From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.fusionio.com ([66.114.96.31]:34586 "EHLO mx2.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758757Ab1FAKqR (ORCPT ); Wed, 1 Jun 2011 06:46:17 -0400 Message-ID: <4DE61875.4070501@fusionio.com> Date: Wed, 1 Jun 2011 12:46:13 +0200 From: Jens Axboe MIME-Version: 1.0 Subject: Re: Unaligned AIO/DIO References: <4DE531D0.40600@arvin.dk> In-Reply-To: <4DE531D0.40600@arvin.dk> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Troels Arvin Cc: fio@vger.kernel.org On 2011-05-31 20:22, Troels Arvin wrote: > Hello, > > Running fio 1.55 on RHEL 6.1 x86_64 with a multipath FC storage backend on an EXT4 file system. > > Some minutes after starting fio, I see the following in syslog: > kernel: EXT4-fs (dm-28): Unaligned AIO/DIO on inode 4063238 by fio; performance will be poor. > > Should I be worried? Is there something wrong with my storage layout? > Or am I using fio in strange way? > > My job file: > > [changed-from-iometer-file-access-server] > bssplit=512/10:1k/5:2k/5:4k/60:8k/2:16k/4:32k/4:64k/10 > rw=randrw > rwmixread=70 > direct=1 > size=10g > ioengine=libaio > iodepth=256 > write_bw_log > write_lat_log > numjobs=6 Do you have the RHEL6.1 kernel sources handy? That message is not in the upstream kernel. Unaligned could be memory, or it could be offset/size. In general O_DIRECT does not work for unaligned IO. Perhaps it's referring to writes that aren't stripe aligned, but that seems fairly expected and something dm should handle. So to render an opinion on this, I'd need to see a copy of the file that prints that message :-) -- Jens Axboe