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Mru-Hit-Free Target Sets for I-Shadow Directory

IP.com Disclosure Number: IPCOM000043836D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Pomerene, JH: AUTHOR [+4]

Abstract

Although the I-Shadow Directory has incremental coverage of 70% and accuracy of 99%, the major cause of loss of coverage is MRU-Hits (that is, prefetch targets are currently Most Recently Used within their congruence class) among the prefetch targets. A target set which involves MRU changes within its congruence class is guaranteed to be free of these MRU-Hits for the prefetch target and, therefore, offers an opportunity to increase coverage by making the approximately 42% of all prefetch opportunities which are MRU-Hits productive. The target set is established as follows. On every MRU change the address of a new line is associated with the line which is MRU within the congruence class into which the MRU change enters. An alternative MRU-Hit-free target set is the next Miss within the congruence class.

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Mru-Hit-Free Target Sets for I-Shadow Directory

Although the I-Shadow Directory has incremental coverage of 70% and accuracy of 99%, the major cause of loss of coverage is MRU-Hits (that is, prefetch targets are currently Most Recently Used within their congruence class) among the prefetch targets. A target set which involves MRU changes within its congruence class is guaranteed to be free of these MRU-Hits for the prefetch target and, therefore, offers an opportunity to increase coverage by making the approximately 42% of all prefetch opportunities which are MRU-Hits productive. The target set is established as follows. On every MRU change the address of a new line is associated with the line which is MRU within the congruence class into which the MRU change enters. An alternative MRU-Hit-free target set is the next Miss within the congruence class.

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