Some improvements to existing profiler code that are also in this pull request solve most of the noise you mentioned (Profiler::xyz and ProfilerStub::xyz). I'd prefer wfProfilerIn/Out to stay ti keep an eye on its performance as well (looking at it when I developed support for xhprof helped me realized how much time we waste on these calls and come up with the improvements). Autoloaded::load can be also useful as it measures how much does it cost us to use the current version of autoloading mechanism (included files are reported separately with "load::<filename>" and "run_init::<filename>" entries.

What do you think about not adding ignored_functions here after I gave this explanation?