Management system for a hierarchical data cache employing preemp

Details Management system for a hierarchical data cache employing preemp Management system for a hierarchical data cache employing preemp

1996-02-07

1997-05-06

Lall, Parshotam S.

395440, 395463, 395465, G06F 1208

Patent

active

056279906

ABSTRACT:
An adaptive hierarchical cache management system for improving effective cache hit ratios by eliminating unnecessary duplicate cache entries in two coupled cache memories. When a cached Storage Controller (SC) is coupled to a Cached Storage Drawer (CSD), the hierarchical coupling of the SC cache memory and CSD cache memory unnecessarily duplicates cache entries during normal operation. A Conditional Purge procedure purges duplicate lines from the CSD cache subject to a DASD activity threshold. A Prenotify Intent parameter allows the SC to request restaging of the purged cache entry preparatory to fast write or LRU demotion in the SC cache. The new procedures substantially and transparently improve the combined caching efficiency without significant new hardware or software overhead.

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