Retrieval of previously accessed data in a multi-core processor
A multi-core processing apparatus may provide a cache probe and data retrieval method. The method may comprise sending a memory request from a requester to a record keeping structure. The memory request may have a memory address of a memory that stores requested data. The method may further comprise determining a last accessor of the memory address, sending a cache probe to the last accessor, determining the last accessor no longer has a copy of the line; and sending a request for the previously accessed version of the line. The request may bypass the tag-directories and obtain the requested data from memory.
1. A processor comprising:
a requester to send a memory request, the memory request having a memory address of a memory that stores requested data;
a record keeping structure to receive the memory request;
circuitry to determine a last accessor of the memory address;
circuitry to send a cache probe to the last accessor;
circuitry to determine the last accessor no longer has a copy of the line; and
circuitry to send a request for previously accessed version of the line, the request bypassing the tag-directories and obtaining the requested data from memory.
2. The processor of claim 1 , wherein the processor is a multi-core processor and the record keeping structure is oblivious that the latest value of the requested data is retrieved from the memory.
3. The processor of claim 2 , wherein the requester is a core and the last accessor is another core of the multi-core processor.
4. The processor of claim 3 , wherein the requester and last accessor belong to a same processing unit domain of the multi-core processor.
5. The processor of claim 3 , wherein the requester and last accessor belong to different processing unit domains of the multi-core processor.
6. The processor of claim 1 , wherein the record keeping structure is a tag directory.
7. The processor of claim 1 , wherein the record keeping structure is a hierarchy of tag directories.
8. A method comprising:
sending a memory request from a requester to a record keeping structure, the memory request having a memory address of a memory that stores requested data;
determining, by the record keeping structure, a last accessor of the memory address;
sending, by the record keeping structure, a cache probe to the last accessor;
determining the last accessor no longer has a copy of the line; and
sending a request for previously accessed version of the line, the request bypassing the tag-directories and obtaining the requested data from memory.
9. The method of claim 8 , wherein the requester is a core and the last accessor is another core of a multi-core processor, and the record keeping structure is oblivious that the latest value of the requested data is retrieved from the memory.
10. The method of claim 9 , wherein the requester and last accessor belong to a same processing unit domain of the multi-core processor.
11. The method of claim 9 , wherein the requester and last accessor belong to different processing unit domains of the multi-core processor.
12. The method of claim 8 , wherein the record keeping structure is a tag directory of a multi-core processor.
13. The method of claim 8 , wherein the record keeping structure is a hierarchy of tag directories of a multi-core processor.
14. A system comprising:
a memory;
a processor coupled to the memory for executing computer instructions stored therein, the processor including:
a requester to send a memory request, the memory request having a memory address of a memory that stores requested data;
a record keeping structure to receive the memory request;
circuitry to determine a last accessor of the memory address;
circuitry to send a cache probe to the last accessor;
circuitry to determine the last accessor no longer has a copy of the line; and
circuitry to send a request for previously accessed version of the line, the request bypassing the tag-directories and obtaining the requested data from memory.
15. The system of claim 14 , wherein the processor is a multi-core processor and the record keeping structure is oblivious that the latest value of the requested data is retrieved from the memory.
16. The system of claim 15 , wherein the requester is a core and the last accessor is another core of the multi-core processor.
17. The system of claim 16 , wherein the requester and last accessor belong to a same processing unit domain of the multi-core processor.
18. The system of claim 16 , wherein the requester and last accessor belong to different processing unit domains of the multi-core processor.
19. The system of claim 14 , wherein the record keeping structure is a tag directory of a multi-core processor.
20. The system of claim 14 , wherein the record keeping structure is a hierarchy of tag directories of a multi-core processor.