I have had the same experience. I’ve found that setting the number of threads to be 1 is necessary to avoid spurious results in the profiler.
Should this be reported as an issue in Julia’s standard library, specifically Profile.jl? The Juno issue mentioned by @Pbellive ( https://github.com/JunoLab/Juno.jl/issues/205 ) is now closed, with the comment that in Juno, “we [now] filter profile traces much better.”
Outside of Juno, though, this still appears to be an issue, and it’s not obvious to a newcomer that multiple threads are the culprit.