Disable specific Ruby regex pattern matching in Vim for performance

Question

I am using vanilla Vim and syntime reports the following costly patterns:

 TOTAL      COUNT  MATCH   SLOWEST     AVERAGE   NAME               PATTERN
  3.526224   3751   1542    0.036641    0.000940  rubySymbol         []})\"':]\@<!\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*[!?]\=:\s\@=
  1.278366   3465   1254    0.012201    0.000369  rubySymbol         \%([{(,]\_s*\)\@<=\l\w*[!?]\=::\@!
  0.730820   2211   0       0.008430    0.000331  rubyPredefinedConstant \%(\%(\.\@<!\.\)\@<!\|::\)\_s*\zs\%(STDERR\|STDIN\|STDOUT\|TOPLEVEL_BINDING\|TRUE\)\>\%(\s*(\)\@!
  0.626906   2211   0       0.006168    0.000284  rubyPredefinedConstant \%(\%(\.\@<!\.\)\@<!\|::\)\_s*\zs\%(MatchingData\|ARGF\|ARGV\|ENV\)\>\%(\s*(\)\@!
  0.515706   2211   0       0.004109    0.000233  rubyPredefinedConstant \%(\%(\.\@<!\.\)\@<!\|::\)\_s*\zs\%(DATA\|FALSE\|NIL\)\>\%(\s*(\)\@!
  0.337235   2211   0       0.007179    0.000153  rubyPredefinedConstant \%(\%(\.\@<!\.\)\@<!\|::\)\_s*\zs\%(RUBY_\%(VERSION\|RELEASE_DATE\|PLATFORM\|PATCHLEVEL\|REVISION\|DESCRIPTION\|COPYRIGHT\|E
NGI

Where do I go to disable one or more of these from being searched? I do not want to install any plugins if possible.

Update: for more clarification, where the above syntime figures aren't specific, I encountered this in a ~1200 line .rb file. Whether or not this file is too long as an aside, such a task as inserting a new blank line in vim was painfully slow (several seconds before a visual response). Comparing this to Rubymine with the same file and not noticing any lag, I hoped there was a solution to improve this performance under vim. Disabling syntax highlighting altogether makes everything extremely snappy, but much harder to read.

Answer 1

Put the following into a file ~/.vim/after/syntax/ruby.vim:

syntax clear rubySymbol

The after directory will ensure that this is called after the original $VIMRUNTIME/syntax/ruby.vim has been sourced, and the command removes the slow syntax definition.

Note that this may interfere with the operation of the syntax plugin; you may see wrong highlighting, and it may even completely mess up the parsing!

An alternative would be disabling syntax for the current file (:setlocal syntax=), or entirely (:syntax off).