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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 363D9C32789 for ; Fri, 2 Nov 2018 18:22:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D12B42082E for ; Fri, 2 Nov 2018 18:22:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linaro.org header.i=@linaro.org header.b="e3U5l5GS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D12B42082E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728311AbeKCDaP (ORCPT ); Fri, 2 Nov 2018 23:30:15 -0400 Received: from mail-lf1-f66.google.com ([209.85.167.66]:43686 "EHLO mail-lf1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727838AbeKCDaO (ORCPT ); Fri, 2 Nov 2018 23:30:14 -0400 Received: by mail-lf1-f66.google.com with SMTP id u18so1942524lff.10 for ; Fri, 02 Nov 2018 11:22:07 -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=EA2qLqIsmx6YLRKG8F4YGbxODLHhQ5/M4zED+i0s4Dg=; b=e3U5l5GSKQyr1C6IBRF52JYfplMMHwvWXRPzw/zFbnuMeh9OH6eLhKuGD0QKOj8P84 IW11l84m3n+dKdsFwC31PHrykaH5gHHA5BX16d/tUuWEN2p5sHXj8ZVg9JQn8ngo17V7 d8xXrSW4e/xJmI+aYEXuiRTrnKYz+U7Feaauw= 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=EA2qLqIsmx6YLRKG8F4YGbxODLHhQ5/M4zED+i0s4Dg=; b=uj2JWeiGMhDu3lXkRSa/PTQYdEhFqQFuL5cZ0nVZuAtfUVAlccrQMvTkKLkTjosQMw Q0gisx0Bc0VhaRhdbWdr+zSe04glw4nBc5ahWiT7/H+FhgtnYkakQh9JJnUzzBPb9eEe gQ2tbkUsDTMV+Fh81a5Mz/ZNbnKO3nEJHe08t/nN7FLGQ5fMZRflzjKsYEQIBOkMpSSE uxmCUqGOM2XG+hSa6+CoERNLI4+MW96HK63ZDwg3MyjtFg+tcmN03mC+bjkl2oiPbnT6 rzt5X2aP06Zjw7anyad+vTNPIXRSDRd/T2+sm+Pwr9BhK2jsosoC04AZ0IKNHlcH/8sa wVbw== X-Gm-Message-State: AGRZ1gK/ICTxwMiKU+AUIweltKop77FYLrx9q5GhCj+6pYZZ2lD33Qpp tNoN3v0g/vKZNrbGFrx2xcCuIQ== X-Google-Smtp-Source: AJdET5d80QLN/xB4dVCk/Vz/2n4pUCI5f8fVE0TvdnkGZUDQPJHFKhUmadp4GUmotnmN09TRuSiv0w== X-Received: by 2002:a19:5a84:: with SMTP id y4mr7739269lfk.156.1541182926657; Fri, 02 Nov 2018 11:22:06 -0700 (PDT) Received: from [10.0.0.171] ([94.72.11.11]) by smtp.gmail.com with ESMTPSA id z8-v6sm3586380lfh.52.2018.11.02.11.22.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Nov 2018 11:22:05 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.0 \(3445.100.39\)) Subject: Re: [PATCH RFC] block, bfq: set default slice_idle to zero for non-rotational devices From: Paolo Valente In-Reply-To: <317076f7-f84f-c08f-5fb5-b227094cabfd@applied-asynchrony.com> Date: Fri, 2 Nov 2018 21:18:26 +0300 Cc: Konstantin Khlebnikov , linux-block , Jens Axboe , linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <154109421062.925711.4117729151502021084.stgit@buzz> <317076f7-f84f-c08f-5fb5-b227094cabfd@applied-asynchrony.com> To: =?utf-8?Q?Holger_Hoffst=C3=A4tte?= X-Mailer: Apple Mail (2.3445.100.39) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Il giorno 1 nov 2018, alle ore 22:06, Holger Hoffst=C3=A4tte = ha scritto: >=20 > On 11/01/18 18:43, Konstantin Khlebnikov wrote: >> With default 8ms idle slice BFQ is up to 10 times slower than CFQ >> for massive random read workloads for common SATA SSD. >> For now zero idle slice gives better out of box experience. >> CFQ employs this since commit 41c0126b3f22 ("block: Make CFQ default >> to IOPS mode on SSDs") >=20 > Well, that's interesting because 3 years ago I made the same = suggestion > and was told that BFQ's heuristics automagically make it not idle when > rotational=3D0. Yep, that automagic is probably 50% of the good of BFQ. If one just sets slice_idle=3D0, then throughput is always maximum with random I/O; but there is no control on I/O any longer. At any rate, Konstantin, if you have some use case where BFQ fails, I'll be very glad to analyze it, and hopefully improve BFQ. Just one request: use at least a 4.19. Thanks, Paolo > Did you actually benchmark this? I just tried and don't > get a noticeable performance difference with slice_idle=3D0 compared = to > deadline. >=20 > Discussion link: > = https://groups.google.com/forum/#!msg/bfq-iosched/iRMw2n3kYLY/6l9cIm3TBgAJ= >=20 > curious.. >=20 > Holger