[petsc-dev] Adding support memkind allocators in PETSc

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:
>     MPI_Comm argument?  PETSc users rarely need to call PetscMalloc()
>     themselves and if they do call it then they should know the
>     properties of the memory they are allocating. Most users won't
>     even notice the change.

I think that's an exaggeration, but what are you going to use for the
"kind" parameter?  The "correct" value depends on a ton of non-local
information.

>    Note that I'd like to add this argument independent of memkind.

What are you going to use it for?  If the allocation is small enough,
it'll probably be resident in cache and if it falls out, the lower
latency to DRAM will be better than HBM.  As it gets bigger, provided it
gets enough use, then HBM becomes the right place, but later it's too
big and you have to go back to DRAM.

What happens if memory of the kind requested is unavailable?  Error or
the implementations tries to find a different kind?  If there are
several memory kinds, what order is used when checking?
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