Structure

Question 1

Explain the layered structure

Answer 1

what is:
- the OS functions are partitioned into layers
- layers only use the functions of the next lowest layer
good because:
- allows for reimplementation without changing other layers
problems:
- loss of efficiency
- hard to decide appropriate levels for functions, ordering is important

Question 2

What is a microkernel?

Answer 2

what is:
- minimally functional kernel
- other non-essential processes are instead implemented in user-space
- provides minimal process and memory management
and IPC to enable user-space stuff
good because:
- smaller, simpler
- easy to extend OS services
- reliable
problems:
- performance decrease because of overhead in syscalls

Question 3

What is a modular kernel?

Answer 3

what is:

• hybrid between micro and monolithic, aims to get best of both
• performance of monolith with stability of micro
• modules are loaded only when needed
• more flexible than layered as modules can call each other
• still offers protection of layered
• similar to micro but more efficient because modules dont need to invoke message passing to communicate