[ofa-general] Re: InfiniBand/RDMA merge plans for 2.6.24

[Shirley Ma]

netdev-owner at vger.kernel.org wrote on 09/13/2007 02:00:43 PM:

>  >         Since ehca can support 4K MTU, we would like to see a patch in

>  > IPoIB to allow link MTU to be up to 4K instead of current 2K for
2.6.24
>  > kernel. The idea is IPoIB link MTU will pick up a return value from
SM's
>  > default broadcast MTU. This patch should be a small patch, I hope you
are
>  > OK with this.
>
> It's actually not small, since it turns the skb allocation into a
> 4100-byte buffer, which ends up being more than 1 page usually, which
> means it fails if memory is fragmented.
>
> Anyway given the backlog anything substantial that hasn't been posted
> already is almost surely going to have to wait until 2.6.25.

The patch is just needed to pick up broadcast MTU size instead of hard
coding 2K right now. SKB allocation shouldn't be different with Ethernet
Jambo Frame and IPoIB-CM which 64K MTU. I don't understand why it's
different. Could you please explain this?

Thanks
Shirley
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