[petsc-users] Memory growth issue

[Smith, Barry F.]

   This is indeed worrisome. 

    Would it be possible to put PetscMemoryGetCurrentUsage() around each call to KSPSolve() and each call to your data exchange? See if at each step they increase? 

    One thing to be aware of with "max resident set size" is that it measures the number of pages that have been set up. Not the amount of memory allocated. So, if, for example, you allocate a very large array but don't actually read or write the memory in that array until later in the code it won't appear in the "resident set size" until you read or write the memory (because Unix doesn't set up pages until it needs to). 

   You should also try another MPI. Both OpenMPI and MPICH can be installed with brew or you can use --download-mpich or --download-openmp to see if the MPI implementation is making a difference.

    For now I would focus on the PETSc only solvers to eliminate one variable from the equation; once that is understood you can go back to the question of the memory management of the other solvers

  Barry


> On May 29, 2019, at 11:51 PM, Sanjay Govindjee via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> I am trying to track down a memory issue with my code; apologies in advance for the longish message.
> 
> I am solving a FEA problem with a number of load steps involving about 3000
> right hand side and tangent assemblies and solves.  The program is mainly Fortran, with a C memory allocator.
> 
> When I run my code in strictly serial mode (no Petsc or MPI routines) the memory stays constant over the whole run.
> 
> When I run it in parallel mode with petsc solvers with num_processes=1, the memory (max resident set size) also stays constant:
> 
> PetscMalloc = 28,976, ProgramNativeMalloc = constant, Resident Size = 24,854,528 (constant) [CG/JACOBI]
> 
> [PetscMalloc and Resident Size as reported by PetscMallocGetCurrentUsage and PetscMemoryGetCurrentUsage (and summed across processes as needed);
> ProgramNativeMalloc reported by program memory allocator.]
> 
> When I run it in parallel mode with petsc solvers but num_processes=2, the resident memory grows steadily during the run:
> 
> PetscMalloc = 3,039,072 (constant), ProgramNativeMalloc = constant, Resident Size = (finish) 31,313,920 (start) 24,698,880 [CG/JACOBI]
> 
> When I run it in parallel mode with petsc solvers but num_processes=4, the resident memory grows steadily during the run:
> 
> PetscMalloc = 3,307,888 (constant), ProgramNativeMalloc = 1,427,584 (constant), Resident Size = (finish) 70,787,072  (start) 45,801,472 [CG/JACOBI]
> PetscMalloc = 5,903,808 (constant), ProgramNativeMalloc = 1,427,584 (constant), Resident Size = (finish) 112,410,624 (start) 52,076,544 [GMRES/BJACOBI]
> PetscMalloc = 3,188,944 (constant), ProgramNativeMalloc = 1,427,584 (constant), Resident Size = (finish) 712,798,208 (start) 381,480,960 [SUPERLU]
> PetscMalloc = 6,539,408 (constant), ProgramNativeMalloc = 1,427,584 (constant), Resident Size = (finish) 591,048,704 (start) 278,671,360 [MUMPS]
> 
> The memory growth feels alarming but maybe I do not understand the values in ru_maxrss from getrusage().
> 
> My box (MacBook Pro) has a broken Valgrind so I need to get to a system with a functional one; notwithstanding, the code has always been Valgrind clean.
> There are no Fortran Pointers or Fortran Allocatable arrays in the part of the code being used.  The program's C memory allocator keeps track of
> itself so I do not see that the problem is there.  The Petsc malloc is also steady.
> 
> Other random hints:
> 
> 1) If I comment out the call to KSPSolve and to my MPI data-exchange routine (for passing solution values between processes after each solve,
> use  MPI_Isend, MPI_Recv, MPI_BARRIER)  the memory growth essentially goes away.
> 
> 2) If I comment out the call to my MPI data-exchange routine but leave the call to KSPSolve the problem remains but is substantially reduced
> for CG/JACOBI, and is marginally reduced for the GMRES/BJACOBI, SUPERLU, and MUMPS runs.
> 
> 3) If I comment out the call to KSPSolve but leave the call to my MPI data-exchange routine the problem remains.
> 
> Any suggestions/hints of where to look will be great.
> 
> -sanjay
> 
>