The Emacs profiler cannot be used to effectively profile, because the reports do not flatten the recursion.

Take for example, this recipie:

;; Naive Fibonacci has terrible time complexity.

(defun fib (n)
(if (< n 3)
      1
    (+ (fib (- n 1))
       (fib (- n 2)))))

(profiler-start 'cpu)
(fib 30)
(profiler-report)
(profiler-stop)

Here, The profiler report assigns (nearly) all of the time to (+ ...), including time from deeper invocations of fib (and their invocations of (+ ...), which makes the profiling report less-than-optimal.

Thanks,

PythonNut