It is  parse_erasure_code_profile https://github.com/dachary/ceph/blob/wip-erasure-code-profiles/src/mon/OSDMonitor.cc#L3971 which populates the map https://github.com/dachary/ceph/blob/wip-erasure-code-profiles/src/mon/OSDMonitor.cc#L2966 before setting the user provided values