QoS scheduler and method for implementing quality of service with cached status array

• US 20030081544A1
• Filed: 11/01/2001
• Published: 05/01/2003
• Est. Priority Date: 11/01/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Norgaard, David Alan, Handlogten, Glen Howard, Mikos, James Francis, Goetzinger, William John
• Granted Patent: US 7,046,676 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 47/521 Static queue service slot or fixed bandwidth allocation
• CPC Class Codes: H04L 47/525 by redistribution of residual bandwidth
• CPC Class Codes: H04L 47/568 Calendar queues or timing rings

Abstract

A QoS scheduler, scheduling method, and computer program product are provided for implementing Quality-of-Service (QoS) scheduling with a cached status array. A plurality of calendars are provided for scheduling the flows. An active flow indicator is stored for each calendar entry in a calendar status array (CSA). A cache copy subset of the active flow indicators from the calendar status array (CSA) is stored in a cache. The calendar status array (CSA) is updated based upon a predefined calendar range and resolution. The cache copy subset of the active flow indicators from the calendar status array (CSA) is used to determine a given calendar for servicing. The subset of the active flow indicators from the calendar status array (CSA) is used to increment a current pointer (CP) by an identified number of positions up to a current time (CT) value, where the identified number of positions is equal to a variable number of inactive flow indicators up to the current time (CT) value and the identified number of positions has a maximum value equal to a number of entries in the cache.

Claims

1. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array and a plurality of calendars for scheduling said flows, said scheduling method comprising the steps of:

storing an active flow indicator for each calendar entry in a calendar status array (CSA);

storing a subset of said active flow indicators from said calendar status array (CSA) in a cache; and

updating calendar status array (CSA) based upon a predefined calendar range and resolution; and

utilizing said subset of said active flow indicators to determine a flow of a calendar for servicing.

2. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 1 wherein the step of storing said active flow indicator for each calendar entry in said calendar status array (CSA) includes the step of storing one bit for each calendar entry in said calendar status array (CSA).

3. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 1 wherein the step of storing said active flow indicator for each calendar entry in said calendar status array (CSA) includes the step of storing said active flow indicator for each weighted fair queue (WFQ) ring entry in a calendar status array (CSA).

4. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 1 wherein said cache includes a predefined number of bits for storing said cache copy subset for each of the calendars and wherein the step of storing said subset of said active flow indicators from said calendar status array (CSA) in a cache includes the step of utilizing a current pointer (CP) to a calendar entry and loading said subset of said active flow indicators from said calendar status array (CSA) starting at said current pointer (CP) CSA entry and increasing through said predefined number of CSA entries equal to said predefined number of bits.

5. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 4 wherein the step of loading said subset of said active flow indicators from said calendar status array (CSA) includes the step of using said current pointer (CP) to determine one of plurality of addressed portions of said calendar status array (CSA) to be accessed.

6. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 5 wherein said predefined number of bits for storing said subset for each of the calendars is thirty-two bits and wherein said calendar status array (CSA) includes four addressed portions of one hundred twenty-eight bits of said calendar status array (CSA), each said addressed portion accessible in one cycle.

7. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 1 wherein the step of storing said active flow indicator for each calendar entry in said calendar status array (CSA) includes the step for each of said plurality of calendars of storing said active flow indicator for each calendar entry in said calendar status array (CSA).

8. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 7 wherein said plurality of calendars include a low latency service (LLS) calendar, a normal latency service (NLS) calendar, and a peak bandwidth service (PBS) calendar and includes the step segmenting each of said plurality of calendars into epochs (0:

p), where epoch 0 has a highest resolution and a lowest range; and

epoch 1 through epoch p have a range of n(p) times a range of epoch 0; and

epoch 1 through epoch p have a resolution of 1/n**p times a resolution of epoch 0, where n is a scaling factor.

9. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 8 wherein the step of updating said calendar status array (CSA) based upon a predefined calendar range and resolution includes the step of updating said calendar status array (CSA) based upon said predefined calendar range and resolution of said epoch 0 through said epoch p.

10. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 8 wherein the step of updating said calendar status array (CSA) based upon said predefined calendar range and resolution of said epoch 0 through said epoch p for said low latency service (LLS) calendar, said normal latency service (NLS) calendar, and said peak bandwidth service (PBS) calendar.

11. A scheduling method for implementing Quality-of-Service (QoS) scheduling for a plurality of flows with a cached status array as recited in claim 1 includes the step of utilizing said subset of said active flow indicators for incrementing a current pointer (CP) by an identified number of positions up to a current time (CT) value, said identified number of positions equal to a variable number of inactive flow indicators up to said current time (CT) value and said identified number of positions having a maximum value equal to a number of entries in said cache.

12. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows comprising:

a queue manager;

a plurality of calendars coupled to said queue manager for scheduling said flows,

a calendar status array (CSA) coupled to said plurality of calendars for storing an active flow indicator for each calendar entry for each of said plurality of calendars;

a cache coupled to calendar status array (CSA) for storing a cache copy subset of said active flow indicators from said calendar status array (CSA); and

a calendar updating algorithm for updating calendar status array (CSA) based upon a predefined calendar range and resolution; and

said queue manager for utilizing said cache copy subset of said active flow indicators to determine a flow of a calendar for servicing.

13. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 12 wherein plurality of calendars include a low latency service (LLS) calendar, a normal latency service (NLS) calendar, and a peak bandwidth service (PBS) calendar.

14. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 12 wherein said calendar updating algorithm for updating calendar status array (CSA) based upon a predefined calendar range and resolution includes segmenting each of said plurality of calendars into epochs (0:

p), where epoch 0 has a highest resolution and a lowest range; and

epoch 1 through epoch p have a range of n(p) times a range of epoch 0; and

epoch 1 through epoch p have a resolution of 1/n**p times a resolution of epoch 0, where n is a scaling factor.

15. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 14 wherein said calendar updating algorithm for updating calendar status array (CSA) based upon a predefined calendar range and resolution is based upon a priority of said low latency service (LLS) calendar, said normal latency service (NLS) calendar, and said peak bandwidth service (PBS) calendar and a number of said epoch.

16. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 14 wherein said calendar updating algorithm for updating calendar status array (CSA) based upon a predefined calendar range and resolution accesses said calendar status array (CSA) by an ascending order said epoch for each of said calendars in an order of said low latency service (LLS) calendar, said normal latency service (NLS) calendar, and said peak bandwidth service (PBS) calendar.

17. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 14 includes a current pointer (CP) to determine one of a plurality of addressed portions of said calendar status array (CSA) to be accessed in a system cycle.

18. A QoS scheduler for implementing Quality-of-Service (QoS) scheduling for a plurality of flows as recited in claim 14 includes current pointer (CP) incrementing means utilizing said cache copy subset of said active flow indicators for incrementing a current pointer (CP) by an identified number of positions up to a current time (CT) value, said identified number of positions equal to a variable number of inactive flow indicators up to said current time (CT) value and said identified number of positions having a maximum value equal to a number of entries in said cache.

19. A computer program product for implementing Quality-of-Service (QoS) scheduling of a plurality of flows with a cached status array and a plurality of calendars for scheduling said flows in a scheduler, said computer program product including a plurality of computer executable instructions stored on a computer readable medium, wherein said instructions, when executed by said scheduler, cause said scheduler to perform the steps of:

storing an active flow indicator for each calendar entry for each of said plurality of calendars in a calendar status array (CSA);

storing a subset of said active flow indicators from said calendar status array (CSA) for each of said plurality of calendars in a cache; and

updating calendar status array (CSA) based upon a predefined calendar range and resolution for each of said plurality of calendars; and

utilizing said subset of said active flow indicators for each of said plurality of calendars to determine a flow of a calendar for servicing.

20. A computer program product for implementing Quality-of-Service (QoS) scheduling of a plurality of flows with a cached status array and a plurality of calendars for scheduling said flows in a scheduler as recited in claim 19 wherein said instructions, when executed by said scheduler, cause said scheduler to perform the steps of utilizing said subset of said active flow indicators for incrementing a current pointer (CP) by an identified number of positions up to a current time (CT) value, said identified number of positions equal to a variable number of inactive flow indicators up to said current time (CT) value and said identified number of positions having a maximum value equal to a number of entries in said cache.