gc overhead

I would like to determine what percentage of my application's cpu time  
is spent in the garbage collector (for tuning purposes, but also just  
to monitor the overhead). Is there any way to obtain this information  
short of using gprof? Additional information provided by Gc.stat would  
be ideal, or perhaps a Gc.alarm that was called at the beginning of  
the gc cycle, but neither of these seem to exist.

Warren