CPU Scheduling

CPU scheduling is the basis ofmultiprogrammedoperating systems. By switch- ing the CPU among processes, the operating system can make the computer more productive. In this chapter, we introduce basic CPU-scheduling concepts and present several CPU-scheduling algorithms, including real-time systems. We also consider the problem of selecting an algorithm for a particular system.

InChapter 4,we introduced threads to the processmodel.Onmodern oper- ating systems it is kernel-level threads—not processes—that are in fact being scheduled by the operating system. However, the terms “process scheduling” and “thread scheduling” are often used interchangeably. In this chapter, we use process scheduling when discussing general scheduling concepts and thread scheduling to refer to thread-specific ideas.

Similarly, in Chapter 1 we describe how a core is the basic computational unit of a CPU, and that a process executes on a CPU’s core. However, in many instances in this chapter, when we use the general terminology of scheduling a process to “run on a CPU”, we are implying that the process is running on a CPU’s core.

CHAPTER OBJECTIVES

• Describe various CPU scheduling algorithms.

• Assess CPU scheduling algorithms based on scheduling criteria.

• Explain the issues related to multiprocessor and multicore scheduling.

• Describe various real-time scheduling algorithms.

• Describe the scheduling algorithms used in the Windows, Linux, and Solaris operating systems.

• Apply modeling and simulations to evaluate CPU scheduling algorithms.

• Design a program that implements several different CPU scheduling algo- rithms.