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title = "A Solution to Emacs Garbage Collection Stutters"
date = 2025-05-12
updated = 2025-05-14
+++
The more you load Emacs up with packages, the more it starts to chug. Throw on a theme and an lsp client, and you might start to notice frequent stuttering.
This problem was very frustrating for me - I want to be able to hold `C-n` and linearly move down the document, micro-stutter *free*. I spent weeks searching for the problem, and considered quitting Emacs altogether.
# Garbage Collection
It turns out that the problem wasn't that packages were executing slowly, it was the garbage that they were building up.
Emacs' garbage collector waits until a byte threshold (the `gc-cons-threshold` variable) has been reached before executing. Its default value feels relatively low for a modern computer - only `800KB`. This results in frequent garbage collections, each causing a small stutter. Luckily, as with most things in Emacs, you can tune this behaviour.
> If you want to see how frequently the GC is triggered, try setting `garbage-collection-messages` to non nil (you might be surprised).
Opinions on the ideal solution differ.
- Some people recommend **increasing** the threshold, leading to longer times without triggering the GC but longer stutters.
- Others recommend **lowering** the threshold, causing more frequent GC triggers but smaller stutters.
- The minibuffer (especially with packages like `vertico`) can use a lot of memory, so some [recommend](https://bling.github.io/blog/2016/01/18/why-are-you-changing-gc-cons-threshold/) increasing the threshold only when using it.
# The Solution
In my opinion, the best solution is to garbage collect **when idle**. When editing, you're often pausing briefly - and if there is little garbage, Emacs can collect it very quickly.
I also *basically* disable the threshold entirely when in the minibuffer. Here's the code from my `init.el`.
```lisp
(defun my-minibuffer-setup-hook ()
(setq gc-cons-threshold most-positive-fixnum))
(defun my-minibuffer-exit-hook ()
(setq gc-cons-threshold 800000000))
(setq gc-cons-threshold most-positive-fixnum)
(run-with-idle-timer 1.2 t 'garbage-collect)
```
I have been using this for a few months and it's worked perfectly. I've tried my best to notice the garbage collections, I haven't been able to.
> There is a package for this, called [the Garbage Collector Magic Hack](https://github.com/emacsmirror/gcmh). Personally I prefer a lower idle time than its default, and I like keeping it in my own config.
# Update: IGC Branch
After posting this article, [some users on reddit](https://www.reddit.com/r/emacs/comments/1km1by3/comment/ms750w3/) informed me that there is a [branch of emacs](https://git.savannah.gnu.org/cgit/emacs.git/tree/README-IGC?h=feature/igc#n1) in development which greatly improves the garbage collector efficiency. People are saying that it has completely eliminated their stutters. I recommend trying it out.
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