Patrick,
based on George's idea, a simpler check is to retrieve the Fortran index
via the (standard) MPI_Type_c2() function
after you create a derived datatype.
If the index keeps growing forever even after you MPI_Type_free(), then
this clearly indicates a leak.
Unfortunately, this simple test cannot be used to definitely rule out
any memory leak.
Note you can also
mpirun --mca pml ob1 --mca btl tcp,self ...
in order to force communications over TCP/IP and hence rule out any
memory leak that could be triggered by your fast interconnect.
In any case, a reproducer will greatly help us debugging this issue.
Cheers,
Gilles
On 12/4/2020 7:20 AM, George Bosilca via users wrote:
Patrick,
I'm afraid there is no simple way to check this. The main reason being
that OMPI use handles for MPI objects, and these handles are not
tracked by the library, they are supposed to be provided by the user
for each call. In your case, as you already called MPI_Type_free on
the datatype, you cannot produce a valid handle.
There might be a trick. If the datatype is manipulated with any
Fortran MPI functions, then we convert the handle (which in fact is a
pointer) to an index into a pointer array structure. Thus, the index
will remain used, and can therefore be used to convert back into a
valid datatype pointer, until OMPI completely releases the datatype.
Look into the ompi_datatype_f_to_c_table table to see the datatypes
that exist and get their pointers, and then use these pointers as
arguments to ompi_datatype_dump() to see if any of these existing
datatypes are the ones you define.
George.
On Thu, Dec 3, 2020 at 4:44 PM Patrick Bégou via users
<users@lists.open-mpi.org <mailto:users@lists.open-mpi.org>> wrote:
Hi,
I'm trying to solve a memory leak since my new implementation of
communications based on MPI_AllToAllW and MPI_type_Create_SubArray
calls. Arrays of SubArray types are created/destroyed at each
time step and used for communications.
On my laptop the code runs fine (running for 15000 temporal
itérations on 32 processes with oversubscription) but on our
cluster memory used by the code increase until the OOMkiller stop
the job. On the cluster we use IB QDR for communications.
Same Gcc/Gfortran 7.3 (built from sources), same sources of
OpenMPI (3.1 or 4.0.5 tested), same sources of the fortran code on
the laptop and on the cluster.
Using Gcc/Gfortran 4.8 and OpenMPI 1.7.3 on the cluster do not
show the problem (resident memory do not increase and we ran
100000 temporal iterations)
MPI_type_free manual says that it "/Marks the datatype object
associated with datatype for deallocation/". But how can I check
that the deallocation is really done ?
Thanks for ant suggestions.
Patrick
