Paging Mechanisms: Copy-on-Write and Swapping

This lecture discusses how the operating system utilizes paging through two primary mechanisms: copy-on-write and swapping. It begins by explaining the concept of copy-on-write, which optimizes the fork system call by allowing processes to share memory until a write operation occurs. The instructor details the naive implementation of fork, which is inefficient due to memory duplication, and contrasts it with the more efficient copy-on-write approach that uses reference counting and read-only mappings. The lecture then transitions to swapping, addressing the challenge of limited main memory when multiple processes are running. It describes how the operating system can store unused pages on disk, allowing for memory reclamation and over-provisioning. The process of handling page faults is explained, including how the memory management unit (MMU) interacts with page tables and the present bit to manage memory effectively. The lecture concludes with a summary of fragmentation, paging, and the importance of TLBs in modern operating systems, emphasizing their role in enabling efficient memory management.