Vim slow with ruby syntax highlighting

The solution to this problem turned out to be the regex engine that vim uses. The speculation on #vim on freenode is that the ruby syntax files use something that is slower on the new regex engine.

Any version older than and including Vim 7.3.969 has the old regex engine. Add in set re=1 to your vimrc to force the old regex engine on any version newer (and don't forget to reload the file you're currently editing with :e).

Thanks to Houl, Dolio and dmedvinsky from #vim for help figuring it out.

I haven't had a chance to try the absolute latest version, there was a commit last night that may help with this issue. I will update this if I get the chance to try the bleeding edge version again.

You should set this tw options in your vimrc:

set ttyfast
set lazyredraw

If this is not solving your problem try to start vim without your vimrc to be sure that none of your current settings are screwing it up.

vim -u NONE