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=-0.8 required=3.0 tests=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 E1DF1C64EB8 for ; Thu, 4 Oct 2018 20:09:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B19EE2083F for ; Thu, 4 Oct 2018 20:09:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B19EE2083F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=acm.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 S1727771AbeJEDD6 (ORCPT ); Thu, 4 Oct 2018 23:03:58 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:40311 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727444AbeJEDD6 (ORCPT ); Thu, 4 Oct 2018 23:03:58 -0400 Received: by mail-pf1-f195.google.com with SMTP id s5-v6so3910147pfj.7; Thu, 04 Oct 2018 13:09:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=828Vwuzv9z3xgzCoJykZprfmqgh9ENoEERPPFWqIA88=; b=sC+K/R79ebCjQs1FlbvNyHWYWORnCiEqnMpiRDNkSLDD/J+v23FP3tanVrM+7xNy9u jyTqEkUT8DFz9FtCi+rcV7SIEQnIEzLa7pOxsbdqaURIkqdXA+hQJCaEs24ZbAd7i88S qoGoTF/v1wP3XU3MPzAXiSUYWkniwOq9xpMmCUl+XN5jQaHbIzJN4mqye28Wx1lhTlp9 wN2F6If9lfAuyK5ZWoVY72pKWV80mY2moiEYdfpPcMHNzbypYkdb4QeceKoTLztWSzCb +mR2gWZMMtYHzrHmP/MIoEYyPvuwxnCFqnz77DVDh5LQjecMbN+2SauYHeP36A9XgqT6 wfyw== X-Gm-Message-State: ABuFfohK9lWiv8FCmJJDslkNd79QgAbHsR4F4/E9pOJsDBWljgF+oKyk C/bhfLwU/fWrR6vUqTFzMLg= X-Google-Smtp-Source: ACcGV61Vq4XTm3LXEYO745k0tJvU832P7ap507Ytw0xN6WPnjTo/IN8ag6pTgrfQXruVhiJOImRSqg== X-Received: by 2002:a62:1095:: with SMTP id 21-v6mr8257039pfq.227.1538683748430; Thu, 04 Oct 2018 13:09:08 -0700 (PDT) Received: from ?IPv6:2620:15c:2cd:203:5cdc:422c:7b28:ebb5? ([2620:15c:2cd:203:5cdc:422c:7b28:ebb5]) by smtp.gmail.com with ESMTPSA id w127-v6sm7843726pfd.112.2018.10.04.13.09.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Oct 2018 13:09:07 -0700 (PDT) Message-ID: <1538683746.230807.9.camel@acm.org> Subject: Re: [PATCH] block: BFQ default for single queue devices From: Bart Van Assche To: Alan Cox Cc: Paolo Valente , Jens Axboe , Linus Walleij , linux-block , linux-mmc , linux-mtd@lists.infradead.org, Pavel Machek , Ulf Hansson , Richard Weinberger , Artem Bityutskiy , Adrian Hunter , Jan Kara , Andreas Herrmann , Mel Gorman , Chunyan Zhang , linux-kernel Date: Thu, 04 Oct 2018 13:09:06 -0700 In-Reply-To: <20181004202553.71c2599c@alans-desktop> References: <20181002124329.21248-1-linus.walleij@linaro.org> <05fdbe23-ec01-895f-e67e-abff85c1ece2@kernel.dk> <1538582091.205649.20.camel@acm.org> <20181004202553.71c2599c@alans-desktop> Content-Type: text/plain; charset="UTF-7" X-Mailer: Evolution 3.26.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-10-04 at 20:25 +-0100, Alan Cox wrote: +AD4 +AD4 I agree with Jens that it's best to leave it to the Linux distributors to +AD4 +AD4 select a default I/O scheduler. +AD4 +AD4 That assumes such a thing exists. The kernel knows what devices it is +AD4 dealing with. The kernel 'default' ought to be 'whatever is usually best +AD4 for this device'. A distro cannot just pick a correct single default +AD4 because NVME and USB sticks are both normal and rather different in needs. Which I/O scheduler works best also depends which workload the user will run. BFQ has significant advantages for interactive workloads like video replay with concurrent background I/O but probably slows down kernel builds. That's why I'm not sure whether the kernel should select the default I/O scheduler. Bart.