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Subject: Re: [OMPI devel] Locality info
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-10-19 16:29:20


Sorry - referenced the wrong commit. It was r25331

On Oct 19, 2011, at 2:28 PM, Ralph Castain wrote:

> Hi folks
>
> For those of you who don't follow the commits...
>
> I just committed (r25323) an extension of the orte_ess.proc_get_locality function that allows a process to get its relative resource usage with any other proc in the job. In other words, you can provide a process name to the function, and the returned bitmask tells you if you share a node, numa, socket, caches (by level), core, and hyperthread with that process.
>
> If you are on the same node and unbound, of course, you share all of those. However, if you are bound, then this can help tell you if you are on a common numa node, sharing an L1 cache, etc. Might be handy.
>
> I implemented the underlying functionality so that we can further extend it to tell you the relative resource location of two procs on a remote node. If that someday becomes of interest, it would be relatively easy to do - but would require passing more info around. Hence, I've allowed for it, but not implemented it until there is some identified need.
>
> Locality info is available anytime after the modex is completed during MPI_Init, and is supported regardless of launch environment (minus cnos, for now), launch by mpirun, or direct-launch - in other words, pretty much always.
>
> Hope it proves of help in your work
> Ralph
>