Yeah, cgroups are pretty awesome! I created a screencast about them @ http://sysadmincasts.com/episodes/14-introduction-to-linux-c... if you wanted to learn more about them and have never used them before.

There is also a great talk by John Wilkes (Google Cluster Management, Mountain View) about job scheduling via Omega at Google Faculty Summit 2011 @ http://www.youtube.com/watch?v=0ZFMlO98Jkc

When you have a lot of machines, the more you utilize them the more efficient your use of that asset. Google saves a ton of money by using cgroups.