[mvapich-discuss] waitsome/testsome memory allocation

[Abhinav Vishnu]

Hi Justin,

Thanks for reporting the problem. It seems strange that Testsome and
Waitsome primitives are actually allocating memory. Is it possible to
get access to the code snippet, which actually reproduces this problem?
Please let us know.

Thanks,

:- Abhinav

> Hi,
> 
> I am tracking down some memory issues in our code.  And I am finding 
> strange memory allocations occurring within MPI_Waitsome and 
> MPI_Testsome.  In one section of our code we use MPI_Pack and MPI_Unpack 
> to combine a bunch of small messages.  We then send out the packed 
> messages using isend.  The receiving processors post irecvs.  To 
> complete the communication we use both testsome and waitsome.  What we 
> are seeing is processors start by allocating a small amount of memory 
> but as the code marches forward in time processors will allocate more 
> memory within one of these mpi calls.  Processors continue allocating 
> larger and larger amounts of memory as time goes on.  For example early 
> on the allocation might be  a couple KB but eventually it will get to 
> around 1MB and i've even seen it as high as 14MB.  I predict that if I 
> ran it further it would allocate a much larger amount that 14MB.  
> Processors are not all allocating this memory at the same time.   In 
> other parts of the code we do not use packing and we do not see this 
> allocation behavior.  I'm guessing that somewhere we are either 
> miss-using packing or some other MPI feature and are causing MPI to leak.
> 
> I was wondering if you could tell me why testsome/waitsome would 
> allocate memory as that could provide a good hint as to how we are 
> miss-using mpi.
> 
> Currently we are using mvapich version 0.9.9  on Atlas at LLNL
> 
> Thanks,
> Justin
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