Transcript RTOS_modeling

RTOS Modeling in Electronic
System Level Design
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Contents
References
Introduction to RTOS modeling in ESL design
Design Flow
RTOS simulation models
RTOS interface in SpecC
Difference in SpecC RTOS and SoCOS
Model refinement
Scheduled model
Experimental results
Conclusions
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References
[1] Embedded Software for SoC, chapter 5
[2] RTOS modeling in system level synthesis by Haobo Yu and
Daniel Gajski
[3] Operating System based Software Generation for Systems-onChip by Dirk Desmet, D. Verkest, and Hugo De Man
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Introduction to RTOS modeling in ESL design
In system-on-a-chip design era, raising the level of abstraction
is generally seen as a solution to increase productivity
Fast
System
RTL
Simulation
time &
Iteration
time
Chip
Slowest
Time
Various system-level design languages have been proposed :
SpecC, SystemC, CynApps, OCAPI, .. etc.
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Introduction to RTOS modeling in ESL design
Dynamic real-time behavior in embedded software can have a
large influence on design quality metrics like performance or
power
SystemC ver. 3.0 will support real-time OS models.
Electronic system
level design
Specification
Design Space Exploration
Partitioning
Implementation
Software process
Hardware process
Embedded software
+ OS
Register transfer
Level design
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Key Issues in ESL RTOS model
Capturing the abstracted RTOS behavior in ESL design
Not requiring any specific language extensions to existing ESL
language
Task management
Real-time scheduling
Preemption
Task synchronization
Interrupt handling
Minimal modeling effort
Early and rapid design space exploration
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Design Flow [1],[2]
Processes map to PEs
Static
Dynamic
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Design Flow [3] : SoCOS
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RTOS Simulation Models
RTOS Interface in SpecC [1], [2]
Task management
Real-time scheduling
Preemption
Task synchronization
Interrupt handling
Only consider two kinds of
tasks :
Periodic hard real time
tasks having a critical
deadline
Non periodic real time
tasks, having a fixed
priority
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RTOS Simulation Models
RTOS Interface in SpecC [1], [2] (cont’d)
Specification to Architectural model
task 1
Process 1
task 2
PE
(processing element)
RTOS interface
calls
Process 2
RTOS channels
Extended RTOS service layer
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RTOS Simulation Models
Difference in SpecC RTOS [1],[2] and SoCOS [3]
Consistency in existing ESL libraries
SoCOS requires its own simulation engine
Timing budget vs. estimating execution time
Refinement methodology
SoCOS only concerns with communication models (sync/async)
SpecC RTOS uses dynamic scheduling refinement process
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Model Refinement
Task refinement :
behavior-to-task conversion
dynamic child task creation
ready queue
Synchronization refinement :
event handling
event queue
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Scheduled model
Scheduled model (=architectural model) calls the scheduler for
selecting a dispatching task from the ready queue
Priority : B3 > B2
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Experimental Result
Example design of a voice codec for mobile phone applications
Contains two tasks; encoding and decoding
Implemented on Motorola DSP56600
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Experimental Result
ADSL modem modeling using SoCOS
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Conclusion
RTOS behaviors are modeled in high level of abstraction.
It allows dynamic real time behaviors to the existing ESL design
without much effort
Using RTOS simulation model, early validation and design space
exploration can be performed.
Small interfaces of RTOS effectively supports the dynamic
behaviors
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