Goals
Explore the essential goals that guide virtual memory systems in operating systems. Learn how transparency ensures programs run as if they have private memory, how efficiency optimizes time and space, and how protection isolates processes to prevent interference. Understand the principle of isolation and how operating systems use it to create reliable and secure environments. This lesson sets the foundation for learning the mechanisms and policies behind effective memory virtualization.
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Thus we arrive at the job of the OS in this set of notes: to virtualize memory. The OS will not only virtualize memory, though; it will do so with style. To make sure the OS does so, we need some goals to guide us. We have seen these goals before (think of the Introduction), and we’ll see them again, but they are certainly worth repeating.
Transparency
One major goal of a virtual memory (VM) system is transparency. The OS should implement virtual memory in a way that is invisible to the running program. Thus, the program shouldn’t be aware of the fact that memory is virtualized; rather, the program behaves as if it has its own private physical memory. Behind the scenes, the OS (and hardware) does all the work to multiplex memory among many different jobs and hence ...