I recently stumbled upon the (so far) best FOSS runtime code profiling tool I ever tried:
KCacheGrindIt is really a front-end for the common *nix debugging tool
valgrind, but the way it visualizes the data makes the valgrind actually allot more usable.
You can navigate through the call graph tree, go into different levels and subtrees, view how much time was spent in each function, detect memory leaks, bugs, etc,...
A nice addition to my debugging arsenal, I thought I would share