QoS inband upgrade

• US 9,053,058 B2
• Filed: 12/20/2012
• Issued: 06/09/2015
• Est. Priority Date: 12/20/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Saund, Gurjeet S., Balkan, Deniz, Wong, Kevin C.
• Primary Examiner(s): HO, DUC CHI
• Application Number:
  US13/721,665
• Publication Number:
  US 20140181824A1
• Time in Patent Office: 901 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 13/14 Handling requests for interconnection or transfer
• CPC Class Codes: G06F 13/1642 with request queuing
• CPC Class Codes: G06F 13/1673 using buffers

Abstract

Systems and methods for upgrading QoS levels of older transactions based on the presence of higher level QoS transactions in a given queue. A counter may be maintained to track the number of transactions in a queue that are assigned a corresponding QoS level. Each separate QoS level can have a corresponding counter. When a transaction is received by the queue, the counter corresponding to the QoS level of the transaction is incremented. When a transaction leaves the queue, the transaction is upgraded to the highest QoS level with a non-zero counter. Also, when the transaction leaves the queue, the counter corresponding to the original QoS level of the transaction is decremented.

Claims

1. A link interface unit comprising:

a queue, wherein the queue is configured to store a plurality of transactions; and

control logic, wherein the control logic is coupled to the queue, and wherein the control logic is configured to;

maintain a first counter to track a number of transactions with a first quality of service (QoS) level that are stored in the queue; and

upgrade a QoS level of a given transaction to the first QoS level responsive to;

reading the given transaction out of the queue, wherein the given transaction has a QoS level lower than the first QoS level; and

determining a value of the first counter is non-zero.

2. The link interface unit as recited in claim 1, wherein the first QoS level is a highest possible QoS level.

3. The link interface unit as recited in claim 2, wherein the control logic is further configured to:

increment the first counter responsive to receiving a transaction with the first QoS level at the queue; and

decrement the first counter responsive to reading a transaction with an original QoS level equal to the first QoS level out of the queue.

4. The link interface unit as recited in claim 3, wherein the control logic is further configured to:

maintain a second counter to track a number of transactions with a second QoS level that are stored in the queue, wherein the second QoS level is below the first QoS level; and

upgrade a QoS level of a given transaction to the second QoS level responsive to;

reading the given transaction out of the queue, wherein the given transaction has a QoS level lower than the second QoS level;

determining a value of the second counter is non-zero; and

determining a value of the first counter is zero.

5. The link interface unit as recited in claim 2, wherein the link interface unit comprises a transmit unit and a receive unit, wherein the queue and the control logic are located in the receive unit, and wherein the receive unit is configured to forward the given transaction to a given agent after upgrading the QoS level of the given transaction to the first QoS level.

6. The link interface unit as recited in claim 1, wherein the control logic is further configured to upgrade the QoS level of the given transaction to the first QoS level responsive to receiving a sideband signal set to the first QoS level.

7. A method comprising:

selecting a first transaction for transmission out of a queue;

detecting an indication that there are one or more younger transactions in the queue that have a higher QoS level than the first transaction;

upgrading a quality of service (QoS) level of the first transaction responsive to detecting said indication; and

reading the first transaction out of the queue with the upgraded QoS level.

8. The method as recited in claim 7, wherein transactions may be assigned any of a plurality of QoS levels.

9. The method as recited in claim 8, wherein the plurality of QoS levels include green, yellow, and red.

10. The method as recited in claim 8, further comprising maintaining a counter for each upper-level QoS level, and wherein detecting said indication comprises checking if any counters corresponding to the upper-level QoS levels have a non-zero value.

11. The method as recited in claim 10, further comprising incrementing a counter corresponding to a first upper-level QoS level responsive to receiving a given transaction at the queue, wherein the given transaction is assigned the first upper-level QoS level.

12. The method as recited in claim 11, further comprising decrementing the counter corresponding to the first upper-level QoS level responsive to reading the given transaction out of the queue.

13. A method comprising:

maintaining a plurality of counters to track a number of transactions in a queue at each quality of service (QoS) level of a plurality of QoS levels;

selecting a given transaction in the queue for de-queuing, the given transaction having a first QoS level;

identifying one or more of said counters with a non-zero value that correspond to QoS levels higher than the first QoS level; and

upgrading a QoS level of the given transaction to a highest QoS level that corresponds to the one or more counters.

14. The method as recited in claim 13, further comprising incrementing a given counter responsive to receiving a transaction with a corresponding QoS level at the queue.

15. The method as recited in claim 14, further comprising decrementing the given counter responsive to reading a transaction with an original QoS level equal to the corresponding QoS level out of the queue.

16. The method as recited in claim 15, wherein the queue is located in a receive unit of a first link interface unit.

17. The method as recited in claim 16, wherein the transaction received by the receive unit of the first link interface unit is sent from a transmit unit of a second link interface unit.

18. The method as recited in claim 13, further comprising:

receiving a first transaction with a first QoS level at the queue;

incrementing a first counter corresponding to the first QoS level;

reading the first transaction out of the queue;

upgrading the first transaction to a second QoS level responsive to determining a second counter corresponding to the second QoS level is non-zero; and

decrementing the first counter.

19. The method as recited in claim 18, wherein the second QoS level is higher than the first QoS level, and wherein the second counter corresponds to a highest QoS level with a non-zero counter.

20. An apparatus comprising:

a queue, wherein the queue is configured to store a plurality of transactions;

one or more counters, wherein each counter is configured to track a number of transactions in the queue at a corresponding quality of service (QoS) level; and

wherein the apparatus is configured to upgrade a QoS level of a given transaction selected for dequeueing responsive to determining a younger transaction enqueued in the queue has a higher QoS level.

21. The apparatus as recited in claim 20, wherein each transaction is assigned a QoS level.

22. The apparatus as recited in claim 21, wherein the apparatus is further configured to upgrade a QoS level of a first transaction to a first QoS level responsive to determining the first QoS level is a highest QoS level with a non-zero counter.

23. The apparatus as recited in claim 22, wherein a sideband signal is set to a QoS level lower than the first QoS level.

24. The apparatus as recited in claim 22, wherein a first counter corresponding to the first QoS level remains the same and wherein a second counter corresponding to the QoS level of the first transaction is decremented when the first transaction is read out of the queue.