Method and apparatus having a snoop filter decoupled from an associated cache and a buffer for replacement line addresses

摘要

An apparatus including a snoop filter decoupled from a cache and an associated method for snoop filtering are disclosed. The snoop filter is decoupled from the cache such that the cache changes states of lines in the cache from a first state that is a clean state, such as an exclusive (E) state, to a second state that is not a clean state, such as a modified (M) state, without the snoop filter's knowledge. The snoop filter buffers addresses of replaced lines that are unknown to be clean until a write-back associated with the replacement lines occurs, or until actual states of the replaced lines are determined by the snoop filter generating a snoop. A multi-level cache system in which a reallocation or replacement policy is biased to favor replacing certain lines such as inclusive lines, non-temporal lines or prefetched lines that have not been accessed, is also disclosed.

主权项

1. A method comprising:
receiving, by a snoop filter, requests on a system bus, the snoop filter being decoupled from an associated cache such that the associated cache changes states of lines in the cache from a first state that is a clean state to a second state that is not a clean state without the snoop filter's knowledge; buffering, by the snoop filter, addresses of replaced lines in the associated cache that are unknown to be clean; matching an organization of a directory of the snoop filter with an organization of the associated cache; and receiving an identification of a cache way to be filled at a time the snoop filter observes a read transaction of the cache.