Transparent sharing of memory pages using content comparison

Details Transparent sharing of memory pages using content comparison Transparent sharing of memory pages using content comparison

2004-06-30

2009-11-17

Song, Jasmine (Department: 2188)

Electrical computers and digital processing systems: memory

Addressing combined with specific memory configuration or...

Virtual machine memory addressing

C711S202000, C711S203000, C711S206000, C711S216000, C718S001000

Reexamination Certificate

active

07620766

ABSTRACT:
A computer system has one or more software contexts that share use of a memory that is divided into units such as pages. In the preferred embodiment of the invention, the contexts are, or include, virtual machines running on a common hardware platform. The contents, as opposed to merely the addresses or page numbers, of virtual memory pages that are accessible to one or more contexts are examined. If two or more context pages are identical, then their memory mappings are changed to point to a single, shared copy of the page in the hardware memory, thereby freeing the memory space taken up by the redundant copies. The shared copy is then preferably marked copy-on-write. Sharing is preferably dynamic, whereby the presence of redundant copies of pages is preferably determined by hashing page contents and performing full content comparisons only when two or more pages hash to the same key.

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