The number 3 is very significant in the Ruby 3 release. Be it release version number, making performance 3x faster, or the trio of core contributors(Matz, TenderLove, Koichi). Ruby 3 comes with an enhanced garbage collector. It has python's buffer-like API which helps in better memory utilization. 

The latest change in garbage collection is Garbage Compaction.  It was introduced in Ruby 2.7 where the process was a bit manual. But in version 3 it is fully automatic. The compactor is invoked aptly to make sure proper memory utilization. The garbage compactor moves objects in the heap. It groups dispersed objects together at a single place in the memory so that this memory can be used even by heavier objects later.