Progressively slower reloading time of .vimrc

Question

My boot time for vim is about a half second (tested with \"--startuptime\"), but after I reload vimrc a couple times via source, it gets slower subsequently. I have

Answer 1

The culprit here is your use of autocmd. When you define an auto-command with

autocmd  

vim defines a new auto command regardless of existing ones. So when you have several such auto commands in your .vimrc and repeatedly source it (in this case, for every write), you end up defining hundreds and thousands of auto commands which all do the same thing repeatedly. Very soon this will blow up and slow your vim session, which is what you've been noticing.

What you need to do instead, is to group your auto commands and then clear the definitions for that group with autocmd!. As a simple example:

augroup Group1  
    autocmd!
    autocmd  
    autocmd  
    ...    
augroup END

You can have as many groups as you like, which allows you to organize them by similar actions/events.