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 P0,0 P0,1 P1,0 P1,1 P2,0 P2,1 P3,0 P3,1 S0,0 S0,1 S1,0

4. Motivational Example P0,0 P0,1 P1,0 P1,1 P2,0 P2,1 P3,0 P3,1 S0,0 S0,1

5. Motivational Example P0,1 L0,1,E P1,1 L1,1,E L1,1,S L2,1,S P2,1 P2,0
Time

6. 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

7. 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)

8. Communication Mapping
S0,0
S0,1
S1,0
S1,1
S2,0
S2,1
S3,0
S3,1 t1 t2 t7 t8 t9
t10
t11 t5 t6 t3 t4

9. Communication Mapping
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
Time

11. 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

12. 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

13. Approach Overview Communication mapping Buffer space analysis
Response-time
Traffic
shaping
Buffer space
analysis
Response-time

14. Experimental Results

15. Experimental Results

16. Experimental Results

17. 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

18. Buffer Space Analysis 15
27.5 35 40
42.5 15
27.5 35 40
42.5