Unit 4: Memory Management — Swapping & Demand Paging

This unit covers the two major memory management strategies used by the UNIX kernel: Swapping and Demand Paging. Swapping moves entire processes between main memory and disk, while demand paging moves individual pages on demand. We study the data structures, algorithms, and kernel processes involved in each approach.

Key Topics:

1. Swapping: Data Structures — Swap map, process table fields, swap device.
2. Swapping In Processes — How the swapper brings processes back into memory.
3. Swapping Out Processes — How the swapper selects and moves processes to disk.
4. Demand Paging: Data Structures — Page table entries, page frame data table (pfdata), disk block descriptors.
5. Page Stealer Process — The kernel daemon that frees memory pages using a clock/two-handed clock algorithm.
6. Page Fault Handler — How the kernel handles page faults (validity and protection faults).

Visual Overview

Above is the visual overview of Unit 4. Please refer to this for a structural understanding before proceeding to the detailed modules.