RTFM ;) If you enter '?' at the prompt (or menu-choice) about
kernel-hacking support, it explains all it does for now is
allow you to get profiles on where exactly the kernel is
spending it's time into the /proc - filesystem. Further it's
noted that to read that information you need a tool called
readprofile, which is available from ftp://sunsite.unc.edu/pub/Linux/kernel/readprofile-2.0.tar.gz (What a surprise;).
Using the mirror-site closest to you is preferable.
It's actually pretty useful for profiling the kernel for optimization purposes, however worth remembering is that since the kernel-source is heavily optimized, there's no direct connection between the results and the actual code in the way one could expect (Ie. a lot of functions get inlined etc; if the entry you're looking for doesn't show even on readprofile -a, it's probably made part of the calling function(s)).