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Subject: Re: [OMPI users] Unknown overhead in "mpirun -am ft-enable-cr"
From: Nguyen Toan (nguyentoan1508_at_[hidden])
Date: 2011-02-13 01:04:45


Hi Josh,

I tried the MCA parameter you mentioned but it did not help, the unknown
overhead still exists.
Here I attach the output of 'ompi_info', both version 1.5 and 1.5.1.
Hope you can find out the problem.
Thank you.

Regards,
Nguyen Toan

On Wed, Feb 9, 2011 at 11:08 PM, Joshua Hursey <jjhursey_at_[hidden]>wrote:

> It looks like the logic in the configure script is turning on the FT thread
> for you when you specify both '--with-ft=cr' and '--enable-mpi-threads'.
>
> Can you send me the output of 'ompi_info'? Can you also try the MCA
> parameter that I mentioned earlier to see if that changes the performance?
>
> I there are many non-blocking sends and receives, there might be
> performance bug with the way the point-to-point wrapper is tracking request
> objects. If the above MCA parameter does not help the situation, let me know
> and I might be able to take a look at this next week.
>
> Thanks,
> Josh
>
> On Feb 9, 2011, at 1:40 AM, Nguyen Toan wrote:
>
> > Hi Josh,
> > Thanks for the reply. I did not use the '--enable-ft-thread' option. Here
> is my build options:
> >
> > CFLAGS=-g \
> > ./configure \
> > --with-ft=cr \
> > --enable-mpi-threads \
> > --with-blcr=/home/nguyen/opt/blcr \
> > --with-blcr-libdir=/home/nguyen/opt/blcr/lib \
> > --prefix=/home/nguyen/opt/openmpi \
> > --with-openib \
> > --enable-mpirun-prefix-by-default
> >
> > My application requires lots of communication in every loop, focusing on
> MPI_Isend, MPI_Irecv and MPI_Wait. Also I want to make only one checkpoint
> per application execution for my purpose, but the unknown overhead exists
> even when no checkpoint was taken.
> >
> > Do you have any other idea?
> >
> > Regards,
> > Nguyen Toan
> >
> >
> > On Wed, Feb 9, 2011 at 12:41 AM, Joshua Hursey <jjhursey_at_[hidden]>
> wrote:
> > There are a few reasons why this might be occurring. Did you build with
> the '--enable-ft-thread' option?
> >
> > If so, it looks like I didn't move over the thread_sleep_wait adjustment
> from the trunk - the thread was being a bit too aggressive. Try adding the
> following to your command line options, and see if it changes the
> performance.
> > "-mca opal_cr_thread_sleep_wait 1000"
> >
> > There are other places to look as well depending on how frequently your
> application communicates, how often you checkpoint, process layout, ... But
> usually the aggressive nature of the thread is the main problem.
> >
> > Let me know if that helps.
> >
> > -- Josh
> >
> > On Feb 8, 2011, at 2:50 AM, Nguyen Toan wrote:
> >
> > > Hi all,
> > >
> > > I am using the latest version of OpenMPI (1.5.1) and BLCR (0.8.2).
> > > I found that when running an application,which uses MPI_Isend,
> MPI_Irecv and MPI_Wait,
> > > enabling C/R, i.e using "-am ft-enable-cr", the application runtime is
> much longer than the normal execution with mpirun (no checkpoint was taken).
> > > This overhead becomes larger when the normal execution runtime is
> longer.
> > > Does anybody have any idea about this overhead, and how to eliminate
> it?
> > > Thanks.
> > >
> > > Regards,
> > > Nguyen
> > > _______________________________________________
> > > users mailing list
> > > users_at_[hidden]
> > > http://www.open-mpi.org/mailman/listinfo.cgi/users
> >
> > ------------------------------------
> > Joshua Hursey
> > Postdoctoral Research Associate
> > Oak Ridge National Laboratory
> > http://users.nccs.gov/~jjhursey
> >
> >
> > _______________________________________________
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> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
> >
> > _______________________________________________
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>
> ------------------------------------
> Joshua Hursey
> Postdoctoral Research Associate
> Oak Ridge National Laboratory
> http://users.nccs.gov/~jjhursey
>
>
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