Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752622AbdCEQC2 (ORCPT ); Sun, 5 Mar 2017 11:02:28 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:36774 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752398AbdCEQC0 (ORCPT ); Sun, 5 Mar 2017 11:02:26 -0500 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH RFC 01/14] block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler From: Paolo Valente In-Reply-To: <91b856e8-2c14-00b6-fdd8-b9879b1b9952@kernel.dk> Date: Sun, 5 Mar 2017 17:02:19 +0100 Cc: Tejun Heo , Fabio Checconi , Arianna Avanzini , linux-block@vger.kernel.org, Linux-Kernal , Ulf Hansson , Linus Walleij , broonie@kernel.org Message-Id: <060CBCB3-AB73-4F88-9CDC-828F502A8FF7@linaro.org> References: <20170304160131.57366-1-paolo.valente@linaro.org> <20170304160131.57366-2-paolo.valente@linaro.org> <91b856e8-2c14-00b6-fdd8-b9879b1b9952@kernel.dk> To: Jens Axboe X-Mailer: Apple Mail (2.3124) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v25G2Wq0032071 Content-Length: 1609 Lines: 46 > Il giorno 05 mar 2017, alle ore 16:16, Jens Axboe ha scritto: > > On 03/04/2017 09:01 AM, Paolo Valente wrote: >> We tag as v0 the version of BFQ containing only BFQ's engine plus >> hierarchical support. BFQ's engine is introduced by this commit, while >> hierarchical support is added by next commit. We use the v0 tag to >> distinguish this minimal version of BFQ from the versions containing >> also the features and the improvements added by next commits. BFQ-v0 >> coincides with the version of BFQ submitted a few years ago [1], apart >> from the introduction of preemption, described below. >> >> BFQ is a proportional-share I/O scheduler, whose general structure, >> plus a lot of code, are borrowed from CFQ. > > I'll take a closer look at this in the coming week. ok > But one quick > comment - don't default to BFQ. Both because it might not be fully > stable yet, and also because the performance limitation of it is > quite severe. Whereas deadline doesn't really hurt single queue > flash at all, BFQ will. > Ok, sorry. I was doubtful on what to do, but, to not bother you on every details, I went for setting it as default, because I thought people would have preferred to test it, even from boot, in this preliminary stage. I reset elevator.c in the submission, unless you want me to do it even before receiving your and others' reviews. > Generally, I think that sort of logic should go into a udev rule. If > a device is rotational it should default to BFQ once the dust has > settled. > ok Looking forward for your feedback, Paolo > -- > Jens Axboe >