[mpich-discuss] Mpich-3.2 slowdown with gforker

[Jeff Hammond]

Why don't you use hydra instead of gforker?

Over subscribing is bad if MPI polls in shared memory code. I believe
nemesis does this. You can use ch3:sock to workaround but it is
discouraged. Best option is to not oversubscribe. Do you need this for more
than debugging? I know PETSc folks like to debug that way.

Is hyper threading turned on or off? /proc/cpuinfo will answer this if you
don't know. It is on by default AFAIK.

Jeff

On Wednesday, June 22, 2016, Shemon, Emily R. <eshemon at anl.gov> wrote:

> Hello,
>
>
>
> We used to use mpich2-1.2 with gforker process manager (Intel 10.1
> compiler).
>
> We are transitioning mpich-3.2 with gforker process manager (Intel 13.1
> compiler) (configuration options are the same as before: ./configure
> --prefix=$MPI_DIR --enable-g=debug,meminit  --enable-fast=O2
> --with-pm=gforker --enable-cxx --enable-fortran CC=icc CXX=icpc FC=ifort
> F77=ifort)
>
> We have noticed extreme slowdowns with the new installation of mpich on
> the same machine (shared memory Linux server with CentOS 7) when attempting
> to use hyperthreading. The old executable works just fine on the same
> machine, but the new executable using mpich-3.2 is running 10-20x slower
> when going past the number of physical cores on the machine. We believe we
> have traced it to our MPI_AllReduce functions. This is a Fortran code.
>
>
>
> In the meantime I’m going to try to install the old mpich2-1.2 again (we
> had a machine OS upgrade) and see what happens.
>
>
>
> Any ideas?
>
>
>
> Thank you,
>
>
>
> Emily Shemon, Ph.D.
>
> Argonne National Laboratory
>
> Nuclear Engineering Division &
>
> Argonne Leadership Computing Facility
>
> P: 630-252-4477
>
> E: eshemon at anl.gov <javascript:_e(%7B%7D,'cvml','eshemon at anl.gov');>
>
>
>


-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mpich.org/pipermail/discuss/attachments/20160622/e815db83/attachment.html>
-------------- next part --------------
_______________________________________________
discuss mailing list     discuss at mpich.org
To manage subscription options or unsubscribe:
https://lists.mpich.org/mailman/listinfo/discuss