Painless Transition to Portable Dumper

I want my configuration to still work without a dump file. This is what I do:

;; in init.el
(defvar luna-dumped nil
  "non-nil when a dump file is loaded.
(Because dump.el sets this variable).")

(defmacro luna-if-dump (then &rest else)
  "Evaluate IF if running with a dump file, else evaluate ELSE."
  (declare (indent 1))
  `(if luna-dumped
       ,then
     ,@else))

;; in dump.el
(setq luna-dumped t)

I use the luna-if-dump in init.el at where two startup process differs:

(luna-if-dump
    (progn
      (setq load-path luna-dumped-load-path)
      (global-font-lock-mode)
      (transient-mark-mode)
      (add-hook 'after-init-hook
                (lambda ()
                  (save-excursion
                    (switch-to-buffer "*scratch*")
                    (lisp-interaction-mode)))))
  ;; add load-path’s and load autoload files
  (package-initialize))

In a dump-file startup, we don’t need to (package-initialize) because it’s done during dumping, but we need to load load-path and fix other gotcha’s.

Blindly dumping every package is a recipe for weird errors. I only dump those I want immediately on startup (company, ivy/helm) and those are big (org). Not that dumping everything won’t work, but it takes more energy to get everything right.

When profiling my startup with esup, I found Emacs spends 70% of the time loading the theme.

Total User Startup Time: 1.063sec
Total Number of GC Pauses: 21
Total GC Time: 0.646sec

doom-one-light-theme.el:5  0.755sec   71%
(def-doom-theme doom-one-light
"A light theme inspired by Atom One"
...

Dumping themes is not as simple as adding (load-theme theme) to dump.el, if you do that, Emacs complains and doesn’t load the theme. I guess that’s because it’s in batch mode. Instead, require your themes like other libraries and loads them without enabling them.

;; in dump.el
(require 'doom-themes)
(require 'doom-one-light-theme)
;; the two flags are no-confirm and no-enable
(load-theme 'doom-one-light-theme t t)

In init.el, we enable the theme, instead of loading it. Unlike require, load-theme doesn’t check if the theme is already loaded. So we need to use enable-theme.

;; in init.el
(when window-system
  (luna-if-dump
      (enable-theme 'doom-one-light)
    (load-theme 'doom-one-light)))

The speed up is significant:

...
init.el:87  0.034sec   7%
(when window-system
(luna-if-dump
(enable-theme 'doom-one-light)
(luna-load-theme nil t)))
...

With everything I just talked about:
dump.el:

(require 'package)
;; load autoload files and populate load-path’s
(package-initialize)
;; store load-path
(setq luna-dumped-load-path load-path
      luna-dumped t)
;; (package-initialize) doens’t require each package, we need to load
;; those we want manually
(dolist (package '(use-package company ivy counsel org helpful
                    general helpful use-package general which-key
                    recentf-ext swiper ivy-prescient find-char
                    aggressive-indent windman doom-themes winner
                    elec-pair doom-one-light-theme
                    doom-cyberpunk-theme rainbow-delimiters
                    highlight-parentheses hl-todo buffer-move
                    savehist eyebrowse minions ws-butler
                    expand-region isolate outshine flyspell magit
                    eglot))
  (require package))
;; pre-load themes
(load-theme 'doom-one-light-theme t t)
(load-theme 'doom-cyberpunk-theme t t)
;; dump image
(dump-emacs-portable "~/.emacs.d/emacs.pdmp")

init.el:

(luna-if-dump
    (progn
      (setq load-path luna-dumped-load-path)
      (global-font-lock-mode)
      (transient-mark-mode)
      (add-hook 'after-init-hook
                (lambda ()
                  (save-excursion
                    (switch-to-buffer "*scratch*")
                    (lisp-interaction-mode)))))
  ;; add load-path’s and load autoload files
  (package-initialize))
;; load theme
(when window-system
  (luna-if-dump
      (enable-theme 'doom-one-light)
    (luna-load-theme)))

After everything works, I wrapped dump file’s path with variables and added defvar for variables I introduced, etc.

(Update <2020-03-08 Sun>) I forgot to mention how I dump Emacs from within Emacs:

(defun luna-dump ()
  "Dump Emacs."
  (interactive)
  (let ((buf "*dump process*"))
    (make-process
     :name "dump"
     :buffer buf
     :command (list "emacs" "--batch" "-q"
                    "-l" (expand-file-name "dump.el"
                                           user-emacs-directory)))
    (display-buffer buf)))

When dumping recentf-ext, I found some problems and changed two places in recentf-ext.el. It has a (recentf-mode 1) as a top level form. That means recentf-mode enables whenever recentf-ext.el loads. Not good. I removed it. It also has a line requiring for cl even though it didn’t use it, I removed that as well. My fork is at here.

(Update <2021-02-13 Sat>: I now recommend benchmark-init over esup.)

esup is a great way to see what package is taking most time in startup. It helps me find what packages to dump. However, esup doesn’t support loading dump files, and we need to modify it a bit. We also want to know if we are in esup child process, so we don’t start an Emacs server (and do other things differently, depends on your configuration). Go to esup in esup.el (by find-library), and change the process-args:

("*esup-child*"
 "*esup-child*"
 ,esup-emacs-path
 ,@args
 "-q"
 "-L" ,esup-load-path
 "-l" "esup-child"
 ;; +++++++++++++++++++++++++++++++++++++++++
 "--dump-file=/Users/yuan/.emacs.d/emacs.pdmp"
 "--eval (setq luna-in-esup t)"
 ;; +++++++++++++++++++++++++++++++++++++++++
 ,(format "--eval=(esup-child-run \"%s\" \"%s\" %d)"
          init-file
          esup-server-port
          esup-depth))

This post talks about early-init.el speedup. Here is my early-init.el.

Normally Emacs starts with a small frame, and if you have (toggle-frame-maximized), it later expands to the full size. You can eliminate this annoying flicker and make Emacs show up with full frame size. I learned it from this emacs-china post. Basically you use -g (for geometry) and --font flags together to size the startup frame. I use

            ~/bin/emacs -g 151x50 -font "SF Mono-13"

At the point (<2020-01-18 Sat>) you can’t use --dump-file with -g and -font because of a bug, but it should be fixed soon. Track it here.

Manateelazycat sets default background to theme background in custom.el. This way Emacs starts with your theme’s background color, instead of white.