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Operating System Source Code Secrets Volume 2: The Virtual Memory System
 Operating System Source Code Secrets Volume 2: The Virtual Memory System, William F. (Bill) Jolitz and Lynne Greer Jolitz . This multivolume series examines the anatomy of an operating system. The brain of an operating system is the virtual memory system. Like a human brain, the virtual memory system is the means through which temporary and permanent memory is stored and accessed. Temporary memory is used as a workspace to assemble a new item before it is stored into permanent memory. Among those most fundamental of functions are: management of kernel and program virtual address spaces (creation, replication, modification, and destruction); management of store backing an address space (naming, protection, sharing, and inheritance of memory contents); persistent and temporary memory; machine dependent (X86) memory management unit control; copy-on-write semantics; main store and secondary store management; page replacement; memory mapped I/O; address space fault handling; demand loading from secondary store; lazy versus industrious evaluation; and UNIX and BSD API’s for address space control. The virtual memory module is not only a key subsystem of the operating system kernel but is itself composed of layers and levels of abstraction. These layers are discussed in terms of future evolution to support the needs of clustering, security, extensibility, and performance.
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