We were seeing 500+ MB of increased virtual memory usage compared to older versions of ManageIQ per process.
Using ManageIQ and require logging, we can measure how long and how much memory EACH require takes:
REQUIRE_LOG=true bin/rails r ""
This writes a log file in vmdb/log/require_DATEXYZ.log.
Note, require_with_logging is required in the preinitializer.rb