Restore PCIe transaction ID on the fly
View Patent ↗Restoring retired transaction identifiers (TID) associated with Direct Memory Access (DMA) commands without waiting for all DMA traffic to terminate is disclosed. A scoreboard is used to track retired TIDs and selectively restore retired TIDs on the fly. DMA engines fetch a TID, and use it to tag every DMA request. If the request is completed, the TID can be recycled to be used to tag a subsequent request. However, if a request is not completed, the TID is retired. Retired TIDs can be restored without having to wait for DMA traffic to end. Any retired TID value may be mapped to a bit location inside a scoreboard. All processors in the system may have access to read and clear the scoreboard. Clearing the TID scoreboard may trigger a DMA engine to restore the TID mapped to that location, and the TID may be used again.
1. A system for managing retired transaction identifiers (TIDs), the system comprising:
a memory operable to maintain an individual status of each TID of a plurality of TIDs, the plurality of TIDs comprising one or more retired TIDs, wherein a TID is retired if an associated command does not complete; and
a processor operable to selectively restore a first retired TID of the one or more retired TIDs, wherein the first retired TID is selectively restored without requiring the processor to be reset.
2. The system of claim 1 , wherein the first retired TID is selectively restored without disturbing active DMA operations.
3. The system of claim 1 , wherein the first retired TID is selectively restored without impacting new DMA commands.
4. The system of claim 1 , wherein the first retired TID is selectively restored without impacting future commands that are in a queue for operation.
5. The system of claim 1 , wherein the first retired TID is selectively restored without depending on a status of an active DMA operation.
6. The system of claim 1 , wherein the processor is operable to periodically poll the memory to determine when the first retired TID should be restored.
7. The system of claim 1 , wherein the first retired TID is selectively restored based on a number of remaining available TIDs in the one or more retired TIDs.
8. The system of claim 1 , wherein the first retired TID is selectively restored based on a ratio of the number of retired TIDs to the number of available TIDs.
9. The system of claim 1 , wherein the first retired TID is selectively restored based on a predetermined rate.
10. The system of claim 1 , wherein the processor is incorporated within a host bus adapter (HBA).
11. A method for managing transaction identifiers (TIDs), the method comprising:
maintaining an individual status of each TID of a plurality of TIDs, the plurality of TIDs comprising one or more retired TIDs, wherein a TID is retired if an associated command does not complete; and
selectively restoring a first retired TID of the one or more retired TIDs, wherein the first retired TID is selectively restored without requiring the processor to be reset.
12. The method of claim 11 , wherein the first retired TID is selectively restored without disturbing active DMA operations.
13. The method of claim 11 , wherein the first retired TID is selectively restored without impacting new DMA commands.
14. The method of claim 11 , wherein the first retired TID is selectively restored without impacting future commands that are in a queue for operation.
15. The method of claim 11 , wherein the first retired TID is selectively restored without depending on a status of an active DMA operation.
16. The method of claim 11 , wherein the method comprises periodically polling to determine when the first retired TID should be restored.
17. The method of claim 11 , wherein the first retired TID is selectively restored based on a number of remaining available TIDs in the one or more retired TIDs.
18. The method of claim 11 , wherein the first retired TID is selectively restored based on a ratio of the number of retired TIDs to the number of available TIDs.
19. The method of claim 11 , wherein the first retired TID is selectively restored based on a predetermined rate.
20. The method of claim 11 , wherein the processor is incorporated within a host bus adapter (HBA).