# Patent

## Title
Method and apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe bridges

## Abstract

A method and apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe Bridges have been described. A single level enqueue method with dynamic buffering and dequeuing based on packet re-ordering is disclosed. Single level packet routing and scheduling to meet SRIO and PCIe rules to enqueue packets based on FType/TType is disclosed. Backpressure based on ingress watermarks for different packet types is disclosed. Use of a circular-reorder queue (CRQ) for both ingress and egress allows packet reordering and packet passing.

## Background
RELATED APPLICATION
This application is related to application Ser. No. 12/916,568 filed this same date titled “Method and Apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe Bridges”, which is hereby incorporated herein by reference in its entirety including all incorporated references therein. This application is related to application Ser. No. 12/916,580 filed this same date titled “Method and Apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe Bridges”, which is hereby incorporated herein by reference in its entirety including all incorporated references therein.
FIELD OF THE INVENTION
The present invention pertains to packet routing, buffering and scheduling. More particularly, the present invention relates to a method and apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe bridges.
BACKGROUND OF THE INVENTION
Serial Rapid Input Output (SRIO) and Peripheral Component Interconnect Express (PCIe) are known to one of skill in the art as input/output (I/O) interfaces. Equally well known to one of skill in the art is that SRIO and PCIe have differing specifications, protocols, and requirements.
SRIO based End-Points (EP) rely on flowid to route, watermarks to store, and Request-Grant-Accept (RGA) type algorithm to schedule packets. When the SRIO EP is used in a bridge application, the existing packet routing and scheduling schemes cannot transfer packets while meeting both SRIO and PCIe ordering rules and may create deadlock in the system. This presents a problem.



BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which:
FIG. 1 illustrates a network environment in which the method and apparatus of the invention may be implemented;
FIG. 2 is a block diagram of a computer system in which some embodiments of the invention may be used;
FIG. 3A, FIG. 3B, and FIG. 3C illustrates one embodiment of the invention showing an overall architecture;
FIG. 4 illustrates one embodiment of the invention in an end-point terminating device application;
FIG. 5 illustrates one embodiment of the invention in a switch application;
FIG. 6 illustrates one embodiment of the invention in a bridging application;
FIG. 7A, and FIG. 7B illustrate one embodiment of the invention showing an enqueue operation summary for a bridge packet routing based on Ftype and Ttype;
FIG. 8 illustrates one embodiment of the invention showing a Transport Layer Block Diagram;
FIG. 9 illustrates one embodiment of the invention showing a Packet Buffer Module (PBM) for Ingress (PBMi);
FIG. 10 illustrates one embodiment of the invention showing a Egress Packet Buffer Module (PBMe);
FIG. 11 illustrates one embodiment of the invention showing the circular re-order queue (CRQ);
FIG. 12 illustrates one embodiment of the invention showing CRQ reordering;
FIG. 13 illustrates one embodiment of the invention showing CRQ reordering;
FIG. 14A, and FIG. 14B illustrate one embodiment of the invention showing the Ingress VOQ Structure;
FIG. 15 illustrates embodiments of the invention showing how Ingress Back Pressure is achieved and packet retry;
FIG. 16 illustrates an embodiment of the invention showing Freeing Data Nodes;
FIG. 17 illustrates an embodiment of the invention showing a Scheduler (for Packet Scheduling);
FIG. 18 illustrates one embodiment of the invention showing an End Point Fabric Module (Ingress);
FIG. 19 illustrates one embodiment of the invention showing an End Point Fabric Module (Egress);
FIG. 20 illustrates one embodiment of the invention showing Bridge Ordering Rule and Scheduling for Dequeue operations with backpressure;
FIG. 21 illustrates one embodiment of the invention showing Packet Ordering and Priorities for VOQ Allocation;
FIG. 22A, and FIG. 22B illustrate one embodiment of the invention showing an FType and TType operation summary;
FIG. 23 illustrates one embodiment of the invention showing Bridge Ordering Rule and Scheduling; and
FIG. 24A, and FIG. 24B illustrate embodiments of the invention.



DETAILED DESCRIPTION
This invention deals in detail with aspects of the Serial Rapid Input Output (SRIO) and Peripheral Component Interconnect Express (PCIe). As such one of ordinary skill in the art is familiar with both of these, their specifications, mnemonics, protocols, etc. References may be found on the Internet, for example, at http://www.wikipedia.org/, http://www.pcisig.com/home, and http://www.rapidio.org/home/.
To assist the reader who may not be one of ordinary skill in the art and familiar with SRIO and PCIe, etc. The following abbreviations/terms are as noted:

    ASIC—application-specific integrated circuit
    BGA—ball grid array
    CMOS—Complementary metal-oxide-semiconductor
    CRC—cyclic redundancy check
    CRF—Critical Request Flow
    CRQ—Circular-reorder queue or Circular Reordering Queue
    destID—destination identification
    DNFL—Data Node Free List
    DNFL-UP—Data Node Free List Unacknowledged Pointer
    DSP—Digital signal processing
    EFM—Endpoint Fabric Module
    EoP or EOP or eop—end of packet
    FIFO—first in first out
    FlowID—flow identification (e.g. the combination of RapidIO packet's PRIOrity and Critical-Request-Flow fields)
    GPIO—general purpose input output
    I/F—interface
    I2C—Inter-Integrated Circuit
    JTAG—Joint Test Action Group
    LLM—Logical Layer Module
    LUT—look up table
    PA—Packet Acknowledgement
    PBM—Packet Buffer Module
    PBM—Packet Buffer Module
    PBMe—Packet Buffer Module egress
    PBMi—Packet Buffer Module ingress
    PCIe—Peripheral Component Interconnect Express
    PLM—Physical Layer Module
    PRIO—prioity
    PWCe—Port Width Conversion
    PWCi—Port Width Conversion Ingress
    RAM—random access memory
    RapidIO—rapid input output
    RGA—Request-Grant-Accept
    SERDES—Serializer/Deserializer
    SoP or SOP or sop—start of packet
    SRIO—Serial Rapid Input Output
    S-RIO—Serial Rapid Input Output
    STOMP or stmp—a control discard signal to stomp a signal
    TLM—Transport Layer Module
    TLM—transport layer module
    TLMe—transport layer module egress
    TLMi—transport layer module ingress
    TSMC—Taiwan Semiconductor Manufacturing Company
    UDI—User Defined Interface Module; also called the User Core Gasket
    VOQ—Virtual Output Queue (e.g. a storage mechanism where packets are segregated but kept in timestamp order within the segregation)

Generally:

    XXXi—denotes XXX ingress)
    XXXe—denotes XXX egress

So for example:

    LLMi—Logical Layer Module ingress
    LLMe—Logical Layer Module egress

That is the lower-case suffix “i” indicates ingress flow, and “e” indicates egress flow. For example, PLMi is the ingress PLM.



In one embodiment of the invention, configurable packet routing is based on Rapid Input Output (RIO) format type (FTYPE) and RIO transaction type (TTYPE) (often denoted FTYPE/TTYPE and corresponding to FTYPE[0:3] and TTYPE[0:3] respectively), link-partner backpressure generation based on configurable watermarks, and re-ordered packet dequeue scheduler together with per queue backpressure which ensures that SRIO and PCIe packet routing rules are met while preventing deadlock and meeting the required throughput, complexity, and power consumption for SRIO-to-PCIe bridges.
In one embodiment of the invention, a SRIO-to-PCIe bridge uses one level of dynamic buffering and scheduling where the enqueue method is chosen based on SRIO FTYPE and TTYPE, SRIO ordering rules and link-partner retry are maintained based on ingress buffer watermarks and the PCIe ordering rules are maintained by a re-ordered packet dequeue scheduler together with per-flow backpressure from the user application layer.
In one embodiment of the invention, a SRIO-to-PCIe bridge supports both SRIO and PCIe ordering while preventing deadlock and while sustaining throughput up to a line rate of the interface (e.g. 20 Gbps, etc.).
In one embodiment of the invention, different types of SRIO packets and backpressures from the PCIe side can be applied to stop particular packet queues.
In one embodiment of the invention, changing the FTYPE/TTYPE and changing the ordering for a stream of packets and changing the watermarks for the corresponding packet queues results in the corresponding packet outputs and orders on the PCIe side matching the expected order.
In one embodiment of the invention, line rate performance for traffic with both S-RIO (SRIO) and PCIe priority and ordering rules while avoiding any deadlock in the system can be achieved.
In one embodiment of the invention in a SRIO-to-PCIe bridge, a single level enqueue approach with dynamic buffering and dequeing based on packet re-ordering is used.
In one embodiment of the invention in a SRIO-to-PCIe bridge, a single level enqueue approach with dynamic buffering and dequeing based on packet re-ordering is used and ensures that both SRIO and PCIe ordering rules are maintained without deadlock.
In one embodiment of the invention in a SRIO-to-PCIe bridge, a single level enqueue approach with dynamic buffering and dequeing based on packet re-ordering is used and ensures that “bubble-less” throughput is sustained up to the line rate of the interface (e.g. 20 Gbps, 40 Gbps, etc.).
In one embodiment of the invention in a SRIO-to-PCIe bridge, the enqueue approach routes and buffers packets with a configurable option to support terminating end points (EP) and bridging EP applications.
In one embodiment of the invention in a SRIO-to-PCIe bridge, the enqueue approach supports dynamic buffer allocation using Virtual Output Queue (VOQ) structure to reduce memory wastage. This dynamic buffer allocation allows the buffer to be dynamically sized based on different packet requirements (e.g. different packet types, different packet sizes, etc.). This allows more effective use of buffer memory versus a buffer memory allocation based on a pre-specified size which is fixed.
In one embodiment of the invention, the enqueue approach supports single level packet routing and scheduling to meet S-RIO and PCIe rules to enqueue packets based on FTYPE/TTYPE, i.e., VOQ allocation.
In one embodiment of the invention, the enqueue approach generates backpressure towards a link-partner based on ingress watermarks.
In one embodiment of the invention, the dequeue approach uses a circular-reorder queue (CRQ) to dequeue packets on ingress flow.
In one embodiment of the invention, the dequeue approach uses CRQ on egress to support packet reorder and track packet acknowledgement.
In one embodiment of the invention, the dequeue approach supports multiple packet flows.
In one embodiment of the invention in a SRIO-to-PCIe bridge, the dequeue approach can generate application layer (e.g. towards the bridge) backpressure for each queue.
FIG. 3A illustrates generally at 300 part of an overall architecture. At 301 is a SERDES (Serializer/Deserializer) interface sending input data A to port 302, input data B to port B 303, input data C to port C 304, and input data D to port D 305. At 306 is PLMi. At 309 is TLMi which has 307, 308, 310, 311. At 307 is Port Mapping. Within 307 is 308 Routing which handles each of input data A, input data B, input data C, and input data D. At 310 is PWC. At 311 is Transport Processing which handles each of input data A, input data B, input data C, and input data D. At 312 is Ingress Packet Buffer Module (PBMi). At 313 is Enqueue Block. At 314 is VOQs. At 317 is Data Memories A (corresponding to input data A). At 318 is Data Memories B (corresponding to input data B). At 319 is Data Memories C (corresponding to input data C). At 320 is Data Memories D (corresponding to input data D). At 321 is Dequeue Block. At 315 is a signal VOQ enqueue notification. At 316 is VOQ I/F (InterFace). At 322 is Grant/Busy. At 323 is Dequeue Block Output. At 326 is LLM Fabric I/F. At 327 is LLM Backpressure. At 325 is Ingress Logical Layer Module (LLMi). At 324 is CAR/CSR+Registers. At 328 is Egress Logical Layer Module (LLMe). At 329 is LLM Fabric I/F (for 328). At 330 is LLM Enqueue. At 331 is LLM Grant. At 332 is an output from 306 PLMi. At 333 is an input to 306 PLMi.
FIG. 3B illustrates generally at 300 part of an overall architecture. At 340 is Endpoint Fabric Module. At 342 is Scheduler. At 315 is a signal VOQ enqueue notification. At 326 is VOQ I/F (InterFace). At 322 is Grant/Busy. At 323 is Dequeue Block Output. At 324 is CAR/CSR+Registers. At 326 is LLM Fabric I/F. At 327 is LLM Backpressure. At 329 is LLM Fabric I/F (for 328). At 330 is LLM Enqueue. At 331 is LLM Grant. At 346 is Backpressure. At 348 is Enqueue. At 350 is PBM Fabric I/F. At 344 is Data Fabric. At 343 is Data Fabric I/F. At 352 is an Arbiter. At 354 is a Port select signal. At 356 is a Port Selector. At 358 is a Data Fabric I/F. At 353 is Halt_ack (Halt Acknowledge). At 355 is a Halt signal. At 357 is a UC (User Core) Enqueue signal. At 359 is a UC Credit. At 364 is a USER CORE that interfaces to the 360 Ingress User Core Gasket via the 361 Ingress UC I/F. At 364 is a USER CORE that interfaces to the 362 Egress User Core Gasket via the 363 Egress UC I/F.
FIG. 3C illustrates generally at 300 part of an overall architecture.
At 301 is a SERDES (Serializer/Deserializer) interface receiving output data A from port 396, output data B from port B 397, output data C from port C 398, and output data D from port D 399. At 395 is PLMe. At 332 is an input to 395 PLMe. At 333 is an output from 395 PLMe. At 392 is TLMe which has 394, 393. At 394 is PWC. At 393 is Transport Processing which handles each of output data A, output data B, output data C, and output data D.
At 390 is Egress Packet Buffer Module (PBMe). At 384 is Enqueue Block. At 385 is CRQ one each corresponding to output data A, output data B, output data C, and output data D. At 386 is Data Memories A (corresponding to output data A). At 387 is Data Memories B (corresponding to output data B). At 388 is Data Memories C (corresponding to output data C). At 389 is Data Memories D (corresponding to output data D). At 391 is Dequeue Block. At 346 is Backpressure. At 348 is Enqueue. At 350 is PBM Fabric I/F.
FIG. 4 illustrates, generally at 400, one embodiment of the invention in an end-point terminating device application.
FIG. 5 illustrates, generally at 500, one embodiment of the invention in a switch application. FIG. 5 shows an embodiment of the invention where there are two instance end points (501 and 502) and yet only one centralized logical layer (503). One of skill in the art will appreciate that more than two instances of end points can be controlled by one centralized logical layer. Thus the end-point architecture as illustrated in FIG. 5 can scale for a switch with one centralized logical layer and multiple path instances.
FIG. 6 illustrates, generally at 600, one embodiment of the invention in a bridging application.
In one embodiment of the invention, ingress packet routing is based on FTYPE/TTYPE in the transport layer inbound packet filter.
In one embodiment of the invention, packet steering is based on FTYPE and TTYPE.
In one embodiment of the invention, up to 8+1 VOQs are allocated with 1 VOQ allocated to logical layer packet and 8 VOQs allocated for other purposes. For example, 8 VOQs may be allocated for 1802 User Core Gasket as illustrated in FIG. 18, and 1 VOQ may be allocated for 1804 LLMi as illustrated in FIG. 18.
In one embodiment of the invention, TLMi selects the VOQ(s) for packet storage. For example, but not limited to, in one embodiment the TLMi selects the VOQ(s) for packet storage for endpoints and select is on {Priority, Critical-Request Flow} (flowID). In one embodiment the TLMi selects the VOQ(s) for packet storage for switches and select is on flowID and Destination Port. In one embodiment the TLMi selects the VOQ(s) for packet storage for bridges and select is on select on FType and TType. One of skill in the art will appreciate that select may be based on other combinations as well.
In one embodiment of the invention, TLMi responds to per flowID backpressure to trigger Packet-Retry.
In one embodiment of the invention, flowID which is composed of {Priority, Critical-Request Flow} is a 3 bit field, 2 bits for the Priority, and 1 bit for the Critical-Request Flow.
FIG. 7A illustrates, generally at 700, part of an FType 702 and TType 704 enqueue operation summary for a bridge packet routing based on Ftype and Ttype. Note that TTypes that are not listed are reserved. For example, FIGS. 7A and 7B illustrate one embodiment of the invention showing bridge packet routing based on FType and TType.
FIG. 7B illustrates, generally at 700, part of an FType 702 and TType 704 enqueue operation summary for a bridge packet routing based on Ftype and Ttype. Note that TTypes that are not listed are reserved.
In one embodiment of the invention, for example as illustrated in FIG. 7A and FIG. 7B, the corresponding VOQ numbers for VOQ allocation for different Packet Types may be as illustrated in FIG. 21, FIG. 22A, and FIG. 22B and described in the corresponding paragraphs in the specification.
In one embodiment of the invention, for example as illustrated in FIG. 7A and FIG. 7B, the register fields as noted at 706 which control enqueue to which VOQ are configurable. For example, in FIG. 7A, F2_GSM could be configured to include what is denoted currently as F2_READ.
In one embodiment of the invention, inbound packet filtering is done in the TLMi. For example, the inbound packet filter identifies packets using FTYPE/TTYPE for which the user may require special handling. In one embodiment of the invention, the filter performs the following operations:
1) The RapidIO TLM Port {0 . . . 3} Ftype Filter Control Register provides a control bit for groups of Ftype/Ttype combinations to cover the full 256 combinations for Ftype and Ttype (see for example, FIG. 7A and FIG. 7B). If the control bit for a packet's Ftype/Ttype is not set, no filtering action is taken.

2) For those packets that meet the above criteria at 1), the packet is acknowledged at the Physical layer, but the packet is not enqueued to the PBMi. The packet discard due to unsupported request is reported to RapidIO Local/Transport Layer Error Detect CSR.ILL_TYPE.

In one embodiment of the invention, an Inbound Port Map Block may be used for terminating EP and Bridge in applications. For example, the Inbound Port Map Block provides packet admission control and routing for ingress packets. Inbound packets that are admitted are routed to VOQs in the PBMi according to their destID, PRIO, CRF, FType and TType.
In one embodiment of the invention there is configurable and scalable dynamic buffering.
For example, in one embodiment of the invention different packet buffering schemes are supported. For example, in one embodiment of the invention, for the Ingress Packet buffer a water-mark based on buffering to sustain throughput up to the line rate of the interface (e.g. 20 Gbps) with 32 byte granularity is supported. For example, in one embodiment of the invention, for the Egress packet buffer a novel circular re-order queue based on buffering is used to ensure packets routing with respect to RapidIO ordering rules while at the same time reducing latency.
In one embodiment of the invention, both ingress and egress buffers support a) 8/16/32 max sized packets for 1x/2x/4x ports, b) maximum 72/144/288 packets (Ingress), and c) maximum 64 packets (Egress).
In one embodiment of the invention, Enqueue back-pressure (e.g. towards SRIO link partner) is provided. In one embodiment of the invention, Enqueue backpressure is provided by PBMi to control admission of new packets into the packet buffer. The watermark based backpressure is provided to indicate on a per-port per flowID (Priority 3 bit and CRF 1 bit) basis which allows PBMi to store a packet of a specific flowID. As packets are enqueued and dequeued, PBMi keeps track of the buffer resources consumed by packet enqueue and packet dequeue. When the amount of resources used rises above the programmable watermarks, backpressure is asserted for the associated flowID(s).
FIG. 8 illustrates, generally at 800, one embodiment of the invention showing a Transport Layer Block Diagram. For illustration purposes, FIG. 8 shows four ports. At 802 are To/From Ingress Physical Layer, Packet Acknowledgment, and Packet Control. At 804 are From Ingress Physical Layer Packet Data (16-bit shown) and Control information for example, but not limited to, SoP, EoP, STOMP, DataValid. At 806 are Back Pressure from PBM on a per FlowID per Channel basis. At 808 are Per portPacket Data (64-bit) and Control information, for example, but not limited to SoP, EoP, STOMP, DataValid. At 810 are Enqueue Interface to PBMi, FlowID, and Port_Mask. At 812 is a Port Width Conversion (PWC) for ingress (PWCi) (as noted for 4 ports). At 814 is a Transport Processing Block (TPB) (again 4 of them). At 816 is a Port Map Block (PMB). Transport Processing Block (TPB) 814 has for each of the ports a CRC-16 (Check), a Parse, a Replace, a CRC-16 (Generate), and Filter block. Port Map Block (PMB) 816 has for each port a 818 DestID Validation (BRR (Base Routing Register)), a Port Mask Select 820 (LUT (Look Up Table)), and a VOQ selection 822.
FIG. 9 illustrates, generally at 900, one embodiment of the invention showing a Packet Buffer Module (PBM) for Ingress (PBMi). At 902 is a Transport Layer. At 904 is an Enqueue Interface. At 906 is a Dequeue Interface. At 910 os a Scheduler, and at 912 a Switch Fabric. At 914 is a Packet Buffer Module (PBMi) for Ingress. At 916 is a Tag Enqueue Block (one for each of 4 ports (A, B, C, D)). At 918 is a Tail VOQ Table, and at 920 are Ingress Tag Memories, and at 922 us a Head VOQ Table, again one for 4 ports as shown is a cascaded block fashion). At 924 is a Packet Dequeue (one for each of the 4 ports). At 926 is a Free data-node (a 32-byte quantum of data) list (again one for each of the 4 ports). At 928 are shown Payload for A, B, C, D (e.g. for A Payload-A), and associated Overhead.
In one embodiment of the invention, an Ingress Packet Buffer Module (PBMi) queues packet data in VOQs. In one embodiment, One VOQ is dedicated for the LLM. In one embodiment, others VOQs are grouped in Port-groups of 8 VOQs. In one embodiment there is one Port-group per egress port. In one embodiment there is one Port-group per egress port.
In one embodiment of the invention, the VOQ is selected by the TLMi.
In one embodiment of the invention, multicast is enqueued to multiple VOQs. This minimizes blocking.
In one embodiment of the invention, backpressure is per FlowID.
In one embodiment of the invention, there are programmable watermarks.
In one embodiment of the invention, the Ingress Packet Buffer Module provides per-packet Time-to-Live support.
In one embodiment of the invention, RAM (Random Access Memory) is dedicated to each channel. In one embodiment of the invention, the RAM bifurcates as a Path is bifurcated. In one embodiment of the invention, there are independent enqueue/dequeue per channel.
In one embodiment of the invention, RAM is managed on Data Nodes. In one embodiment of the invention the managed RAM support each data node with 32-bytes plus any OverHead.
In one embodiment of the invention, packet storage is limited only by the number of Data Nodes and the number of Tags.
FIG. 10 illustrates, generally at 1000, one embodiment of the invention showing a Egress Packet Buffer Module (PBMe). At 1002 is Fabric (e.g. Switch Fabric). At 1004 is the Packet Buffer Module (PBMe) block. At 1006 is the TLMe block. At 1008 is a Tag Enqueue Block (one for each of 4 ports as shown cascaded). At 1010 are Egress Tag Memories (again one for each port) shown here as a CRQ. At 1012 is a Packet Dequeue (again one for each port). At 1014 is a Free data-node list (one for each port). At 1018 are shown each of the four separate Data RAM and Overheard for each of the ports. For example, at 1016 are shown the Data RAM and Overhead for a first port (e.g. A). What is to be appreciated is that for each port there are associated blocks that are functionally tied together. For example, if we use 1016 as an example, there is associated and in communication with it (not shown in FIG. 10 so as to avoid confusing the diagram) 1008, 1010, 1012, and 1014. That is, Data RAM and Overhead 1016 is in communication with 1008 Tag Enqueue Block, 1010 Egress Tag Memories, 1012 Packet Dequeue, and 1014 Free data-node list which are all in communication with each other to handle all operations associated with that port (e.g. Port A in this example).
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) queues packet data in the CRQs (Circular Reordering Queues).
In one embodiment of the invention, the Circular Reordering Queue maintains the arrival order of packets.
In one embodiment of the invention, the Circular Reordering Queue allows reordering under user control. For example, but not limited to, reordering under user control based on packet retry, reordering under user control based on Packet-not-Accepted, reordering under user control based on Always (Oldest-Highest-Priority First), etc.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) allows backpressure per FlowID.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) has programmable watermarks for triggering backpressure.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) provides packet discard based on per-packet Time-to-Live (TTL) timers. The TTL timer is started when the packet is enqueued in the PBMi.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) has RAM dedicated to each channel. In one embodiment of the invention, the Egress Packet Buffer Module RAM bifurcates as the Path is bifurcated. In one embodiment of the invention, the Egress Packet Buffer Module there are independent enqueue/dequeue per channel.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe)
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) RAM is managed based on Data Nodes. For example, but not limited to, one embodiment of the PBMe uses 32-bytes plus OverHead per data node.
In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) packet storage limited by the number of Data Nodes. In one embodiment of the invention, the Egress Packet Buffer Module (PBMe) packet storage is limited by the number the number of CRQ entries. For example, in one embodiment of the PBMe there are 64 CRQ entries which is fewer than the number of Data Nodes and thus limits the packet storage.
FIG. 11 illustrates, generally at 1100, one embodiment of the invention showing the CRQ. At 1102 is a Last Free pointer to an open location. At 1104 is a pointer to Next to send. At 1106 is a pointer to the Last Packet enqueued. At 1108 is a pointer to a First Free location. Shown are packets and the ackID associated with each. For example, 1110 shows Packet D {2,0} and the associated ackID=n+3 at 1112. At 1114 is a clock-wise dequeue arrow. At 1116 is a clock-wise enqueue arrow.
In one embodiment of the invention, the CRQ replaces the Tags, and VOQ tables.
In one embodiment of the invention, the CRQ Packets are enqueued in order. For example, in FIG. 11 the CRQ packets are enqueued in order clock-wise as shown by the arrow at 1116.
In one embodiment of the invention, the CRQ Packets are dequeued in order and AckIDs are assigned on dequeue. For example, in FIG. 11 the CRQ packets are dequeued in clock-wise order and AckIDs are assigned on dequeue in clock-wise order as shown by the arrow at 1114.
In one embodiment of the invention, the CRQ Packet Accept frees one packet. For example, in FIG. 11 the CRQ Packet Accept Free pointer moves one 1 step clock-wise.
In one embodiment of the invention, the CRQ on Packet Retry moves ‘Next-to-Send’ (also denoted Next to send) at 1104 back to the first packet. By doing this the CRQ eliminates outstanding unacknowledged packets and forces a re-order event.
In one embodiment of the invention, the CRQ in response to a Link-Response may move both ‘Free’ (e.g. 1102 and/or 1108) and ‘Next-to-Send’ 1104 pointers.
FIG. 12 illustrates, generally at 1200, one embodiment of the invention showing CRQ reordering. At 1210 is one state of the CRQ before reordering and at 1220 is a second state of the CRQ after reordering. As can be seen at CRQ 1210 before reordering: 1212 is Packet A {0,0}, followed by Packet B {0,0} at 1212, which is followed by 1216 Packet C {1,0}.
After reordering of CRQ 1210 we have the CRQ as shown at 1220. As can be seen at CRQ 1220 after reordering the order of the packets is: first is 1222 Packet C, which is followed by 1224 Packet A {0,0}, which is followed by 1226 Packet B {0,0}. As can been seen from 1210 to 1220, Packet C {1,0} has been reordered from third ‘place’ in CRQ 1210 to first ‘place’ in CRQ 1220 (i.e. in CRQ 1220 is has been brought to the front of the CRQ).
In one embodiment of the invention CRQ reordering brings a higher FlowID packet to the front of the CRQ.
In one embodiment of the invention CRQ reordering brings a higher FlowID packet to the front of the CRQ by pushing all other packets back one step.
In one embodiment of the invention CRQ reordering supports two programmable modes. For example, one mode is a Higher mode which is shown in FIG. 12 and promotes any packet with a higher FlowID.
FIG. 13 illustrates, generally at 1300, one embodiment of the invention showing CRQ reordering.
In one embodiment of the invention CRQ reordering supports two programmable modes. For example, a second mode is a Highest mode which is shown in FIG. 13 and promotes the oldest highest FlowID packet. For example, in the embodiment illustrated in FIG. 13, the CRQ reordering would promote packet ‘N’ on first retry. And in one embodiment of the invention the CRQ reordering would keep packet ‘N’ at head on second retry. At the CRQ 1310 is seen the order of the packets before reordering being 1312 Packet D {2,0}, then next 1314 Packet C {1,0}, then next Packet A {0,0}, and much further down the order 1318 Packet N {3,0}. After reordering as shown at CRQ 1320, the first three packets in order are 1322 Packet N {3,0}, then packet 1324 Packet D {2,0}, then packet 1326 Packet C {1,0}. The arrows (not labeled) toward the center of the CRQ 1310 indicate figuratively the shifting of the packets while the large arrow (not labeled) outside CRQ 1310 figuratively shows the shifting of Packet N {3,0} to the head of the CRQ queue as shown (i.e. at the head of the queue as shown in CRQ 1320 at position 1322).
FIG. 14A illustrates, generally at 1400, one part of an embodiment of the invention showing the Ingress VOQ Structure. At 1402 is Tail VOQ Table. As shown at 1402 the cascaded boxes show 4 ports. Each Tail VOQ Table has VOQ 0, VOQ 1, through VOQ n. At 1404 is shown Free Tag RAM (again for 4 ports). At 1406 Free Tag Head and at 1408 Free Tag Tail associated with Free Tag RAM1404. At 1410 is Tag Linked List RAM (again for each of 4 ports). At 1412 is Head VOQ Table. As shown at 1412 the cascaded boxes show 4 ports. Each Head VOQ Table has VOQ 0, VOQ 1, through VOQ n. Shown by arrows are numerous examples of linking. Arrows 1421, 1423, 1425, 1427, 1429, 1431, 1433, 1435, 1437, and 1439 go to various points in a Data Node Linked List RAMs 1440 as shown in FIG. 14B.
In one embodiment of the invention, the Ingress VOQ Structure Tail VOQ Table (e.g. 1402 in FIG. 14A) tracks the ‘youngest’ packet in each VOQ. In one embodiment of the invention, the Tail VOQ Table (e.g. 1402 in FIG. 14A) is used to enqueue a new tag to a VOQ.
In one embodiment of the invention, the Ingress VOQ Structure Head VOQ Table (e.g. 1412 in FIG. 14A) tracks the ‘oldest’ packet in each VOQ. In one embodiment of the invention, the Head VOQ Table (e.g. 1412 in FIG. 14A) is used by the scheduler to dequeue packets.
In one embodiment of the invention, the Free Tag RAM (e.g. 1404 in FIG. 14A) tracks free Tags.
FIG. 14B illustrates, generally at 1400, one part of an embodiment of the invention showing the Ingress VOQ Structure. Arrows 1421, 1423, 1425, 1427, 1429, 1431, 1433, 1435, 1437, and 1439 come from various points as shown in FIG. 14A. At 1440 is Data Node RAMs (again shown for 4 ports via the cascaded boxes). At 1442 is Data Node Free List RAMs (again shown for 4 ports via the cascaded boxes). At 1444 is Free Data-node Head—D (for 4 ports), and at 1446 is Free Data-node Tail—D (for 4 ports), both as associated with 1442 Data Node Free List RAMs. Shown by the arrows (some not labeled) and boxes are the linking and EOP, SOP, FREE, nxt_dat_ptr (next data pointer), multicast packet, etc.
In one embodiment of the invention, for example, as illustrated in FIG. 14B, 1442 the Data Node Free List RAMs tracks free Data Nodes.
FIG. 15 illustrates, generally at 1500, embodiments of the invention showing how Ingress Back Pressure is achieved and packet retry.
In one embodiment of the invention, there are Programmable watermarks for each FlowID per port 1502. In one embodiment of the invention, there are programmable watermarks for each FlowID per port, and additionally CRF and non-CRF watermarks may be set equal to allow more unreserved Data Nodes 1504. In one embodiment of the invention, programmable watermarks provided for on a Data Node granularity level 1506. In one embodiment of the invention, programmable watermarks are provided separately for Tags 1508. In one embodiment of the invention, programmable watermarks may be fixed for Multicast FIFO 1510. In one embodiment of the invention, a Packet Retry is issued when a packet arrives and the level is above the watermark 1520.
FIG. 16 illustrates, generally at 1600, an embodiment of the invention showing Freeing Data Nodes. At 1602 is a Data Node Free List (DNFL). 1602 shows FREE_DAT_PTR (free data pointers), UA_DAT_PTR (unacknowledged data pointers), and INUSE_DAT_PTR (in use data pointers). At 1604 are shown Provisional Free List—Pointers to Data Nodes of Packets that have not been acknowledged. At 1606 are shown Pseudo Active List—Entries for Data Nodes of Packets waiting to be dequeued. At 1608 are shown Free List—Pointers to Data Nodes that are ‘free’ for use (note that as illustrated here, Free List wraps from the bottom of the 1602 box to the top of the 1602 box). 1610 denotes the DNFL Tail Pointer. 1612 denotes the DNFL Unacknowledged Pointer. 1614 denotes the DNFL Head Pointer. At noted at 1616 the Head Pointer moves this direction on packet discard. And as noted to 1618 Pointers move this direction.
In one embodiment of the invention, with regard to freeing data nodes, PBMi Data Nodes are Freed on dequeue one-by-one.
In one embodiment of the invention, with regard to freeing data nodes, PBMe must wait for PA (Packet Acknowledgements) before freeing Data Nodes.
In one embodiment of the invention, with regard to freeing data nodes, CRQ tracks unacknowledged packets.
In one embodiment of the invention, with regard to freeing data nodes, DNFL tracks Data Nodes of unacknowledged packets.
In one embodiment of the invention, with regard to freeing data nodes, for example as shown in FIG. 16, Packet Acknowledgements move the pointers.
In one embodiment of the invention, with regard to freeing data nodes, for example as shown in FIG. 16, Packet Acknowledgements (PA) increments Tail.
In one embodiment of the invention, with regard to freeing data nodes, for example as shown in FIG. 16, Packet Retires (PR) returns DNFL-UP (DNFL Unacknowledged Pointer) to Tail (DNFL Tail Pointer).
FIG. 17 illustrates, generally at 1700, an embodiment of the invention showing a Scheduler (for Packet Scheduling). The scheduler connects the packet buffer module (PBM (e.g. PBMi 312 in FIG. 3A, PBMe 390 in FIG. 3C) with the user core (e.g. USER CORE 364 in FIG. 3B). In one embodiment of the invention Ingress and Egress data-paths are supported with two separate schedulers. At 1702 is User Core. At 1704 is User Interface Gasket. Within the User Interface Gasket 1704 are 1706, 1708, 1710, and 1712. 1706 is Ingress Transaction Mapping and associated 1708 FIFO (First In First Out) memory. At 1710 is Backpressure Control. At 1712 is Egress Transaction Mapping. At 1714 is EFM (Endpoint Fabric Module) showing Arbitration 1716 and Fabric 1718. Shown but not labeled with numbers are a variety of signals as notes between blocks 1702, 1704, 1714.
In one embodiment of the invention, there is an endpoint scheduler. In one embodiment of the invention, the endpoint scheduler is capable of performance throughput up to the line rate of the interface (e.g. 20 Gbps, 60 Gbps) for 32-Byte (or larger) packets, supports up to 8+1 VOQs per port, and is capable of dequeing 2 packets simultaneously: one to User Core, one to LLM.
In one embodiment of the invention, the endpoint scheduler supports up to 4 ports from PBMi and additionally, up to 9 virtual output queues per port.
In one embodiment of the invention, the endpoint scheduler has an Ingress Scheduling Policy. In one embodiment of the invention, the Ingress Scheduling Policy is maintenance packets to LLM have highest priority. In one embodiment of the invention, the Ingress Scheduling Policy is within each port select the highest priority VOQ. In one embodiment of the invention, the Ingress Scheduling Policy is within each port select the highest priority VOQ and the oldest packet is always at the head of the VOQ. In one embodiment of the invention, the Ingress Scheduling Policy selects the port with the highest priority request. In one embodiment of the invention, the Ingress Scheduling Policy is to use Round-Robin arbitration to break ties. In one embodiment of the invention, the Ingress Scheduling Policy is to use two different grant arbiters for LLM and User Core.
In one embodiment of the invention, the endpoint scheduler has an Egress Scheduling Policy.
In one embodiment of the invention, the Egress Scheduling Policy is that the LLMe is provided access as soon as it is permitted by the User Core. In one embodiment of the invention, the Egress Scheduling Policy is Free data node information (credit) is used on a per-port per-flowID basis.
FIG. 18 illustrates, generally at 1800, one embodiment of the invention showing an End Point Fabric Module (Ingress). At 1802 is User Core Gasket. At 1804 is LLMi. At 1806 is EFMi which includes 1808 Scheduler having a variety of functions (not numerically labeled) for 4 ports and 1810 a 4×2 Crossbar (for 4 ports). At 1812 is PBMi which includes 1820 Tag Enqueue, 1816 showing the Head VOQ Table of port A, B, C, and D, 1818 Packet Dequeue and Data Memories A, B, C, and D for 4 ports.
FIG. 19 illustrates, generally at 1900, one embodiment of the invention showing an End Point Fabric Module (Egress). At 1902 is an Egress User Core Gasket. At 1904 is an Egress Endpoint Fabric which includes 1906 Arbiter and Port Selector 1908. 1910 is an Egress Logical Layer Module (LLMe). At 1912 is Egress Packet Buffer Module (PBMe) which includes 1914 Packet Dequeue Block, 1916 VOQs, 1918 showing explicitly Data Memories A, B, C, and D for the four ports, and 1920 Tag Enqueue Block.
FIG. 20 illustrates, generally at 2000, one embodiment of the invention showing Bridge Ordering Rule and Scheduling for Dequeue operations with backpressure. The table in FIG. 20 is read in the following manner. Looking first to column 2002 for a packet type. When found in column 2002 then move horizontally across in the 2004 direction and at each column may be found at the intersection whether this packe type may pass or not pass the packet type in each column. For example from the table it may be seen that if there is backpressure, packets from RFDID, MR, MWR, DB, and M may pass each other. Likewise it is clear that if there is backpressure on any of the P or NP or CPL, then RFDID, MR, MWR, DB, and M may pass P or NP or CPL. Also if there is backpressure on any of the RFDID, MR, MWR, DB, and M, then P or NP or CPL can pass any of the RFDID, MR, MWR, DB, and M as long as priorities between P, NP, and CPL are followed. Also, P packets shall not pass another P but may pass NP and CPL, NP packets shall not pass P or CPL or another NP, and CPL packets shall not pass P or another CPL but may pass NP. The packet types shown in FIG. 20 are RFDID, Messaging Response (MR), Maintenance Write Response (MWR), Doorbell Maintenance (DB), Messaging (M), Posted (P), Completion (CPL), and Non-Posted (NP). RFDID is: R: Reserved Ftype 0, 1, 3, 4, 12, 14; F: Flow control (Ftype 7); D: Data Streaming Ftype 9; ID: Implementation Defined (Ftype 15).
In one embodiment of the invention the Bridge Ordering Rule and Scheduling for VOQ selection is performed by TLM based on RapidIO packet type (not priority). Using this approach separates packets for implementation of PCIe ordering rules.
In one embodiment of the invention the Bridge Ordering Rule and Scheduling uses PBMi backpressure applied based on RapidIO priority (not packet type). Using this approach allows support for RapidIO ordering rules and RapidIO deadlock prevention.
In one embodiment of the invention the Bridge Ordering Rule and Scheduling allows for PCIe rules to be respected while packets are dequeued for the User Core. Using this embodiment a CRQ maintains packet ordering and time arrival order. Using this embodiment a CRQ controls packet dequeue. Using this embodiment backpressure per queue is used to prevent deadlock and to sustain throughput.
FIG. 21 illustrates, generally at 2100, one embodiment of the invention showing Packet Ordering and Priorities for VOQ Allocation. As illustrated VOQ allocation is performed for different Packet Types for Bridging. In column 2102 is Packet Type. In column 2104 is PBM Ingress VOQ, in column 2106 is request[7:0], and at column 2108 is sri_buf_full[7:0]. Note that in FIG. 20 RFDID is: R: Reserved Ftype 0, 1, 3, 4, 12, 14; F: Flow control (Ftype 7); D: Data Streaming Ftype 9; ID: Implementation Defined (Ftype 15).
FIG. 22A illustrates, generally at 2200, part of an FType 2202 and TType 2204 operation summary. As shown are FType and TType Mapping to VOQ Selection.
FIG. 22B illustrates, generally at 2200, part of an FType 2202 and TType 2204 operation summary. As shown are FType and TType Mapping to VOQ Selection.
In one embodiment of the invention once the FType and TType Mapping to VOQ Selection is completed the TLMi notified the PBMi of its decision for proper queuing of the packet and its request. The enqueue command provides the PBM with the port-group and the VOQ within that group to which the packet is to be enqueued.
FIG. 23 illustrates, generally at 2300, one embodiment of the invention showing Bridge Ordering Rule and Scheduling. At 2302 is an Ingress UDI Gasket which includes 2304 UDI Control and 2308 UDI Datapath. 2304 UDI Control includes 2306 CRQ and Packet Dequeue Control. 2308 UDI Datapath includes 2310 ECC/Parity Detection and ECC Correction and 2312 Transaction Mapping FIFO and Backpressure Control. At 2314 is PBMi which includes 2316 Tag Enqueue. At 2318 is EFMi. At 2320 is sri_buf_full[7:0] such as illustrated previously at 2108 in FIG. 21. 2320 sri_buf_full[7:0] allows for selective backpressure based on the packet type. At 2322 is request[7:0] such as illustrated previously at 2106 in FIG. 21. 2322 request[7:0] is a request to dequeue a packet type. In 2306 CRQ and Packet Dequeue Control hp denotes head pointer, rp denotes request pointer, and tp denotes tail pointer.
As one of skill in the art will appreciate from the description above and the figures the present invention allows for Bridge Priority and Deadlock Prevention.
In one embodiment of the invention, Bridge Priority and Deadlock Prevention, is through use of the CRQ with per Queue backpressure. This approach keeps track of packet arrival order in a stream of packets, and performs packet reorder when various flows are backpressured, and ensures deadlock prevention for the non-backpressured flows.
In one embodiment of the invention, Bridge Priority and Deadlock Prevention, is through use of the CRQ scheduler making Dequeue decisions. These decisions are based on arrival order, and are based on per queue backpressure, and are based on Bridge specific ordering rules.
In one embodiment of the invention, Bridge Priority and Deadlock Prevention, is through use of Packet Queue and Packet Dequeue. Using this approach, external to the CRQ, packets are stored in multiple VOQ structures. Additionally, each VOQ stores packets of one or more specific packet types. And within each VOQ the packets are dequeued in timestamp arrival order, and with a VOQ backpressured, the oldest packet from the ‘other’ VOQs is chosen. Finally rules about which packet types may pass others in the CRQ enforces PCIe ordering rules.
FIG. 24A and FIG. 24B illustrate, generally at 2400, embodiments of the invention.
At 2401 is 1. A method for a circular-reorder queue (CRQ) for dequeuing packets on an ingress flow, the method comprising:
keeping track of arrival times for all packets received; and
generating an ingress backpressure wherein said ingress backpressure is based on user configurable watermarks for user defined one or more packet types.
At 2402 is 2. A method for a circular-reorder queue (CRQ) for handling packets on an egress flow, the method comprising:
positioning a first free pointer;
receiving a packet;
enqueuing said packet at said first free pointer position;
positioning a next to send pointer at said first free pointer position;
dequeuing said packet at said next to send pointer position and assigning an acknowledgment identification (AckID) to said packet;
transmitting to a link partner said dequeued packet and said AckID;
receiving from said link partner a link-response signal related to said transmitted dequeued packet and said AckID; and
when said link-response signal is a packet accept for said transmitted dequeued packet and said AckID then moving said free pointer in said CRQ one step and moving said next to send pointer position one step;
when said link-response signal is a packet retry for said transmitted dequeued packet and said AckID then not moving said next to send pointer.
At 2403 is 3. A method for a circular-reorder queue (CRQ) for handling packets on an egress flow, the method comprising:
receiving in said CRQ one or more packets in an order;
enqueuing said one or more packets in said order;
positioning a free pointer in said CRQ at a location where a new packet may be enqueued;
maintaining in said CRQ a next-to-send pointer;
dequeuing from said CRQ at said next-to-send pointer a packet for transmission and assigning said packet for transmission an acknowledgment identification (AckID);
transmitting said packet to a link partner;
receiving from said link partner a link-response signal related to said transmitted packet; and
when said link-response signal is a packet accept for said transmitted packet then moving said free pointer in said CRQ one step;
when said link-response signal is a packet retry for said packet transmitted then moving said next-to-send pointer to said packet transmitted.
At 2404 is 4. The method of claim 3 wherein said link-response signal may move both said free pointer and said next-to-send pointer.
At 2405 is 5. The method of claim 3 wherein said moving said next-to-send pointer to said packet transmitted further comprises:
re-ordering said one or more packets in said CRQ.
At 2406 is 6. A method comprising: receiving in a circular-reorder queue (CRQ) a plurality of packets wherein for each packet in said plurality of packets there is an associated flow identification (FlowID) and wherein a first packet is a first received packet in said plurality of packets and wherein a last packet is a last received packet in said plurality of packets;
receiving a mode signal for re-ordering said CRQ; and
when said mode signal is a higher signal then sequentially searching in order from said first packet to said last packet for a packet having a higher FlowID than said first packet and when said higher FlowID packet is found moving said higher FlowID packet to a position of said first packet and sequentially moving said first packet and any intervening packets between said first packet and one less than said higher FlowID packet one position toward said last packet.
when said mode signal is a highest signal then sequentially searching in order from said first packet to said last packet for a packet having a highest FlowID and when said highest FlowID packet is found moving said highest FlowID packet to a position of said first packet and sequentially moving said first packet and any intervening packets between said first packet and one less than said highest FlowID packet one position toward said last packet.
At 2407 is 7. An apparatus comprising:
a circular-reorder queue (CRQ) having a plurality of memory locations;
a plurality of pointers to one or more of said plurality of memory locations;
a means for keeping track of packet arrival order in a stream of packets;
a means for performing packet reordering when various flows are backpressured.
At 2408 is 8. The apparatus of claim 7 further comprising:
a CRQ scheduler for making dequeuing decisions based on said packet arrival order.
At 2409 is 9. The apparatus of claim 8 further comprising:
said CRQ scheduler making dequeuing decisions based on a per queue for said various flows are backpressured.
At 2410 is 10. The apparatus of 8 further comprising:
said CRQ scheduler making dequeuing decisions based on a bridge specific ordering rules.
At 2411 is 11. The apparatus of claim 8 further comprising:
a storage external to said CRQ wherein said stream of packets are stored in multiple virtual output queue (VOQ) structures.
At 2412 is 12. The apparatus of claim 11 wherein each of said multiple VOQ structures stores packets of one or more specific packet types.
At 2413 is 13. The apparatus of claim 12 wherein within each VOQ said packets are dequeued in a timestamp arrival order.
At 2414 is 14. An apparatus comprising:
a plurality of virtual output queues (VOQs);
one of said VOQs allocated to a logical layer packet manager (LLM); and
all but said one of said VOQs allocated to a user defined interface.
At 2415 is 15. The apparatus of claim 14 wherein said LLM is an ingress LLM (LLMi).
At 2416 is 16. The apparatus of claim 14 further comprising:
an ingress transport layer module (TLMi), wherein said TLMi selects said VOQs for packet storage.
At 2417 is 17. The apparatus of claim 16 further comprising:
an endpoint terminating device; and
wherein said TLMi selects is based on packet priority, and packet critical request flow (CRF), and packet flow identification.
At 2418 is 18. The apparatus of claim 16 further comprising:
a switch device; and
wherein said TLMi selects is based on packet priority, CRF, and packet destination port.
At 2419 is 19. The apparatus of claim 16 further comprising:
a bridge device; and
wherein said TLMi selects is based on packet FType, and packet TType.
At 2420 is 20. The apparatus of claim 16 wherein said TLMi responds to a per packet flow identification to trigger a packet retry.
At 2421 is 21. The apparatus of claim 14 wherein said VOQs size are user programmable.
Thus a method and apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe Bridges have been described.
FIG. 1 illustrates a network environment 100 in which the techniques described may be applied. The network environment 100 has a network 102 that connects S servers 104-1 through 104-S, and C clients 108-1 through 108-C. More details are described below.
FIG. 2 is a block diagram of a computer system 200 in which some embodiments of the invention may be used and which may be representative of use in any of the clients and/or servers shown in FIG. 1, as well as, devices, clients, and servers in other Figures. More details are described below.
Referring back to FIG. 1, FIG. 1 illustrates a network environment 100 in which the techniques described may be applied. The network environment 100 has a network 102 that connects S servers 104-1 through 104-S, and C clients 108-1 through 108-C. As shown, several computer systems in the form of S servers 104-1 through 104-S and C clients 108-1 through 108-C are connected to each other via a network 102, which may be, for example, a corporate based network. Note that alternatively the network 102 might be or include one or more of: the Internet, a Local Area Network (LAN), Wide Area Network (WAN), satellite link, fiber network, cable network, or a combination of these and/or others. The servers may represent, for example, disk storage systems alone or storage and computing resources. Likewise, the clients may have computing, storage, and viewing capabilities. The method and apparatus described herein may be applied to essentially any type of visual communicating means or device whether local or remote, such as a LAN, a WAN, a system bus, etc. Thus, the invention may find application at both the S servers 104-1 through 104-S, and C clients 108-1 through 108-C.
Referring back to FIG. 2, FIG. 2 illustrates a computer system 200 in block diagram form, which may be representative of any of the clients and/or servers shown in FIG. 1. The block diagram is a high level conceptual representation and may be implemented in a variety of ways and by various architectures. Bus system 202 interconnects a Central Processing Unit (CPU) 204, Read Only Memory (ROM) 206, Random Access Memory (RAM) 208, storage 210, display 220, audio, 222, keyboard 224, pointer 226, miscellaneous input/output (I/O) devices 228, and communications 230. The bus system 202 may be for example, one or more of such buses as a system bus, Peripheral Component Interconnect (PCI), Advanced Graphics Port (AGP), Small Computer System Interface (SCSI), Institute of Electrical and Electronics Engineers (IEEE) standard number 1394 (FireWire), Universal Serial Bus (USB), etc. The CPU 204 may be a single, multiple, or even a distributed computing resource. Storage 210, may be Compact Disc (CD), Digital Versatile Disk (DVD), hard disks (HD), optical disks, tape, flash, memory sticks, video recorders, etc. Display 220 might be, for example, an embodiment of the present invention. Note that depending upon the actual implementation of a computer system, the computer system may include some, all, more, or a rearrangement of components in the block diagram. For example, a thin client might consist of a wireless hand held device that lacks, for example, a traditional keyboard. Thus, many variations on the system of FIG. 2 are possible.
For purposes of discussing and understanding the invention, it is to be understood that various terms are used by those knowledgeable in the art to describe techniques and approaches. Furthermore, in the description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one of ordinary skill in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, and other changes may be made without departing from the scope of the present invention.
Some portions of the description may be presented in terms of algorithms and symbolic representations of operations on, for example, data bits within a computer memory. These algorithmic descriptions and representations are the means used by those of ordinary skill in the data processing arts to most effectively convey the substance of their work to others of ordinary skill in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of acts leading to a desired result. The acts are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, can refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices.
An apparatus for performing the operations herein can implement the present invention. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer, selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, hard disks, optical disks, compact disk-read only memories (CD-ROMs), and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), electrically programmable read-only memories (EPROM)s, electrically erasable programmable read-only memories (EEPROMs), FLASH memories, magnetic or optical cards, etc., or any type of media suitable for storing electronic instructions either local to the computer or remote to the computer.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method. For example, any of the methods according to the present invention can be implemented in hard-wired circuitry, by programming a general-purpose processor, or by any combination of hardware and software. One of ordinary skill in the art will immediately appreciate that the invention can be practiced with computer system configurations other than those described, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, digital signal processing (DSP) devices, set top boxes, network PCs, minicomputers, mainframe computers, and the like. The invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network.
The methods of the invention may be implemented using computer software. If written in a programming language conforming to a recognized standard, sequences of instructions designed to implement the methods can be compiled for execution on a variety of hardware platforms and for interface to a variety of operating systems. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, application, driver, . . . ), as taking an action or causing a result. Such expressions are merely a shorthand way of saying that execution of the software by a computer causes the processor of the computer to perform an action or produce a result.
It is to be understood that various terms and techniques are used by those knowledgeable in the art to describe communications, protocols, applications, implementations, mechanisms, etc. One such technique is the description of an implementation of a technique in terms of an algorithm or mathematical expression. That is, while the technique may be, for example, implemented as executing code on a computer, the expression of that technique may be more aptly and succinctly conveyed and communicated as a formula, algorithm, or mathematical expression. Thus, one of ordinary skill in the art would recognize a block denoting A+B=C as an additive function whose implementation in hardware and/or software would take two inputs (A and B) and produce a summation output (C). Thus, the use of formula, algorithm, or mathematical expression as descriptions is to be understood as having a physical embodiment in at least hardware and/or software (such as a computer system in which the techniques of the present invention may be practiced as well as implemented as an embodiment).
Various spellings may be used for terms used in the description. These variations are to be understood to relate to the same term unless denoted otherwise. For example: TType is also spelled Ttype, TTYPE, ttype, etc.
Throughout the description various terms have been used that should be familiar to one of skill in the art, for example VOQ—Virtual Output Queue—a storage mechanism where packets are segregated but kept in timestamp order within the segregation should be known to one of skill in the art. Additionally terms where needed have been defined, for example, FlowID is the combination of RapidIO packet's PRIOrity and Critical-Request-Flow fields; CRQ—Circular Reordering Queue, etc. RFDID has been explained and one of skill in the art is familiar with TTYPE[0:3] and FTYPE[0:3] type TRANSACTION[0:3] as defined by RapidIO (e.g. Format type is a RapidIO packet field. It is represented as a 4-bit value, and is the first four bits in the logical packet stream. A RapidIO packet field, the specific transaction within the format type to be performed by the recipient. It is also called TYPE, TTYPE, or TType; e.g. transaction is understood by one of skill in the art as the specific transaction within the format class to be performed by the recipient; also called type or ttype; etc.).
Reference has been made to RapidIO and Serial RapidIO. One of skill in the art is familiar with the two incarnations of the RapidIO technology and is aware of the many common features and that the main difference between the parallel and serial RapidIO is the interface and the clock.
A machine-readable medium is understood to include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals which upon reception causes physical movement in matter (e.g. electrons, atoms, etc.) (e.g., carrier waves, infrared signals, digital signals, etc.); etc.
As used in this description, “one embodiment” or “an embodiment” or similar phrases means that the feature(s) being described are included in at least one embodiment of the invention. References to “one embodiment” in this description do not necessarily refer to the same embodiment; however, neither are such embodiments mutually exclusive. Nor does “one embodiment” imply that there is but a single embodiment of the invention. For example, a feature, structure, act, etc. described in “one embodiment” may also be included in other embodiments. Thus, the invention may include a variety of combinations and/or integrations of the embodiments described herein.
As used in this description, “substantially” or “substantially equal” or similar phrases are used to indicate that the items are very close or similar. Since two physical entities can never be exactly equal, a phrase such as “ ”substantially equal” is used to indicate that they are for all practical purposes equal.
As used in this description, “acknowledgment” and “acknowledgement” are variant spellings of the same word and are to be considered the same even if both variants are used in a sentence, claim, etc.
It is to be understood that in any one or more embodiments of the invention where alternative approaches or techniques are discussed that any and all such combinations as might be possible are hereby disclosed. For example, if there are five techniques discussed that are all possible, then denoting each technique as follows: A, B, C, D, E, each technique may be either present or not present with every other technique, thus yielding 2^5 or 32 combinations, in binary order ranging from not A and not B and not C and not D and not E to A and B and C and D and E. Applicant(s) hereby claims all such possible combinations. Applicant(s) hereby submit that the foregoing combinations comply with applicable EP (European Patent) standards. No preference is given any combination.
Thus a method and apparatus for a configurable packet routing, buffering and scheduling scheme to optimize throughput with deadlock prevention in SRIO-to-PCIe Bridges have been described.

## Claims

1. A method for bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the method comprising:
keeping track of arrival times for all packets received at an ingress port, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port, said ingress port having a dequeue block, and said ingress port operatively coupled to a plurality of virtual output queues;
selecting said plurality of virtual output queues for storing said all packets based on packet priority, packet critical request flow, and packet flow identification;
generating an ingress backpressure wherein the ingress backpressure is based on user configurable watermarks for user defined one or more packet types and for each of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port;
placing said all packets received at said ingress port in a circular-reorder queue, said circular-reorder queue having a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue, and wherein said circular-reorder queue stores an acknowledgement identification for each of said all packets received at said ingress port; and
dequeuing said circular-reorder queue.

2. A method for bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the method comprising:
handling packets on an ingress flow with an ingress port, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port, said ingress port operatively coupled to a plurality of virtual output queues, and said plurality of virtual output queues operatively coupled to a circular-reorder queue;
selecting said plurality of virtual output queues for storing said packets on said ingress flow based on packet priority, packet critical request flow, and packet flow identification;
handling packets on an egress flow in said circular-reorder queue, said circular-reorder queue having a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue, and wherein said circular-reorder queue stores an acknowledgement identification for each of said packets, the handling packets in said circular-reorder queue further comprising:
positioning said first-free-location pointer in said circular-reorder queue;
receiving a packet on said egress flow;
enqueuing said packet at said first-free-location pointer position in said circular-reorder queue;
positioning said next-to-send-location pointer in said circular-reorder queue at said first-free-location-pointer position in said circular-reorder queue;
dequeuing said packet at said next-to-send-location pointer position and assigning said acknowledgment identification to said packet;
transmitting to a link partner said dequeued packet and said acknowledgment identification;
receiving from said link partner a link-response signal related to said transmitted dequeued packet and said acknowledgment identification; and
when said link-response signal is a packet accept for said transmitted dequeued packet and said acknowledgment identification then moving said first-free-location pointer in said circular-reorder queue one step and moving said next-to-send-location pointer position one step in said circular-reorder queue;
when said link-response signal is a packet retry for said transmitted dequeued packet and said acknowledgment identification then not moving said next-to-send-location pointer in said circular-reorder queue.

3. A method for bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the method comprising:
handling packets on an ingress flow with an ingress port, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port, said ingress port operatively coupled to a plurality of virtual output queues, and said plurality of virtual output queues operatively coupled to a circular-reorder queue;
selecting said plurality of virtual output queues for storing said packets on said ingress flow based on packet priority, packet critical request flow, and packet flow identification;
handling packets on an egress flow in said circular-reorder queue, said circular-reorder queue having a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue, and wherein said circular-reorder queue stores an acknowledgement identification for each of said packets, the handling packets in said circular-reorder queue further comprising:
receiving in said circular-reorder queue one or more packets on said egress flow in an order;
enqueuing said one or more packets in said order;
positioning said first-free-location pointer in said circular-reorder queue at a location where a new packet may be enqueued;
maintaining in said circular-reorder queue said next-to-send pointer;
dequeuing from said circular-reorder queue at said next-to-send-location pointer a packet for transmission and assigning said packet for transmission an acknowledgment identification;
transmitting said packet to a link partner;
receiving from said link partner a link-response signal related to said transmitted packet; and when said link-response signal is a packet accept for said transmitted packet then moving said first-free-location pointer in said circular-reorder queue one step;
when said link-response signal is a packet retry for said packet transmitted then moving said next-to-send-location pointer in said circular-reorder queue to said packet transmitted.

4. The method of claim 3 wherein said link-response signal may move both said first-free-location pointer in said circular-reorder queue and said next-to-send-location pointer in said circular-reorder queue.

5. The method of claim 3 wherein said moving said next-to-send-location pointer in said circular-reorder queue to said packet transmitted further comprises:
re-ordering said one or more packets in said circular-reorder queue.

6. A method bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the method comprising:
handling packets on an ingress flow with an ingress port, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port, said ingress port operatively coupled to a plurality of virtual output queues, and said plurality of virtual output queues operatively coupled to a circular-reorder queue;
selecting said plurality of virtual output queues for storing said packets on said ingress flow based on packet priority, packet critical request flow, and packet flow identification;
receiving in said circular-reorder queue, said circular-reorder queue having a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue, and wherein said circular-reorder queue stores an acknowledgement identification for each of said packets, a plurality of packets wherein for each packet in said plurality of packets there is an associated flow identification and wherein a first packet is a first received packet in said plurality of packets and wherein a last packet is a last received packet in said plurality of packets;
receiving a mode signal for re-ordering said circular-reorder queue; and
when said mode signal is a higher signal then sequentially searching in order from said first packet to said last packet for a packet having a higher flow identification than said first packet and when said higher flow identification packet is found moving said higher flow identification packet to a position of said first packet and sequentially moving said first packet and any intervening packets between said first packet and one less than said higher flow identification packet one position toward said last packet;
when said mode signal is a highest signal then sequentially searching in order from said first packet to said last packet for a packet having a highest flow identification and when said highest flow identification packet is found moving said highest flow identification packet to a position of said first packet and sequentially moving said first packet and any intervening packets between said first packet and one less than said highest flow identification packet one position toward said last packet.

7. An apparatus for bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the apparatus comprising:
a circular-reorder queue for handling packets on an egress flow, said circular-reorder queue having a plurality of memory locations, a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue, and wherein said circular-reorder queue stores an acknowledgement identification for each of said packets on said egress flow;
a plurality of pointers to one or more of said plurality of memory locations in said circular-reorder queue;
an ingress port for keeping track of packet arrival order in a stream of packets on an ingress flow, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port, said ingress port operatively coupled to a plurality of virtual output queues, and said plurality of virtual output queues operatively coupled to said circular-reorder queue; and
an ingress transport layer module, said ingress transport layer module selects said plurality of virtual output queues for packet storage for said ingress flow based on packet priority, packet critical request flow, and packet destination port;
wherein said circular-reorder queue is further configured to perform packet reordering when various flows are backpressured.

8. The apparatus of claim 7 further comprising: a circular-reorder queue scheduler for making dequeuing decisions based on said packet arrival order.

9. The apparatus of claim 8 further comprising: said circular-reorder queue scheduler making dequeuing decisions based on a per queue for said various flows are backpressured.

10. The apparatus of 8 further comprising: said circular-reorder queue scheduler making dequeuing decisions based on a bridge specific ordering rules.

11. The apparatus of claim 7 wherein each of said plurality of virtual output queues stores packets of one or more specific packet types.

12. The apparatus of claim 11 wherein within each of said plurality of virtual output queues said packets are dequeued in a timestamp arrival order.

13. An apparatus for bridging between a Serial RapidIO® (SRIO) port and a PCI Express® (PCIe) port, the apparatus comprising:
an ingress port, said ingress port selected from the group consisting of said Serial RapidIO® (SRIO) port and said PCI Express® (PCIe) port for handling packets on an ingress flow;
a plurality of virtual output queues, said virtual output queues operatively coupled to one or more queuing blocks, said one or more queuing blocks operatively coupled to at least one circular-reorder queue which handles packets on an egress flow, said circular-reorder queue having a last-free-location pointer to a first open location in said circular-reorder queue, a next-to-send-location pointer to a first occupied location in said circular-reorder queue, a first-free-location pointer to a second open location in said circular-reorder queue, a last-packet-enqueued-location pointer to a second occupied location in said circular-reorder queue;
one of said virtual output queues allocated to a logical layer packet manager;
all but the one of said virtual output queues allocated to a user defined interface; and
an ingress transport layer module, said ingress transport layer module selects said plurality of virtual output queues for packet storage for said ingress flow based on packet priority, packet critical request flow, and packet destination port.

14. The apparatus of claim 13 wherein said logical layer packet manager is an ingress logical layer packet manager.

15. The apparatus of claim 13 further comprising:
an endpoint terminating device.

16. The apparatus of claim 13 further comprising:
a switch device.

17. The apparatus of claim 13 further comprising:
a bridge device; and
wherein said ingress transport layer module selects is based on packet FType, and packet TType.

18. The apparatus of claim 13 wherein said ingress transport layer module responds to a per packet flow identification to trigger a packet retry.

19. The apparatus of claim 13 wherein said virtual output queues size are user programmable.