From: Jens Axboe <jaxboe@fusionio.com>
To: Troels Arvin <troels@arvin.dk>
Cc: fio@vger.kernel.org
Subject: Re: Unaligned AIO/DIO
Date: Wed, 1 Jun 2011 12:46:13 +0200 [thread overview]
Message-ID: <4DE61875.4070501@fusionio.com> (raw)
In-Reply-To: <4DE531D0.40600@arvin.dk>
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
next prev parent reply other threads:[~2011-06-01 10:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-31 18:22 Unaligned AIO/DIO Troels Arvin
2011-06-01 10:46 ` Jens Axboe [this message]
2011-06-01 12:51 ` Troels Arvin
2011-06-01 13:17 ` Jens Axboe
2011-06-01 14:33 ` Troels Arvin
2011-06-02 11:51 ` Jens Axboe
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