From: James Bottomley <James.Bottomley@SteelEye.com>
To: Saeed Bishara <Saeed.Bishara@il.marvell.com>
Cc: SCSI Mailing List <linux-scsi@vger.kernel.org>
Subject: Re: IO buffer alignment for block devices
Date: 13 Sep 2004 10:14:30 -0400 [thread overview]
Message-ID: <1095084876.1762.8.camel@mulgrave> (raw)
In-Reply-To: <41459729.5060106@il.marvell.com>
On Mon, 2004-09-13 at 08:48, Saeed Bishara wrote:
> Is there any minimal alignment for the IO buffers (sg and single)
> sent to a scsi LLD?
> I found that buffers that come from buffer cache, page cache and sg
> are page aligned , and the raw driver send sector aligned buffers.
> so can I assume that the minimal alignment of the buffer is 512 bytes?
You can assume it will be whatever you set blk_queue_dma_alignment() to
in your slave configure routines. If the LLD doesn't set this, then it
will be 8 bytes. However, beware, setting this higher can cause user
generated commands to be errored if they fail the alignment checks.
James
next prev parent reply other threads:[~2004-09-13 14:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-13 12:48 IO buffer alignment for block devices Saeed Bishara
2004-09-13 14:14 ` James Bottomley [this message]
2004-09-13 15:16 ` Saeed Bishara
2004-09-13 15:28 ` James Bottomley
2004-09-13 17:12 ` Kai Makisara
2004-09-13 19:02 ` Jens Axboe
2004-09-13 19:56 ` Kai Makisara
2004-09-13 20:23 ` Jens Axboe
2004-09-13 22:08 ` Kai Makisara
2004-09-14 7:44 ` Jens Axboe
2004-09-14 17:39 ` Kai Makisara
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