I had Ruby 2.0.0-p0 working with Ubuntu 12.10, in which a test suite of mine runs in about 3 minutes. The same test suite takes about 7 min to complete with Ruby 2.0.0-p0 in Ubuntu 13.04. I'm wondering if something changed on Ubuntu side that could be causing that.
My machine is a HP Probook with Core i5, 4gb RAM, an SSD disk of 180GB. My environment consist on rbenv to manage ruby versions, and they are installed through ruby-build.