I see, so if I understand correctly, the best scenario for threads would be to bind 2 procs to sockets as --map-by socket:pe=4 and use 4 threads in each proc.
Also, as you've mentioned binding threads to get memory locality, I guess this has to be done at application level and not an option in OMPI Thank you, Saliya On Wed, Feb 26, 2014 at 4:50 PM, Ralph Castain <r...@open-mpi.org> wrote: > Sorry, had to run some errands. > > On Feb 26, 2014, at 1:03 PM, Saliya Ekanayake <esal...@gmail.com> wrote: > > 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? > > > In that scenario, you won't get any benefit from binding as we only bind > at the proc level (and binding to the entire node does nothing). You might > want to bind your threads, however, as otherwise the threads will not > necessarily execute local to any memory they malloc. > > > 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 > _______________________________________________ > 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
