Hello We have a platform with an old MLX4 partition and another OPA partition. We want a single OMPI installation working for both kinds of nodes. When we enable UCX in OMPI for MLX4, UCX ends up being used on the OPA partition too, and the performance is poor (3GB/s instead of 10). The problem seems to be that UCX gets enabled because they added support for OPA in UCX 1.6 even that's just poor OPA support through Verbs.
The only solution we found is to bump the mtl_psm2_priority to 52 so that PSM2 gets used before PML UCX. Seems to work fine but I am not sure it's a good idea. Could OMPI rather tell UCX to disable itself when it only finds OPA? Thanks Brice
