Abstract: Embodiments of the invention address deficiencies of the art in respect to cache coherency management and provide a novel and non-obvious method, system and apparatus for silent invalid state transition handling in an SMP environment. In one embodiment of the invention, a cache coherency method can be provided. The cache coherency method can include identifying an invalid state transition for a cache line in a local node, evicting a corresponding cache directory entry for the cache line, forwarding an invalid state transition notification to a node controller for a home node for the cache line in order for the home node to evict a corresponding cache directory entry for the cache line, and relinquishing ownership of the cache line to the home node.

Abstract: A method includes receiving a first packet at an input of a switching device and determining whether to insert first data associated with the first packet into a normal buffer of the input. The determination of whether to insert first data associated with the first packet into the normal buffer includes determining whether the first output identifier matches a second output identifier corresponding to second data in the normal buffer that is associated with a second packet. The first data is inserted into the normal buffer when the first output identifier matches the second output identifier.

Abstract: Techniques are disclosed to implement a scheduling scheme for a crossbar scheduler that provides distributed request-grant-accept arbitration between input group arbiters and output group arbiters in a distributed switch. Input and output ports are grouped and assigned a respective arbiter. The input group arbiters communicate requests indicating a count of respective ports having data packets to be transmitted via one of the output ports. The output group arbiter attempts to accommodate the requests for each member of an input group before proceeding to a next input group.

Abstract: The distributed switch may include a plurality of chips (i.e., sub-switches) on a switch module. These sub-switches may receive from a computing device connected to a Tx/Rx port a multicast data frame (e.g., an Ethernet frame) that designates a plurality of different destinations. Instead of simply using one egress connection interface to forward the copies of the data frame to each of the destinations sequentially, the sub-switch may use a plurality of a connection interfaces to transfer copies of the multicast data frame simultaneously. The port that receives the multicast data frame can borrow the connection interfaces (and associated hardware such as buffers) assigned to these other ports to transmit copies of the multicast data frame simultaneously.

Abstract: The distributed switch may include a plurality of chips (i.e., sub-switches) on a switch module. These sub-switches may receive from a computing device connected to a Tx/Rx port a multicast data frame (e.g., an Ethernet frame) that designates a plurality of different destinations. Instead of simply using one egress connection interface to forward the copies of the data frame to each of the destinations sequentially, the sub-switch may use a plurality of a connection interfaces to transfer copies of the multicast data frame simultaneously. The port that receives the multicast data frame can borrow the connection interfaces (and associated hardware such as buffers) assigned to these other ports to transmit copies of the multicast data frame simultaneously.

Abstract: A design structure embodied in a machine readable storage medium for designing, manufacturing, and/or testing a design can be provided. The design structure includes a symmetric multiprocessing (SMP) system. The system includes a plurality of nodes. Each of the nodes includes a node controller and a plurality of processors cross-coupled to one another. The system also includes at least one cache directory coupled to each node controller, and, invalid state transition logic coupled to each node controller. The invalid state transition logic includes program code enabled to identify an invalid state transition for a cache line in a local node, to evict a corresponding cache directory entry for the cache line, and to forward an invalid state transition notification to a node controller for a home node for the cache line in order for the home node to evict a corresponding cache directory entry for the cache line.

Abstract: A method, apparatus, system, and signal-bearing medium that, in an embodiment, select a command to send to memory. In an embodiment, the oldest command in a write queue that does not collide with a conflict queue is sent to memory and added to the conflict queue if some or all of the following are true: all of the commands in the read queue collide with the conflict queue, any read command incoming from the processor does not collide with the write queue, the number of commands in the write queue is greater than a first threshold, and all commands in the conflict queue have been present for less than a second threshold. In an embodiment, a command does not collide with a queue if the command does not access the same cache line in memory as the commands in the queue. In this way, in an embodiment, write commands are sent to the memory at a time that reduces the impact on the performance of read commands.

Abstract: In a shared memory architecture, early coherency indication is used to notify a communications interface, prior to the data for a memory request is returned, and prior to updating a coherency directory in response to the memory request, that the return data can be used by the communications interface when it is received thereby from a source of the return data. By doing so, the communications interface can often begin forwarding the return data over its associated communication link with little or no latency once the data is retrieved from its source. In addition, the communications interface is often no longer required to wait for updating of the coherency directory to complete prior to forwarding the return data over the communication link. As such, the overall latency for handling the memory request is typically reduced.

Abstract: Uncontested priority is provided to out-of-order data transfers over in-order data transfers on a data bus shared by a plurality of memory requesters. By always granting priority to out-of-order transfers such as deferred read data transfers over in-order transfers such as write and/or cache-to-cache data transfers, it is assured that no newer command or transaction ever negatively affects the latency of an older command or transaction.

Abstract: A memory controller receives read requests from a processor into a read queue. The memory controller dynamically modifies an order of servicing the requests based on how many pending requests are in the read queue. When the read queue is relatively empty, requests are serviced oldest first to minimize latency. When the read queue becomes progressively fuller, requests are progressively, using three or more memory access modes, serviced in a manner that increases throughput on a memory bus to reduce the likelihood that the read queue will become full and further requests from the processor would have to be halted.

Abstract: A method, system, and computer program product for tuning a set of chipset parameters to achieve optimal chipset performance under varying workload characteristics. A set of workload characteristics of a current workload type is determined. An instruction stream is generated using weighted parameters derived from the set of workload characteristics of the current workload type. A set of chipset parameters is generated and integrated within the instruction stream. The instruction stream is loaded to one or more processors and executed to collect and analyze performance data relating to the chipset's performance. The analysis includes comparing the set of performance data of a plurality of different instruction streams having the same set of workload characteristics. Each executed instruction stream is executed with at least one different combination of chipset parameters. A determination is made regarding which combination of chipset parameters provides the best performance data for the current workload.

Abstract: In one aspect, a processor is provided. The processor may include logic, coupled to the processor, and to issue a currently issued memory fetch over a processor bus. The currently issued memory fetch may include a next fetch hint that may include information about a next memory fetch.

Abstract: A method is provided for processing commands issued by a processor over a bus. The method includes the steps of (1) transmitting the command to a remote node to obtain access to data required to complete the command; (2) receiving from the remote node a response packet including a header and a header CRC; (3) validating the response packet based on the header CRC; and (4) before receiving the data required to complete the command, arranging to return the data to the processor over the bus.

Abstract: A method is provided for processing a command issued by a processor over a bus. The method includes (1) transmitting the command to a remote node to obtain access to data required to complete the command; (2) receiving from the remote node a response packet including a header and a variable gap; and (3) before receiving the data required to complete the command, arranging to return the data to the processor over the bus.

Abstract: A method is provided for processing a command issued by a processor over a bus. The method includes (1) transmitting the command to a remote node to obtain access to data required to complete the command; (2) receiving from the remote node a response packet including a header and a header CRC; (3) validating the response packet including the header and the header CRC; (4) loading a timer to run until data required to complete the command is received or the timer expires; and (5) before receiving the data required to complete the command, arranging to return the data to the processor over the bus.

Abstract: A method, apparatus, and computer program are provided for assessing fairness, performance, and livelock in a logic development process utilizing comparative parallel looping. Multiple loop macros are generated, the multiple loop macros respectively correspond to multiple processor threads, and the multiple loop macros are parallel comparative loop macros. The multiple processor threads for the multiple loop macros are executed in which a common resource is accessed. A forward performance of each of the multiple processor threads is verified. The forward performance of the multiple processor threads is compared with each other. It is determined whether any of the multiple processor threads fails to meet a minimum loop count or a minimum loop time. It is determined whether any of the multiple processor threads exceeds a maximum loop count or a maximum loop time. It is recognized whether fairness is maintained during the execution of the multiple processor threads.

Abstract: A computer system having patrol snoop sequencer that sequences through addresses of cache lines held in a higher level cache, making snoop reads using those addresses to a lower level cache. If a particular cache line held in the higher level cache is not held in the lower level cache, the particular cache line is identified as an eviction candidate in the higher level cache when a new cache line must be loaded into the higher level cache.

Abstract: An early return indication is used to notify a first communications interface, prior to a response being received from any of a plurality of sources coupled to a second communications interface, that the return data can be used by the first communications interface when it is received thereby from a source of the return data if the source has an exclusive copy of the return data. By doing so, the first communications interface can often prepare for forwarding the return data over its associated communication link such that the data can be forwarded with little or no latency once the data is retrieved from its source, and may be able to initiate the return of data over the communication link prior to all responses being received from the other sources.

Abstract: A circuit and method for using hardware to calculate a first derivative of the number of performance events that occur in a microprocessor during a predetermined period of time. This first derivative indicates a frequency of such performance events, which can be used as either a predictor of future problems or needs, or may be used to invoke a corrective action.

Abstract: A method, system, and computer program product for tuning a set of chipset parameters to achieve optimal chipset performance under varying workload characteristics. A set of workload characteristics of a current workload type is determined. An instruction stream is generated using weighted parameters derived from the set of workload characteristics of the current workload type. A set of chipset parameters is generated and integrated within the instruction stream. The instruction stream is loaded to one or more processors and executed to collect and analyze performance data relating to the chipset's performance. The analysis includes comparing the set of performance data of a plurality of different instruction streams having the same set of workload characteristics. Each executed instruction stream is executed with at least one different combination of chipset parameters. A determination is made regarding which combination of chipset parameters provides the best performance data for the current workload.