Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754610AbcJZPaF (ORCPT ); Wed, 26 Oct 2016 11:30:05 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:60821 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723AbcJZPaC (ORCPT ); Wed, 26 Oct 2016 11:30:02 -0400 Date: Wed, 26 Oct 2016 08:29:55 -0700 From: Christoph Hellwig To: Arnd Bergmann Cc: Bart Van Assche , Jan Kara , Christoph Hellwig , Paolo Valente , Jens Axboe , Tejun Heo , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org, hare@suse.de, grant.likely@secretlab.ca, James.Bottomley@hansenpartnership.com Subject: Re: [PATCH 00/14] introduce the BFQ-v0 I/O scheduler as an extra scheduler Message-ID: <20161026152955.GA21262@infradead.org> References: <1477474082-2846-1-git-send-email-paolo.valente@linaro.org> <20161026113443.GA13587@quack2.suse.cz> <4ed3e291-b3e5-5ee3-6838-58644bd3d99b@sandisk.com> <12386463.fJy0cVexVD@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <12386463.fJy0cVexVD@wuerfel> User-Agent: Mutt/1.6.1 (2016-04-27) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 617 Lines: 12 On Wed, Oct 26, 2016 at 05:13:07PM +0200, Arnd Bergmann wrote: > The question to ask first is whether to actually have pluggable > schedulers on blk-mq at all, or just have one that is meant to > do the right thing in every case (and possibly can be bypassed > completely). That would be my preference. Have a BFQ-variant for blk-mq as an option (default to off unless opted in by the driver or user), and not other scheduler for blk-mq. Don't bother with bfq for non blk-mq. It's not like there is any advantage in the legacy-request device even for slow devices, except for the option of having I/O scheduling.