Cache allocation mechanism for saving elected unworthy member via substitute victimization and imputed worthiness of substitute victim member
View Patent ↗A method and apparatus in a data processing system for protecting against a displacement of one type of cache line using a least recently used cache management process. A first member in a class of cache lines is selected as a substitute victim. The substitute victim is unselectable by the least-recently-used cache management process, and the substitute victim is associated with a second member in the class of cache lines. The substitute victim is replaced in response to a selection of the second member as a victim in response to a cache miss in the data processing system, wherein the second member remains in the class of cache lines.
1. A method in a data processing system for processing a class of cache lines with a least recently used cache management process, the method comprising:
selecting a first member in the class of cache lines as a substitute victim, wherein the substitute victim is unselectable by the least recently used cache management process and wherein the substitute victim is associated with a second member in the class of cache lines; and
replacing the substitute victim in response to a selection of the second member as a victim when a cache miss occurs in the data processing system, wherein the second member remains in the class of cache lines.
2. The method of claim 1 , wherein the second member is associated with the substitute victim using a pointer.
3. The method of claim 1 , wherein the class of cache lines is defined by a least recently used tree.
4. The method of claim 1 further comprising:
crediting a cache hit on the substitute victim back to the second member.
5. The method of claim 1 , wherein the class is a congruence class.
6. The method of claim 5 , wherein the congruence class includes nine members.
7. A data processing system comprising:
a cache directory containing a class of cache lines; and
victim selection logic connected to the class directory, wherein the victim selection logic selects a first member in the class of cache lines as a substitute victim, wherein the substitute victim is unselectable by the least recently used cache management process and wherein the substitute victim is associated with a second member in the class of cache lines; and replaces the substitute victim in response to a selection of the second member as a victim when a cache miss occurs in the data processing system, wherein the second member remains in the class of cache lines.
8. A data processing system for processing a class of cache lines with a least recently used cache management process, the method comprising:
selecting means for selecting a first member in the class of cache lines as a substitute victim, wherein the substitute victim is unselectable by the least recently used cache management process and wherein the substitute victim is associated with a second member in the class of cache lines; and
replacing means for replacing the substitute victim in response to a selection of the second member as a victim when a cache miss occurs in the data processing system, wherein the second member remains in the class of cache lines.
9. The data processing system of claim 8 , wherein the second member is associated with the substitute victim using a pointer.
10. The data processing system of claim 8 , wherein the class of cache lines is defined by a least recently used tree.
11. The data processing system of claim 8 further comprising:
crediting means for crediting a cache hit on the substitute victim back to the second member.
12. The data processing system of claim 8 , wherein the class is a congruence class.
13. The data processing system of claim 12 , wherein the congruence class includes nine members.
14. A computer program product in a computer readable medium for processing a class of cache lines with a least recently used cache management process, the computer program product comprising:
first instructions for selecting a first member in the class of cache lines as a substitute victim, wherein the substitute victim is unselectable by the least recently used cache management process and wherein the substitute victim is associated with a second member in the class of cache lines; and
second instructions for replacing the substitute victim in response to a selection of the second member as a victim when a cache miss occurs in the data processing system, wherein the second member remains in the class of cache lines.
15. The computer program product of claim 14 , wherein the second member is associated with the substitute victim using a pointer.
16. The computer program product of claim 14 , wherein the class of cache lines is defined by a least recently used tree.
17. The computer program product of claim 14 further comprising:
third instructions for crediting a cache hit on the substitute victim back to the second member.
18. The computer program product of claim 14 , wherein the class is a congruence class.
19. The computer program product of claim 18 , wherein the congruence class includes nine members.