Method and apparatus for prioritizing delivery of data transfer requests

• US 6,295,553 B1
• Filed: 12/22/1998
• Issued: 09/25/2001
• Est. Priority Date: 12/22/1998
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: Unisys Corporation
• Inventors: Gilbertson, Roger Lee, DePenning, James L.
• Primary Examiner(s): Etienne, Ario
• Application Number:
  US09/218,210
• Time in Patent Office: 1,008 Days
• Field of Search: 709/207, 710/40, 710/36, 710/111, 710/240, 710/264, 710/107, 710/113, 710/241, 710/244, 710/110, 710/112, 710/116, 710/119, 710/128, 711/151, 711/150, 711/158
• US Class Current: 709/207
• CPC Class Codes: G06F 13/1657 Access to multiple memories
• CPC Class Codes: G06F 13/36 for access to common bus or bus system

Abstract

A system and method for prioritizing the delivery of information transfer requests using a least-recently-serviced rotational priority technique in a data processing system having one or more requesters to supply the information transfer requests. Active requesters have currently pending information transfer requests, and non-active requesters have no currently pending information transfer requests. Transfer authorization is granted to an information transfer request associated with an active requester that is currently assigned to the highest priority level in a range of priority levels. Each of the active and non-active requesters that have a priority level less than the priority level of the active requester that was granted the transfer have their priority levels incremented, while the non-active requesters having a priority level greater than the priority level of the active requester that was granted the transfer is maintained at its current priority level. The priority level of the active requester that was granted the transfer is then reassigned to the lowest priority level in the range of priority levels.

Claims

1. A method for prioritizing the delivery of information transfer requests in a system having one or more requesters to supply the information transfer requests, wherein active ones of the requesters have currently pending information transfer requests and non-active ones of the requesters have no currently pending information transfer requests, the method comprising:

granting transfer authorization to the information transfer request associated with an active requester that is currently assigned to the highest priority level in a range of priority levels;

incrementing the priority levels assigned to each of the active and non-active requesters having a priority level less than the priority level of the active requester that was granted the transfer;

maintaining a current priority level for each of the non-active requesters having a priority level greater than the priority level of the active requester that was granted the transfer; and

reassigning the priority level of the active requester that was granted the transfer to the lowest priority level in the range of priority levels.

2. The method of claim 1, wherein granting transfer authorization comprises concurrently outputting a request grant enable signal and information corresponding to the granted information transfer request.

3. The method of claim 2, further comprising selecting the information corresponding to the granted information transfer request from a plurality of registers each storing information from their corresponding one of the information transfer requests.

4. The method of claim 3, wherein selecting the information comprises receiving a control signal indicative of which of the plurality of registers is storing the information corresponding to the granted information transfer request, and enabling output of the information corresponding to the granted information transfer request in response to the control signal.

5. The method of claim 1, wherein the number of the priority levels in the range of priority levels is equal to the number of requesters in the system.

6. The method of claim 1, wherein the one or more requesters target the information transfer requests to a single destination.

7. The method of claim 6, wherein incrementing the priority levels comprises incrementing the priority levels a maximum number of times equal to a total number N of the requesters in the system, whereby an active one of the requesters is guaranteed a maximum delay from its activation to its grant of transfer authorization that is substantially equal to N×

t_G, where t_G is an average time between subsequent grants of transfer authorization.

8. The method of claim 1, wherein the system comprises one requester to supply the information transfer requests, and wherein the one requester supplies a plurality of the information transfer requests to a plurality of destinations.

9. The method of claim 1, further comprising transmitting a Request Busy signal to each of the active requesters to prohibit additional information transfer requests from the active ones of the requesters until each respective one of the active requesters has received its grant of transfer authorization.

10. The method of claim 1, further comprising prohibiting incrementing of the priority level assigned to an active one of the requesters if the requester'"'"'s destination is unavailable to receive the information transfer request.

11. The method of claim 1, wherein the number of the priority levels in the range of priority levels is greater than the number of requesters in the system, and wherein the method further comprises increasing a particular requester'"'"'s likelihood of obtaining the grant of transfer authorization relative to other ones of the requesters by assigning multiple ones of the priority levels to the particular requester.

12. The method of claim 1, further comprising initializing each of the requesters to have a corresponding one of the priority levels in the range of priority levels.

13. A data transfer request prioritization circuit for use in a data processing system having a plurality of requesters that initiate data transfer requests, wherein active ones of the requesters have currently pending data transfer requests and non-active requesters have no currently pending data transfer requests, the prioritization circuit comprising:

means for granting transfer authorization to the data transfer request associated with an active requester that is currently assigned to the highest priority level in a range of priority levels;

means for incrementing the priority levels assigned to each of the active and non-active requesters having a priority level less than the priority level of the active requester that was granted the transfer;

means for maintaining a current priority level for each of the non-active requesters having a priority level greater than the priority level of the active requester that was granted the transfer; and

means for reassigning the priority level of the active requester that was granted the transfer to the lowest priority level in the range of priority levels.

14. The data transfer request prioritization circuit as in claim 13, further comprising a data request information storage device to store the information associated with each of the pending data transfer requests.

15. The data transfer request prioritization circuit as in claim 14, wherein the means for granting transfer authorization comprises means for concurrently outputting a request grant enable signal and the information associated with the data transfer request granted transfer authorization.

16. The data transfer request prioritization circuit as in claim 13, wherein the means for incrementing the priority levels comprises means for incrementing the priority levels a maximum number of times equal to a total number N of the requesters in the system.