Abstract: Statistical data is used to enable or disable snooping on a bus of a processor. A command is received via a first bus or a second bus communicably coupling processor cores and caches of chiplets on the processor. Cache logic on a chiplet determines whether or not a local cache on the chiplet can satisfy a request for data specified in the command. In response to determining that the local cache can satisfy the request for data, the cache logic updates statistical data maintained on the chiplet. The statistical data indicates a probability that the local cache can satisfy a future request for data. Based at least in part on the statistical data, the cache logic determines whether to enable or disable snooping on the second bus by the local cache.

Abstract: Operation of a multi-slice processor implementing datapath steering, where the multi-slice processor includes a plurality of execution slices. Operation of such a multi-slice processor includes: identifying, from a set of instructions, a second instruction that is dependent upon a first instruction in the set of instructions; and responsive to the second instruction being dependent upon the first instruction in the set of instructions, issuing each of the instructions in the set of instructions to a particular set of execution slices configured with bypass logic between execution slices that reduces execution latencies between dependent instructions.

Abstract: Operation of a multi-slice processor implementing datapath steering, where the multi-slice processor includes a plurality of execution slices. Operation of such a multi-slice processor includes: identifying, from a set of instructions, a second instruction that is dependent upon a first instruction in the set of instructions; and responsive to the second instruction being dependent upon the first instruction in the set of instructions, issuing each of the instructions in the set of instructions to a particular set of execution slices configured with bypass logic between execution slices that reduces execution latencies between dependent instructions.

Abstract: Methods and apparatus for identifying an effective address (EA) using an interrupt instruction tag (ITAG) in a multi-slice processor including receiving, by an instruction fetch unit of the processor, the interrupt ITAG; retrieving an effective address table (EAT) row from an EAT, wherein the EAT row comprises a range of EAs and a first ITAG of a range of ITAGs; accessing a processor instruction vector comprising a plurality of elements, each element corresponding to one of a plurality of ITAGs; applying a mask to the processor instruction vector to obtain a portion of the processor instruction vector that begins with an element corresponding to the first ITAG and is defined by an element corresponding to the interrupt ITAG; calculating an EA offset; and identifying the EA for the interrupt ITAG using the EA offset and the range of EAs in the retrieved EAT row.

Abstract: Supporting even instruction tag (‘ITAG’) requirements in a multi-slice processor with null internal operations (IOPs) includes: receiving an IOP with an even ITAG requirement; determining that the IOP is to be assigned an odd ITAG; and inserting a null IOP into an instruction lane ahead of the IOP, wherein the null IOP is assigned the odd ITAG, and the IOP is assigned an even ITAG.

Abstract: Methods and apparatus for thread migration using a microcode engine of a multi-slice processor including issuing a thread migration instruction to the microcode engine of a decode unit, the thread migration instruction comprising an indication that the thread migration instruction is to be processed by the microcode engine; decoding, by the microcode engine, the thread migration instruction into a plurality of internal operations each targeting a different register entry; transmitting the plurality of internal operations to a dispatcher of the multi-slice processor; and manipulating, by the multi-slice processor, a plurality of register entries according to the plurality of internal operations.

Abstract: A data processing system includes an upper level cache memory and a lower level cache memory employing different replacement policies. The lower level cache memory provides a respective one of a plurality of counters for each of a plurality of cache lines in a particular congruence class. The lower level cache memory initializes a counter value for a cache line in the particular congruence class that was castout from the upper level cache memory based on an indication of whether the cache line was accessed in the upper level cache memory following installation in the upper level cache memory. The lower level cache memory selects a victim cache line from among the plurality of cache lines in the particular congruence class for eviction from the lower level cache memory by reference to counter values of the plurality of counters.

Abstract: A technique for operating a memory system for a node includes interrogating, by a cache, an associated cache directory to determine whether a shared cache line to be installed in the cache is associated with an invalid global state in the cache. The invalid global state specifies that a version of the shared cache line has been intervened off-node. In response to the shared cache line being in the invalid global state the cache spawns a castout invalid global command for the shared cache line. The shared cache line is installed in the cache. A coherence state for the shared cache line is updated in the associated cache directory to indicate the shared cache line is shared.

Abstract: In response to a transactional store request, the higher level cache transmits, to the lower level cache, a backup copy of an unaltered target cache line in response to a target real address hitting in the higher level cache, updates the target cache line with store data to obtain an updated target cache line, and records the target real address as belonging to a transaction footprint of the memory transaction. In response to a conflicting access to the transaction footprint prior to completion of the memory transaction, the higher level cache signals failure of the memory transaction to the processor core, invalidates the updated target cache line in the higher level cache, and causes the backup copy of the target cache line in the lower level cache to be restored as a current version of the target cache line.

Abstract: In response to a transactional store request, the higher level cache transmits, to the lower level cache, a backup copy of an unaltered target cache line in response to a target real address hitting in the higher level cache, updates the target cache line with store data to obtain an updated target cache line, and records the target real address as belonging to a transaction footprint of the memory transaction. In response to a conflicting access to the transaction footprint prior to completion of the memory transaction, the higher level cache signals failure of the memory transaction to the processor core, invalidates the updated target cache line in the higher level cache, and causes the backup copy of the target cache line in the lower level cache to be restored as a current version of the target cache line.

Abstract: A technique for operating a memory system for a node includes interrogating, by a cache, an associated cache directory to determine whether a shared cache line to be installed in the cache is associated with an invalid global state in the cache. The invalid global state specifies that a version of the shared cache line has been intervened off-node. In response to the shared cache line being in the invalid global state the cache spawns a castout invalid global command for the shared cache line. The shared cache line is installed in the cache. A coherence state for the shared cache line is updated in the associated cache directory to indicate the shared cache line is shared.

Abstract: Statistical data is used to enable or disable snooping on a bus of a processor. A command is received via a first bus or a second bus communicably coupling processor cores and caches of chiplets on the processor. Cache logic on a chiplet determines whether or not a local cache on the chiplet can satisfy a request for data specified in the command. In response to determining that the local cache can satisfy the request for data, the cache logic updates statistical data maintained on the chiplet. The statistical data indicates a probability that the local cache can satisfy a future request for data. Based at least in part on the statistical data, the cache logic determines whether to enable or disable snooping on the second bus by the local cache.

Abstract: In response to a transactional store request, the higher level cache transmits, to the lower level cache, a backup copy of an unaltered target cache line in response to a target real address hitting in the higher level cache, updates the target cache line with store data to obtain an updated target cache line, and records the target real address as belonging to a transaction footprint of the memory transaction. In response to a conflicting access to the transaction footprint prior to completion of the memory transaction, the higher level cache signals failure of the memory transaction to the processor core, invalidates the updated target cache line in the higher level cache, and causes the backup copy of the target cache line in the lower level cache to be restored as a current version of the target cache line.

Abstract: In response to a transactional store request, the higher level cache transmits, to the lower level cache, a backup copy of an unaltered target cache line in response to a target real address hitting in the higher level cache, updates the target cache line with store data to obtain an updated target cache line, and records the target real address as belonging to a transaction footprint of the memory transaction. In response to a conflicting access to the transaction footprint prior to completion of the memory transaction, the higher level cache signals failure of the memory transaction to the processor core, invalidates the updated target cache line in the higher level cache, and causes the backup copy of the target cache line in the lower level cache to be restored as a current version of the target cache line.

Abstract: A technique for operating a memory system for a node includes interrogating, by a cache, an associated cache directory to determine whether a shared cache line to be installed in the cache is associated with an invalid global state in the cache. The invalid global state specifies that a version of the shared cache line has been intervened off-node. In response to the shared cache line being in the invalid global state the cache spawns a castout invalid global command for the shared cache line. The shared cache line is installed in the cache. A coherence state for the shared cache line is updated in the associated cache directory to indicate the shared cache line is shared.

Abstract: A technique for operating a memory system for a node includes interrogating, by a cache, an associated cache directory to determine whether a shared cache line to be installed in the cache is associated with an invalid global state in the cache. The invalid global state specifies that a version of the shared cache line has been intervened off-node. In response to the shared cache line being in the invalid global state the cache spawns a castout invalid global command for the shared cache line. The shared cache line is installed in the cache. A coherence state for the shared cache line is updated in the associated cache directory to indicate the shared cache line is shared.

Abstract: Statistical data is used to enable or disable snooping on a bus of a processor. A command is received via a first bus or a second bus communicably coupling processor cores and caches of chiplets on the processor. Cache logic on a chiplet determines whether or not a local cache on the chiplet can satisfy a request for data specified in the command. In response to determining that the local cache can satisfy the request for data, the cache logic updates statistical data maintained on the chiplet. The statistical data indicates a probability that the local cache can satisfy a future request for data. Based at least in part on the statistical data, the cache logic determines whether to enable or disable snooping on the second bus by the local cache.

Abstract: 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.

Abstract: Statistical data is used to enable or disable snooping on a bus of a processor. A command is received via a first bus or a second bus communicably coupling processor cores and caches of chiplets on the processor. Cache logic on a chiplet determines whether or not a local cache on the chiplet can satisfy a request for data specified in the command. In response to determining that the local cache can satisfy the request for data, the cache logic updates statistical data maintained on the chiplet. The statistical data indicates a probability that the local cache can satisfy a future request for data. Based at least in part on the statistical data, the cache logic determines whether to enable or disable snooping on the second bus by the local cache.

Abstract: Disclosed is a computer system (100) comprising a processor unit (110) adapted to run a virtual machine in a first operating mode; a cache (120) accessible to the processor unit, said cache comprising a plurality of cache rows (1210), each cache row comprising a cache line (1214) and an image modification flag (1217) indicating a modification of said cache line caused by the running of the virtual machine; and a memory (140) accessible to the cache controller for storing an image of said virtual machine; wherein the processor unit comprises a replication manager adapted to define a log (200) in the memory prior to running the virtual machine in said first operating mode; and said cache further includes a cache controller (122) adapted to periodically check said image modification flags; write only the memory address of the flagged cache lines in the defined log and subsequently clear the image modification flags.