International Business Machines Corporation

John Peyton Bannister

David Brian Glasco

Gary Dale Carpenter

Mark Edward Dean

Richard Nicholas Iachetta, Jr

A method for avoiding data loss due to cancelled transactions within a non-uniform memory access (NUMA) data processing system is disclosed. A NUMA data processing system includes a node interconnect to which at least a first node and a second node are coupled. The first and the second nodes each includes a local interconnect, a system memory coupled to the local interconnect, and a node controller interposed between the local interconnect and a node interconnect. The node controller detects certain situations which, due to the nature of a NUMA data processing system, can lead to data loss. These situations share the common feature that a node controller ends up with the only copy of a modified cache line and the original transaction that requested the modified cache line may not be issued again with the same tag or may not be issued again at all. The node controller corrects these situations by issuing its own write transaction to the system memory for that modified cache line using its own tag, and then providing the data the modified cache line is holding. This ensures that the modified data will be written to the system memory.

Method and system for avoiding data loss due to cancelled transactions within a non-uniform memory access system

A data recirculation apparatus for a data processing system includes at least one output buffer from which data are output onto an interconnect, a plurality of input storage areas from which data are selected for storage within the output buffer, and selection logic that selects data from the plurality of input storage areas for storage within the output buffer. In addition, the data recirculation apparatus includes buffer control logic that, in response to a determination that a particular datum has stalled in the output buffer, causes the particular datum to be removed from the output buffer and stored in one of the plurality of input storage areas. In one embodiment, the recirculated data has a dedicated input storage area.

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Austin, TX, United States of America

John Peyton Bannister