[ofa-general] RE: [UPDATE] [V3] [PATCH 3/3] ib/ipoib: IPoIB-UD RX S/G supportfor 4K MTU

[Shirley Ma]

Hello Eli,

On Mon, 2008-02-04 at 15:54 +0200, Eli Cohen wrote
> Another thing to consider is use a 3 entries receive scatter list:
> 1. The first will point to 40 bytes generic buffer (allocated once per
> netdevice). All receive buffer will point to this buffer. As Roland
> suggested before, this will save us the skb_pull on the GRH.
> 
> 2. A 128 bytes buffer which comes from the linear part of the SKB - we
> can align this buffer to ensure IP is aligned at 16 byte boundary.
> 
> 3. A 4K page to in the first fragment.
> We can then check when the packet is received whether the overall
> packet
> length is small enough such that it did not touch the page. If it did
> not we can use this page for the newly posted buffer.
> 
> ** the above 128 bytes value can be a macro and we can determine what
> is
> the correct value.

Are you saying we also do this for 2K MTU? Otherwise the if condition
check can't not be avoid. And I don't know how much performance gain
from this approach.

Thanks
Shirley