David Edmondson wrote:
> On Tue, Sep 25, 2007 at 07:57:02AM -0700, Garrett D'Amore wrote:
>
>> One might imagine that soft LSO works differently. Imagine soft-lso as a
>> subroutine, which, given a large TCP segment, and the MTU size, builds a
>> series of header mblks, and maps the data segment in one operation (perhaps
>> making use of multiple DMA cookies, etc. to deal with page boundaries,
>> etc.) giving the appearance of LSO to the upper layers, while allowing a
>> NIC that only has the simple ability to use more than 1 descriptor per
>> ethernet frame to use a single DMA setup operation.
>>
>
> The approach you describe would require that a mac driver be updated
> to support it. That would be bad. Keeping things in the common layer
> is good.
>
Soft-LSO will require this anyway. If you don't push anything down to
the Mac layer or below, then what advantage is there to LSO versus
normal IP fragmentation?
You can do *most* of the work in the common layer, by having the mac
layer "upcall" to common code functionality. I think that is a good
compromise.
-- Garrett
