1-x630.google.com with SMTP id qq21so4070587ejb.10 for ; Wed, 15 Sep 2021 00:37:02 -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=415Blr3Q/Gqr6sE+2qW0icFFyR7iU8ysTZ1/UKJFKvk=; b=gS7tx1MuDrOQeAB0qPWwo5Rou2795lkeTLNHk1iErOumxHljeKE+36FKX0LkSmKG6L znZCynIIyUdX+ccYI01/s9IJafOENawwt4vokbUkPaxmdqxk1+TJdCcXGQJKAW+sH+Kc 1klnd8l9rEYajeqnwymD+UYS5ySmE4qKU23Od9XrurcFWyBQu9ZHmlf+FJD+A8ScfSKI fxTolFKzO97rGtYq6KSzrR7J0B9kyNiVCIMGVcfT5qInc7vfJe6B0CEPLLlxV8zG/k42 j7PdLXLNKWf7iF+RmXVYcayEIH7aM9ncbo7OLho/Rz6NyrR1FUWrRIEgzreAE5Al45CV Q3Pw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=415Blr3Q/Gqr6sE+2qW0icFFyR7iU8ysTZ1/UKJFKvk=; b=Sis1Ne4oghxVpGGIJjPKkO+ysNKtBC/V90iXuO8iTi05M0QefNj4vLBBWd2JI7NDfw YX9KUWW6Al9DqdGizrJPTX5vNqgM6NNo+v1W2z3isFpWnWCydNPqyqOuL6I7DTQ7NxkP /2O8LemEqrbahKwtUmOVect+2o4d3vqzCZDv29MQQO3Q5SX7hbCCURI2H7MVjZRAX12E Tt2b1BXarrO54MctGhcWzxfbI+oI+EihUzIm4+lTSrUDYbDGFWb8TbfbOhkmx2W0J8wC oWyvmZ4vpq08cZEcqqexL09aa3knWW6AdLMfrIgqlCIPxP52CkJxP1X4AytL0L9yXjCa I4WQ== X-Gm-Message-State: AOAM531AFC+j0izCmZBo3AcEwdonVfxAaIKB2EU04guBW9DQIzBqk3r5 gJl58zyjWtzxSGKMQQe3bDQOgw== X-Google-Smtp-Source: ABdhPJxEPsmiA59Fnh54y6VEPVQUfyGawMpxS8b0tugd2vhbZmZAyqpkOCTpQmHmEUVwk/N0fRRv0g== X-Received: by 2002:a17:906:2cd6:: with SMTP id r22mr22921688ejr.398.1631691421078; Wed, 15 Sep 2021 00:37:01 -0700 (PDT) Received: from [192.168.0.13] ([83.216.184.132]) by smtp.gmail.com with ESMTPSA id t3sm6609895edt.61.2021.09.15.00.36.59 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Sep 2021 00:37:00 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: [PATCH v2 4/4] block, bfq: consider request size in bfq_asymmetric_scenario() From: Paolo Valente In-Reply-To: <143fa1a2-de5f-b18a-73d9-8e105844709c@huawei.com> Date: Wed, 15 Sep 2021 09:36:58 +0200 Cc: Jens Axboe , linux-block , linux-kernel@vger.kernel.org, yi.zhang@huawei.com Content-Transfer-Encoding: quoted-printable Message-Id: <68A2B4C8-48A5-45F3-8782-2440C0028161@linaro.org> References: <20210806020826.1407257-1-yukuai3@huawei.com> <20210806020826.1407257-5-yukuai3@huawei.com> <8601F280-2F16-446A-95BA-37A07D1A1055@linaro.org> <143fa1a2-de5f-b18a-73d9-8e105844709c@huawei.com> To: "yukuai (C)" X-Mailer: Apple Mail (2.3445.104.11) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Il giorno 7 set 2021, alle ore 13:29, yukuai (C) = ha scritto: >=20 > On 2021/08/27 1:00, Paolo Valente wrote: >>> Il giorno 6 ago 2021, alle ore 04:08, Yu Kuai = ha scritto: >>>=20 >>> There is a special case when bfq do not need to idle when more than >>> one groups is active: >>>=20 >> Unfortunately, there is a misunderstanding here. If more than one >> group is active, then idling is not needed only if a lot of symmetry >> conditions also hold: >> - all active groups have the same weight >> - all active groups contain the same number of active queues >=20 > Hi, Paolo >=20 > I didn't think of this contition. >=20 > It's seems that if we want to idle when more than one group is active, > there are two additional conditions: >=20 > - all dispatched requests have the same size > - all active groups contain the same number of active queues >=20 Also the weights and the I/O priorities of the queues inside the groups needs to be controlled, unfortunately. > Thus we still need to track how many queues are active in each group. > The conditions seems to be too much, do you think is it worth it to > add support to idle when more than one group is active? >=20 I think I see your point. The problem is that these states are dynamic. So, if we suspend tracking all the above information while more than one group is active, then we are with no state in case only one group remains active. Thanks, Paolo > Thanks > Kuai >=20 >> - all active queues have the same weight >> - all active queues belong to the same I/O-priority class >> - all dispatched requests have the same size >> Similarly, if only one group is active, then idling is not needed = only >> if the above last three conditions hold. >> The current logic, including your changes up to your previous patch, >> is simply ignoring the last condition above. >> So, unfortunately, your extra information about varied request size >> should be used in the opposite way than how you propose to use it.