Re: IO buffer alignment for block devices

[Saeed Bishara <Saeed.Bishara@il.marvell.com>]

James Bottomley wrote:

>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
>  
>
    isn't the default 512, this is what I see in blk_queue_make_request.

<http://lxr.linux.no/ident?v=2.6.8.1;i=blk_queue_make_request>

>generated commands to be errored if they fail the alignment checks.
>
>James
>
>  
>
any Ideas about lk 2.4?

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>  
>