Operating Systems I

Tutorial 6

1. What is the meaning of the term 'working set'?
2. Describe how an OS might simulate 'accessed' and 'dirty' bits for a page, if the hardware does not directly support them.
3. Say how the NRU (Not Recently Used page replacement algorithm) uses the accessed and dirty bits to decide which pages to evict.
4. What would be the advantage in a memory management unit supporting 'context IDs' for processes' address spaces?
5. What are the respective pros and cons of bitmap and linked list memory allocation schemes?
6. The Amiga OS uses the linked-list method of heap allocation. It uses a single list of memory holes. It does not explicitly keep track of allocated memory, but when memory is deallocated, a new hole is created, and added to the end of the list of holes. Think of one advantage and one disadvantage of this method.
7. What happens to a memory block in the buddy system when it is deallocated?