Importance

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Abstract

A method and apparatus operating within an object-oriented virtual memory management system. In the virtual memory management system, each page is referenced by traversing a series of mapping tables. Each mapping table is associated with one of a plurality of Partitioned Memory Objects (PMOs). Each PMO includes a plurality of MORs (Memory Object References). PMOs and NSKMPage data structures are collectively referred to as memory objects. When a memory object is duplicated (also called a 'copy on write' or a 'virtual copy'), the actual copy of the duplicated memory object is deferred until a write to the memory object actually occurs. MORs have a VCState field, which can have values of VCOriginal, VCDuplicate, VCSubdupFull, or VCSubdupPart. During a copy on write operation, a VCState of a MOR referring to the duplicated memory object is set to 'VCDuplicate' and set to point to the memory object that was copied. The VCState of MORs referring to memory within the copied memory are set to 'subduplicate (which can be either VCSubdupFull or VCSubdupPart).' During subsequent copy operations, MORs having a VCState of either VCDuplicate of VCSubdupFull do not need to be visited again, since their VCState field has already been set. MORs having a VCState of VCSubdupPart, however, still need to be visited during subsequent write operations.

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First Claim