James Cherti has another excellent post, this time on optimizing Emacs startup with use-package. The idea is that many configurations load a substantial number of packages and that this can cause a significant increase in startup time.
Most of you know by now that we here at the Irreal bunker refuse to worry about that because, after all, we hardly ever restart Emacs. Still, plenty of people do worry about it and there’s nothing wrong with learning a few easy to implement principles that will speedup Emacs startup without having to obsess about tiny details.
The TL;DR is to get use-package to defer loading of packages until they are actually needed. Most Emacers who aren’t complete n00bs already know this. The question is, how exactly, to specify the use-package commands to achieve that.
The obvious answers aren’t the right ones. For example, the :defer keyword seems like the natural answer but Cherti explains why this isn’t usually necessary and that it doesn’t do what you probably think it does. It’s much better to use one of the commands that implicitly defer loading but also arrange for autoloading the required functions when they’re needed.
Cherti also explains how to get use-package to add logging information to the *Messages* buffer to help with understanding the load process. There’s a lot of information in Cherti’s post and it serves as a handy reference for how to use use-package to control the loading of packages at startup time. If you’re at all worried about startup time or just want to understand how to use use-package to control package loading, take a look at his post.