From: Erik Mouw <erik@harddisk-recovery.com>
To: Jens Axboe <axboe@suse.de>
Cc: colin <colin@realtek.com.tw>, linux-kernel@vger.kernel.org
Subject: Re: A problem about DIRECT IO on ext3
Date: Wed, 31 Aug 2005 13:12:48 +0200 [thread overview]
Message-ID: <20050831111248.GA2347@harddisk-recovery.nl> (raw)
In-Reply-To: <20050831080744.GM4018@suse.de>
On Wed, Aug 31, 2005 at 10:07:45AM +0200, Jens Axboe wrote:
> On Mon, Aug 29 2005, Erik Mouw wrote:
> > There are four prerequisites for direct IO:
> > - the file needs to be opened with O_DIRECT
> > - the buffer needs to be page aligned (hint: use getpagesize() instead
> > of assuming that a page is 4k
> > - reads and writes need to happen *in* multiples of the soft block size
> > - reads and writes need to happen *at* multiples of the soft block size
>
> Actually, the buffer only needs to be hard block size aligned, same goes
> for the chunk size used for reads/writes.
OK, so that's different from 2.4 where reads/writes needed to be soft
block aligned and buffers page aligned.
Erik
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| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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next prev parent reply other threads:[~2005-08-31 11:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-29 12:15 colin
2005-08-29 13:29 ` Erik Mouw
2005-08-31 8:07 ` Jens Axboe
2005-08-31 11:12 ` Erik Mouw [this message]
2005-08-31 11:15 ` Jens Axboe
2005-10-17 8:52 ` li nux
2005-10-17 8:58 ` li nux
2005-10-17 9:03 ` Jens Axboe
2005-10-17 9:15 ` Grzegorz Kulewski
2005-10-17 9:17 ` Jens Axboe
2005-10-17 9:41 ` li nux
2005-10-17 9:51 ` Jens Axboe
2005-10-17 16:36 ` Badari Pulavarty
2005-10-17 17:53 ` Jens Axboe
2005-08-29 13:21 colin
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