Memory Virtualisation

Question 1

Why do we need virtual memory?

Answer 1

To give programs the impression that they have much more memory available to them than they actually do. It also avoids programs overwriting each other’s memory.

Question 2

What are the three main sections of an address space?

Answer 2

Code section, Stack and Heap

Question 3

True or false, the stack grows negatively?

Answer 3

True. The stack grows negatively, while the heap grows positively.

Question 4

What is address translation?

Answer 4

The translation between virtual and physical memory addresses.

Question 5

What is Dynamic Hardware Relocation? What registers does it use? How do we modify these registers?

Answer 5

This is when we have a base and bounds register, which are used to mark where in memory an address space begins, and how large the address space is. So, the physical address = virtual address + base register.
We can only modify the values of these registers when in kernel mode.

Question 6

How do we make sure that base and bounds registers are saved when making a context switch?

Answer 6

There is a process control block, which is where we store the values of these registers.

Question 7

What are the pros and cons of base and bounds in Dynamic Relocation?

Answer 7

Pros: it is transparent, simple to implement, and simple to switch.
Cons: How do we share memory, internal fragmentation