Why is Vim so slow? - vim

Question

I am a beginning vim user and I am a little confused. It looks like Vim is slower than Geany. And it is a very noticeable difference. When I hold any key in Geany it prints it without any lag (llllllll for example). In Vim it is slow and jumping. Autocomplete in vim is horrible in comparison to Geany. I thought Vim is as fast as light. It looks like it isn't. Is there any advice to change that, make vim faster?
This is my _vimrc file:
" This must be first, because it changes other options as side effect
set nocompatible
" Use pathogen to easily modify the runtime path to include all
" plugins under the ~/.vim/bundle directory
call pathogen#helptags()
call pathogen#infect()
" change the mapleader from \ to ,
let mapleader=","
" Quickly edit/reload the vimrc file
nmap <silent> <leader>ev :e $MYVIMRC<CR>
nmap <silent> <leader>sv :so $MYVIMRC<CR>
set hidden
set nowrap " don't wrap lines
set tabstop=4 " a tab is four spaces
set backspace=indent,eol,start
" allow backspacing over everything in insert mode
set autoindent " always set autoindenting on
set copyindent " copy the previous indentation on autoindenting
set number " always show line numbers
set shiftwidth=4 " number of spaces to use for autoindenting
set shiftround " use multiple of shiftwidth when indenting with '<' and '>'
set showmatch " set show matching parenthesis
set ignorecase " ignore case when searching
set smartcase " ignore case if search pattern is all lowercase,
" case-sensitive otherwise
set smarttab " insert tabs on the start of a line according to
" shiftwidth, not tabstop
set hlsearch " highlight search terms
set incsearch " show search matches as you type
set history=1000 " remember more commands and search history
set undolevels=1000 " use many muchos levels of undo
set wildignore=*.swp,*.bak,*.pyc,*.class
set title " change the terminal's title
set visualbell " don't beep
set noerrorbells " don't beep
set nobackup
set noswapfile
filetype plugin indent on
autocmd filetype python set expandtab
if &t_Co >= 256 || has("gui_running")
colorscheme badwolf
endif
if &t_Co > 2 || has("gui_running")
" switch syntax highlighting on, when the terminal has colors
syntax on
endif
" Vim can highlight whitespaces for you in a convenient way:
set list
set listchars=tab:>.,trail:.,extends:#,nbsp:.
set pastetoggle=<F2>
set mouse=a " Enable mouse
set encoding=utf-8
set langmenu=en_US
let $LANG = 'en_US'
source $VIMRUNTIME/delmenu.vim
source $VIMRUNTIME/menu.vim
set autochdir " working directory is always the same as the file you are editing
noremap <F5> :w !python %<CR>
inoremap <F5> <ESC>:w !python %<CR>
nmap <leader>t :NERDTree<CR>
autocmd bufenter * if (winnr("$") == 1 && exists("b:NERDTreeType") && b:NERDTreeType == "primary") | q | endif
set guifont=Hack:h10:cDEFAULT
let g:Powerline_symbols = 'fancy'
set laststatus=2
python from powerline.vim import setup as powerline_setup
python powerline_setup()
python del powerline_setup
filetype plugin on
set omnifunc=syntaxcomplete#Complete
au CompleteDone * pclose
set completeopt=longest,menuone,preview
set guioptions-=T
set nofoldenable " disable folding
nmap <silent> ,/ :nohlsearch<CR>

Answer 1

It could be a lot of things, not necessarily Vim's fault. Actually it's unlikely to be vim's fault.
First, get a feel for how fast Vim can be: run with vim -u NONE and comment out everything in your .vimrc - then do the single thing that seems slow.
Run without the -u NONE and compare. It should be just as fast, or some plugin is autoloaded and is causing problems. If so, try and temporarily move files away from the ~/.vim/bundle directory.
Next, uncomment half of your .vimrc and check if it causes the slowness or not. Keep commenting/uncommenting until you find the exact line.
Google the line that caused the slowness and find out if there are alternatives.
I'm guessing you could be doing an expensive operation with every scroll, such as checking the file syntax.
It's best to hunt down the slowness step by step.
Another issue may be slow terminal and/or drivers (so compare Vim with GVim). If you have a slow terminal with fancy fonts, transparency, small font and big screen size, terminals can be very, very, VERY slow.

Answer 2

If you use vim in terminal like me (and not GVim), I just found that, try, and it seems pretty good :
add this in your ~/.vimrc :
set timeoutlen=1000
set ttimeoutlen=0
and this (even more important) in your ~/.screenrc :
maptimeout 0
Since I did that, everything is better.

Answer 3

My vim started to fly after I added the following config to my vimrc, this is extremely useful when you keep vim running all day/week long editing a lot of different files with opening and closing them often.
function! CloseHiddenBuffers()
" >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
" close any buffers hidden
" <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
let open_buffers = []
for i in range(tabpagenr('$'))
call extend(open_buffers, tabpagebuflist(i + 1))
endfor
for num in range(1, bufnr("$") + 1)
if buflisted(num) && index(open_buffers, num) == -1
exec "bdelete ".num
endif
endfor
endfunction
au BufEnter * call CloseHiddenBuffers()

Answer 4

I had a similar problem where pasting paragraphs of text or just typing at a typical speed would hang vim.
You could troubleshoot your .vimrc, and if you are, take a look at this question to see which plugins are slow. You could also skip the troubleshooting and use neovim, which is fully compatible with vim and asynchronous.
My issues with input lag disappeared once I started using it. It uses an async library libuv, which is the same library powering node. I'm using the same .vimrc as with vim (copied to ~/.config/nvim/init.vim), so it's not a matter of different plugins. I also see this responsiveness improvement on both Ubuntu 20.04 and Macos 10.14.
I'm posting this answer because I wish it had existed when I last read this question.