[racket] question: how to profile allocation?

I'm a little stuck with a problem in one of my programs: some place is
generating so much garbage that I'm triggering a garbage collection
once every few seconds, and that's bad because the program is meant to
be used interactively.

I'm having some difficulty pinpointing what I should be looking at.  I
looked at the Racket profiler, but it appears to concentrate on CPU
usage and not allocation.  Are there tools in Racket that can help me
pinpoint allocation hotspots?