[openib-general] SA cache design

[Hal Rosenstock]

Hi Eitan,

[snip...]

> >>  So if a new client wants to connect to another node a new PathRecord
> >>  query will not need to be sent to the SA. However, recent work on QoS has
> >>pointed out
> >>  that under some QoS schemes PathRecord should not be shared by different
> >>clients
> > 
> > 
> > I'm not sure that QoS handling is the responsibility of the cache.  The module
> > requesting the path records should probably deal with this.
> In IB QoS properties are mainly the PathRecord parameters: SL, Rate, MTU, PathBits (LMC bits).
> So if traditionally we had PathRecord requested for each Src->Dst port now we will need to 
> track at least:
> Src->Dst * #QoS-levels. (a non optimal implementation will require even more: #Src->Dst * #Clients * #Servers * #Services).

Perhaps QoS requests (I'm referring to those with the new proposed key)
are not cached as I think this may end up with the cache needing to know
the path record policies). I would propose deferring this aspect until
the new QoS work is a little firmer and the cache direction in OpenIB is
also a little firmer (e.g. QoS = phase 2 or beyond of this work).

[snip...]

-- Hal