US 7,321,954 B2
Method for software controllable dynamically lockable cache line replacement system
James N. Dieffenderfer, Apex, N.C. (US); Richard W. Doing, Raleigh, N.C. (US); Brian E. Frankel, Morrisville, N.C. (US); and Kenichi Tsuchiya, Cary, N.C. (US)
Assigned to International Business Machines Corporation, Armonk, N.Y. (US)
Filed on Aug. 11, 2004, as Appl. No. 10/915,982.
Prior Publication US 2006/0036811 A1, Feb. 16, 2006
Int. Cl. G06F 13/16 (2006.01); G06F 13/00 (2006.01)
U.S. Cl. 711—134  [711/133; 711/136; 711/160] 12 Claims
OG exemplary drawing
 
1. A method for tracking the accessing of lines of an associative cache for selecting a line to be considered a least recently used line (LRU), the method comprising:
storing, for each line first data corresponding to each of said lines in an LRU memory array having a common address portion,
said first data including a plurality of fields, each of said fields containing a bit identifying a relative age of a cache line in a pair of ways, said first data thereby identifying which way of a pair is a least recently used (LRU) cache line; and
storing second data in association with said first data, wherein said second data includes cache line lock information for selectively identifying whether cache lines for any of a plurality of ways are to be prevented from replacement; and
processing said first data and not said second data to select a line for replacement when said second data indicates no line is prevented from replacement and processing said first and second data to select a line for replacement when said second data indicates at least one line is prevented from replacement, said processing allowing replacement of only a single line when all lines, are prevented from replacement.