[openib-general] Re: Re: [PATCH] change Mellanox SDP workaround to a moduleparameter

[Michael S. Tsirkin]

Quoting r. Hal Rosenstock <halr at voltaire.com>:
> Subject: Re: Re: [PATCH] change Mellanox SDP workaround to a moduleparameter
> 
> On Wed, 2006-02-15 at 19:03, Roland Dreier wrote:
> >     mst> I thought about it some more: what happens if nodes with
> >     mst> different max MTU values try to connect?
> > 
> > This should never happen.  The SM should never give a path with an MTU
> > that is not supported by both end nodes.
> 
> True, but the description for the CM REJ code 26 for Invalid Path MTU
> states something a little different (p. 667):
> 
> "The recepient of the REQ message cannot support the maximum packet
> payload size requested."

Right.

> is being interpreted as "prefers not to support the max payload size
> requested" which is probably OK.
> 
> > I guess the question is what to do when a Tavor (with the performance
> > bug that makes a 1K MTU faster) connects to someone else.
> 
> Isn't it the other way 'round (when something with a larger MTU connects
> to Tavor) ?

Right. I wish we had an MTU field in the REP packet, but we dont.

-- 
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies