Vim programming editor speed

Question

Problem is: vim gets slow when I add the following lines to my vimrc:

set foldmethod=syntax 
set foldlevelstart=1 
let javaScript_fold=1 " JavaScript 
let perl_fold=1 " Perl 
let php_folding=1 " PHP 
let r_syntax_folding=1 " R 
let ruby_fold=1 " Ruby 
let sh_fold_enabled=1 " sh 
let vimsyn_folding='af' " Vim script 
let xml_syntax_folding=1 " XML 

Context: whilst editing a sh file

I think it's fair enough for it to slow down when:

• opening a new file, recalculating syntax-based folds (e.g. collapse function defs)
• creating a new function definition

... but... for it to do so everywhere?

Do you use/see the same? What could be done to ameliorate the sluggishness, if anything?

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It took me a day to identify this, successfully reproduce it anywhere on my (virtual and non-) machines, eliminating candidate contributors to overall slowness by a process of vimrc binary search.

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My environment

vim VIM - Vi IMproved 7.3 (2010 Aug 15, compiled Mar 12 2013 14:05:25)

osx OS X v10.8.3 (build 12D78)

bash v3.2.48(1)-release

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Answer 1

You can play with some auto commands. Turning on features depending on the type of files, vim can speed up. Example:

autocmd BufRead *.pt set filetype=xml
au FileType xml setlocal foldmethod=syntax