RE: [PATCH] mlx4: allow for 4K mtu configuration of IB ports

["Bob Pearson" <rpearson-klaOcWyJdxkshyMvu7JE4pqQE7yCjDx5@public.gmane.org>]

With lash+mesh redsky required 6-7 VLs to wire up without deadlocks. I think
that Jim's version uses 8 SLs but only 2VLs to work.
If someone was using a torus and also wanted to support QOS and also wanted
to separate multicast and management on a separate VL to be absolutely sure
that there is no possibility of a deadlock you might end up with #QOS * 2 +
1 which would be 5 using the current algorithm.

-----Original Message-----
From: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
[mailto:linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Roland Dreier
Sent: Wednesday, May 25, 2011 4:28 PM
To: Or Gerlitz
Cc: Or Gerlitz; linux-rdma; Vladimir Sokolovsky
Subject: Re: [PATCH] mlx4: allow for 4K mtu configuration of IB ports

On Wed, May 25, 2011 at 2:05 PM, Or Gerlitz <or.gerlitz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> Does anyone really care about max VL cap with 2K MTU?
>
> I'm not with you... can you elaborate a little further here? the 
> current HW generation support four VLs with 4k mtu, newer HW might 
> support more.

I mean is there anyone who really uses >4 VLs?  Presumably the HW designers
didn't think so, because they limited HW to 4 VLs with 4K MTU.

At least can we make this a runtime thing?  If we're able to set a port as
IB vs ethernet then # of VLs seems like it should be doable too.

And 4K MTU should probably be the default, since almost all users want 4K
MTU vs. caring about VLs.  (Probably 99% of IB users never set SL of
anything)

 - R.
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