Method for reducing processing latency in a multi-thread packet processor with at least one re-order queue

• US 9,083,563 B2
• Filed: 06/29/2012
• Issued: 07/14/2015
• Est. Priority Date: 06/29/2012
• Status: Active Grant

• Current Assignee: Extreme Networks, Inc.
• Original Assignee: Avaya Incorporated
• Inventors: Assarpour, Hamid
• Primary Examiner(s): Rinehart, Mark
• Assistant Examiner(s): YEUNG, MANG HANG
• Application Number:
  US13/539,207
• Publication Number:
  US 20140003439A1
• Time in Patent Office: 1,110 Days
• Field of Search: 370/230, 370/230.1, 370/231, 370/235, 370/394, 370412-417, 370/440
• US Class Current: 1/1
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 2213/3808 Network interface controller
• CPC Class Codes: H04L 12/6418 Hybrid transport

Abstract

Packet processing is broken into two or more stages. In particular, the network processing unit 26 performs a first stage of packet processing related to packet forwarding and packet modification, and then performs a second stage of packet processing unrelated to packet forwarding and packet modification. Example processes unrelated to packet forwarding and packet modification may include state updates on the network element, such as statistics counter updates, stateful flow tracking, IPFix processing, MAC learning, and other processes important to operation of the network element, but which do not affect the appearance of the packet (e.g. packet format) and which do not affect the forwarding decision of the packet. Once the first stage of packet processing related to packet forwarding and packet modification has been completed, the flag associated with the packet is cleared in the scoreboard, to allow the packet to be transmitted from the reorder queue.

Claims

1. A method of reducing processing latency in a multi-thread packet processor with at least one first-in-first-out re-order queue, the method comprising the steps of:

implementing stage 1 packet processing;

marking a packet as ready to be transmitted from the first-in-first-out re-order queue in a scoreboard table;

reading an identifier at the head of the re-order queue,

using the identifier to locate a flag in the scoreboard table,

reading the flag in the scoreboard table associated with the identifier, and

transmitting the packet if the flag in the scoreboard table indicates that stage 1 processing has been completed for the packet; and

implementing stage 2 packet processing after the step of marking the packet for transmission from the re-order queue.

2. The method of claim 1, wherein stage 1 packet processing and stage 2 packet processing collectively form a multi-stage packet processing pipeline, in which one stage of packet processing occurs at each stage of the pipelined process.

3. The method of claim 2, wherein the packet processor maintains a separate thread for each packet in the pipeline.

4. The method of claim 1, wherein the stage 1 packet processing contains processing stages associated with actions that must be implemented in connection with forwarding the packet.

5. The method of claim 4, wherein the stage 1 packet processing includes operations associated with packet formatting and making packet forwarding decisions.

6. The method of claim 1, wherein the stage 2 packet processing contains processing stages associated with actions that are not required to be implemented in connection with forwarding the packet.

7. The method of claim 6, wherein the stage 2 packet processing includes operations not associated with packet formatting and not associated with making packet forwarding decisions.

8. The method of claim 7, wherein the stage 2 packet processing includes operations that include network element state updates.

9. The method of claim 1, wherein the scoreboard table contains a set of flags, each flag representing a state of one of the threads of the multi-thread packet processor.

10. The method of claim 9, wherein the flags are used to mark the packets as ready to be transmitted from the re-order queue.

11. The method of claim 1, further comprising the steps of receiving a plurality of packets, assigning an identifier to each packet, and including the identifier in the re-order queue.

12. The method of claim 1, further comprising transmitting a packet identified via the identifier at the head of the re-order queue only if the packet at the head of the re-order queue is marked as ready to be transmitted.

13. The method of claim 1, wherein at least some of the processes associated with of implementing stage 2 packet processing occur after the step of transmitting the packet from the re-order queue.

14. A network element, comprising:

a multi-threaded packet processor, each thread of the multi-threaded packet processor being assigned to a separate packet, the processor being configured to implemented a pipelined packet processing scheme in which one stage of packet processing occurs at each stage of the pipelined packet processing scheme;

a scoreboard table containing flags associated with packets assigned to threads in the multi-threaded packet processor; and

a re-order queue maintaining packet order;

wherein the network element is configured to identify a packet at a head of the re-order queue, check one of the flags in the scoreboard table associated with the packet at the head of the re-order queue to determine if the packet is ready to be forwarded, and forward the packet only when the one of the flags in the scoreboard table associated with the packet at the head of the re-order queue indicates that the packet is ready to be forwarded; and

wherein the multi-threaded packet processor will cause the one of the flags in the scoreboard table associated with the packet at the head of the re-order queue to indicate that the packet is ready to be forwarded prior to completion of all stages of packet processing of the pipelined packet processing scheme.

15. The method of claim 14, wherein a first set of stages of packet processing associated with packet formatting and making packet forwarding decisions is implemented before the one of the flags in the scoreboard table associated with the packet at the head of the re-order queue is caused to indicate that the packet is ready to be forwarded.

16. The method of claim 15, wherein a second set of stages of packet processing associated with actions that are not required to be implemented in connection with forwarding the packet are implemented after the one of the flags in the scoreboard table associated with the packet at the head of the re-order queue is caused to indicate that the packet is ready to be forwarded.

17. The method of claim 14, wherein the multi-threaded packet processor will complete at least some of the stages of packet processing associated with the packet at the head of the re-order queue after forwarding the packet at the head of the re-order queue.