摘要:
A system and method for cache management in a data processing system having a memory hierarchy of upper memory and lower memory cache. A lower memory cache controller accesses a coherency state table to determine replacement policies of coherency states for cache lines present in the lower memory cache when receiving a cast-in request from one of the upper memory caches. The coherency state table implements a replacement policy that retains the more valuable cache coherency state information between the upper and lower memory caches for a particular cache line contained in both levels of memory at the time of cast-out from the upper memory cache.
摘要:
A system and method for cache management in a data processing system having a memory hierarchy of upper memory and lower memory cache. A lower memory cache controller accesses a coherency state table to determine replacement policies of coherency states for cache lines present in the lower memory cache when receiving a cast-in request from one of the upper memory caches. The coherency state table implements a replacement policy that retains the more valuable cache coherency state information between the upper and lower memory caches for a particular cache line contained in both levels of memory at the time of cast-out from the upper memory cache.
摘要:
A system and method for cache management in a data processing system having a memory hierarchy of upper memory and lower memory cache. A lower memory cache controller accesses a coherency state table to determine replacement policies of coherency states for cache lines present in the lower memory cache when receiving a cast-in request from one of the upper memory caches. The coherency state table implements a replacement policy that retains the more valuable cache coherency state information between the upper and lower memory caches for a particular cache line contained in both levels of memory at the time of cast-out from the upper memory cache.
摘要:
In response to execution of program code, a control register within scrubbing logic in a local coherency domain is initialized with at least a target address of a target memory block. In response to the initialization, the scrubbing logic issues to at least one cache hierarchy in a remote coherency domain a domain indication scrubbing request targeting a target memory block that may be cached by the at least one cache hierarchy. In response to receipt of a coherency response indicating that the target memory block is not cached in the remote coherency domain, a domain indication in the local coherency domain is updated to indicate that the target memory block is cached, if at all, only within the local coherency domain.
摘要:
A cache, system and method for reducing the number of rejected snoop requests. An incoming snoop request is entered in the first available latch in a pipeline of latches in a stall/reorder unit if the stall/reorder unit is not full. The entered snoop request is dispatched to a selector upon entering a bottom latch in the pipeline. The stall/reorder unit is not informed as to whether the dispatched snoop request is accepted by an arbitration mechanism for several clock cycles after the dispatch occurred. A copy of the dispatched snoop request is stored in a top latch in an overrun pipeline of latches in the first unit upon dispatching the snoop request. By maintaining information about the snoop request, the snoop request may be dispatched again to the selector in case the dispatched snoop request was rejected thereby increasing the chance that the snoop request will ultimately be accepted.
摘要:
A processing unit for a multiprocessor data processing system includes a store-through upper level cache, an instruction sequencing unit that fetches instructions for execution, at least one instruction execution unit that executes a store-conditional instruction to determine a store target address, a store queue that, following execution of the store-conditional instruction, buffers a corresponding store operation, sequencer logic associated with the store queue. The sequencer logic, responsive to receipt of a latency indication indicating that resolution of the store-conditional operation as passing or failing is subject to significant latency, invalidates, prior to resolution of the store-conditional operation, a cache line in the store-through upper level cache to which a load-reserve operation previously bound.
摘要:
A cache coherent data processing system includes at least first and second coherency domains. In a first cache memory within the first coherency domain of the data processing system, a memory block is held in a storage location associated with an address tag and a coherency state field. A determination is made if a home system memory assigned an address associated with the memory block is within the first coherency domain. If not, the coherency state field is set to a coherency state that indicates that the address tag is valid, that the storage location does not contain valid data, the first coherency domain does not contain the home system memory, and that, following formation of the coherency state, the memory block is cached outside of the first coherency domain.
摘要:
In an entry of a first cache memory within a first coherency domain of a data processing system including at least first and second coherency domains, a coherency state field is set to a first state that indicates that an associated address tag is valid, an associated storage location does not contain valid data, and a memory block identified by the address tag is likely cached outside the first coherency domain. In response to snooping a castout operation, the first cache memory determines if the castout operation hits in the entry and, if so, updates the coherency state field from the first state to a second state indicating that the associated address tag is invalid.
摘要:
Scrubbing logic in a local coherency domain issues to at least one cache hierarchy in a remote coherency domain a domain reset request that forces invalidation of any cached copy of a target memory block then held in said remote coherency domain. A coherency response to said domain reset request is received. In response to said coherency response indicating that said target memory block is not cached in said remote coherency domain, a domain indication of said local coherency domain is updated to indicate that said target memory block is cached, if at all, only within said local coherency domain.
摘要:
A cache, system and method for reducing the number of rejected snoop requests. A “stall/reorder unit” in a cache receives a snoop request from an interconnect. Information, such as the address, of the snoop request is stored in a queue of the stall/reorder unit. The stall/reorder unit forwards the snoop request to a selector which also receives a request from a processor. An arbitration mechanism selects either the snoop request or the request from the processor. If the snoop request is denied by the arbitration mechanism, information, e.g., address, about the snoop request may be maintained in the stall/reorder unit. The request may be later resent to the selector. This process may be repeated up to “n” clock cycles. By providing the snoop request additional opportunities (n clock cycles) to be accepted by the arbitration mechanism, fewer snoop requests may ultimately be denied.