Quoting from http://fedoraproject.org/wiki/Features/MemoryDebuggingTools
"The new "gdb-heap" package adds a new "heap" command to /usr/bin/gdb.
The command allows you to get a breakdown of how that process is using
It allows for unplanned memory usage debugging: if a process
unexpectedly starts using large amounts of memory you can attach to it
with gdb, and use the heap command to figure out where the memory is
going. You should also be able to use it on core dumps.
We believe this approach is entirely new, and is unique to Fedora 14. "