(defun find-directory-files-recursively (dir regexp &optional include-directories _p follow-symlinks)
  (cl-assert (null _p) t "find-directory-files-recursively can't accept arbitrary predicates")
  (with-temp-buffer
    (setq case-fold-search nil)
    (cd dir)
    (let* ((command
	    (append
	     (list "find" (file-local-name dir))
	     (if follow-symlinks
		 '("-L")
	       '("!" "(" "-type" "l" "-xtype" "d" ")"))
	     (unless (string-empty-p regexp)
	       (list "-regex" (concat ".*" regexp ".*")))
	     (unless include-directories
	       '("!" "-type" "d"))
	     '("-print0")
	     ))
	   (remote (file-remote-p dir))
	   (proc
	    (if remote
		(let ((proc (apply #'start-file-process
				   "find" (current-buffer) command)))
		  (set-process-sentinel proc (lambda (_proc _state)))
		  (set-process-query-on-exit-flag proc nil)
		  proc)
	      (make-process :name "find" :buffer (current-buffer)
			    :connection-type 'pipe
			    :noquery t
			    :sentinel (lambda (_proc _state))
			    :command command))))
      (while (accept-process-output proc))
      (let ((start (goto-char (point-min))) ret)
	(while (search-forward "\0" nil t)
	  (push (concat remote (buffer-substring-no-properties start (1- (point)))) ret)
	  (setq start (point)))
	ret))))

(defun find-directory-files-recursively-2 (dir regexp &optional include-directories _p follow-symlinks)
  (cl-assert (null _p) t "find-directory-files-recursively can't accept arbitrary predicates")
  (cl-assert (not (file-remote-p dir)))
  (let* (buffered
         result
         (proc
	  (make-process
           :name "find" :buffer nil
	   :connection-type 'pipe
	   :noquery t
	   :sentinel (lambda (_proc _state))
           :filter (lambda (proc data)
                     (let ((start 0))
                       (when-let (end (string-search "\0" data start))
                         (push (concat buffered (substring data start end)) result)
                         (setq buffered "")
                         (setq start (1+ end))
                         (while-let ((end (string-search "\0" data start)))
                           (push (substring data start end) result)
                           (setq start (1+ end))))
                       (setq buffered (concat buffered (substring data start)))))
	   :command (append
	             (list "find" (file-local-name dir))
	             (if follow-symlinks
		         '("-L")
	               '("!" "(" "-type" "l" "-xtype" "d" ")"))
	             (unless (string-empty-p regexp)
	               (list "-regex" (concat ".*" regexp ".*")))
	             (unless include-directories
	               '("!" "-type" "d"))
	             '("-print0")
	             ))))
    (while (accept-process-output proc))
    result))

(defun find-directory-files-recursively-3 (dir regexp &optional include-directories _p follow-symlinks)
  (cl-assert (null _p) t "find-directory-files-recursively can't accept arbitrary predicates")
  (cl-assert (not (file-remote-p dir)))
  (let ((args `(,(file-local-name dir)
	        ,@(if follow-symlinks
		      '("-L")
	            '("!" "(" "-type" "l" "-xtype" "d" ")"))
	        ,@(unless (string-empty-p regexp)
	            (list "-regex" (concat ".*" regexp ".*")))
	        ,@(unless include-directories
	            '("!" "-type" "d"))
	        "-print0")))
    (with-temp-buffer
      (let ((status (apply #'process-file
                           "find"
                           nil
                           t
                           nil
                           args))
            (pt (point-min))
            res)
        (unless (zerop status)
          (error "Listing failed"))
        (goto-char (point-min))
        (while (search-forward "\0" nil t)
          (push (buffer-substring-no-properties pt (1- (point)))
                res)
          (setq pt (point)))
        res))))

(defun my-bench (count path regexp)
  (setq path (expand-file-name path))
  ;; (let ((old (directory-files-recursively path regexp))
  ;;       (new (find-directory-files-recursively-3 path regexp)))
  ;;   (dolist (path old)
  ;;     (unless (member path new) (error "! %s not in" path)))
  ;;   (dolist (path new)
  ;;     (unless (member path old) (error "!! %s not in" path))))
  (list
   (cons "built-in" (benchmark count (list 'directory-files-recursively path regexp)))
   (cons "with-find" (benchmark count (list 'find-directory-files-recursively path regexp)))
   (cons "with-find-p" (benchmark count (list 'find-directory-files-recursively-2 path regexp)))
   (cons "with-find-sync" (benchmark count (list 'find-directory-files-recursively-3 path regexp)))))