Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754553AbYHHHUe (ORCPT ); Fri, 8 Aug 2008 03:20:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753183AbYHHHU0 (ORCPT ); Fri, 8 Aug 2008 03:20:26 -0400 Received: from fms-01.valinux.co.jp ([210.128.90.1]:40311 "EHLO mail.valinux.co.jp" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753135AbYHHHUZ (ORCPT ); Fri, 8 Aug 2008 03:20:25 -0400 Date: Fri, 08 Aug 2008 16:20:24 +0900 (JST) Message-Id: <20080808.162024.189720323.ryov@valinux.co.jp> To: taka@valinux.co.jp Cc: fernando@oss.ntt.co.jp, dave@linux.vnet.ibm.com, yoshikawa.takuya@oss.ntt.co.jp, uchida@ap.jp.nec.com, ngupta@google.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com, containers@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xensource.com, agk@sourceware.org, righi.andrea@gmail.com Subject: Re: RFC: I/O bandwidth controller From: Ryo Tsuruta In-Reply-To: <20080808.152119.43521725.taka@valinux.co.jp> References: <1217870433.20260.101.camel@nimitz> <1217985189.3154.57.camel@sebastian.kern.oss.ntt.co.jp> <20080808.152119.43521725.taka@valinux.co.jp> X-Mailer: Mew version 5.2.52 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1690 Lines: 40 Hi, > > - Implement a block layer resource controller. dm-ioband is a working > > solution and feature rich but its dependency on the dm infrastructure is > > likely to find opposition (the dm layer does not handle barriers > > properly and the maximum size of I/O requests can be limited in some > > cases). In such a case, we could either try to build a standalone > > resource controller based on dm-ioband (which would probably hook into > > generic_make_request) or try to come up with something new. > > I doubt about the maximum size of I/O requests problem. You can't avoid > this problem as far as you use device mapper modules with such a bad > manner, even if the controller is implemented as a stand-alone controller. > There is no limitation if you only use dm-ioband without any other device > mapper modules. The following is a part of source code where the limitation comes from. dm-table.c: dm_set_device_limits() /* * Check if merge fn is supported. * If not we'll force DM to use PAGE_SIZE or * smaller I/O, just to be safe. */ if (q->merge_bvec_fn && !ti->type->merge) rs->max_sectors = min_not_zero(rs->max_sectors, (unsigned int) (PAGE_SIZE >> 9)); As far as I can find, In 2.6.27-rc1-mm1, Only some software RAID drivers and pktcdvd driver define merge_bvec_fn(). Thanks, Ryo Tsuruta -- 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/