Virtual Memory: Principles and Mechanisms

This lecture discusses the case for virtual memory in computer systems, emphasizing the need for virtualization to enable process isolation and efficient memory management. It begins by outlining the historical context of uniprogramming, where only one program could run at a time, leading to a lack of isolation between the operating system and processes. The instructor highlights the goals of memory virtualization, including transparency, protection, and efficiency, which are essential for modern multi-programming environments. The lecture explains how virtual memory allows multiple processes to coexist in memory without being aware of each other, while ensuring that each process can only access its own address space. The concept of a Memory Management Unit (MMU) is introduced, detailing how it translates virtual addresses to physical addresses. The lecture also covers different approaches to memory virtualization, including base and bounds mechanisms, and discusses their advantages and limitations, particularly regarding security and memory sharing. The session concludes with a look at the implications of these mechanisms for operating system design and performance.