[OMPI users] Binding to thread 0
Hello, Up to now, I have been using numerous ways of binding with wrappers (numactl, taskset) whenever I wanted to play with core placing. Another way I have been using is via -rankfile, however I notice that some ranks jump from thread 0 to thread 1 on SMT chips. I can control this with numactl for instance, but it would be great to see similar behaviour when using -rankfile. Is there a way to pack all ranks to one of the threads of each core (preferibly to thread 0) so I can nicely see all ranks with htop on either left or right of the screen? The command I am using is pretty simple: mpirun -np $MPIRANKS --rankfile ./myrankfile and ./myrankfile looks like rank 33=argon slot=33 rank 34=argon slot=34 rank 35=argon slot=35 rank 36=argon slot=36 Thanks!
Re: [OMPI users] Binding to thread 0
Luis, you can pass the --bind-to hwthread option in order to bind on the first thread of each core Cheers, Gilles On Fri, Sep 8, 2023 at 8:30 PM Luis Cebamanos via users < users@lists.open-mpi.org> wrote: > Hello, > > Up to now, I have been using numerous ways of binding with wrappers > (numactl, taskset) whenever I wanted to play with core placing. Another way > I have been using is via -rankfile, however I notice that some ranks jump > from thread 0 to thread 1 on SMT chips. I can control this with numactl for > instance, but it would be great to see similar behaviour when using > -rankfile. Is there a way to pack all ranks to one of the threads of each > core (preferibly to thread 0) so I can nicely see all ranks with htop on > either left or right of the screen? > > The command I am using is pretty simple: > > mpirun -np $MPIRANKS --rankfile ./myrankfile > > and ./myrankfile looks like > > rank 33=argon slot=33 > rank 34=argon slot=34 > rank 35=argon slot=35 > rank 36=argon slot=36 > > Thanks! >
Re: [OMPI users] Binding to thread 0
In addition to what Gilles mentioned, I'm curious: is there a reason you have hardware threads enabled? You could disable them in the BIOS, and then each of your MPI processes can use the full core, not just a single hardware thread. From: users on behalf of Luis Cebamanos via users Sent: Friday, September 8, 2023 7:10 AM To: Ralph Castain via users Cc: Luis Cebamanos Subject: [OMPI users] Binding to thread 0 Hello, Up to now, I have been using numerous ways of binding with wrappers (numactl, taskset) whenever I wanted to play with core placing. Another way I have been using is via -rankfile, however I notice that some ranks jump from thread 0 to thread 1 on SMT chips. I can control this with numactl for instance, but it would be great to see similar behaviour when using -rankfile. Is there a way to pack all ranks to one of the threads of each core (preferibly to thread 0) so I can nicely see all ranks with htop on either left or right of the screen? The command I am using is pretty simple: mpirun -np $MPIRANKS --rankfile ./myrankfile and ./myrankfile looks like rank 33=argon slot=33 rank 34=argon slot=34 rank 35=argon slot=35 rank 36=argon slot=36 Thanks!
