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Employing Ghost Cache Directory Hits in Multiprocessing

IP.com Disclosure Number: IPCOM000057190D
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-15

Publishing Venue

IBM

Related People

Authors:
Emma, PG Knight, JW Pomerene, JH Rechtschaffen, RN Sparacio, RJ [+details]

Abstract

A technique is described whereby "ghost hits" are employed so as to improve cache performance. In multiprocessors with large private caches, those lines that are subject to frequent cross-invalidation will leave "ghost" entries in the cache. The presence of these entries, and perhaps other information recorded in anticipation of their subsequent use, is exploited to improve the performance of the caches. In multiprocessor systems with large private caches, some lines are subject to frequent cross-invalidation and may be re-referenced in the same cache before the entry corresponding to their previous residency has been replaced. When the absolute address tags of a memory request match the tags in such an entry, a "ghost hit" occurs.