Virtual Memory

Question 1

Explain the banker’s algorithm

Answer 1

Thought experiment, try to give a resource to thread A, then B and check if threads could run without deadlocking, if there is a potential deadlock, put thread B to sleep

Question 2

What is the cause of a deadlock

Answer 2

A deadlock occurs when there is a circular dependency of resources between two threads

Question 3

How is an address space defined?

Answer 3

It’s the set of memory addresses accessible to a program (for read or write)

Question 4

What is a process in essence?

Answer 4

Instance of a running program + one or more threads

Question 5

What is a trap?

Answer 5

A kind of interrupt that gives execution control to the kernel.

Question 6

How does the OS protect from errors in user processes?

Answer 6

Using a mode bit: 0 is kernel mode and 1 is user mode

Question 7

What syscall is used to allocate space into the heap?

Answer 7

The sbrk syscall

Question 8

What hardware is between CPU address references and physical addresses?

Answer 8

Memory Management Unit

Question 9

How does the CPU check if a memory reference is valid for a program

Answer 9

It uses the base and bound registers and performs hardware aided arithmetic