Page 60 - DCAP608_REAL TIME SYSTEMS

Unit 5: Real-time System Dependencies

Notes

Task Prepare a chart depicting certain performance measure of jobs that have soft
deadlines and compare it with those having hard deadlines.

For many soft real applications, it is acceptable to complete some jobs late or discard late jobs.
For such application, suitable performance measure includes the miss rate and loss rate. The
former gives the percentage of jobs that are executed but completed too late, and the latter give
the percentage of jobs thwart are discarded. When it is impossible to complete all the jobs in
time, a scheduler may choose to discard some jobs. Thus scheduler may increases the loss rate
but would complete more jobs in time. Similarly, reducing the loss rate may lead to an increase
in miss rate. Depends on the application invalid rate is the sum of miss and loss rates and the
percentage of all jobs that do not produce a useful result. We want to keep invalid rate as small
as possible.

Lab Exercise Search a well-labelled diagram for internal component parameter.

Self Assessment

State whether the following statements are True or False:
7. The configuration of the resources cannot be described using a resource graph.
8. Jobs are scheduled and allocated resources according to a chosen set of scheduling algorithms
and resource access-control protocols.
9. The most frequently used performance measure of jobs that have soft deadlines is heir
average response time.
10. For many soft real applications, it is acceptable to complete some jobs late or discard late
jobs.

11. When it is impossible to complete all the jobs in time, a scheduler may choose to discard
some jobs.
12. Scheduler may increase the loss rate but would complete more jobs in time.



Case Study Python as Technology Enabler for TTTech’s

Development Software

TTech, founded in 1998, focuses on developing a technology for safety-critical real-
time systems. Our central technology is the Time-Triggered Protocol (TTP), a
Tcommunication protocol used in embedded systems for distributed fault-tolerant
applications, such as drive-by-wire and fly-by-wire vehicles. For TTP, we provide chip
models for implementing the necessary hardware in silicon, services to customers using
the technology, and a broad range of tools.
When starting out in 1998, we urgently needed tools for configuring TTP-based networks.
Several people in the team already had experience in writing configuration tools for
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