Devel::SmallProf claims "return 1" needs much time !?

I'm trying to do some profiling on DBM::Deep. I started with Devel::DProf and Devel::Profile but for some subs I had no idea *why* they took long, so I tried Devel::SmallProf for additional detail. Much of what I see makes sense but results like this puzzle me (these are the subs that do the low-level disc read and write):