[ofw] [RFC] Locally generated path records

[Hal Rosenstock]

Sean,

On Tue, Jul 15, 2008 at 3:38 PM, Sean Hefty <sean.hefty at intel.com> wrote:
>>To create a path record, IPoIB needs the following values (in addition to the
>>ones it has access to for the AV creation):
>
> You don't need to create a PR, versus just creating the AV.
>
>>Reversible: Hard code to 1
>>NumbPath: Hard code to 1
>
> You shouldn't need these, at least for UD.  Reversible is needed if you end up
> with IPoIB connected mode,

Does RC require reversible paths ? Can't the two directions use
different paths or is that only UD ?

> but NumbPath is only used in a PR query.

Get Table needs this; Get doesn't.

> If you want
> to support any arbitrary topology with connected mode IPoIB, then you would need
> to know if a path is truly reversible, and potentially want to use different
> forward and reverse paths.
>
>>PKey: Same as IPoIB port object
>>MTU: broadcast group
>>Rate: broadcast group
>
> The rate seems to be the only real limitation to me.  In the worst case, you
> slow down traffic between a given pair of nodes, but at least things keep
> working.  Avoiding the PR queries seems like a good idea to me, but it should
> probably be user configurable.
>
>>Preference: 0
>
> Only used for PR queries.
>
> I'm not sure that most MPI apps will run through an IB router, so always
> querying for off subnet paths will probably be needed.

That seems contradictory. Do you mean not needed rather than needed ?

>  (The current PR format
> only works for UD traffic between IB subnets anyway.)

Not sure why you say that.

-- Hal

> - Sean
>
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