How do I profile my emacs configuration?

Question

My emacs configuration takes a very long time to load. How can I easily find the offending parts and optimize them?

How long is "very long" ? I never imagined emacs being something that would take long to load. — Mike Bailey, Apr 23 '11 at 04:19
Be sure to look at http://stackoverflow.com/questions/778716/how-can-i-make-emacs-start-up-faster to see how to fix the problem. — Trey Jackson, Apr 24 '11 at 04:38
@Trey, thanks. I already do everything there but autoloads, which seem tedious. — Phob, May 23 '11 at 04:09

score 31 · Accepted Answer · answered Apr 23 '11 at 05:53

31

Very useful package: http://www.emacswiki.org/emacs/ProfileDotEmacs

Just skip loading your init file and let ProfileDotEmacs load/profile it for you:

emacs -Q -l profile-dotemacs.el -f profile-dotemacs

answered Apr 23 '11 at 05:53

Jürgen Hötzel

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The wiki is a source of infinite wisdom for all things Emacs. – Noufal Ibrahim Apr 23 '11 at 05:56
This is awesome!! Exactly what I was looking for. – Phob Apr 24 '11 at 03:02
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@Phob: I encourage you to click on the tick mark next to this answer, just below the up/down vote buttons. :-) – Chris Jester-Young Apr 24 '11 at 04:27
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Fails with 'Wrong type argument: number-or-marker-p, nil' for me. – Sam Brightman Oct 28 '12 at 12:05
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@Micha90 if it shows 0 seconds, it may mean that you need to define the correct .el file to run the profiler on. By default it is `~/.emacs`, but in my case I needed to change it to `~/.emacs.d/init.el`. In the file `profile-dotemacs.el` change the value of the variable named `profile-dotemacs-file`. – rottweiler Jul 11 '16 at 20:12

score 7 · Answer 2 · answered Mar 04 '16 at 16:11

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Another solution is ESUP, the Emacs Start Up Profiler. It can profile your config file without leaving Emacs - it accomplishes this by starting a new Emacs as a child process, getting profile information from it.

answered Mar 04 '16 at 16:11

legoscia

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I installed esup, did M-x esup... and that's it. IDK how it was in 2016, but in 2020 `esup`was really simple to use to me. – YoungFrog Jul 28 '20 at 07:25

score 2 · Answer 3 · answered Apr 23 '11 at 04:19

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By using divide and conquer, of course!

Drop the bottom half of your .emacs. See if the speed improves. (If so, the culprit is within the bottom half; otherwise it's in the top half.) Restore the working half. Chop off half of the broken half, and repeat the process until you have isolated the problem.

answered Apr 23 '11 at 04:19

Chris Jester-Young

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This takes O(startup_time * log(config_size)). Startup time = 30 seconds, config_size = 20,000 lines. This works for most people, but is really inconvenient for me. – Phob Apr 24 '11 at 03:03
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@Phob: Yeah, 20k lines is seriously more over-the-top than I thought ever possible. ;-) – Chris Jester-Young Apr 24 '11 at 03:07
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@Phob, no offense, but 20,000 lines means you're doing it wrong. – Trey Jackson Apr 24 '11 at 04:40
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My config is DRY. I am just doing it _more_ . – Phob Aug 11 '11 at 00:19
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That's fine if there's one thing that is causing a big slowdown. But it won't work if there are many things culminating in an overall slowdown. – asmeurer May 13 '13 at 00:02

How do I profile my emacs configuration?

3 Answers3