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. The snoop request is entered in the first available latch of the stall/reorder unit unless the stall/reorder unit is full in which case the new snoop request is transmitted to a second unit configured to transmit a request to retry resending the new snoop request. Snoop requests have a higher priority than requests from processors and snoop requests are selected by the arbitration mechanism over processor requests unless the arbitration mechanism requests otherwise (“stall request”) to the stall/reorder unit. By snoop requests having a higher priority than processor requests, the number of snoop requests rejected is reduced. By having the arbitration mechanism issue a stall request, the processor will not be starved.
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 system and method for re-ordering store operations from a processor core to a store queue. When a store queue receives a new processor-issued store operation from the processor core, a store queue controller allocates a new entry in the store queue. In response to allocating the new entry in the store queue, the store queue controller determines whether or not the new entry is dependent on at least one other valid entry in the store queue. In response to determining the new entry is dependent on at least one other valid entry in the store queue, the store queue controller inhibits requesting of the new entry to the RC dispatch logic until each valid entry on which the new entry is dependent has been successfully dispatched to an RC machine by the RC dispatch logic.
摘要:
According to a method of data processing, a predictor is maintained that indicates a historical scope of broadcast for one or more previous operations transmitted on an interconnect of a data processing system. A scope of broadcast of a subsequent operation is predictively selected by reference to the predictor.
摘要:
Scrubbing logic in a local coherency domain issues a domain query request to at least one cache hierarchy in a remote coherency domain. The domain query request is a non-destructive probe of a coherency state associated with a target memory block by the at least one cache hierarchy. A coherency response to the domain query request is received. In response to the 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 method, system, and device for enabling intervention across same-level cache memories. In a preferred embodiment, responsive to a cache miss in a first cache memory a direct intervention request is sent from the first cache memory to a second cache memory requesting a direct intervention that satisfies the cache miss.
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 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.
摘要:
A cache coherent data processing system includes at least first and second coherency domains each including at least one processing unit. The first coherency domain includes a first cache memory and a second cache memory, and the second coherency domain includes a remote coherent cache memory. The first cache memory includes a cache controller, a data array including a data storage location for caching a memory block, and a cache directory. The cache directory includes a tag field for storing an address tag in association with the memory block and a coherency state field associated with the tag field and the data storage location. The coherency state field has a plurality of possible states including a state that indicates that the memory block is possibly shared with the second cache memory in the first coherency domain and cached only within the first coherency domain.
摘要:
A data processing system includes at least first and second coherency domains, each including at least one processor core and a memory. In response to an initialization operation by a processor core that indicates a target memory block to be initialized, a cache memory in the first coherency domain determines a coherency state of the target memory block with respect to the cache memory. In response to the determination, the cache memory selects a scope of broadcast of an initialization request identifying the target memory block. A narrower scope including the first coherency domain and excluding the second coherency domain is selected in response to a determination of a first coherency state, and a broader scope including the first coherency domain and the second coherency domain is selected in response to a determination of a second coherency state. The cache memory then broadcasts an initialization request with the selected scope. In response to the initialization request, the target memory block is initialized within a memory of the data processing system to an initialization value.