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Subject: Re: [OMPI devel] RFC: hwloc object userdata
From: George Bosilca (bosilca_at_[hidden])
Date: 2012-10-03 10:22:35


In the case such a functionality become necessary, I would suggest we use a mechanism similar to the attributes in MPI (but without the multi-language mess). That will allow whoever want to attach data to a hwloc node, to do it without the mess of dealing with reserving a slot. It might require a little bit more memory, but so far the number of nodes in the HWLOC data is limited.

  george.

On Oct 3, 2012, at 16:13 , Jeff Squyres <jsquyres_at_[hidden]> wrote:

> WHAT: allowing multiple entities in the OMPI code base to hang data off hwloc_obj->userdata
>
> WHY: anticipating that more parts of the OMPI code base will be using the hwloc data
>
> WHERE: hwloc base
>
> WHEN: no real hurry; Ralph and I just identified the potential for this issue this morning. We're not aware of it being an actual problem (yet).
>
> MORE DETAIL:
>
> The rmaps base (in mpirun) is currently hanging its own data off various objects in the hwloc topology tree. However, it should be noted that the hwloc topology tree is a global data structure in each MPI processes; multiple upper-level entities in the ORTE and OMPI layers may want to hang their own userdata off hwloc objects.
>
> Ralph and I figured that some functionality could be added to the hwloc base to hang a opal_pointer_array off each hwloc object; each array value will be a (void*). Then upper-level entities can reserve a slot in all the pointer arrays and store whatever they want in their (void*) slot.
>
> For example, if the openib BTL wants to use the hwloc data and hang its own userdata off hwloc objects, it can call the hwloc base and reserve a slot. The hwloc base will say "Ok, you can have slot 7". Then the openib BTL can always use slot 7 in the opal_pointer_array off any hwloc object.
>
> Does this sound reasonable?
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
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