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An Analytical Model for Worst-case Reorder Buffer Size of Multi-path Minimal Routing NoCs

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Title: Worst-case Performance Analysis of 2-D Mesh NoCs using Multi-path Minimal Routing Author: Administrator Last modified by: gaoming Created Date – PowerPoint PPT presentation

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Title: An Analytical Model for Worst-case Reorder Buffer Size of Multi-path Minimal Routing NoCs


1
An Analytical Model for Worst-case Reorder
Buffer Size of Multi-path Minimal Routing NoCs
  • Gaoming Du1, Miao Li 1, Zhonghai Lu2, Minglun
    Gao1, Chunhua Wang1
  • 1 Hefei University of Technology, Anhui
    Province, China
  • 2 KTH Royal Institute of Technology, Sweden
  • 2014.09.17

2
Outline
3
Multi-path Routing NoC
  • Prospects
  • Minimize network congestion and packet delay
  • Improve the load balance
  • Reduce power consumption
  • Fault tolerant routing
  • Problem
  • Out of order

P1
P2
P3
P4
4
Out of Order
Out of order packets
Packet in need
  • Solution 1 flow control
  • Prospects
  • Easy to control
  • Less hardware overhead
  • Side effect
  • More congestion
  • Longer packet delay

With worst-case analysis, it can reduce the
reorder buffer size with proper flow splitting
configuration effectively.
  • 1 S. Murali, D. Atienza, L. Benini, and G. De
    Micheli, A method for routing packets across
    multiple paths in NoCs with In-Order delivery and
    Fault- Tolerance gaurantees, VLSI Design, vol.
    2007, pp. 111, 2007.

5
Out of Order
Out of order packets
Packet in need
  • Solution 2 reorder buffer
  • Prospects
  • Less on chip congestion
  • Less re-arbitration time
  • Side effect
  • Area overhead

11 M. Daneshtalab, M. Ebrahimi, P. Liljeberg,
J. Plosila, and H. Tenhunen, Memory-efficient
on-chip network with adaptive interfaces,
Computer-Aided Design of ntegrated Circuits and
Systems, IEEE Transactions on, vol. 31, no. 1,
pp. 146159, 2012.
6
Reorder Buffer Size
  • Traditional approaches
  • By experience
  • No formal method
  • Too pessimistic
  • Our target
  • A general analytical model for worst-case reorder
    buffer size
  • A method to diminish the reorder buffer size
  • Traffic splitting proportion

7
Outline
8
NoC Architecture
  • Assumption
  • Non-intersecting sub-flows
  • Sub-flow number 2
  • Delay bounds for sub-flows already known

9
Network Calculus Basics Results
Assume Linear arrival curve
Latency-Rate (LR) server

The delay bound is
10
Outline
11
General Analysis
  • Srb Size of reorder buffer
  • D1 Packet delay in path f1
  • D2 Packet delay in path f2
  • ?t Packet injection interval
  • Ideal case
  • No contention

12
Worst-case Reorder Buffer Size
13
NC Model for Multi-path Routing
  • Step 1
  • Non-intersecting sub-flow identification
  • Traffic split proportion calculation

14
NC Model for Multi-path Routing
  • Step 2
  • Equivalent Service Curve (ESC) Calculation
  • R equivalent minimum service rate
  • T equivalent maximum processing latency

2 G. Du, C. Zhang, Z. Lu, A. Saggio, and M.
Gao, Worst-case performance analysis of 2-d mesh
nocs using multi-path minimal routing, in
ISSSCODES 2012.
15
NC Model for Multi-path Routing
  • Step 3
  • Calculation of Worst-case Reorder Buffer Size.

16
Algorithm
  • Step 1
  • Path identification

Step 2 ESC calculation
Step 3 Worst case reorder buffer size calculation
17
Outline
18
Evaluation
  • Experiments targets
  • ?D ?
  • ? ?
  • Experiments methods
  • Synthetic pattern
  • Industry pattern

19
Experiments Setup
Flow type arrival curve Service curve
Target flow
Contention flows
f(1,16)
f(2,12) f(3,8) f(6,11)
20
Delta Delay VS. Buffer Size
  • The bigger the delay difference, the larger the
    reorder buffer size
  • To balance the traffic proper path
    configuration
  • Maximum reduction 56.99

21
Full Traffic Splitting
  • Target flow full traffic splitting
  • The more balanced traffic, the smaller the
    reorder buffer size
  • Average improvement of 57.04

22
Simulation
  • Setup
  • Px 0.1
  • Results
  • No packet loss
  • Fully covered by analytical results

23
Industry Case
  • Less number of reorder buffers
  • Number of reorder buffers 3
  • Shorter long-path
  • Max hops 3

24
Node 4, 6, and 7
  • Mapping 1
  • Less worst-case reorder buffer size
  • Shorter path delays

25
Total Size
  • Mapping 2
  • Reduction of maximum 36.50 (76 packets)
  • Average 29.20 (61packets)
  • Minimum 22.12 (46 packets)

26
Summary
  • Our analytical model
  • Reduce worst case reorder buffer size
  • To choose proper sub-flows pairs
  • To alter traffic splitting proportion
  • Explore mapping effects
  • Reorder buffer size
  • Future work
  • To extend to more general cases

27
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Conclusion
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3
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4
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5
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ways to communicate with consumers
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