International Business Machines Corporation

Compagnie Ibm France

David Alan Norgaard

Glen Howard Handlogten

James Francis Mikos

William John Goetzinger

Lyle Edwin Grosbach

John David Irish

Mark David Bellows

Fabrice Jean Verplanken

Jean Louis Calvignac

Marco C Heddes

Joseph Franklin Logan

Kent Harold Haselhorst

Tolga Ozguner

Daniel James Sucher

Merwin Herscher Alferness

In a first aspect of the invention, a first method is provided for hierarchical scheduling. The first method includes the steps of (1) receiving data from one or more pipes, each pipe including a plurality of pipe flows (2) selecting a winning pipe from the one or more pipes from which to transmit data based upon one or more quality of service parameters corresponding to the winning pipe (3) selecting a pipe flow from the plurality of pipe flows included in the winning pipe based upon one or more quality of service parameters corresponding to the selected pipe flow and (4) transmitting data from the selected pipe flow. Numerous other aspects are provided.

Hierarchical scheduling

A data communication apparatus includes a plurality of output ports and a scheduler for assigning priorities for outbound data frames. The scheduler includes one or more scheduling queues. Each scheduling queue indicates an order in which data flows are to be serviced. At least one scheduling queue has a respective plurality of output ports assigned to the scheduling queue. That is, the scheduling queue is shared by two or more output ports.

Weighted fair queue serving plural output ports

In an aspect, a first method of interfacing a processor and memory is provided. The first method includes the steps of (1) generating a first command and associated address of a first type that does not indicate a rank of memory targeted by the first command; (2) determining whether the memory includes a plurality of ranks; (3) if the memory includes a plurality of ranks, employing the processor to update the address associated with the first command to indicate a memory rank targeted by the first command; (4) if the memory does not include a plurality of ranks, employing the processor to update the address associated with the first command to indicate the memory does not include a plurality of ranks; and (5) converting the first command and associated updated address to a second command and associated address that are employed to access the memory. Numerous other aspects are provided.

Rank select operation between an XIO interface and a double data rate interface

A command translation method, apparatus and system are provided for interfacing a processor and a memory. The processor initiates a memory system command in an extreme data rate (XDR) command format which is automatically converted by the command translation method, apparatus and system into a memory system command in a double data rate (DDR) format for forwarding to the memory. Associated with converting the memory system command to the DDR command format is controlling timing of one or more signals presented to the memory interface, the one or more signals being associated with processing the memory system command in the DDR command format. The processor has associated therewith an XDR memory interface controller which adjusts one or more timing parameters of the memory system command in the XDR command format so that DDR timing requirements for the memory system command in the DDR command format are met.

Memory command and address conversion between an XDR interface and a double data rate interface

In a first aspect, a network processor services a plurality of flows including a first flow and a discard flow. The first flow includes a first flow queue and the discard flow includes a discard queue that lists frames to be discarded. An indication is made that the first flow is to be disabled. In response to the indication, all frames included in the first flow queue are transferred to the discard queue. Because the first flow queue is now empty, reconfiguration of the first flow may proceed immediately.

Network processor having fast flow queue disable process

A method and apparatus are provided for implementing hierarchical scheduling of oversubscribed virtual paths with underutilized bandwidth that works for both ATM (cell) and IP (frame) scheduling. A scheduler includes a first calendar for pipes and autonomous flows and a second calendar for pipe flows. A winner of a pipe or an autonomous flow is identified from the first calendar. Responsive to an identified winner pipe, a pipe queue is checked for an associated pipe flow for the winner pipe. Responsive to identifying an empty pipe queue for the winner pipe, a pipe win credit is assigned to the pipe without reattaching the winner pipe to the first calendar. Then a next winner is identified from the first calendar. When a winner pipe flow is identified from the second calendar and the pipe win credit is assigned to the pipe for the winner pipe flow, then the winner pipe flow is serviced without delay.

Method and apparatus for hierarchial scheduling of virtual paths with underutilized bandwidth

Embodiments of the present invention provide methods and systems for allocating multiple tags to multiple requesters in back to back clock cycles. A tag pool may be divided into a predetermined number of sections. Each requester may be associated with at least one of the sections in the tag pool. When multiple tag requests are received from multiple requesters each section containing available tags may provide a tag to a requester associated with the section per clock cycle. Therefore, multiple tags may be provided to multiple requesters in back to back clock cycles, thereby increasing efficiency and improving performance.

Tag allocation method

In a first aspect, a first method of reissuing a command involving bus access is provided. The first method includes the steps of (1) storing information associated with commands that are to be reissued, wherein the commands are each associated with respective input/output (I/O) devices seeking bus access; (2) storing a count for each of the commands, each count indicating a number of times the associated command has been reissued; (3) selecting a command to be reissued, from among the commands, based on the information associated with the command; and (4) determining a delay after which the selected command will be reissued, wherein the delay is determined based on the count associated with the selected command. Numerous other aspects are provided.

Apparatus for using information and a count in reissuing commands requiring access to a bus and methods of using the same

In a first aspect, a method is provided for scheduling connections for a network processor. The method includes the steps of, in a cache, scheduling a plurality of connections to be serviced based on quality of service parameters stored in a control structure corresponding to each connection and during a scheduling opportunity (1) identifying one or more of the plurality of connections in the cache to be serviced; (2) selecting one of the connections identified to be serviced; (3) servicing the selected connection; (4) accessing one or more portions of the control structure in the cache; (5) calculating a next service time when the selected connection is to be serviced; and (6) determining whether to schedule the selected connection to be serviced in one of the cache and a calendar based on the next service time. Numerous other aspects are provided.

High-speed scheduler

A scheduler for a network processor includes one or more scheduling queues. Each scheduling queue defines a respective sequence in which flows are to be serviced. A respective empty indicator is associated with each scheduling queue to indicate whether the respective scheduling queue is empty. By referring to the empty indicators, it is possible to avoid wasting operating cycles of the scheduler on searching scheduling queues that are empty.

Empty indicators for weighted fair queues

A scheduler for a network processor includes a scheduling queue in which weighted fair queuing is applied. The scheduling queue has a range R. Flows are attached to the scheduling queue at a distance D from a current pointer for the scheduling queue. The distance D is calculated for each flow according to the formula D=((WF&#xd7;FS)/SF), where WF is a weighting factor applicable to a respective flow; FS is a frame size attributable to the respective flow; and SF is a scaling factor. The scaling factor SF is adjusted depending on a comparison of the distance D to the range R.

Weighted fair queue having adjustable scaling factor

In a first aspect, a network processor includes a scheduler in which a scheduling queue is maintained. A last frame is dispatched from a flow queue maintained in the network processor, thereby emptying the flow queue. Data indicative of the size of the dispatched last frame is stored in association with the scheduler. A new frame corresponding to the emptied flow queue is received, and the flow corresponding to the emptied flow queue is attached to the scheduling queue. The flow is attached to the scheduling queue at a distance D from a current pointer for the scheduling queue. The distance D is determined based at least in part on the stored data indicative of the size of the dispatched last frame.

Method and apparatus for improving the fairness of new attaches to a weighted fair queue in a quality of service (QoS) scheduler

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.

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Rochester, MN, United States of America

David Alan Norgaard