Memory Management

Memory Management

• Chapter 3

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

Memory

• Paraphrase of Parkinson’s Law, ‘‘Programs expand to fill the memory available to hold them.’’
• Average home computer nowadays has 10,000 times more memory than the IBM 7094, the largest computer in the world in the early 1960s

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

No Memory Abstraction

• Figure 3-1. Three simple ways of organizing memory with an operating system and one user process. Other possibilities also exist

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

Running Multiple Programs Without a Memory Abstraction

• Figure 3-2. Illustration of the relocation problem. (a) A 16-KB program. (b) Another 16-KB program. (c) The two programs loaded consecutively into memory.

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

Base and Limit Registers

• Figure 3-3. Base and limit registers can be used to give each process a separate address space.

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

Swapping (1)

• Figure 3-4. Memory allocation changes as processes come into memory and leave it. The shaded regions are unused memory

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

Swapping (2)

• Figure 3-5. (a) Allocating space for a growing data segment. (b) Allocating space for a growing stack and a growing data segment.

• Tanenbaum & Bos, Modern Operating Systems: 4th ed., Global Edition (c) 2015 Pearson Education Limited. All rights reserved.

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