emacs_config_prelude/personal/preload/10-startup-time.el

;; Startup time
(defun efs/display-startup-time ()
  (message
   "Emacs loaded in %s with %d garbage collections."
   (format
    "%.2f seconds"
    (float-time
     (time-subtract after-init-time before-init-time)))
   gcs-done))

(add-hook 'emacs-startup-hook #'efs/display-startup-time)