Abstract: In one embodiment, a node for a multi-node computer system comprises a coherence directory and a coherence controller. The coherence directory comprises a plurality of entries, wherein each entry corresponds to a respective coherence unit and stores a state identifying which nodes in the computer system are storing a copy of the coherence unit and further identifying a coherence state of the coherence unit according to a coherence protocol implemented in the computer system. Coupled to the directory and coupled to receive a first request for a requested coherence unit having a first entry in the coherence directory, the coherence controller is coupled to receive a second request for the requested coherence unit. The coherence controller is configured to selectively initiate coherence activity for the second request, if coherence activity for the first request is not yet complete, dependent on a type of the second request.

Abstract: In one embodiment, a processor comprises a coherence trap unit and a trap logic coupled to the coherence trap unit. The coherence trap unit is also coupled to receive data accessed in response to the processor executing a memory operation. The coherence trap unit is configured to detect that the data matches a designated value indicating that a coherence trap is to be initiated to coherently perform the memory operation. The trap logic is configured to trap to a designated software routine responsive to the coherence trap unit detecting the designated value. In some embodiments, a cache tag in a cache may track whether or not the corresponding cache line has the designated value, and the cache tag may be used to trigger a trap in response to an access to the corresponding cache line.

Abstract: In one embodiment, a node for a multi-node computer system comprises a coherence directory configured to store coherence states for coherence units in a local memory of the node and a coherence controller configured to receive a coherence request for a requested coherence unit. The requested coherence unit is included in a memory region that includes at least two coherence units, and the coherence controller is configured to read coherence states corresponding to two or more coherence units from the coherence directory responsive to the coherence request. The two or more coherence units are included in a previously-accessed memory region, and the coherence controller is configured to provide the requested coherence unit with a predicted coherence state responsive to the coherence states in the previously accessed memory region.