How to profile garbage collection in Ruby

I am trying to profile GC in an application without Rails, preferably using YARV Ruby.

perftools.rb tells me that most of my CPU time is spent on garbage_collector (6061 (61.4%)).

I can also get how many objects are created using methods with perftools.rb. Some methods create more objects than others, but are not very distorted.

Where do I go next? Can I get more detailed information about why he spends so much time on the GC? Is it possible to find out if time has been spent getting rid of objects or is a check being carried out on whether to collect garbage or not?

I have access to OS X Lion, Windows 7, and Ubuntu 12.04.