What does "In file [heap]" mean?

[aconway redhat com]

First: great job on sysprof. The only "just walk up and learn
something" profiler I've used on linux. Not as flexible as some but the
near-zero "getting started" time is worth a lot of flex.

Now a question:

I double click on my program of interest. Sorting by cumulative the
first and largest entry is "In file [heap]" followed by functions from
my program. I open "In file [heap]" and find more functions from my
program, many of the same functions mentioned at the top level - but
with different (larger mostly) percentages against them.

What does this mean? Which are the actuall percentages of CPU used by
those functions within my program, or do I have to add them?

Sorry if this is in a FAQ, I couldn't find a FAQ or any form of
documentation. sysprof is remarkably self-explanatory (well done) but
there are some points that are puzzling on first contact. Id be happy
to contribute the beginning of a FAQ if there isn't one already.

Thanks
Alan.