Vimrc file takes longer and longer to reload [duplicate]

Answer 1

Maybe you encountered a phenomenon that it outlined in

:h autocommand

The help sais:

When your .vimrc file is sourced twice, the autocommands will appear twice. To avoid this, put this command in your .vimrc file, before defining autocommands:

:autocmd!   " Remove ALL autocommands for the current group.

If you don't want to remove all autocommands, you can instead use a variable to ensure that Vim includes the autocommands only once:

:if !exists("autocommands_loaded")
:  let autocommands_loaded = 1
:  au ...
:endif

I get used to grouping of my autocommands like this

augroup BWCCreateDir
    autocmd!
    autocmd BufWritePre * :call s:MkNonExDir(expand('<afile>'), +expand('<abuf>'))
augroup END

Answer 2

Every time the autocmd is sourced it is added to the autocmd list. So you might be sourcing your vimrc thousands of times when you save because everytime you source you add the autocmd to the list. (You can see that the autocmd is added multiple time by doing :au bufwritepost)

To fix this you just need to wrap the autocmd in a augroup and clear the group when it is loaded.

augroup NAME_OF_GROUP
  autocmd!
  autocmd bufwritepost .vimrc source $MYVIMRC
augroup end

The autocmd! removes all autocmds from the group.

Help pages to read :h autocmd-define and :h autocmd-groups