But the address translation mechanism can be extended


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Unformatted text preview: If some process inadvertently writes to the memory used by another process, that process might fail in some bewildering fashion totally unrelated to the program logic. In order to manage memory more efﬁciently and robustly, modern systems provide an abstraction of main memory known as virtual memory (VM). Virtual memory is an elegant interaction of hardware exceptions, hardware address translation, main memory, disk ﬁles, and kernel software that provides each process with a large, uniform, and private address space. With one clean mechanism, virtual memory provides three important capabilities. (1) It uses main memory efﬁciently by treating it as a cache for an address space stored on disk, keeping only the active areas in main memory, and transferring data back and forth between disk and memory as needed. (2) It simpliﬁes memory management by providing each process with a uniform address space. (3) It protects the address space of each process from corruption by other processes. Virtual memory is one of the great ideas in computer systems. A big reason for its success is that it works silently and automatically, without any intervention from the application programmer. Since virtual memory works so well behind the scenes, why would a programmer need to understand it? There are several reasons. ¯ ¯ Virtual memory is central. Virtual memory pervades all levels of computer systems, playing key roles in the de...
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