emacs could open huge file without any problem

[redguardtoo]

The key point is to turn off inefficient linum-mode when file is too big.

Set up Emacs to turn off syntax highlight and linum-mode by adding below code into ~/.emacs:

(defun buffer-too-big-p ()
  (or (> (buffer-size) (* 5000 64))
      (> (line-number-at-pos (point-max)) 5000)))
(defun generic-setup ()
  ;; turn off `linum-mode' when there are more than 5000 lines
  (if (buffer-too-big-p) (linum-mode -1)))
(add-hook 'prog-mode-hook 'generic-setup)
(add-hook 'text-mode-hook 'generic-setup)

My complete Emacs setup is at https://github.com/redguardtoo/emacs.d

Linux cli to create huge 3g.txt:
base64 /dev/urandom | head -c 3000000000 > 3g.txt

Then run emacs -nw 3g.txt, here is the screenshot. I can edit this file without any problem.