Department of Computer Science Course: CS 3725

Process scheduling

Although in a ``modern'' multi-tasking system, each process can make use of the full resources of the ``virtual machine'' while actually sharing these resources with other processes, the perceived use of these resources may depend considerably on the way in which the various processes are given access to the processor. We will now look at some of the things which may be important ehen processes are to be scheduled.

We can think of the scheduler as the algorithm which determines which ``virtual machine'' is currently mapped onto the ``physical machine.''

Actually, two types of scheduling are required; a ``long term scheduler'' which determines which processes are to be loaded into memory, and a ``short term scheduler'' which determines which of the processes in memory will actually be running at any given time. The short-term scheduler is also called the ``dispatcher.''

Most scheduling algorithms deal with one or more queues of processes; each process in each queue is assigned a priority in some way, and the process with the highest priority is the process chosen to run next.