Method and apparatus for transaction tag assignment and maintenance in a distributed symmetric multiprocessor system
View Patent ↗A distributed system structure for a large-way, symmetric multiprocessor system using a bus-based cache-coherence protocol is provided. The distributed system structure contains an address switch, multiple memory subsystems, and multiple master devices, either processors, I/O agents, or coherent memory adapters, organized into a set of nodes supported by a node controller. The node controller receives transactions from a master device, communicates with a master device as another master device or as a slave device, and queues transactions received from a master device. Since the achievement of coherency is distributed in time and space, the node controller helps to maintain cache coherency. A transaction tag format for a standard bus protocol is expanded to ensure unique transaction tags are maintained throughout the system. A sideband signal is used for intervention and Reruns to preserve transaction tags at the node controller in certain circumstances.
1. A method of managing transaction tags in a multiprocessor system, the transactions tags identifying transactions in the multiprocessing system, the method comprising the steps of:
receiving a transaction from a master device, wherein the transaction comprises a port-bus transaction tag, wherein the port-bus transaction tag comprises a source identifier that uniquely identifies the master device within a node that issued the transaction, and a transaction identifier that uniquely identifies the transaction in a set of transactions issued by the master device;
translating the port-bus transaction tag for the transaction to a system-level transaction tag by adding a node identifier to the port-bus transaction tag to form the system-level transaction tag, the node identifier being an identifier that uniquely identifies a node having a node controller that the master device is connected to;
registering the transaction in an entry in a transaction registry, the transaction registry being a place for registering transactions;
broadcasting a second transaction, wherein the second transaction comprises the system-level transaction tag for the transaction that is broadcast as a part of the broadcasting step; and
registering the second transaction in an entry in a second transaction registry, the second transaction registry being a place for registering transactions and associating address portions of transactions with corresponding data portions of transactions of a split transaction bus.
2. The method of claim 1 further comprising:
storing the port-bus transaction tag for the transaction in the entry in the transaction registry.
3. The method of claim 1 further comprising:
translating the system-level transaction tag for the second transaction to a snoop tag;
storing the system-level transaction tag for the second transaction in the entry in the second transaction registry; and
forwarding the second transaction with the snoop tag to master devices.
4. The method of claim 3 further comprising:
receiving intervention data;
matching a system transaction tag for the intervention data with the port-bus transaction tag for the transaction in the entry in the transaction registry; and
forwarding the intervention data with the port-bus transaction tag for the transaction.
5. The method of claim 3 further comprising:
receiving a Rerun command;
matching a system transaction tag for the Rerun command with the port-bus transaction tag for the transaction in the entry in the transaction registry;
reissuing the transaction with its port-bus transaction tag with an address modifier bit set.
6. The method of claim 1 wherein the multiprocessor system comprises a plurality of master devices and a plurality of node controllers, wherein the node controller organizes a subset of one or more of the plurality of master devices into a node, and a plurality of bidirectional master device buses, and wherein a master device bus connects one or more master devices within a node to a port of the node controller, and wherein the plurality of node controllers are coupled together by another bus having a wider bus width than individual ones of the master device buses.
7. An apparatus for managing transaction tags in a multiprocessor system, the transactions tags identifying transactions in the multiprocessing system, the apparatus comprising:
first receiving means for receiving a transaction from a master device, wherein the transaction comprises a port-bus transaction tag, wherein the port-bus transaction tag comprises a source identifier that uniquely identifies the master device within a node that issued the transaction, and a transaction identifier that uniquely identifies the transaction in a set of transactions issued by the master device;
first translating means for translating the port-bus transaction tag for the transaction to a system-level transaction tag by adding a node identifier to the port-bus transaction tag to form the system-level transaction tag, the node identifier being an identifier that uniquely identifies a node having a node controller that the master device is connected to;
first registering means for registering the transaction in an entry in a transaction registry, the transaction registry being a place for registering transactions;
broadcasting means for broadcasting a second transaction, wherein the second transaction comprises the system-level transaction tag for the transaction; and
first registering means for registering the second transaction in an entry in a second transaction registry, the second transaction registry being a place for registering transactions and associating address portions of transactions with corresponding data portions of transactions of a split transaction bus.
8. The apparatus of claim 7 further comprising:
first storing means for storing the port-bus transaction tag for the transaction in the entry in the transaction registry.
9. The apparatus of claim 7 further comprising:
first translating means for translating the system-level transaction tag for the second transaction to a snoop tag;
first storing means for storing the system-level transaction tag for the second transaction in the entry in the second transaction registry; and
forwarding means for forwarding the second transaction with the snoop tag to master devices.
10. The apparatus of claim 9 further comprising:
first receiving means for receiving intervention data;
first matching means for matching a system transaction tag for the intervention data with the port-bus transaction tag for the transaction in the entry in the transaction registry;
forwarding means for forwarding the intervention data with the port-bus transaction tag for the transaction.
11. The apparatus of claim 9 further comprising:
second receiving means for receiving a Rerun command;
second matching means for matching a system transaction tag for the Rerun command with the port-bus transaction tag for the transaction in the entry in the transaction registry;
reissuing means for reissuing the transaction with its port-bus transaction tag with an address modifier bit set.
12. The apparatus of claim 7 wherein the multiprocessor system comprises a plurality of master devices and a plurality of node controllers, wherein the node controller organizes a subset of one or more of the plurality of master devices into a node, and a plurality of bidirectional master device buses, and wherein a master device bus connects one or more master devices within a node to a port of the node controller, and wherein the plurality of node controllers are coupled together by another bus having a wider bus width than individual ones of the master device buses.
13. A computer program product in a computer-readable medium for use in a multiprocessor system for managing transaction tags in the multiprocessor system, the transactions tags identifying transactions in the multiprocessing system, the computer program product comprising:
instructions for receiving a transaction from a master device, wherein the transaction comprises a port-bus transaction tag, wherein the port-bus transaction tag comprises a source identifier that uniquely identifies the master device within a node that issued the transaction, and a transaction identifier that uniquely identifies the transaction in a set of transactions issued by the master device;
instructions for translating the port-bus transaction tag for the transaction to a system-level transaction tag by adding a node identifier to the port-bus transaction tag to form the system-level transaction tag, the node identifier being an identifier that uniquely identifies a node having a node controller that the master device is connected to;
instructions for registering the transaction in an entry in a transaction registry, the transaction registry being a place for registering transactions;
instructions for broadcasting a second transaction, wherein the second transaction comprises the system-level transaction tag for the transaction; and
instructions for registering the second transaction in an entry in a second transaction registry, the second transaction registry being a place for registering transactions and associating address portions of transactions with corresponding data portions of transactions of a split transaction bus.
14. The computer program product of claim 13 further comprising:
instructions for storing the port-bus transaction tag for the transaction in the entry in the transaction registry.
15. The computer program product of claim 13 further comprising:
instructions for translating the system-level transaction tag for the second transaction to a snoop tag;
instructions for storing the system-level transaction tag for the second transaction in the entry in the second transaction registry; and
instructions for forwarding the second transaction with the snoop tag to master devices.
16. The computer program product of claim 15 further comprising:
instructions for receiving intervention data;
instructions for matching a system transaction tag for the intervention data with the port-bus transaction tag for the transaction in the entry in the transaction registry;
instructions for forwarding the intervention data with the port-bus transaction tag for the transaction.
17. The computer program product of claim 15 further comprising:
instructions for receiving a Rerun command;
instructions for matching a system transaction tag for the Rerun command with the port-bus transaction tag for the transaction in the entry in the transaction registry;
instructions for reissuing the transaction with its port-bus transaction tag with an address modifier bit set.
18. The computer program product of claim 13 wherein the multiprocessor system comprises a plurality of master devices and a plurality of node controllers, wherein the node controller organizes a subset of one or more of the plurality of master devices into a node, and a plurality of bidirectional master device buses, and wherein a master device bus connects one or more master devices within a node to a port of the node controller, and wherein the plurality of node controllers are coupled together by another bus having a wider bus width than individual ones of the master device buses.
19. The method of claim 1 , wherein the system-level transaction tag comprises an index to the entry of the transaction in the transaction registry.
20. The system of claim 7 , wherein the system-level transaction tag comprises an index to the entry of the transaction in the transaction registry.
21. The computer program product of claim 13 , wherein the system-level transaction tag comprises an index to the entry of the transaction in the transaction registry.