How to speed up your vim startup time

My go-to editor for pretty much anything is vim. And like any serious vim user I use numerous plugins to extend and improve the editing experience. Natually there’s a cost to that, namely an increase in vim startup time. Compared to almost any GUI application vim starts up almost instantaneously. Still I noticed that slight delay and it had been bothering me for a while until I finally got round to investigate and tweak.

Thankfully vim makes profiling the startup time really convenient by providing a --startuptime flag to write timings for loading your .vimrc and plugins to a file, which looks something like this:

times in msec
 clock   self+sourced   self:  sourced script
 clock   elapsed:              other lines

000.007  000.007: --- VIM STARTING ---
002.399  002.392: Allocated generic buffers
002.468  000.069: locale set
004.946  002.478: GUI prepared
004.954  000.008: clipboard setup
004.967  000.013: window checked
016.181  011.214: inits 1
016.187  000.006: parsing arguments
016.188  000.001: expanding arguments
016.212  000.024: shell init
017.230  001.018: Termcap init
018.203  000.973: inits 2
018.390  000.187: init highlight
022.090  002.745  002.745: sourcing /usr/share/vim/vim74/debian.vim
026.679  000.296  000.296: sourcing /usr/share/vim/vim74/syntax/syncolor.vim
026.805  001.004  000.708: sourcing /usr/share/vim/vim74/syntax/synload.vim
...

The interesting measurements are those concerned with sourcing files, so focus your attention on the 3rd column to see where time is spent. Short of trimming down your vimrc (mine takes about 18ms to load by itself) and cutting down on the number of plugins, the plugin manager can also make a difference. I used pathogen for a long time, before switching to Vundle (because it’s easier to have your plugin manager handle Git repositories rather than having to manually add them as submodules to your dotfile repository or similar). Then I came across vim-plug and was intrigued by its on-demand loading feature. That allows loading plugins for specific file types or only on the first invocation of a certain command. The latter is particularly useful for plugins you don’t need to have active all the time. In my case this was particularly useful for NERDtree and DokuVimKi, which both take a significant time to load. Looking carefully at the startup time output I also noticed I was sourcing filetype plugins twice! The offending line in my vimrc was quickly found, which shaved off some additional milliseconds.

TL;DR Switching to vim-plug, getting rid of some unnecessary plugins, loading others only on demand and uncluttering my vimrc I managed to cut down my vim startup by more than half, from close to 250ms to only about 120ms.