Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Patent
1996-05-03
1999-11-09
Chan, Eddie P.
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
711145, 711150, 711152, G06F 1214
Patent
active
059833297
ABSTRACT:
A virtual memory lock is placed upon a region of physical memory within a computer system in response to an I/O request through the use of a range lock. Each range lock represents pages of virtual memory that are present and locked in the physical memory. The range locks are cached in memory and used subsequently to process a lock or unlock request, thus avoiding constant locking or unlocking. Regions of memory that are locked, but have no outstanding I/O operations may still have a range lock existing corresponding to that region. If no range lock exists for an I/O request, the virtual memory lock function is called and a range lock is created for that region. If a range lock exists, its usage counter is incremented. Upon notification of the completion of an I/O operation upon a particular region, the usage counter for the range lock corresponding to that region is decremented, and the range lock continues to exist even if there are no outstanding I/O requests for that region. The range locks may be stored and accessed through the use of a hash table and associated hash function. Physical memory is freed up upon receiving a low memory request or a notification of released pages by a search of the cached range locks to determine which range locks to remove. For these range locks to be removed, the pages in physical memory corresponding to these range locks will be unlocked and the range locks themselves will be removed from memory.
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Bertoni Jonathan L.
Thaler Wolfgang J.
Chan Eddie P.
Nguyen Than V.
Sun Microsystems Inc.
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