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

This is my solution that also clears previous mappings:

augroup VimrcGroup
  autocmd!
  " Make changes effective after saving .vimrc. Beware that autocommands are
  " duplicated if .vimrc gets sourced again, unless they are wrapped in an
  " augroup and the autocommands are cleared first using 'autocmd!'
  autocmd bufwritepost $MYVIMRC call OnSavingVimrc()
augroup END

" Avoid infinite loops
if !exists("*OnSavingVimrc")
  function! OnSavingVimrc()
    " Clear previous mappings, they don't go away automatically when sourcing vimrc
    mapclear
    echo "Sourcing Vimrc after saving it"
    source $MYVIMRC
  endfunction
endif