1. A processing system, comprising: plural computing units having corresponding threads, the plural computing units including a first computing unit having a first number of first threads and a second computing unit having a second number of second threads, the first computing unit and the second computing unit having performance levels that vary with the number of jobs currently running thereon; a scheduling module configured to: receive a new job; determine that the first computing unit and the second computing unit that are executing the same number of jobs; assign the new job to the first computing unit instead of the second computing unit based at least on respective ages of other jobs executing on the first computing unit and the second computing unit; and a computing system configured to execute the scheduling module.