Electrical computers and digital processing systems: memory – Address formation – Address mapping
Patent
1997-11-26
1999-11-30
Chan, Eddie P.
Electrical computers and digital processing systems: memory
Address formation
Address mapping
G06F 1210
Patent
active
059960558
ABSTRACT:
A method and apparatus for reclaiming a page of physical memory in a computer system for subsequent mappings to a virtual address is provided in a system wherein the physical memory is apportioned into a number of pages. The computer system includes a temporary storage device, such as a cache, for storing a subset of the pages in memory. Each of the pages stored in the cache are accessed using a cache page address. Virtual addresses are mapped to physical addresses responsive to monitoring use of the cache page addresses associated with the allocated physical addresses. According to the present invention, a page of physical memory is reclaimed such that a substantially even distribution of cache page addresses is maintained in physical addresses of both mapped and available pages of memory. Pages are originally placed on the clean list in response to characteristics of each page including the cache page address of the page. Pages are also selected from the clean list for reclaiming based on their cache page addresses, such that the reclaiming of a page with that cache page address provides an even distribution of cache page addresses both in use in the system and available for subsequent mappings of virtual addresses. By providing a substantially even distribution of cache page addresses for mapped virtual addresses and available physical addresses, the amount of thrashing that is encountered in the cache is minimized, and concomitantly the overall performance of the computer system is enhanced.
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Chan Eddie P.
Digital Equipment Corporation
Ellis Kevin L.
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