I added the following two lines to the top of my init.el :

(setq gc-cons-threshold (eval-when-compile (* 1024 1024 1024))) (run-with-idle-timer 2 t (lambda () (garbage-collect)))

That means that instead of collecting garbage every 800kb of allocated memory, Emacs does so when idle, i.e. when the pausing does not bother me. (It also collects after allocating 1GB of memory, but I don't think that will happen).

This improved my startup time by about two thirds. In theory, it should also improve performance in general. Are there any downsides to this approach?