See https://github.com/jenkinsci/role-strategy-plugin/blob/a2069c1fcb56ff0cd8b80a0655931f5974634eee/src/main/java/com/michelin/cio/hudson/plugins/rolestrategy/RoleMap.java#L353 

Each time the method is invoked, a new intermediate collection is created. Instead of such implementation, it would be preferable to have calling logic to be executed in the RoleWalker directly. RoleMap#hasPermission() method could be refactored in such way so that it has lower memory footprint and performance overheads