摘要:
A data processing system includes first and second processing units and a system memory. The first processing unit has first upper and first lower level caches, and the second processing unit has second upper and lower level caches. In response to a data request, a victim cache line to be castout from the first lower level cache is selected, and the first lower level cache selects between performing a lateral castout (LCO) of the victim cache line to the second lower level cache and a castout of the victim cache line to the system memory based upon a confidence indicator associated with the victim cache line. In response to selecting an LCO, the first processing unit issues an LCO command on the interconnect fabric and removes the victim cache line from the first lower level cache, and the second lower level cache holds the victim cache line.
摘要:
A data processing system includes a processor core supported by upper and lower level caches. In response to executing a deallocate instruction in the processor core, a deallocation request is sent from the processor core to the lower level cache, the deallocation request specifying a target address associated with a target cache line. In response to receipt of the deallocation request at the lower level cache, a determination is made if the target address hits in the lower level cache. In response to determining that the target address hits in the lower level cache, the target cache line is retained in a data array of the lower level cache and a replacement order field in a directory of the lower level cache is updated such that the target cache line is more likely to be evicted from the lower level cache in response to a subsequent cache miss.
摘要:
Fine-grained detection of data modification of original data is provided by associating separate guard bits with granules of memory storing the original data from which translated data has been obtained. The guard bits facilitate indicating whether the original data stored in the associated granule is indicated as protected. The guard bits are set and cleared by special-purpose instructions. Responsive to initiating a data store operation to modify the original data, the associated guard bit(s) are checked to determine whether the original data is indicated as protected. Responsive to the checking indicating that a guard bit is set for the associated original data, the data store operation to modify the original data is faulted and the translated data is discarded, thereby facilitating data coherency between the original data and the translated data.
摘要:
A first SMP computer has first and second processing units and a first system memory pool, a second SMP computer has third and fourth processing units and a second system memory pool, and a third SMP computer has at least fifth and sixth processing units and third, fourth and fifth system memory pools. The fourth system memory pool is inaccessible to the third, fourth and sixth processing units and accessible to at least the second and fifth processing units, and the fifth system memory pool is inaccessible to the first, second and sixth processing units and accessible to at least the fourth and fifth processing units. A first interconnect couples the second processing unit for load-store coherent, ordered access to the fourth system memory pool, and a second interconnect couples the fourth processing unit for load-store coherent, ordered access to the fifth system memory pool.
摘要:
A data processing system includes an interconnect fabric, a system memory coupled to the interconnect fabric and including a virtual barrier synchronization region allocated to storage of virtual barrier synchronization registers (VBSRs), and a plurality of processing units coupled to the interconnect fabric and operable to access the virtual barrier synchronization region. Each of the plurality of processing units includes a processor core and a cache memory including a cache controller and a cache array that caches VBSR lines from the virtual barrier synchronization region of the system memory. The cache controller of a first processing unit, responsive to a memory access request from its processor core that targets a first VBSR line, transfers responsibility for writing back to the virtual barrier synchronization region a second VBSR line contemporaneously held in the cache arrays of first, second and third processing units. The responsibility is transferred via an election held over the interconnect fabric.
摘要:
In response to a memory access request of a processor core that targets a target cache line, the lower level cache of a vertical cache hierarchy associated with the processor core supplies a copy of the target cache line to an upper level cache in the vertical cache hierarchy and retains a copy in a shared coherence state. The upper level cache holds the copy of the target cache line in a private shared ownership coherence state indicating that each cached copy of the target memory block is cached within the vertical cache hierarchy associated with the processor core. In response to the upper level cache signaling replacement of the copy of the target cache line in the private shared ownership coherence state, the lower level cache updates its copy of the target cache line to the exclusive ownership coherence state without coherency messaging with other vertical cache hierarchies.
摘要:
A first SMP computer has first and second processing units and a first system memory pool, a second SMP computer has third and fourth processing units and a second system memory pool, and a third SMP computer has at least fifth and sixth processing units and third, fourth and fifth system memory pools. The fourth system memory pool is inaccessible to the third, fourth and sixth processing units and accessible to at least the second and fifth processing units, and the fifth system memory pool is inaccessible to the first, second and sixth processing units and accessible to at least the fourth and fifth processing units. A first interconnect couples the second processing unit for load-store coherent, ordered access to the fourth system memory pool, and a second interconnect couples the fourth processing unit for load-store coherent, ordered access to the fifth system memory pool.
摘要:
A processing unit for a data processing system includes a processor core having one or more execution units for processing instructions and a register file for storing data accessed in processing of the instructions. The processing unit also includes a multi-level cache hierarchy coupled to and supporting the processor core. The multi-level cache hierarchy includes at least one upper level of cache memory having a lower access latency and at least one lower level of cache memory having a higher access latency. The lower level of cache memory, responsive to receipt of a memory access request that hits only a partial cache line in the lower level cache memory, sources the partial cache line to the at least one upper level cache memory to service the memory access request. The at least one upper level cache memory services the memory access request without caching the partial cache line.
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 data processing system includes an interconnect fabric, a system memory coupled to the interconnect fabric and including a virtual barrier synchronization region allocated to storage of virtual barrier synchronization registers (VBSRs), and a plurality of processing units coupled to the interconnect fabric and operable to access the virtual barrier synchronization region. Each of the plurality of processing units includes a processor core and a cache memory including a cache controller and a cache array that caches VBSR lines from the virtual barrier synchronization region of the system memory. The cache controller of a first processing unit, responsive to a memory access request from its processor core that targets a first VBSR line, transfers responsibility for writing back to the virtual barrier synchronization region a second VBSR line contemporaneously held in the cache arrays of first, second and third processing units. The responsibility is transferred via an election held over the interconnect fabric.