Mru-Hit-Free Target Sets for I-Shadow Directory
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
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.