Gemfile snippet to speed-up therubyrhino on JRuby - you might gain up to 30% in speed (e.g. during assets:precompile) if your JavaScripts are Rhino bytecode-compilable ...

Gemfile

source 'https://rubygems.org'

gem 'rails', '3.2.16' # or whatever

# ...

group :assets do
  # make sure you have the latest rhino :
  gem 'therubyrhino', '>= 2.0.2', :platform => :jruby
  
  # ExecJS with a patch that does not force interpreted mode :
  gem 'execjs', :github => 'kares/execjs'
  # PR at https://github.com/sstephenson/execjs/pull/112
  
  # ...
  
end

# ...