Rotating rationed buffer refresh

Details Rotating rationed buffer refresh Rotating rationed buffer refresh

1999-03-16

2001-11-27

Kim, Matthew (Department: 2186)

Electrical computers and digital processing systems: memory

Storage accessing and control

Control technique

C710S052000, C711S129000, C711S133000

Reexamination Certificate

active

06324625

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
In many systems in which streams of data share an arrival medium, such as frame relay traffic streams arriving on different channels of a shared T
1
line or Asynchronous Transfer Mode (ATM) traffic streams arriving from a shared ATM switch fabric, the traffic streams share a common buffer pool. In such a system the possibility exists for one of the traffic streams to request and use all of the available free buffers while starving the remaining traffic streams and precluding some data streams from obtaining buffers. One channel can thus consume all the available free buffers and prevent the remaining channels from obtaining free buffers that they may require. Accordingly, performance of the remaining channels as well as performance of the system as a whole may suffer. It would be desirable to provide a system wherein a single data stream is not allowed to allocate more than its share of free buffers and the remaining channels are not prevented from obtaining free buffers for their respective applications in accordance with defined limits for the respective data stream. Additionally, it would be desirable to provide a system which allocates free buffers to the data streams in an efficient and fair manner.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention a method and apparatus are disclosed in which each data stream of a plurality of data streams is assigned to a queue and each queue is allocated a predetermined maximum numbers of buffers. Once the queue has exhausted its supply of buffers, the data from the corresponding data stream is discarded until buffers are refreshed thereby allowing the remaining data streams to operate in a normal fashion. Accordingly, excessive buffer usage by an individual data stream is prevented, as well as excessive demand of other related system resources such as CPU time. The data stream which has had its data discarded will begin having its incoming data processed upon the next refresh operation providing the queue associated with that data stream has had additional buffers allocated. The discarded data is lost and is not recovered. The refresh operation is performed in a manner that provides prioritization of the queues and a high degree of fairness within each priority level. The refresh operation may be scheduled to happen synchronously, such as being synchronized to a real-time clock within the system, or it may be constructed to occur asynchronously. When the refresh operations occur asynchronously the refresh operation will occur more often in a lightly loaded system and less frequently in a heavily loaded system, thereby allowing data streams exhibiting high buffer demands access to available buffers while the idle data streams are not requiring free buffers.


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Affidavit of Neil Singer executed on Oct. 19, 1999 along with Exhibits A and B.

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