this post was submitted on 22 Aug 2025
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Emacs

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Even stock/vanilla Emacs is too slow (leminal.space)
submitted 4 months ago by tetrislife@leminal.space to c/emacs@lemmy.ml
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I "live in Emacs", like most of us (atleast at work). It has been getting slower release on release, async support doesn't seem to have been picked up by most packages and native-comp has made it more brittle.

Over this time, we moved from running the OS on hardware to running in VMs, so fractional slowdown was expected. But what I have is a few X slower Emacs. I had never seen Emacs take a minute to indent a few thousand lines, for example. Maybe some modes have slower code.

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[–] donio@lemmy.world 7 points 4 months ago (1 children)

I appreciate your frustration but several times slower is not normal, something is broken in the environment or setup. I've been using Emacs for decades and I would never put up with any kind of slowdown, not to mention several times slower. Yikes.

To make sure that I am not just talking out of my ass I ran elisp-benchmarks between emacs-28 from about 4 years ago and emacs-30. Every benchmark was either faster or unchanged with emacs-30 and overall it was almost twice as fast as emacs-28. Many of these benchmarks are compute heavy but the more interactive ones like elb-scroll and elb-smie were faster too.

[–] tetrislife@leminal.space 2 points 4 months ago (1 children)

I need a fast setup on the same hardware to compare against, but I don't have it. This is the experience on VMs. I don't know what is fast for people. I stated one of my observations that indenting a couple of thousand lines is slow. How fast is that for you, in a VM or on hardware?

[–] donio@lemmy.world 3 points 3 months ago (1 children)

I don't have a VM based setup but on my aging laptop:

  • Indenting a single line in a buffer with ~5K lines of code is instantaneous
  • Indenting the entire 5K line buffer using C-x h C-M-\ varies depending on the language and mode used. For elisp or fennel it's instantaneous, for Go it's about 1.5 second.
  • A slow case I've found was indenting a C or Go buffer where every line needed to be touched, this was about 7 seconds which is admittedly slower than I thought it would be
  • Indenting such a file while in c-ts-mode (so with tree-sitter enabled) is about 1s.
  • Same but using LSP and M-x eglot-format-buffer is instantaneous if a small number of fixes are required or about 1s if every line needs to be touched.
[–] tetrislife@leminal.space 2 points 3 months ago

Thanks gor the numbers. They don't make Emacs look unusable, so we could blame these darn cloud-provisioned VMs!