I am not sure why the distances are being computed as you are seeing. I do not have a dual rail card system to reproduce with. However, short term, I think you could get what you want by running like the following. The first argument tells the selection logic to ignore locality, so both cards will be available to all ranks. Then, using the application specific notation you can pick the exact port for each rank.
Something like: mpirun -gmca btl_openib_ignore_locality -np 1 --mca btl_openib_if_include mlx4_0:1 a.out : -np 1 --mca btl_openib_if_include mlx4_0:2 a.out : -np 1 --mca btl_openib_if_include mlx4_1:1 a.out : --mca btl_openib_if_include mlx4_1:2 a.out Kind of messy, but that is the general idea. Rolf >-----Original Message----- >From: users [mailto:users-boun...@open-mpi.org] On Behalf Of >marcin.krotkiewski >Sent: Friday, August 28, 2015 10:49 AM >To: us...@open-mpi.org >Subject: [OMPI users] Wrong distance calculations in multi-rail setup? > >I have a 4-socket machine with two dual-port Infiniband cards (devices >mlx4_0 and mlx4_1). The cards are conneted to PCI slots of different CPUs (I >hope..), both ports are active on both cards, everything connected to the >same physical network. > >I use openmpi-1.10.0 and run the IBM-MPI1 benchmark with 4 MPI ranks >bound to the 4 sockets, hoping to use both IB cards (and both ports): > > mpirun --map-by socket --bind-to core -np 4 --mca btl openib,self --mca >btl_openib_if_include mlx4_0,mlx4_1 ./IMB-MPI1 SendRecv > >but OpenMPI refuses to use the mlx4_1 device > > [node1.local:28265] [rank=0] openib: skipping device mlx4_1; it is too far >away > [ the same for other ranks ] > >This is confusing, since I have read that OpenMPI automatically uses a closer >HCA, so at least some (>=one) rank should choose mlx4_1. I use binding by >socket, here is the reported map: > > [node1.local:28263] MCW rank 2 bound to socket 2[core 24[hwt 0]]: >[./././././././././././.][./././././././././././.][B/././././././././././.][./././././././././. >/./.] > [node1.local:28263] MCW rank 3 bound to socket 3[core 36[hwt 0]]: >[./././././././././././.][./././././././././././.][./././././././././././.][B/././././././././. >/./.] > [node1.local:28263] MCW rank 0 bound to socket 0[core 0[hwt 0]]: >[B/././././././././././.][./././././././././././.][./././././././././././.][./././././././././. >/./.] > [node1.local:28263] MCW rank 1 bound to socket 1[core 12[hwt 0]]: >[./././././././././././.][B/././././././././././.][./././././././././././.][./././././././././. >/./.] > >To check what's going on I have modified btl_openib_component.c to print >the computed distances. > > opal_output_verbose(1, ompi_btl_base_framework.framework_output, > "[rank=%d] openib: device %d/%d distance %lf", >ORTE_PROC_MY_NAME->vpid, > (int)i, (int)num_devs, > (double)dev_sorted[i].distance); > >Here is what I get: > > [node1.local:28265] [rank=0] openib: device 0/2 distance 0.000000 > [node1.local:28266] [rank=1] openib: device 0/2 distance 0.000000 > [node1.local:28267] [rank=2] openib: device 0/2 distance 0.000000 > [node1.local:28268] [rank=3] openib: device 0/2 distance 0.000000 > [node1.local:28265] [rank=0] openib: device 1/2 distance 2.100000 > [node1.local:28266] [rank=1] openib: device 1/2 distance 1.000000 > [node1.local:28267] [rank=2] openib: device 1/2 distance 2.100000 > [node1.local:28268] [rank=3] openib: device 1/2 distance 2.100000 > >So the computed distance for mlx4_0 is 0 on all ranks. I believe this should >not >be so. The distance should be smaller on 1 rank and larger for 3 others, as is >the case for mlx4_1. Looks like a bug? > >Another question is, In my configuration two ranks will have a 'closer' >IB card, but two others will not. Since the correct distance to both devices >will >likely be equal, which device will they choose, if they do that automatically? >I'd >rather they didn't both choose mlx4_0.. I guess it would be nice if I could by >hand specify the device/port, which should be used by a given MPI rank. Is >this (going to be) possible with OpenMPI? > >Thanks a lot, > >Marcin > >_______________________________________________ >users mailing list >us...@open-mpi.org >Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >Link to this post: http://www.open- >mpi.org/community/lists/users/2015/08/27503.php ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------
