Introduction Performance is a very important aspect of computer systems. This has been true since the very birth of modern computers, where they were seen as calculators whose reason d'tre was their ability to perform calculations faster than the human being. Performance is important to all areas of Computer Science, from Algorithms to Data Bases, from Operating Systems to Cryptography. Today, performance remains a major concern for both industry and academia. Among the factors that affect performance, scheduling is of fundamental importance. The execution time of an application strongly depends on the ordering of the pieces of work that form the application, which resources carry out each piece, and when such resources do so. Scheduling has been traditionally done by the operating system [Bunt 76]. This is because the operating system controls the resources of interest to most applications (processors, memory, disks, etc). One salient characteristic of traditional scheduling i
