MRI has implemented a new Hash that has some innovative features:

• Open addressing for better cache locality
• Automatically switching over to a secure hash when a "hash DOS" attack is detected.

We currently have the original "chained buckets" implementation of Hash with no generalized hash randomization except for strings. This is open work to be done for JRuby.

See https://bugs.ruby-lang.org/issues/12142
See https://bugs.ruby-lang.org/issues/13002

Part of TBD work for 2.4 support in #4293.