[Users] Librdmacm - mckey

[Hal Rosenstock]

Hi again Miljen,

No; there is no such API which is why sleep approach was chosen for this in
mckey.

-- Hal

On Fri, Mar 31, 2017 at 8:40 AM, Miljen Mikić <miljen.mikic at mireo.hr> wrote:

> Hi Hal,
>
>
>
> thanks for your answer!
>
>
>
> I understand that we cannot determine for sure how much time would it take
> to refresh the state, that's why my goal is to avoid any sleep(<SOME NUMBER
> OF SECONDS>) call in the code while keeping fingers crossed. Is there any
> API function that could inform us that multicast group is ready, e.g. some
> event that we could listen on?
>
>
>
> Best regards,
>
> Miljen Mikic
>
>
>
> *From:* Hal Rosenstock [mailto:hal.rosenstock at gmail.com]
> *Sent:* Friday, March 31, 2017 2:16 PM
> *To:* Miljen Mikić <miljen.mikic at mireo.hr>
> *Cc:* users at lists.openfabrics.org
> *Subject:* Re: [Users] Librdmacm - mckey
>
>
>
> 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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