[petsc-dev] [Minor issue] Lag during PetscInitialize on Fedora 36 (never seen before with other OS)

[LEDAC Pierre]

Ok thanks all, so with Satish test, we know it is MPI_Init call from PetscInitialize.

Probably, as Matt said, something related to gethostbyname() ...


I will do some other test, contact MPICH support and will report any workaround,


Thanks again for your reactivity !


Pierre LEDAC
Commissariat à l’énergie atomique et aux énergies alternatives
Centre de SACLAY
DES/ISAS/DM2S/STMF/LGLS
Bâtiment 451 – point courrier n°43
F-91191 Gif-sur-Yvette
+33 1 69 08 04 03
+33 6 83 42 05 79
________________________________
De : Satish Balay <balay at mcs.anl.gov>
Envoyé : mercredi 27 juillet 2022 18:57:16
À : LEDAC Pierre
Cc : petsc-dev at mcs.anl.gov
Objet : Re: [petsc-dev] [Minor issue] Lag during PetscInitialize on Fedora 36 (never seen before with other OS)

I'm seeing this behavior on a laptop - but not desktop [both F36] (with both mpich and openmpi buids)

>>>> laptop/mpich <<<<
balay at p1 /home/balay/petsc/src/ksp/ksp/tests (main =)
$ sleep 30; time ./ex39; time ./ex39

real    0m1.709s
user    0m0.079s
sys     0m0.042s

real    0m0.116s
user    0m0.077s
sys     0m0.014s
<<<<

However --with-mpi=0 is fine

>>>>
balay at p1 /home/balay/petsc/src/ksp/ksp/tests (main =)
$ sleep 30; time ./ex39; time ./ex39

real    0m0.116s
user    0m0.108s
sys     0m0.008s

real    0m0.081s
user    0m0.072s
sys     0m0.008s
<<<<<

Here is the desktop run (with mpich)

>>>
[balay at pj01 tests]$ sleep 30; time ./ex39; time ./ex39

real    0m0.065s
user    0m0.033s
sys     0m0.019s

real    0m0.053s
user    0m0.029s
sys     0m0.013s
<<<<

And --with-mpi=0

>>>
[balay at pj01 tests]$ sleep 30; time ./ex39; time ./ex39

real    0m0.087s
user    0m0.046s
sys     0m0.015s

real    0m0.024s
user    0m0.018s
sys     0m0.006s
<<<

But don't know why its behaving this way [on the laptop]

Satish

On Wed, 27 Jul 2022, LEDAC Pierre wrote:

> Hello,
>
>
> Recently migrated from Fedora34 to Fedora36, using PETSc I have some lag during the PetscInitialize, which
>
> disappeared if I run again immediately the binary. But after few seconds, the lag happens again (see below).
>
>
> I suspected MPICH 4.0.2 on Fedora36, but a small reproducer indicated the issue is not in MPI_Init but really during PetscInitialize
>
>
> Just annoying during testing, not very important, but did someone already see this ?
>
>
> Thanks,
>
>
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m3,593s
> user    0m0,872s
> sys    0m0,433s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,310s
> user    0m0,884s
> sys    0m0,023s
>
> # Wait ~20 seconds then again:
>
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m3,507s
> user    0m0,897s
> sys    0m0,025s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,154s
> user    0m0,725s
> sys    0m0,015s
> portable: /volatile/ledacp/petsc/src/ksp/ksp/tests (main) > time ./ex39
>
> real    0m0,176s
> user    0m0,875s
> sys    0m0,021s
>
>
>
> Pierre LEDAC
> Commissariat à l’énergie atomique et aux énergies alternatives
> Centre de SACLAY
> DES/ISAS/DM2S/STMF/LGLS
> Bâtiment 451 – point courrier n°43
> F-91191 Gif-sur-Yvette
> +33 1 69 08 04 03
> +33 6 83 42 05 79
>
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