Is it possible to bind to cores of multiple sockets? Say I have a machine with 2 sockets each with 4 cores and if I run 8 threads with 1 proc can I utilize all 8 cores for 8 threads?
Thank you for speedy replies Saliya On Wed, Feb 26, 2014 at 3:21 PM, Ralph Castain <r...@open-mpi.org> wrote: > > On Feb 26, 2014, at 12:17 PM, Saliya Ekanayake <esal...@gmail.com> wrote: > > I have a followup question on this. In our application we have parallel > for loops similar to OMP parallel for. I noticed that in order to gain > speedup with threads I've to set --bind-to none, otherwise multiple threads > will bind to same core giving no increase in performance. For example, I > get following (attached) performance for a simple 3point stencil > computation run with T threads on 1 MPI process on 1 node (Tx1x1). > > My understanding is even when there are multiple procs per node we should > use --bind-to none in order to get performance with threads. Is this > correct? Also, what's the disadvantage of not using --bind-to core? > > > Your best performance with threads comes when you bind each process to > multiple cores. Binding helps performance by ensuring your memory is always > local, and provides some optimized scheduling benefits. You can bind to > multiple cores by adding the qualifier "pe=N" to your mapping definition, > like this: > > mpirun --map-by socket:pe=4 .... > > The above example will map processes by socket, and bind each process to 4 > cores. > > HTH > Ralph > > > Thank you, > Saliya > > > On Wed, Feb 26, 2014 at 11:01 AM, Saliya Ekanayake <esal...@gmail.com>wrote: > >> Thank you Ralph, I'll check this. >> >> >> On Wed, Feb 26, 2014 at 10:04 AM, Ralph Castain <r...@open-mpi.org> wrote: >> >>> It means that OMPI didn't get built against libnuma, and so we can't >>> ensure that memory is being bound local to the proc binding. Check to see >>> if numactl and numactl-devel are installed, or you can turn off the warning >>> using "-mca hwloc_base_mem_bind_failure_action silent" >>> >>> >>> On Feb 25, 2014, at 10:32 PM, Saliya Ekanayake <esal...@gmail.com> >>> wrote: >>> >>> Hi, >>> >>> I tried to run an MPI Java program with --bind-to core. I receive the >>> following warning and wonder how to fix this. >>> >>> >>> WARNING: a request was made to bind a process. While the system >>> supports binding the process itself, at least one node does NOT >>> support binding memory to the process location. >>> >>> Node: 192.168.0.19 >>> >>> This is a warning only; your job will continue, though performance may >>> be degraded. >>> >>> >>> Thank you, >>> Saliya >>> >>> -- >>> Saliya Ekanayake esal...@gmail.com >>> Cell 812-391-4914 Home 812-961-6383 >>> http://saliya.org >>> _______________________________________________ >>> users mailing list >>> us...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>> >>> >>> >>> _______________________________________________ >>> users mailing list >>> us...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>> >> >> >> >> -- >> Saliya Ekanayake esal...@gmail.com >> Cell 812-391-4914 Home 812-961-6383 >> http://saliya.org >> > > > > -- > Saliya Ekanayake esal...@gmail.com > Cell 812-391-4914 Home 812-961-6383 > http://saliya.org > <3pointstencil.png>_______________________________________________ > > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- Saliya Ekanayake esal...@gmail.com Cell 812-391-4914 Home 812-961-6383 http://saliya.org
