摘要:
A second lower level cache receives an LCO command issued by a first lower level cache on an interconnect fabric. The LCO command indicates an address of a victim cache line to be castout from the first lower level cache and indicates that the second lower level cache is an intended destination of the victim cache line. The second lower level cache determines whether to accept the victim cache line from the first lower level cache based at least in part on the address of the victim cache line indicated by the LCO command. In response to determining not to accept the victim cache line, the second lower level cache provides a coherence response to the LCO command refusing the identified victim cache line. In response to determining to accept the victim cache line, the second lower level cache updates an entry corresponding to the identified victim cache line.
摘要:
A second lower level cache receives an LCO command issued by a first lower level cache on an interconnect fabric. The LCO command indicates an address of a victim cache line to be castout from the first lower level cache and indicates that the second lower level cache is an intended destination of the victim cache line. The second lower level cache determines whether to accept the victim cache line from the first lower level cache based at least in part on the address of the victim cache line indicated by the LCO command. In response to determining not to accept the victim cache line, the second lower level cache provides a coherence response to the LCO command refusing the identified victim cache line. In response to determining to accept the victim cache line, the second lower level cache updates an entry corresponding to the identified victim cache line.
摘要:
In response to a data request of a first of a plurality of processing units, the first processing unit selects a victim cache line to be castout from the lower level cache of the first processing unit and determines whether a mode is set. If not, the first processing unit issues on the interconnect fabric an LCO command identifying the victim cache line and indicating that a lower level cache is the intended destination. If the mode is set, the first processing unit issues a castout command with an alternative intended destination. In response to a coherence response to the LCO command indicating success of the LCO command, the first processing unit removes the victim cache line from its lower level cache, and the victim cache line is held elsewhere in the data processing system. The mode can be set to inhibit castouts to system memory, for example, for testing.
摘要:
In response to a data request of a first of a plurality of processing units, the first processing unit selects a victim cache line to be castout from the lower level cache of the first processing unit and determines whether a mode is set. If not, the first processing unit issues on the interconnect fabric an LCO command identifying the victim cache line and indicating that a lower level cache is the intended destination. If the mode is set, the first processing unit issues a castout command with an alternative intended destination. In response to a coherence response to the LCO command indicating success of the LCO command, the first processing unit removes the victim cache line from its lower level cache, and the victim cache line is held elsewhere in the data processing system. The mode can be set to inhibit castouts to system memory, for example, for testing.
摘要:
In response to a data request, a victim cache line is selected for castout from a lower level cache, and a target lower level cache of one of the plurality of processing units is selected. A determination is made whether the selected target lower level cache has provided more than a threshold number of retry responses to lateral castout (LCO) commands of the first lower level cache, and if so, a different target lower level cache is selected. The first processing unit thereafter issues a LCO command on the interconnect fabric. The LCO command identifies the victim cache line to be castout and indicates that the target lower level cache is an intended destination of the victim cache line. In response to a successful coherence response to the LCO command, the victim cache line is removed from the first lower level cache and held in the second lower level cache.
摘要:
In response to a data request, a victim cache line is selected for castout from a lower level cache, and a target lower level cache of one of the plurality of processing units is selected. A determination is made whether the selected target lower level cache has provided more than a threshold number of retry responses to lateral castout (LCO) commands of the first lower level cache, and if so, a different target lower level cache is selected. The first processing unit thereafter issues a LCO command on the interconnect fabric. The LCO command identifies the victim cache line to be castout and indicates that the target lower level cache is an intended destination of the victim cache line. In response to a successful coherence response to the LCO command, the victim cache line is removed from the first lower level cache and held in the second lower level cache.
摘要:
A data processing system includes a processor core having an associated upper level cache and a lower level victim cache. In response to a memory access request of the processor core that specifies a non-modifying access to a target coherency granule, a determination is made whether the memory access request hits or misses in a directory of the lower level victim cache. In response to determining that the memory access request hits in the lower level victim cache in a data-valid coherence state, the lower level victim cache provides the target coherency granule of the memory access request to the upper level cache. The lower level victim cache preserves the target coherency granule in the lower level victim cache in a shared coherence state if the memory access request is of a first type and invalidates the target coherency granule if the memory access request is of a second type.
摘要:
A data processing system includes a processor core having an associated upper level cache and a lower level victim cache. In response to a memory access request of the processor core that specifies a non-modifying access to a target coherency granule, a determination is made whether the memory access request hits or misses in a directory of the lower level victim cache. In response to determining that the memory access request hits in the lower level victim cache in a data-valid coherence state, the lower level victim cache provides the target coherency granule of the memory access request to the upper level cache. The lower level victim cache preserves the target coherency granule in the lower level victim cache in a shared coherence state if the memory access request is of a first type and invalidates the target coherency granule if the memory access request is of a second type.
摘要:
A cache memory includes a cache array including a plurality of congruence classes each containing a plurality of cache lines, where each cache line belongs to one of multiple classes which include at least a first class and a second class. The cache memory also includes a cache directory of the cache array that indicates class membership. The cache memory further includes a cache controller that selects a victim cache line for eviction from a congruence class. If the congruence class contains a cache line belonging to the second class, the cache controller preferentially selects as the victim cache line a cache line of the congruence class belonging to the second class based upon access order. If the congruence class contains no cache line belonging to the second class, the cache controller selects as the victim cache line a cache line belonging to the first class based upon access order.
摘要:
A processing unit for a multiprocessor data processing system includes a processor core and a cache hierarchy coupled to the processor core to provide low latency data access. The cache hierarchy includes an upper level cache coupled to the processor core and a lower level victim cache coupled to the upper level cache. In response to a prefetch request of the processor core that misses in the upper level cache, the lower level victim cache determines whether the prefetch request misses in the directory of the lower level victim cache and, if so, allocates a state machine in the lower level victim cache that services the prefetch request by issuing the prefetch request to at least one other processing unit of the multiprocessor data processing system.