#1722: hwloc could warn the user if a process spans more than one NUMA node ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: confirmed Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: development version Resolution: | Keywords: ------------------------------------+---------------------------------------
Comment (by eschnett):
In the same spirit, hwloc should detect if the current MPI process started up with a sub-ideal memory affinity. Other libraries, in particular MPI, may be initialized before hwloc runs, and these would see and use the sub- ideal memory affinity. This is actually causing slow-downs on some systems.
Another remedy for this could be to run hwloc very early, before MPI is initialized. This would require passing in the current MPI rank, which may not be possible before initializing MPI.