Granted Patent B1

US 8,751,753 · App. 11/102,171 · Granted Jun 10, 2014

Abstract

Claims (18)

1. A cache system comprising:

a cache memory including a plurality of cache lines, wherein the cache memory is configured to receive a local access; and

a coherence decoupling buffer configured to store at least a portion of a cache line evicted from the cache memory and configured to receive a snoop, wherein if the snoop causes a miss, the snoop is propagated to the cache memory, wherein if the local access causes a cache miss in the cache memory, the local access is propagated to the coherence decoupling buffer, wherein responsive to the local access being propagated from the cache memory to the coherence decoupling buffer, if the local access causes a hit in the coherence decoupling buffer, an entry of the coherence decoupling buffer is re-inserted from the coherence decoupling buffer into the cache memory and removed from the coherence decoupling buffer.

2. The system of claim 1 wherein the coherence decoupling buffer comprises a capacity that is of substantially less capacity than a total capacity of the cache memory.

3. The system of claim 1 wherein the coherence decoupling buffer is configured to be free of value information of the cache memory.

4. The system of claim 1 wherein the cache memory is within a single caching agent.

5. A method comprising:

determining if a tag of a snooped cache line is present in a coherence decoupling buffer coupled to a cache, wherein the cache includes a plurality of cache lines, wherein the cache is configured to receive a local access, wherein the coherence decoupling buffer is configured to store at least a portion of a cache line evicted from the cache and is configured to receive a snoop, wherein if the snoop causes a miss, the snoop is propagated to the cache, wherein if the local access causes a cache miss in the cache, the local access is propagated to the coherence decoupling buffer, wherein responsive to the local access being propagated from the cache to the coherence decoupling buffer, if the local access causes a hit in the coherence decoupling buffer, an entry of the coherence decoupling buffer is re-inserted from the coherence decoupling buffer into the cache and removed from the coherence decoupling buffer; and

granting, by the coherence decoupling buffer, access to the cache line responsive to a presence of the tag.

6. The method of claim 5 further comprising propagating the snoop to the cache responsive to an absence of the tag.

7. The method of claim 6 further comprising inserting permissions of an evicted cache line into the coherence decoupling buffer.

8. The method of claim 7 further comprising granting access to the evicted cache line.

9. A computer system comprising:

a main memory;

a cache memory including a plurality of cache lines, wherein the cache memory is configured to receive a local access; and

a coherence decoupling buffer coupled to the main memory and to the cache memory, wherein the coherence decoupling buffer is configured to store at least a portion of a cache line evicted from the cache memory and is configured to receive a snoop, wherein if the snoop causes a miss, the snoop is propagated to the cache memory, wherein if the local access causes a cache miss in the cache memory, the local access is propagated to the coherence decoupling buffer, wherein responsive to the local access being propagated from the cache memory to the coherence decoupling buffer, if the local access causes a hit in the coherence decoupling buffer, an entry of the coherence decoupling buffer is re-inserted from the coherence decoupling buffer into the cache memory and removed from the coherence decoupling buffer.

10. The computer system of claim 9 wherein the coherence decoupling buffer has a capacity that is of substantially less capacity than a total capacity of the cache memory.

11. The computer system of claim 9 wherein the coherence decoupling buffer comprises a FIFO buffer.

Assignments (8)