Managing idle time and performing lookup operations to adapt to refresh requirements or operational rates of the particular associative memory or other devices used to implement the system

• US 7,028,136 B1
• Filed: 01/31/2003
• Issued: 04/11/2006
• Est. Priority Date: 08/10/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Eatherton, William N., Lee, Jaushin, Priyadarshan, Bangalore L.
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): Farrokh, Hashem
• Application Number:
  US10/355,694
• Time in Patent Office: 1,166 Days
• Field of Search: 711/108, 711105-106, 365/149, 365/222
• US Class Current: 711/108
• CPC Class Codes: G06F 16/90339 by using parallel associative memories or content-addressable memories

Abstract

Methods and apparatus are disclosed for, inter alia, managing idle time and performing lookup operations to adapt to refresh requirements and/or operational rates of the particular associative memory or other devices used to implement the system. A system typically a controller coupled to a circuit including includes multiple associative memories. The controller receives performance information from at least one of the associative memories and generates idle time corresponding to the performance information. This performance information may include an actual refresh requirement for each of the associate memories or the worst-case requirement of one of the associative memories, so that the controller can intermittently provide the actual refresh cycles required, if any, by a particular implementation. This performance information may indicate for some or all instructions the actual time required by a particular instruction, so that the controller can operate based on the actual time required, rather than inefficiently operating on a worst-case time defined in a specification or data sheet.

Claims

1. A method for managing idle time in a system including a controller coupled to a circuit, the circuit including a plurality of associative memories, the method comprising:

the controller receiving performance information from at least one of the plurality of associative memories; and

the controller generating idle time corresponding to said performance information;

a first associative memory of the plurality of associative memory collecting associative memory performance information from each of the other associative memories of the plurality of associative memories; and

wherein said receiving the performance information includes receiving from the first associative memory a worst case set of said associative memory performance information.

2. The method of claim 1, wherein said performance information includes a refresh requirement and said idle time includes a refresh idle time;

wherein said generating idle time includes intermittently generating the refresh idle time according to the refresh requirement; and

wherein at least one of the plurality of associative memories refreshes its memory during the refresh idle time.

3. The method of claim 2, further comprising:

the controller identifying a particular instruction to be performed; and

the controller communicating the particular instruction to at least one particular associative memory of the plurality of associative memories;

wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction; and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

4. The method of claim 1, further comprising:

the controller identifying a particular instruction to be performed; and

the controller communicating the particular instruction to at least one particular associative memory of the plurality of associative memories;

wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction; and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

5. A method for managing idle time in a system including a controller coupled to a circuit, the circuit including a plurality of associative memories, the method comprising:

the controller receiving performance information from at least one of the plurality of associative memories; and

the controller generating idle time corresponding to said performance information;

wherein said performance information includes a refresh requirement and said idle time includes a refresh idle time;

wherein said generating idle time includes intermittently generating the refresh idle time according to the refresh requirement; and

wherein at least one of the plurality of associative memories refreshes its memory during the refresh idle time.

6. The method of claim 5, further comprising:

the controller identifying a particular instruction to be performed; and

the controller communicating the particular instruction to at least one particular associative memory of the plurality of associative memories;

wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction; and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

7. A method for managing idle time in a system including a controller coupled to a circuit, the circuit including a plurality of associative memories, the method comprising:

the controller receiving performance information from at least one of the plurality of associative memories; and

the controller generating idle time corresponding to said performance information;

the controller identifying a particular instruction to be performed; and

the controller communicating the particular instruction to at least one particular associative memory of the plurality of associative memories;

wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction; and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

8. The method of claim 7, wherein said performance information includes a refresh indication received from a particular associative memory of the plurality of associative memories that said one of the plurality of associative memories requires time to refresh;

wherein said idle time includes a refresh idle time;

wherein said generating idle time includes generating the refresh idle time in response to receiving the refresh indication; and

wherein the particular associative memory refreshes at least a portion of its memory during the refresh idle time.

9. A method for managing idle time in a system including a controller coupled to a circuit, the circuit including a plurality of associative memories, the method comprising:

the controller receiving performance information from at least one of the plurality of associative memories; and

the controller generating idle time corresponding to said performance information;

wherein said performance information includes a refresh indication received from a particular associative memory of the plurality of associative memories that said one of the plurality of associative memories requires time to refresh;

wherein said idle time includes a refresh idle time;

wherein said generating idle time includes generating the refresh idle time in response to receiving the refresh indication; and

wherein the particular associative memory refreshes at least a portion of its memory during the refresh idle time.

10. A method for managing idle time in a system including a controller coupled to a circuit, the circuit including a plurality of associative memories, the method comprising:

the controller receiving performance information from at least one of the plurality of associative memories; and

the controller generating idle time corresponding to said performance information;

the controller identifying a particular instruction to be performed; and

the controller communicating the particular instruction and a particular instruction sync field to at least one particular associative memory of the plurality of associative memories;

said at least one particular associative memory generating a lookup result based on said particular instruction;

the controller receiving a result message including the lookup result and a result sync field; and

the controller validating the lookup result, said validating including comparing the particular instruction sync field with the result sync field.

11. The method of claim 10, wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction;

and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

12. The method of claim 10, wherein the particular instruction sync field comprises a single bit.

13. The method of claim 10, wherein the particular instruction sync field includes a plurality of bits.

14. The method of claim 10, further comprising generating a flush amount of idle time in response to determining that the particular instruction sync field does not equal the result sync field.

15. The method of claim 10, wherein said at least one particular associative memory of the plurality of associative memories copies the particular instruction sync field into the result message.

16. The method of claim 10, wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction;

and

wherein said generating idle time includes generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

17. The method of claim 10, wherein the result message includes a refresh indication;

wherein said idle time includes a refresh idle time;

wherein said generating idle time includes generating the refresh idle time in response to receiving the result message; and

wherein the particular associative memory refreshes at least a portion of its memory during the refresh idle time.

18. The method of claim 10, further comprising:

a first associative memory of the plurality of associative memory collecting associative memory performance information from each of the other associative memories of the plurality of associative memories; and

wherein said receiving the performance information includes receiving from the first associative memory a worst case set of said associative memory performance information.

19. The method of claim 10, wherein said performance information includes a refresh requirement and said idle time includes a refresh idle time;

wherein said generating idle time includes intermittently generating the refresh idle time according to the refresh requirement; and

wherein at least one of the plurality of associative memories refreshes its memory during the refresh idle time.

20. An apparatus for managing idle time, the apparatus comprising:

a controller; and

a circuit, coupled to the controller, including a plurality of associative memories;

wherein the controller includes;

means for receiving performance information from at least one of the plurality of associative memories; and

means for generating idle time corresponding to said performance information;

wherein a first associative memory of the plurality of associative memory includes means for collecting associative memory performance information from each of the other associative memories of the plurality of associative memories; and

wherein said means for receiving the performance information includes means for receiving from the first associative memory a worst case set of said associative memory performance information.

21. An apparatus for managing idle time, the apparatus comprising:

a controller; and

a circuit, coupled to the controller, including a plurality of associative memories;

wherein the controller includes;

means for receiving performance information from at least one of the plurality of associative memories; and

means for generating idle time corresponding to said performance information;

wherein said performance information includes a refresh requirement and said idle time includes a refresh idle time;

wherein said means for generating idle time includes means for intermittently generating the refresh idle time according to the refresh requirement; and

wherein at least one of the plurality of associative memories refreshes its memory during the refresh idle time.

22. An apparatus for managing idle time, the apparatus comprising:

a controller; and

a circuit, coupled to the controller, including a plurality of associative memories;

wherein the controller includes;

means for receiving performance information from at least one of the plurality of associative memories; and

means for generating idle time corresponding to said performance information;

wherein the controller includes;

means for identifying a particular instruction to be performed; and

means for communicating the particular instruction to at least one particular associative memory of the plurality of associative memories;

wherein a portion of said performance indication indicates a particular idle requirement for the particular instruction; and

wherein said means for generating idle time includes means for generating, after said communicating the instruction, idle time corresponding to the particular idle time requirement.

23. An apparatus for managing idle time, the apparatus comprising:

a controller; and

a circuit, coupled to the controller, including a plurality of associative memories;

wherein the controller includes;

means for receiving performance information from at least one of the plurality of associative memories; and

means for generating idle time corresponding to said performance information;

wherein said performance information includes a refresh indication received from a particular associative memory of the plurality of associative memories that said one of the plurality of associative memories requires time to refresh;

wherein said idle time includes a refresh idle time;

wherein said means for generating idle time includes means for generating the refresh idle time in response to receiving the refresh indication; and

wherein the particular associative memory refreshes at least a portion of its memory during the refresh idle time.

24. An apparatus for managing idle time, the apparatus comprising:

a controller; and

a circuit, coupled to the controller, including a plurality of associative memories;

wherein the controller includes;

means for receiving performance information from at least one of the plurality of associative memories; and

means for generating idle time corresponding to said performance information;

wherein the controller includes;

means for identifying a particular instruction to be performed; and

means for communicating the particular instruction and a particular instruction sync field to at least one particular associative memory of the plurality of associative memories, said at least one particular associative memory generating a lookup result based on said particular instruction;

means for receiving a result message including the lookup result and a result sync field; and

means for validating the lookup result, said means for validating including means for comparing the particular instruction sync field with the result sync field.