From: Jens Axboe <axboe@suse.de>
To: Erik Mouw <erik@harddisk-recovery.com>
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 13:15:19 +0200 [thread overview]
Message-ID: <20050831111518.GR4018@suse.de> (raw)
In-Reply-To: <20050831111248.GA2347@harddisk-recovery.nl>
On Wed, Aug 31 2005, Erik Mouw wrote:
> 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.
Yes, 2.6 has relaxed the restrictions there somewhat.
--
Jens Axboe
next prev parent reply other threads:[~2005-08-31 11:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-29 12:15 A problem about DIRECT IO on ext3 colin
2005-08-29 13:29 ` Erik Mouw
2005-08-31 8:07 ` Jens Axboe
2005-08-31 11:12 ` Erik Mouw
2005-08-31 11:15 ` Jens Axboe [this message]
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
-- strict thread matches above, loose matches on Subject: below --
2005-08-29 13:21 colin
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