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

[Shirley Ma]

general-bounces at lists.openfabrics.org wrote on 02/03/2008 09:07:29 AM:

> Hi Shirley,
>
> I have reviewed the patches against Roland's tree and have the following
> comments:

Appreciate you quick review.

> 1. I see that there are a few if statements added on the fast pass and I
> am concerned they might hurt performance of slow UDP messages.
> Unfortunately I have not been able to test with an SM defining the
> broadcast group to 4K MTU (currently opensm uses 2K).
What kind of parameters you prefer here for me to test this patch? I can
test it right away when you send me your recommendations.

> 2. The usage of ipoib_ud_skb_put_frags() seems to be redundant and will
> only hurt performance since you would never reuse anything from the old
> SKB. This is because the headlen is 40 bytes for GRH and the rest of the
> data is in the first (and only) fragment.
The header is 44 bytes, the IP payload data is in the first fragment.

> 3. I think it would be better to allocate room for real data in the head
> of the SKB since the tcp/ip stack seems to have less overhead if the
> headers are on the linear data.
> 4. I would consider using a pre-allocated buffer for the GRH of all
> received data (not as part of the SKB).

Comments 2,3,4 can be combined of one if we use a pre-allocated buffer for
GRH+IPoIB-head for all IP payload data, right? This is a performance
enhancement if any. I think this could be done after this patch being
checked in. And I will fix it before RC4 out. Do you agree?

Thanks
Shirley
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