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Cheddar – Real Time Simulator
Scheduling with task dependencies
Task Dependencies
Meaning…… resources shared by several tasks (ex :
semaphores)
precedencies relationship between several tasks (like constraints between the end of a task and the start of another one).
Types Of Tools
Shared resources analysis tools
Task precedencies analysis tools
Buffer analysis tools
Task precedencies analysis toolsWith Cheddar, dependencies are links
between at least two tasks
Three different types of dependencies Precedencies Message and Buffer dependencies
Types Of Dependencies
Precendencies express order constraints between end or begin of task execution.
Message dependencies expressed relationship between a sender and a receiver task of a given message.
Buffer dependencies expressed relationship between producer and consumer of data in a given buffer.
Precedencies Graph
Tasks -> circles.
Messages -> rectangles.
Buffers -> envelopes.
Typical Precedencies Graph
An Example
Different Parameters
Periodic Tasks - T1(4,1), T2(5,2), T3(5,1) Aperiodic Task – T4(10,2) EDF Scheduler Preemptive Precedence: T3 T2
Precedence Graph
Simulation Result
Some Limitations…
Capacity Is Integer Only.
Aperiodic Job Cannot Be Done On Rate Monotonic Scheduler.
For Task Precedencies, Tasks Must Have Equal Periods…
Project Files
Information stored during a simulation can be saved into Project Files
A project file is a XML file Correct structure of the Project Files can
be checked by the tool dump_sysdump_sys just read, parses and displays
to the screen the content of a XML Cheddar project file.