Buffer Space Optimisation with Communication Mapping and Traffic Shaping for NoCs

1
Buffer Space Optimisation with Communication
Mapping and Traffic Shaping for NoCs

• Sorin Manolache, Petru Eles, Zebo Peng
• Linköping University, Sweden

2
Outline

• System model
• Motivational example
• Problem formulation
• Solution outline
• Experimental results
• Conclusions

3
System Model
4
Motivational Example
t1
t2
t5
t3
t4
t6
5
Motivational Example
P0,1
L0,1,E
P1,1
L1,1,E
L1,1,S
L2,1,S
P2,1
P2,0
L1,0,E
P1,0
L0,0,E
P0,0
L0,1,S
L2,0,E
P3,0
Time
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Buffer Space Minimisation

• Scenario in which an application-specific NoC is
  built
• There is freedom in deciding how much buffer
  memory to put at each switch ?
• Minimisation of the total buffer space demand of
  the application

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Solution Techniques

• Problem solved with the combination of two
  techniques
• Off-line mapping of data packets to network links
• Setting the release time of each packet on the
  link (traffic shaping)

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Communication Mapping
t1
t2
t5
t3
t4
t6
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Communication Mapping
P0,1
L0,1,E
P1,1
L1,1,E
L1,1,S
L2,1,S
P2,1
P2,0
L1,0,E
P1,0
L0,0,E
P0,0
L0,1,S
L2,0,E
P3,0
Time
10
Traffic Shaping
P0,1
L0,1,E
P1,1
L1,1,E
L1,1,S
L2,1,S
P2,1
P2,0
L1,0,E
P1,0
L0,0,E
P0,0
L0,1,S
L2,0,E
P3,0
Time
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Problem 1 Application-Specific NoCs

• Scenario in which an application-specific NoC is
  built
• Find a communication mapping and the packet
  release times of all packets and determine the
  amount of buffer memory at each switch such that
• No deadline is missed and no buffer overflow
  occurs
• The total amount of buffer memory is minimised
• Message arrival probability is above a specified
  threshold given a link failure model

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Problem 2 Predefined NoC Platform

• Scenario in which the application is implemented
  on an existing NoC with given buffer memory at
  each switch
• Find a communication mapping and the packet
  release times of all packets such that
• No deadline is missed and no buffer overflow
  occurs
• Message arrival probability is above a specified
  threshold given a link failure model

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Approach Overview
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Experimental Results
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Experimental Results
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Experimental Results
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Conclusions

• It is important for a communication synthesis
  method to consider buffer space minimisation
• Communication mapping and traffic shaping
  heuristic for buffer space minimisation under
  real-time constraints
• Fast buffer space analysis

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Buffer Space Analysis
0
15
27.5
35
40
42.5
15
35
42.5
0
27.5
40