Opportunistic cache replacement policy
View Patent ↗A cache management system employs a replacement policy in a manner that manages concurrent accesses to cache. The cache management system comprises a cache, a replacement policy storage for storing replacement statuses of cache lines of the cache, and an update module. The update module, comprising access filtering and a concurrent update handling, determines how updates to the replacement policy storage are handled. In a multi-threaded compute environment, a concurrent access to shared cache causes a selective update to the replacement policy storage.
1. A processing system, comprising:
one or more processors for issuing cache requests; and
a cache management system, comprising:
a cache comprising a plurality of cache lines;
a replacement policy storage to store a replacement status for each cache line;
an update module to selectively update the replacement statuses of cache lines in the replacement policy storage, the update module comprising:
a concurrent update unit to perform a single update request for the replacement policy storage from a plurality of concurrent update requests, the concurrent update requests resulting from concurrent cache accesses; and
an access filter unit to filter update requests to the replacement policy storage based on a type of cache access and to provide the concurrent update requests, the access filter unit to:
inhibit update requests to the replacement policy storage for store accesses to the cache; and
permit update requests to the replacement policy storage for load accesses to the cache.
2. The processing system of claim 1 , wherein a concurrent update unit is to discard unselected update requests of the plurality of concurrent update requests.
3. The processing system of claim 1 , wherein the replacement policy storage comprises a single port memory.
4. The processing system of claim 1 , wherein the concurrent update unit is to select the single update request to be performed from a plurality of concurrent update requests based on a round robin scheme.
5. The processing system of claim 1 , wherein the concurrent update unit is to select the single update request to be performed from a plurality of concurrent update requests based on a first-in, first-out (FIFO) scheme.
6. The processing system of claim 1 , wherein the replacement policy storage is a component of a cache tag memory.
7. The processing system of claim 1 , wherein the one or more processors share the cache.
8. The processing system of claim 7 , wherein the one or more processors and the cache management system are implemented on an integrated circuit.
9. A method of cache management, comprising:
generating update requests for a replacement policy storage responsive to accesses to a cache, the replacement policy storage storing a replacement status for each cache line of the cache; and
selectively updating the replacement policy storage responsive to the update requests, wherein the selectively updating includes:
selecting and performing a single update request to the replacement policy storage for a concurrent update request using a selection process, the concurrent updates resulting from concurrent cache accesses filtering the update requests based on type of the corresponding cache accesses, said concurrent update request comprising a plurality of filtered concurrent update requests, wherein filtering the update requests comprises:
inhibiting update requests to the replacement policy storage for store accesses to the cache; and
permitting update requests to the replacement policy storage for load accesses to the cache.
10. The method of claim 9 , further comprising:
selecting a cache line of the cache for replacement using the replacement policy storage and a pseudo-least recently used (PLRU) scheme.
11. The method of claim 9 , wherein the concurrent cache accesses are generated by a plurality of threads executing concurrently at a plurality of processor cores sharing the cache.
12. The method of claim 9 , further comprising discarding unselected update requests of a plurality of concurrent update requests.
13. The method of claim 9 , further comprising selecting the single update request to be performed from a plurality of concurrent update requests based on a round robin scheme.
14. The method of claim 9 , further comprising selecting the single update request to be performed from a plurality of concurrent update requests based on a first-in, first-out (FIFO) scheme.
15. In a processing system comprising a cache and a replacement policy storage storing a replacement status for each cache line of the cache, a method comprising:
concurrently generating a first plurality of update requests for the replacement policy storage responsive to a plurality of concurrent cache accesses;
filtering the first plurality of update requests based on a type of cache access for each update request to generate a second plurality of update requests;
selecting and performing a single update request of the second plurality of update requests to update the replacement policy storage; and
not performing the remaining update requests of the second plurality of update requests.
16. The method of claim 15 , wherein filtering the first plurality of update requests comprises:
not performing update requests for store accesses to the cache.
17. The method of claim 15 , further comprising:
selecting a cache line for removal from the cache based on the replacement statuses of the cache lines stored at the replacement policy storage.
18. The method of claim 15 , wherein filtering the first plurality of update requests comprises:
not performing update requests for load accesses to the cache.