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

[Eli Cohen]

Thanks. 

-----Original Message-----
From: Hal Rosenstock [mailto:hrosenstock at xsigo.com] 
Sent: ב 04 פברואר 2008 19:39
To: Eli Cohen
Cc: Shirley Ma; Roland Dreier; general at lists.openfabrics.org; sashak at voltaire.com
Subject: Re: [ofa-general] RE: [UPDATE] [V3] [PATCH 3/3] ib/ipoib: IPoIB-UDRX S/G supportfor 4K MTU

Eli,

On Sun, 2008-02-03 at 19:07 +0200, Eli Cohen wrote:
> Hi Shirley,
> 
> I have reviewed the patches against Roland's tree and have the 
> following
> comments:
> 
> 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).

The default is 2K (mtu=4). You can get opensm to make it 4K if you want as follows:

/etc/ofa/opensm-partitions.conf:
Default=0x7fff,ipoib,mtu=5:ALL=full;

-- Hal

> 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.
> 
> 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).
> 
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