Easy way to monitor gc activity?

[Tofu Ninja via Digitalmars-d-learn]

Basicly what the title said.

What is an easy way to monitor gc activity?
I am finding it hard to know when and where the gc is running and 
how much.

Preferably I would like a way to do it in app so I can make 
adjustments based on gc load.

Also I would prefer to not have to recompile the runtime if I can 
avoid it.

-Tofu