Apparatus, system and method for limiting latency

• US 20040117791A1
• Filed: 12/17/2002
• Published: 06/17/2004
• Est. Priority Date: 12/17/2002
• Status: Abandoned Application

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Prasad, Ajith, Moleyar, Prabhanjan, Philip, Jain, Ayyasamy, Ananthan
• Application Number:
  US10/321,054
• Publication Number:
  US 20040117791A1
• Time in Patent Office: Days
• US Class Current: 718/100
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues

Abstract

A method, apparatus, and system for limiting latency.

Claims

1. A queue latency limitation method, comprising:

storing a time stamp associated with a task when the task is placed in the queue;

calculating a latency period by comparing the time stamp to a timer value; and

servicing the task based on the latency period calculated.

2. The method of claim 1, wherein the timer value increments as time passes.

3. The method of claim 2, wherein the timer value periodically returns to a minimum value.

4. The method of claim 3, wherein the minimum value is zero.

5. The method of claim 4, wherein a one is placed in the most significant position of the timer value when the time stamp value exceeds the timer value.

6. The method of claim 4, wherein a one is placed in the most significant position of the timer value when the time stamp value is equal to the timer value.

7. The method of claim 1, further comprising removing the task from the queue.

8. The method of claim 1, wherein servicing the task includes reading the task from the queue and performing the task.

9. The method of claim 1, wherein a plurality of tasks reside in the queue and the time stamp compared is a time stamp associated with a task that has resided in the queue for the longest time.

10. The method of claim 1, wherein the task and the time stamp are stored in a field in the queue.

11. The method of claim 1, wherein the task is serviced when the latency period reaches a maximum amount of time that a low priority task is desired to be held in the queue.

12. The method of claim 1, wherein the latency period is calculated by subtracting the time stamp from the timer value.

13. The method of claim 1, wherein the timer value decrements as time passes.

14. A queue latency limitation device, comprising:

a queue having a plurality of task fields, each task field having a data field containing data and a time stamp field containing a value corresponding to a time when the data was placed in the data field, the task field that has been in the queue for the longest time being a head task field;

a timer having an incrementing value;

control logic determining a latency period by comparing the time stamp value in the head task field to the timer value; and

an arbiter that services the data field in the head task field when the latency period is greater than a predetermined time.

15. The queue latency limitation device of claim 14, wherein the timer value periodically returns to a minimum value.

16. The queue latency limitation device of claim 15, wherein the minimum value is zero.

17. The queue latency limitation device of claim 16, wherein a one is placed in the most significant position of the timer value when the time stamp value exceeds the timer value.

18. The queue latency limitation device of claim 16, wherein a one is placed in the most significant position of the timer value when the time stamp value is equal to the timer value.

19. The queue latency limitation device of claim 14, wherein a plurality of tasks reside in the queue and the time stamp compared is a time stamp associated with a task that has resided in the queue for the longest time.

20. The queue latency limitation device of claim 14, wherein comparing the time stamp value in the head task field to the timer value further comprises subtracting the time stamp value in the head task field from the timer value.

21. An article of manufacture comprising:

a computer readable medium having stored thereon instructions which, when executed by a processor, cause the processor to;

store a time stamp associated with a task when the task is placed in the queue;

calculate a latency period by comparing the time stamp to a timer value; and

service the task when the latency period is greater than a predetermined time.

22. The article of manufacture of claim 21, wherein a plurality of tasks reside in the queue and a time stamp associated with a task that has resided in the queue for the longest time is subtracted from the timer value when calculating the latency period.

23. The article of manufacture of claim 21, wherein the task is serviced when the latency period is greater than or equal to a predetermined time.

24. A queue latency limitation system, comprising:

a first queue having a first priority and a plurality of task fields;

a second queue having a second priority lower than the first priority and a plurality of task fields, each task field having a data field containing data and a time stamp field containing a value corresponding to a time when the data was placed in the data field, the task field that has been in the queue for the longest time being a head task field for the second queue;

a timer having an incrementing value;

control logic determining a latency period by comparing the time stamp value in the head task field for the second queue to the timer value; and

an arbiter that services the data field in the head task field for the second queue when the latency period is greater than a predetermined time regardless of whether a task exists in the first queue.

25. The queue latency limitation system of claim 24, wherein comparing the time stamp value in the head task field for the second queue to the timer value further comprises subtracting the time stamp value in the head task field for the second queue from the timer value.

26. A service class for network traffic with limited service latency on a low priority queue, comprising:

associating a time stamp with a task when the task is placed in the queue;

calculating a latency period by comparing the time stamp to a timer value; and

servicing the task based on the latency period calculated.

27. The service class of claim 26, wherein a plurality of tasks reside in the low priority queue and the time stamp compared is a time stamp associated with a task that has resided in the queue for the longest time.

28. The service class of claim 26, wherein comparing the time stamp value to the timer value further comprises subtracting the time stamp value from the timer value.