title: rake assets:precompile is slow in production
body: <p>My ruby on rails app take about half an hour to complete a deployment. 
  The longest step is </p>
  
  <pre><code>RAILS_ENV=production RAILS_GROUPS=assets bundle exec rake assets:precompile
  </code></pre>
  
  <p>which takes about 1073155ms</p>
  
  <p>I have to wait for a long time for each deployment.</p>
  
  <p>I use </p>
  
  <pre><code>ckeditor
  rails_admin
  </code></pre>
  
  <p>I guess it is them who slow down my deployment, but I don't evidence and I don't know how to </p>
  
  <p>solve it, either.</p>
  
  <p>My other environments are as follows:</p>
  
  <pre><code>rails 4.0.3
  ruby 2.1.1
  </code></pre>
  
  <p>My production.rb about assets is</p>
  
  <pre><code>config.serve_static_assets = false
  
  # Compress JavaScripts and CSS.
  config.assets.js_compressor = :uglifier
  # config.assets.css_compressor = :sass
  
  # Do not fallback to assets pipeline if a precompiled asset is missed.
  config.assets.compile = true
  
  # Generate digests for assets URLs.
  config.assets.digest = true
  
  # Version of your assets, change this if you want to expire all your assets.
  config.assets.version = '1.0'
  </code></pre>