(setq remote-host "/sshx:jim@localhost:")

(defun fill-directory-abbrev-alist (count)
  (setq directory-abbrev-alist
        (let (result)
          (dotimes (i count result)
            (setq result (cons (cons (format "\\`/home/abbr%d" (1+ i))
                                     (format "/home/abbr%d" i))
                               result))))))

(defun run-test (count &optional path)
  (let* ((abbreviate-home-dir nil)
         (path (or path "/home/user/src/project"))
         (remote-path (concat remote-host path)))
    (benchmark 1000 `(abbreviate-file-name ,path))
    (benchmark 1000 `(abbreviate-file-name ,remote-path))))

(find-file (concat remote-host "~"))

(message "Empty `directory-abbrev-alist'")
(run-test 1000)
(message "")

(fill-directory-abbrev-alist 100)
(message "100 items in `directory-abbrev-alist' (no matches)")
(run-test 1000)
(message "")

(message "100 items in `directory-abbrev-alist' (all matches)")
(run-test 1000 "/home/abbr100/src/project")
(message "")

(fill-directory-abbrev-alist 500)
(message "500 items in `directory-abbrev-alist' (no matches)")
(run-test 1000)
(message "")

(message "500 items in `directory-abbrev-alist' (all matches)")
(run-test 1000 "/home/abbr100/src/project")