[Users] Librdmacm - mckey

[Hal Rosenstock]

Hi,

In order to setup the multicast group tree (for mckey), SM must first route
the MC tree and then program MulticastForwardingTables of switches that
tree passes through. The amount of time depends on the topology (how many
switches in subnet), processor speed of SM machine, and lastly delivering
the modified forwarding tables to the IB switches involved in that
multicast tree. This time is non deterministic.

IB multicast is inherently unreliable as it is based on UD transport. Are
you looking for reliable multicast mechanism for IB or is it just the
startup issue that's important for your application ?

-- Hal

On Fri, Mar 31, 2017 at 6:47 AM, Miljen Mikić <miljen.mikic at mireo.hr> wrote:

> Hello,
>
>
>
> I went through the source code of mckey utility (available e.g. here:
> https://github.com/ofiwg/librdmacm/blob/master/examples/mckey.c ). There
> is an interesting comment at the line 524:
>
>
>
> /*
>
>   *  Pause to give SM chance to configure switches. We don't want to
>
>  *  handle reliability issue in this simple test program.
>
>   */
>
>   sleep(3);
>
>
>
> If we remove sleep function call, mckey does not work properly anymore
> (receiver side does not get all messages that were sent). Does anyone know
> how long does it take for SM to „configure switches“, and what is the
> proper way to „handle reliability issue“?
>
>
>
> Many thanks in advance.
>
>
>
> Best regards,
>
> Miljen Mikic
>
>
>
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