[ofa-general] [PATCH] ipoib: refresh path when remote lid changes

[Yossi Etigin]

On 31/07/09 19:58, Todd Rimmer wrote:
>> Yossi Etigin wrote:
>  
>> What if we query the remote port LMC once, when the path is resolved,
>> and then
>> use it to mask the LID until the path is refreshed again?
> 
> Doing the LMC query when the PathRecord query is made makes, sense.
> 
> I assume you are proposing a query of the SA for the PortInfoRecord?
> 
> Note that a direct query of the remote SMA would be a bad idea and has at least the following issues:
> 1. There are limited VL15 queuing resources and no VL15 flow control, hence if multiple nodes queried the same SMA at the same time, packet loss could be significant which would impact SM operation as well (note how carefully the recent opensm work for parallel queries has had to tune operations to SMAs)
> 2. If MKey security is enabled, the client will not (and should not) know the MKey of the remote SMA and hence can't make a query.
> 3. The intent of the IB Architecture is for the SM to be the only entity which interacts with SMAs.  A handful of diagnostic tools (like ibdiagnet) may be an acceptable exception, but it would not be recommended to make non-SM queries of an SMA as part of a normal protocol.
> 

Actually I wasn't sure which is better, but given all these issues SM should be the one and not the SA.