Weighted fair queue having extended effective range

Abstract

A scheduler for a network processor includes a scheduling queue in which weighted fair queuing is applied to define a sequence in which flows are to be serviced. The scheduling queue includes at least a first subqueue and a second subqueue. The first subqueue has a first range and a first resolution, and the second subqueue has an extended range that is greater than the first range and a lower resolution that is less than the first resolution. Flows that are to be enqueued within the range of highest precision to the current pointer of the scheduling queue are attached to the first subqueue. Flows that are to be enqueued outside the range of highest precision from the current pointer of the scheduling queue are attached to the second subqueue. Numerous other aspects are provided.

Description

[0001] The present application is a continuation of and claims priority from U.S. patent application Ser. No. 10 / 016,518, filed Nov. 1, 2001 which is hereby incorporated by reference herein in its entirety. CROSS REFERENCE TO RELATED PATENT APPLICATIONS [0002] The present application is related to the following U.S. patent applications, each of which is hereby incorporated by reference herein in its entirety: U.S. patent application Ser. No. 10 / 015,994, filed Nov. 1, 2001, titled “WEIGHTED FAIR QUEUE SERVING PLURAL OUTPUT PORTS” (IBM Docket No. ROC920010200US1); U.S. patent application Ser. No. 10 / 015,760, filed Nov. 1, 2001, titled “WEIGHTED FAIR QUEUE HAVING ADJUSTABLE SCALING FACTOR” (IBM Docket No. ROC920010201US1); U.S. patent application Ser. No. 10 / 002,085, filed Nov. 1, 2001, titled “EMPTY INDICATORS FOR WEIGHTED FAIR QUEUES” (IBM Docket No. ROC920010202US1); U.S. patent application Ser. No. 10 / 004,373, filed Nov. 1, 2001, titled “QoS SCHEDULER AND METHOD FOR IMPLEMENTIN...

AI Technical Summary

Benefits of technology

[0024] The first and second subqueues may, but need not, have equal numbers of slots. In one embodiment, the range of the second subqueue may be sixteen times the range of the first subqueue, and the resolution of the second subqueue may be one-sixteenth of the resolution of the first subqueue. Other relationships between range and / or resolution may be employed. For example, the range of the second subqueue may be larger than the range of the first subqueue by any amount, and the resolution of the second subqueue may be less than the resolution of the first subqueue by any amount (e.g., regardless of the amount by which the range of the second subqueue exceeds the range of the first subqueue). However, in embodiments of the invention wherein the first and the second subqueues have the same number of slots, maintaining a direct inverse relationship between the resolution and the range of the second subqueue allows for an “effective” increase in scheduling queue range without an accompanying increase in consumed chip area.

[0027] By configuring a scheduling queue as two or more subqueues having different ranges and resolutions, the present invention allows the scheduling queue to offer an enhanced range, without adding to the total number of queue slots, while providing much of the benefit of high resolution.

Problems solved by technology

However, this has disadvantages in terms of increased chip area, greater manufacturing cost and power consumption, and increased queue searching time.

However, if resolution is decreased, flows that should be assigned different priorities according to their respective QoS may appear to “tie” by being assigned to the same slot, thereby improperly being assigned essentially equal service priority.

Images