Hello all.
Had a thought for improving ruby's GC the other day.

Currently it's

*stop world*
mark
sweep
*start world*

suggestion:

*stop world*
mark
sweep a little bit
*start world*
finish sweep in another thread.

(Obviously there's be some ramifications, like having to add some
locks here or there, and doing some thread joins, but hopefully that
wouldn't cost too much cpu-wise).
Thoughts?
-roger-