Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762933AbYBSKFv (ORCPT ); Tue, 19 Feb 2008 05:05:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754717AbYBSKFk (ORCPT ); Tue, 19 Feb 2008 05:05:40 -0500 Received: from brick.kernel.dk ([87.55.233.238]:17104 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754078AbYBSKFj (ORCPT ); Tue, 19 Feb 2008 05:05:39 -0500 Date: Tue, 19 Feb 2008 11:05:36 +0100 From: Jens Axboe To: Andrew Morton Cc: Paul Clements , randy.dunlap@oracle.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] NBD: make nbd default to deadline I/O scheduler Message-ID: <20080219100536.GW23197@kernel.dk> References: <20080208204713.GF23197@kernel.dk> <47ACC835.4070102@steeleye.com> <20080208140244.c850a5d3.akpm@linux-foundation.org> <47ADAB00.90306@steeleye.com> <20080212151602.f1803ef0.akpm@linux-foundation.org> <20080218181630.GI23197@kernel.dk> <20080218155001.97bf5976.akpm@linux-foundation.org> <20080219091943.GS23197@kernel.dk> <20080219092428.GT23197@kernel.dk> <20080219020204.2d448269.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080219020204.2d448269.akpm@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2031 Lines: 54 On Tue, Feb 19 2008, Andrew Morton wrote: > On Tue, 19 Feb 2008 10:24:28 +0100 Jens Axboe wrote: > > > On Tue, Feb 19 2008, Jens Axboe wrote: > > > On Mon, Feb 18 2008, Andrew Morton wrote: > > > > > + > > > > > if (e && !try_module_get(e->elevator_owner)) > > > > > e = NULL; > > > > > > > > Looks nice and simple. There might be some of the usual ordering problems > > > > when this is called during boot, maybe is-initramfs-available-yet problems, > > > > etc. But it's unlikely to make things regress from where they are now. > > > > > > Isn't request_module() and below robust enough to handle that? > > > > BTW, I've verified that it works as expected (at least after boot): > > > > carl:/sys/block/sda/queue # cat scheduler > > noop [cfq] > > carl:/sys/block/sda/queue # echo anticipatory > scheduler > > carl:/sys/block/sda/queue # dmesg > > [...] > > io scheduler anticipatory registered > > carl:/sys/block/sda/queue # cat scheduler > > noop cfq [anticipatory] > > > > So it properly loads as-iosched instead of failing, like it would have > > done before and required the user to do a modprobe as-iosched first. > > > > carl:/sys/block/sda/queue # echo foobar > scheduler > > -bash: echo: write error: Invalid argument > > carl:/sys/block/sda/queue # dmesg > > [...] > > elevator: type foobar not found > > Looks promising - let's run with it. If there _are_ startup ordering > problems then we won't be any worse off than we are now. I've merged it for inclusion, since it tests fine here. > otoh, the system must have _some_ io scheduler installed when talking to > disks, so perhaps there won't be any such problems at all. We are guarenteed to always have noop available, since you cannot de-select that. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/