1. NoCVision: A Network-on-Chip Dynamic Visualization Solution http://nocvision.eecs.umich.edu
Vaibhav Gogte†, Doowon Lee†, Ritesh Parikh* and Valeria Bertacco†
†University of Michigan *Intel

2. Why visualization?
Architectures are moving toward heterogeneous computing
Future NoCs need to support wide range of complex IPs
We need a tool to help explore complex NoCs
Snapdragon
Intel i7 980X
Intel Xeon Phi –
6 core; point-to-point bus
>50 cores; 2D mesh
SoC; custom network on chip

3. Traditional NoC traffic analysis
network-on-chip simulation
log file 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
router 0:
congested
Analyzing millions of cycles…
Debugging with large logs…

4. NoCVision overview Visualization with NoCVision traditional log
input file
Compact
Dynamically tunable

5. Contributions Visualization of NoC dynamics
Intuitive charts and plots
Graphical user interface
Fine-granularity support
Time (up to single cycle), Component (up to virtual channel)
Support various analysis cases
Three modes of operation: interval, plot and event modes
High-level traffic characteristics
E.g.: Variation in average packet latency over time
Fine-grained behavior
E.g.: Congested components, specific packet flow

6. NoCVision analysis flow
Topology configuration
Design-space exploration
NoC design
NoCVision input file
Functional validation
Simulation parameters
Analysis data
Performance evaluation
NoCVision GUI

7. Input file Specifies network configuration and data to be analyzed
analysis data
[clock = 100]
avg_latency = 43.3
[clock = 200]
avg_latency = 56.2
network configuration
topology: ‘mesh’
k:8
n:2
num_vcs:4
metric
value
Network component
Metric input syntax
Network
Single value
Router
1-D array (# routers)
Link
2-D array (# routers X # links)
Virtual channel
3-D array (# routers X # links X # VCs)

8. How to create an input file
Users should instrument NoC simulators (e.g., Booksim) to collect data to be analyzed
Example 1: Link utilization
increase counter
simulation time
interval 2
interval 3
interval 4
interval 5
interval 1
For every interval, record counter to file and reset counter
Example 2: Packet traversal
packet A arrives at router X
A arrives at Y
A arrives at Z
simulation time
packet A departs from router X
A departs from Y
every event (red, pink) is recorded in file
* Full description can be found at: nocvision.eecs.umich.edu

9. Modes of operation 1. interval mode 2. plot mode 3. event mode
congested

10. (accumulate, average, maximum, mininum)
Interval mode
Interval mode visualizes…
network metrics associated routers, links, virtual channels
snapshots of network traffic per interval
E.g.: injection rate, traffic congestion
Setting up for interval mode
Specify interval
(where to start,
size of interval)
Choose metric
Choose property
(accumulate, average, maximum, mininum)

11. Layout of interval mode
color bar
data representation on the network
navigation controls

12. Plot mode Plot mode draws… multiple metrics together on the same chart
difference of a metric between two simulations (diff mode)
plots that can be zoomed along both axes (time and value)
E.g.: Variation of average packet latency during simulation
Setting up for plot mode
Select router, link and network metrics to display
Plotting in diff mode

13. Layout of plot mode
Selected components
Select components

14. Example of plotted metric
(router parameter – router0 link1)

15. Event mode Event mode visualizes…
discrete events occurring during simulation
multiple events in different components of network
E.g.: Packet traversal, hotspot routers
Two event types
(1) “on”: start of the event (2) “off”: end of the event
Event 1
“on” event
Event 2
“off” event
Event 3

16. Evaluation
Evaluation goal: to showcase analysis applications with NoCVision
NoC simulation parameters
Network: 8x8 mesh
Router: 3-stage pipeline, 4 virtual channels/port
Routing: XY routing
Traffic workloads
SPEC CPU 2006 applications
Three applications
Characterizing application workloads
Comparing latency of two network configurations
Investigating power-efficient NoC solution

17. 1. Analysis of application workloads
35 SPEC applications are classified in two groups based on network traffic
: High-traffic vs. Low-traffic applications
Then generated three workloads
High-traffic workload: all nodes running high-traffic applications
Low-traffic workload: all nodes running low-traffic applications
Medium-traffic workload: a mix of high-traffic and low-traffic applications
high-traffic workload
low-traffic workload

18. Injection rate analysis
Application-to-core mapping table (medium-traffic workload)
Node type
Node numbers
Memory
High-traffic
Edge-center (3, 4, 24 and 32), Center (27, 28, 35 and 36)
Low-traffic
Rest of the nodes
interval mode
plot mode
Router 0
Router 27
Router 18
Router 26

19. 2. Analysis of application-aware routing
Regular mesh
Fixed link-port binding
High diameter  High latency
HiROIC
application-aware NoC reconfiguration*
* A. Jain, R. Parikh and V. Bertacco, “High-radix on-chip networks with low-radix routers,” ICCAD 2014
Link-port decoupling
Lower diameter for frequently communicating nodes  Low average latency

20. Plot mode for comparing latencies
Regular mesh 2 4 6 8 10
time (millions of clock cycles)
Average packet latency (cycle)
HiROIC 2 4 6 8 10
time (millions of clock cycles)
Average packet latency (cycle)
Difference of average packet latency between regular mesh and HiROIC

21. 3. Analysis of power-efficient solution
Panthre (Power-aware NoCs through Reconfiguration)*
Fine-grained power-gating of NoC components
Topology reconfiguration and routing-update to bypass sleeping components
sleeping
src
sleeping
src 1 2 1 2
routers
routers 3 4 5 3 4 5 6 7 8 6 7 8
dest
dest
Conventional power-gating
Panthre
* R. Parikh, R. Das and V. Bertacco, “Power-aware NoCs through routing and topology reconfiguration,” DAC 2014

22. Visualization of Panthre’s execution flow
reconfiguration
reconfiguration
collect traffic statistics
interval
interval
interval
boundary
power-gating decisions
power-gating decisions
underutilized
Link utilization (interval mode)
underutilized
Disabled link (event mode)
disabled

23. Thank you! Questions? Conclusions
NoCVision is a network visualization tool that enables intuitive analyses of various NoC aspects
Three modes of operation support various analysis cases
Publicly available at:
Thank you!
Questions?