simSCHD

Evaluation of the Static Scheduling and Timing Budget

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Abstract: ???

Keywords: Multitasking, Multicore, Loosely Timed Model, Timing Budget, Static Scheduler, System Simulation, Timing Model, Hard Real Time, Model Based Development and Optimization, SystemC

Overview

• A simulation platform for the evaluation of the scheduling and timing budget

• Simplifies the initial stages of the architecture development for Hard Real Time systems.

  • Allow for the simulation driven development and optimization of the architecture

• Flexible, highly abstract and independent of the implementation target (HW or SW)

• Input:

  • Top-level timing requirements
  • Outline of the processing flow

• Output:

  • Processing schedule and timing diagrams
  • List of the execution blocks and common resources as well as the requirements for both

• Benefits of using SystemC

  • Reduced update-simulation-analysis cycle which allows for simulation driven development and optimization of the architecture
  • High level of abstraction for the scheduler and execution core preferences to stay focused on the architectural tasks
  • Integration into the existing simulation frameworks and workflows
  • Open source

Simulated System

System Model

• Real-Time System is simulated as a number of concurrently running Threads
• Each Thread is a succession of the Tasks to execute and the Events to generate
• New Thread is initiated when the specific set of the Events has been generated
  • Thread synchronization
• Each Task is a specification of
  • Execution time,
  • Set of the Execution Blocks to be occupied for the duration of the execution time, and
  • Demand requested from the Common Resources by the Execution Blocks from the set.
• Competition for the Execution Block is resolved by the priorities which were specified in the Thread preferences

Execution Blocks and Common Resources

• Each Common Resource simulates an instance which is shared by multiple Execution Blocks in the cooperative manner.
• The Common Resource is characterized by its capacity
• Examples
  • Shared memory interface with throughput limit. Capacity: max throughput.
  • Power source with the current limit. Capacity: max current.

Block Diagram of the Simulation Platform

Planner

• Executes multiple concurrent Threads
• Keeps the register of the Events generated by the running Threads
  • Events are used for the synchronization between the Threads
• Assigns the available Execution Blocks to the Tasks which are called by the running Threads
  • Resolves Thread priorities
• Transmits runtime configuration to the Execution Blocks and receives their state
  • Keeps the record of the available and busy Execution Blocks

Execution Block

• Receives runtime configuration from the Planner
• Transmits requests with the demand values to the Common Resources
• Receives the information from the Common Resource about its total demand, combines the information from the multiple Common Resources and adjusts the execution time accordingly
• Transmits “available” status to the Planner when the execution time is expired

Common Resource

• Receives requests with the demand values from the Execution Blocks
• Calculates total demand requested by all of the Execution Blocks which are using this Resource
• Broadcasts the value of the total demand to all of the Execution Blocks which are using this Resource

Simulator Configuration and Preferences

Examples

For more details and application examples please refer to doc/simschd.pptx

Source Directories:

doc            - documentation
mat            - matlab models  
examples       - application examples
schd_core      - Processing modules and core assembly
schd_common    - top-level functions  
schd_pref      - simulation and system preferences  
schd_dump      - data dump   
schd_report    - logging and reporting functions  
schd_systemc   - Files taken from SystemC sources  
schd_trace     - waveform trace  
schd_time      - simulation time and resolution  

Prerequisites:
GCC (4.8.5)
cmake (3.16)
make (3.82)
SystemC (2.3.3)
Boost (1.68.0)
matIO (1.5.16)
gtkwave (3.3.95) or other VCD viewer

Environment:

export  CC=$(command -v gcc)
export GCC=$(command -v gcc)
export CXX=$(command -v g++)
$BOOST_HOME    contains Boost   installation path
$MATIO_HOME    contains matIO   installation path
$SYSTEMC_HOME  contains SystemC installation path

Quick start:

Skim through the slides:
./doc/simschd.pptx

Build:
$ mkdir build
$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Release ..
$ make all

Run:
$ ./simschd ./examples/test_short_gtkwave.json

Inspect the results:
In gtkwave File->Open New Window->trace.vcd 
Apply trace.trn translation file

Timing diagrams for test_short