Emacs 27.1 has a 'sort' function that takes longer than stable-sort of
SBCL. Maybe
by a factor of 2. See also my attached file 'ms.lisp'.

There may be a lot that can be improved in Emacs'
handling of cl-loop, setf, elt, or cl-random.

;; First some Emacs, with times on my $100 Chromebook.

(setq n 6)
(defun make-random-array (n)
  (let ((a (make-vector n 0)))
    (cl-loop for i below n do
             (setf (elt a i) (cl-random 1000000)))
    a))
(byte-compile 'make-random-array)
(benchmark '(setq foo (make-random-array (expt 10 n))) 1) -- 2.3 seconds
(benchmark '(sort foo '<) 1) -- 1 second

;; Second some Common Lisp, with times for SBCL on my $100 Chromebook.

(defparameter n 6)
(defun make-random-array (n)
  (declare (fixnum n))
  (let ((a (make-array n)))
    (declare (type array a))
    (loop for i fixnum below n do
          (setf (aref a i) (random most-positive-fixnum)))
    a))
(time (defparameter foo (make-random-array (expt 10 n))))  -- .041 seconds
(time (progn (stable-sort foo '<) nil)) -- .45 seconds

Thanks so much for Emacs, which is so great that I cannot put it
into words.

Bob