Week 7 - Memory Management

Question 1

What is internal memory fragmentation?

Answer 1

When memory is split into equal size blocks, if the data stored in a block is less than the size of the block, there are gaps in memory that are left unused.

Question 2

What is external memory fragmentation?

Answer 2

When there is enough space in memory to store new data, but the data can’t be stored in one continuous segment.

Question 3

What causes internal fragmentation?

Answer 3

Paging and fixed partitioning

Question 4

What causes external fragmentation?

Answer 4

Segmentation and dynamic partitioning

Question 5

What is a page fault?

Answer 5

An interrupt that occurs when a process tries to access a block of memory not currently stored in memory

Question 6

Virtual memory is implemented using demand paging. What is demand paging?

Answer 6

A page is only copied from virtual memory into physical memory when a program tries to access it.

Question 7

What are the two solutions to prevent thrashing?

Answer 7

Working set model - Define the working set as the set of pages used in the most recent x page references. Keep only the working set in main memory.
Page-fault frequency – Give process additional frames if page fault frequency high. Remove frame from process if page fault rate low.