[petsc-dev] Adding support memkind allocators in PETSc

[Jed Brown]

Richard Mills <rtm at utk.edu> writes:
>> > but it screws up memkind's partitioning of the heap (it won't be aware
>> > that the pages have been moved).
>>
>> Then memkind is stupid or the kernel isn't exposing the correct
>> information to memkind.  Tell them to not be lazy and do it right.
>>
>
> I believe that it really comes down to a problem with what the Linux kernel
> allows right now.  To do this "right" we need to hack the kernel.  Memkind
> is working within the constraints of what the kernel currently does.

What exactly is memkind trying to do?  Does it somehow discover the
number of "compute" processes running on the node and partition their
allocation from MCDRAM?  Surely not because that would be as comically
naive as Blue Gene partitioning memory at boot, but what *does* it do
about other processes?  If you spawn new processes, can they use MCDRAM?
How much?  How is memkind budgeting affected by a users' direct use of
mmap or shm_open?  When a process exits, does memkind in the remaining
processes know that more MCDRAM is available?
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