Complexity bug in garbage collector?

Hi all, I've had some fun chasing around a couple of space leaks lately. One of the graphs that I produced looked like this: www.cs.chalmers.se/~josefs/coresa.ps Notice the shape of the graph. It shows a perfect squareroot function. But my program should be allocating at a constant rate. From previous experience this suggests that there is a time complexity bug in the garbage collector. This makes it take time proportional to the square of the amount of allocated memory. Can someone confirm this? Cheers, /Josef