(defun foo ()
  (interactive)
  (while (not (eobp))
    (c-end-of-defun)))


(defun bar ()
  (interactive)
  (while (not (bobp))
    (c-beginning-of-defun)))

(defun bench ()
  (find-file "xdisp.c")
  (goto-char (point-min))
  (let* ((t1 (current-time))
         (t2 (progn
               (foo)
               (current-time)))
         (t3 (progn
               (bar)
               (current-time))))
    (cons (float-time (time-subtract t2 t1))
          (float-time (time-subtract t3 t2)))))