Probably if the function execution time is too small, the overhead isn't worth it? And if it's too large, there's too little granularity? I guess it's the same

Probably if the function execution time is too small, the overhead isn't worth it? And if it's too large, there's too little granularity? I guess it's the same ideas that guide "ordinary" programming styles, only adjusted to the timings of large networks (milliseconds instead of microseconds).