Ruby Garbage Collection Deep Dive: Compaction

The author of this post was a recent guest on an episode[1] of the Rails with Jason podcast. She discussed the book she's working on, which I believe is based on the series of blog posts of which this one is a member. The episode was a bit of an introduction to garbage collection in Ruby, as opposed to the deep dive into one particular aspect in this article.

https://railswithjason.simplecast.com/episodes/093-garbage-c...

Interesting. Oftentimes compaction is part of generational GC and the tenured objects are literally moved to an older space. So the compaction naturally fits in the big picture. But the article suggests it's still under development, which means that Ruby implements generational GC without compaction? It must have been a difficult endeavour.

It seems like the “two-finger” compaction only works with equal sized values (like rvalues). What about items like strings that can be variable length?