Buffer Space Optimisation with Communication
Mapping and Traffic Shaping for NoCs
Sorin Manolache, Petru Eles, Zebo Peng
Linköping University, Sweden
Outline
 System model
 Motivational example
 Problem formulation
 Solution outline
 Experimental results
 Conclusions
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
2
System Model
S0,1
P0,1
S1,1
P1,1
t2
t1
S0,0
P0,0
t5
t9
P1,0
S2,1
P2,1
t7
P3,1
S1,0
t10
S3,1
S2,0
S3,0
P2,0
t8
P3,0
t6
t3
t4
t11
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
3
Motivational Example
S0,1
P0,1
S1,1
P1,1
t2
t1
S0,0
P0,0
t5
t9
P1,0
S2,1
P2,1
t7
P3,1
S1,0
t10
S3,1
S2,0
S3,0
P2,0
t8
P3,0
t6
t3
t4
t11
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
4
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
5
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
6
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)
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
7
Communication Mapping
S0,1
P0,1
S1,1
P1,1
t2
t1
S0,0
P0,0
t5
t9
P1,0
S2,1
P2,1
t7
P3,1
S1,0
t10
S3,1
S2,0
S3,0
P2,0
t8
P3,0
t6
t3
t4
t11
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
8
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
9
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
10
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
11
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
12
Approach Overview
Communication
mapping
Response-time
analysis
Buffer space
analysis
Traffic
shaping
Response-time
analysis
Buffer space
analysis
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
13
Experimental Results
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
14
Experimental Results
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
15
Experimental Results
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
16
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
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
17
Buffer Space Analysis
0
15
27.5
35
40 42.5
0
15
27.5
35
40 42.5
S. Manolache, P. Eles, Z. Peng, Buffer Space Optimisation with Communication Synthesis and Traffic Shaping for NoCs
18