Real-Time Mixed-Criticality Wormhole Networks Leandro Soares - - PowerPoint PPT Presentation

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Real-Time Mixed-Criticality Wormhole Networks Leandro Soares - - PowerPoint PPT Presentation

Jan 28, 2023 343 likes •1.37k views

Leandro Soares Indrusiak Real-Time Mixed-Criticality Wormhole Networks Leandro Soares Indrusiak Real-Time Systems Group Department of Computer Science University of York United Kingdom 1 Real-Time Systems Group Leandro Soares Indrusiak

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1 Leandro Soares Indrusiak Real-Time Systems Group

Real-Time Mixed-Criticality Wormhole Networks

Leandro Soares Indrusiak

Real-Time Systems Group Department of Computer Science University of York United Kingdom

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2 Leandro Soares Indrusiak Real-Time Systems Group

Outline

  • Wormhole Networks
  • Networks-on-Chip
  • Real-Time Analysis
  • Mixed-Criticality Analysis
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3 Leandro Soares Indrusiak Real-Time Systems Group

Motivation

  • Multiprocessor and multicore systems

forced a shift towards communication- centric design

abundant computation resources shared communication media

  • Inter-processor communication

point-to-point bus networks

source: IBM, Intel

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4 Leandro Soares Indrusiak Real-Time Systems Group

Networks – key characteristics

  • topology

mesh, star, torus…

  • routing protocol

deterministic, adaptive…

  • arbitration

round-robin, priority preemptive, priority non- preemptive, TDM…

  • buffering

FIFO, SAFC, SAMQ, DAMQ, hot potato…

  • flow control protocol

handshake, credit-based…

  • switching protocol

circuit, store-and-forward, wormhole

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5 Leandro Soares Indrusiak Real-Time Systems Group

Networks – key characteristics

  • topology

mesh, star, torus…

  • routing protocol

deterministic, adaptive…

  • arbitration

round-robin, priority preemptive, priority non- preemptive, TDM…

  • buffering

FIFO, SAFC, SAMQ, DAMQ, hot potato…

  • flow control protocol

handshake, credit-based…

  • switching protocol

circuit, store-and-forward, wormhole

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6 Leandro Soares Indrusiak Real-Time Systems Group

Circuit Switching

Terminal

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

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7 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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8 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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9 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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10 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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11 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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12 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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13 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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14 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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15 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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16 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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17 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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18 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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19 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

A segment of reserved path is idle for a significant period

  • f time.

Circuit Switching

Terminal Terminal

Packet Header Packet Data

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20 Leandro Soares Indrusiak Real-Time Systems Group

Circuit switching

  • Packets are forwarded through dedicated paths that are

kept until the transmission is finished

  • Contention can arise when establishing a path

 no further contention once path is established

  • Temporary packet buffering in routers is not required
  • Suitable to long and infrequent messages

 time to establish a path can be high

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21 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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22 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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23 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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24 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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25 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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26 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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27 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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28 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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29 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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30 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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31 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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32 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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33 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

SAF Switching

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34 Leandro Soares Indrusiak Real-Time Systems Group

SAF Switching

  • SAF - Store And Forward
  • Routers can only forward a packet once it is completely

received and stored

 packet acquires one link at a time

  • Router input ports must have enough buffering space to

temporarily store a complete packet

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35 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Switching

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

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36 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Switching

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

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37 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Switching

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

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38 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Switching

Switch Switch Switch Switch Switch Switch

Terminal

Packet Header Packet Data

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39 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Wormhole Switching

Terminal

Packet Header Packet Data

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40 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Wormhole Switching

Terminal

Packet Header Packet Data

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41 Leandro Soares Indrusiak Real-Time Systems Group

Switch Switch Switch Switch Switch Switch

Wormhole Switching

Terminal

Packet Header Packet Data

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42 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole switching

  • Packet is routed and forwarded as soon the header flit has

arrived

 payload flits follow header

  • Input ports does not need to buffer a complete packet

flits of a packet can be stored across multiple routers

  • Trade-off between buffer overheads and network contention
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43 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Networks-on-Chip

  • Small buffering overheads
  • f wormhole networks was

particularly attractive to a special class of resource- constrained networks: Networks-on-Chip (NoCs)

small buffers mean smaller area and lower energy dissipation

PE PE PE PE PE PE PE PE R PE R R R R R R R R

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44 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Networks-on-Chip

PE PE PE PE PE PE PE PE R PE R R R R R R R R

Core Router Link

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45 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Networks-on-Chip

PE PE PE PE PE PE PE PE R PE R R R R R R R R

Link

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46 Leandro Soares Indrusiak Real-Time Systems Group

arbitration routing & transmission control routing & transmission control

data out data in data out data in data out data in data out data in data out data in

PE PE PE PE PE PE PE PE R PE R R R R R R R R

Wormhole Networks-on-Chip

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47 Leandro Soares Indrusiak Real-Time Systems Group

NoC parallelism and scalability

CPU CPU CPU CPU RAM CPU I/O CPU

Multiple connections simultaneously

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48 Leandro Soares Indrusiak Real-Time Systems Group

NoC performance

link contention leads to latency variability

CPU CPU CPU CPU RAM CPU I/O CPU

task contention leads to latency variability

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49 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Networks-on-Chip

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R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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51 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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52 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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53 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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54 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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55 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

packet is blocked Packet Header Packet Data

PE

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56 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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57 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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58 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

new packet released Packet Header Packet Data

PE

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59 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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61 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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62 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Wormhole Networks-on-Chip

PE

Packet Header Packet Data

PE

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63 Leandro Soares Indrusiak Real-Time Systems Group

Wormhole Networks-on-Chip

  • Packets can acquire multiple links, making

it hard to predict worst-case latency due to complex contention patterns

  • Alternative: wormhole NoCs using virtual

channels with priority preemptive arbitration

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64 Leandro Soares Indrusiak Real-Time Systems Group

Priority preemptive virtual channels

…

highest priority with remaining credit data_in credit_out data_out credit_in

…

routing & transmission control priority ID

…

highest priority with remaining credit

…

routing & transmission control

PE PE PE PE PE PE PE PE R PE R R R R R R R R

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65 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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66 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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67 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

high priority packet released

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68 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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69 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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70 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

first packet is preempted

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71 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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72 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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73 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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74 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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75 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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76 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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77 Leandro Soares Indrusiak Real-Time Systems Group

R R R R R R

Priority preemptive virtual channels

PE

wormhole NoC with priority preemptive virtual channels

Packet Header Packet Data

PE

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78 Leandro Soares Indrusiak Real-Time Systems Group

Performance evaluation

  • How to estimate performance figures for a particular

application mapped to a Network-on-Chip?

 full system prototyping

  • cores + NoC in FPGA, running OS + application
  • extremely costly setup time, can only explore few design alternatives

 accurate system simulation

  • cycle-accurate model of cores + NoC, running OS + application
  • extremely long simulation time, can only explore few design alternatives

 approximately-timed system simulation

  • approximately-timed model of cores + NoC, executing an abstract model of

the OS + application

 analytical system performance models

  • average or worst-case latency estimation for restricted application styles

(periodic independent tasks, synchronous dataflow, etc.)

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79 Leandro Soares Indrusiak Real-Time Systems Group

Performance evaluation

  • How to estimate performance figures for a particular

application mapped to a Network-on-Chip?

 full system prototyping

  • cores + NoC in FPGA, running OS + application
  • extremely costly setup time, can only explore few design alternatives

 accurate system simulation

  • cycle-accurate model of cores + NoC, running OS + application
  • extremely long simulation time, can only explore few design alternatives

 approximately-timed system simulation

  • approximately-timed model of cores + NoC, executing an abstract model of

the OS + application

 analytical system performance models

  • average or worst-case latency estimation for restricted application styles

(periodic independent tasks, synchronous dataflow, etc.)

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80 Leandro Soares Indrusiak Real-Time Systems Group

  • The worst-case end-to-end response time of a task is the longest

time consumed between its release and the moment when the last packet it transmits arrives at the destination core

  • It can be found by a specific composition of:

 worst case response time of tasks based on classical single processor schedulability analysis (Audsley et al., 1993)  worst case latency of traffic flows based on the NoC schedulability analysis (Shi and Burns, 2008)

  • It assumes that:

 the minimum inter-release time of each task (T) and its worst case computation time (C) are known  the source task only starts transmitting packets after it finishes its execution  system uses priority-preemptive arbitration

L.S. Indrusiak, “End-to-End Schedulability Tests for Multiprocessor Embedded Systems based on Networks-on-Chip with Priority-Preemptive Arbitration”, Journal of Systems Architecture, v. 60, n. 7, Aug 2014.

End-to-End Response Time Analysis (E2ERTA)

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81 Leandro Soares Indrusiak Real-Time Systems Group

End-to-End Response Time Analysis (E2ERTA)

period (T) = deadline (D) response time

  • f the task

computation response time

  • f the task

communication

L.S. Indrusiak, “End-to-End Schedulability Tests for Multiprocessor Embedded Systems based on Networks-on-Chip with Priority-Preemptive Arbitration”, Journal of Systems Architecture, v. 60, n. 7, Aug 2014.

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82 Leandro Soares Indrusiak Real-Time Systems Group

End-to-End Response Time Analysis (E2ERTA)

L.S. Indrusiak, “End-to-End Schedulability Tests for Multiprocessor Embedded Systems based on Networks-on-Chip with Priority-Preemptive Arbitration”, Journal of Systems Architecture, v. 60, n. 7, Aug 2014.

  • Deadline (D) = Period of Task (T)
  • End-to-end response time analysis:

 a task is schedulable if  a packet flow is schedulable if

  • Otherwise, system is unschedulable
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End-to-End Response Time Analysis (E2ERTA)

precedence relationship must solve task’s response time first, and add it as the release jitter of the flow’s response time calculation

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84 Leandro Soares Indrusiak Real-Time Systems Group

End-to-End Response Time Analysis (E2ERTA)

recurrence relationships can be solved iteratively until convergence require safe initial value

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85 Leandro Soares Indrusiak Real-Time Systems Group

End-to-End Response Time Analysis (E2ERTA)

must identify interference sets, i.e. which tasks Taskj (or flows Flowj) can preempt a given task Taski (or flow Flowi)

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86 Leandro Soares Indrusiak Real-Time Systems Group

End-to-End Response Time Analysis (E2ERTA)

  • Complexity of E2ERTA scales with

size of NoC complexity of application (# tasks and # flows) and of the allocation (amount of resource contention)

  • Performance of E2ERTA is orders of magnitude

faster than the fastest available NoC simulation

  • E2ERTA has been further optimised and

hardware-accelerated

  • Y. Ma and L.S. Indrusiak, “Hardware-accelerated Response Time Analysis for Priority-Preemptive Networks-on-Chip”, in Int Symposium on

Reconfigurable Communication-centric Systems-on-Chip (ReCoSoC), 2015.

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87 Leandro Soares Indrusiak Real-Time Systems Group

Outline

  • Wormhole Networks
  • Networks-on-Chip
  • Real-Time Analysis
  • Mixed-Criticality Analysis
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88 Leandro Soares Indrusiak Real-Time Systems Group

Outline

  • Wormhole Networks
  • Networks-on-Chip
  • Real-Time Analysis
  • Mixed-Criticality Analysis

rant time!!

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89 Leandro Soares Indrusiak Real-Time Systems Group

Outline

  • Wormhole Networks
  • Networks-on-Chip
  • Real-Time Analysis
  • Mixed-Criticality Analysis
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90 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Packet flows of different levels of criticality can share the

NoC infrastructure

 Initial work considers only two levels of criticality, and packet flows are assigned a criticality level at design time: HI-CRIT or LO-CRIT  Packet flows are also assigned fixed priorities at design time

  • HI-CRIT packet flows make more conservative assumptions

about the environment and therefore have more conservative upper bounds for their resource provisions

 however, it is expected that during normal operation mode their resource usage stays within the bounds obtained using less conservative assumptions used for LO-CRIT packets

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91 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Possible sources of uncertainty

 packet length  packet flow period

  • All packet flows must be schedulable

under normal mode

  • Runtime monitoring detects when

packets go “beyond normal”

 e.g. packets longer than expected, or injected more often than expected in normal mode

C R R R R C R R C R R C R C C C C C

network interface

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92 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Runtime monitoring detects

when packets go “beyond normal”

if it is a LO-CRIT packet exceeding its normal budget, reject it if it is a HI-CRIT packet exceeding its normal budget, signal a mode change to the NoC, aiming to notify that a service degradation to LO-CRIT packets is needed so that HI-CRIT packets can still be scheduled despite

  • f potential increase of interference

due to overbudget packets C R R R R C R R C R R C R C C C C C

mode change notification

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93 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Two mode change

propagation protocols

WPMC: mode change flag “piggybacked” on packets that pass through a router that has changed mode WPMC-FLOOD: mode change is flooded to the entire NoC

C R R R R C R R C R R C R C C C C C

  • A. Burns, J. Harbin, L. S. Indrusiak: A Wormhole NoC Protocol for Mixed Criticality Systems. RTSS 2014: 184-195
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94 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Two mode change

propagation protocols

WPMC: mode change flag “piggybacked” on packets that pass through a router that has changed mode WPMC-FLOOD: mode change is flooded to the entire NoC

C R R R R C R R C R R C R C C C C C

  • L. S. Indrusiak, J. Harbin, A. Burns: Average and Worst-Case Latency Improvements in Mixed-Criticality Wormhole Networks-on-Chip. ECRTS 2015.
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95 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Two HI-CRIT mode

arbitration schemes

routers that change mode ignore arbitration requests of LO-CRIT packets routers that change mode arbitrate links in criticality order (HI-CRIT then LO-CRIT), and in priority order within the same criticality

C R R R R C R R C R R C R C C C C C

  • A. Burns, J. Harbin, L. S. Indrusiak: A Wormhole NoC Protocol for Mixed Criticality Systems. RTSS 2014: 184-195
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96 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

C R R R R C R R C R R C R C C C C C

  • Two HI-CRIT mode

arbitration schemes

routers that change mode ignore arbitration requests of LO-CRIT packets routers that change mode arbitrate links in criticality

  • rder (HI-CRIT then LO-CRIT),

and in priority order within the same criticality

  • L. S. Indrusiak, J. Harbin, A. Burns: Average and Worst-Case Latency Improvements in Mixed-Criticality Wormhole Networks-on-Chip. ECRTS 2015.
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97 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Response Time Analysis formulations for

each of the protocols were developed

  • Evaluation with synthetic flowsets (against

no criticality awareness and criticality- monotonic arbitration) and cycle-accurate NoC simulation

 WPMC-FLOOD slightly better in general, significantly better in stress scenarios

  • Less restrictive arbitration allows LO-CRIT

packets to flow when there are no HI-CRIT packets or when they are blocked due to interferences

  • A. Burns, J. Harbin, L. S. Indrusiak: A Wormhole NoC Protocol for Mixed Criticality Systems. RTSS 2014: 184-195
  • L. S. Indrusiak, J. Harbin, A. Burns: Average and Worst-Case Latency Improvements in Mixed-Criticality Wormhole Networks-on-Chip. ECRTS 2015.
slide-98
SLIDE 98

98 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Response Time Analysis formulations for

each of the protocols were developed

  • Evaluation with synthetic flowsets

(against no criticality awareness and criticality-monotonic arbitration) and cycle-accurate NoC simulation

 WPMC-FLOOD slightly better in general, significantly better in stress scenarios

  • Less restrictive arbitration allows LO-CRIT

packets to flow when there are no HI-CRIT packets or when they are blocked due to interferences

  • L. S. Indrusiak, J. Harbin, A. Burns: Average and Worst-Case Latency Improvements in Mixed-Criticality Wormhole Networks-on-Chip. ECRTS 2015.
slide-99
SLIDE 99

99 Leandro Soares Indrusiak Real-Time Systems Group

Mixed-criticality packet communication in NoCs

  • Response Time Analysis formulations for

each of the protocols were developed

  • Evaluation with synthetic flowsets (against

no criticality awareness and criticality- monotonic arbitration) and cycle-accurate NoC simulation

 WPMC-FLOOD slightly better in general, significantly better in stress scenarios

  • Less restrictive arbitration allows LO-

CRIT packets to flow when there are no HI-CRIT packets or when they are blocked due to interferences

  • L. S. Indrusiak, J. Harbin, A. Burns: Average and Worst-Case Latency Improvements in Mixed-Criticality Wormhole Networks-on-Chip. ECRTS 2015.
slide-100
SLIDE 100

100 Leandro Soares Indrusiak Real-Time Systems Group

Open questions

  • How to detect that the network has returned to

normal mode, so LO-CRIT service and guarantees can be restored?

  • Can we give reasonable guarantees in networks

with non-preemptive arbitration?

  • Can we optimise task allocation and packet

routing?

  • Benchmarks?
slide-101
SLIDE 101

101 Leandro Soares Indrusiak Real-Time Systems Group

Real-Time Mixed-Criticality Wormhole Networks

Mixed Criticality Embedded Systems on Many-Core Platforms EPSRC EP/K011626/1 Project

Leandro Soares Indrusiak, with contributions from: Alan Burns, Rob Davis, Iain Bate, James Harbin

www.cs.york.ac.uk/research/research-groups/rts/mcc www.cs.york.ac.uk/rts

MCCps - Mixed Criticality Cyber- Physical Systems EPSRC EP/P003664/1 Project