Real time systems in software engineering ppt

Ch15 software reuse. Ch10 dependable systems. Ch22 project management. Ch16 component based software engineering. Ch9 evolution. Ch23 project planning. Ch24 quality management.

Ch18 service oriented software engineering. Related Books Free with a 30 day trial from Scribd. Uncommon Carriers John McPhee. The Art of War Sun Tsu. Related Audiobooks Free with a 30 day trial from Scribd. Elizabeth Howell. Neeraj Alavelli , Pursuing B. Naveen Narayanan. Yesuko George. Shreya Ambaliya. Mustafa Zaydoun.

Arwa Saad , Student at Hail University. Show More. Views Total views. Actions Shares. No notes for slide. Ch21 real time software engineering 1. Real-time Software Engineering 1 2. Real-time Software Engineering 2 3. Real-time Software Engineering 3 4. If the system takes too long to respond, then the required response may be ineffective. Real-time Software Engineering 4 5. Real-time Software Engineering 5 6. Real-time Software Engineering 6 7. Real-time Software Engineering 7 8. Real-time Software Engineering 8 9.

Given a stimulus, the system must produce a reaction or response within a specified time. Real-time Software Engineering 9 Stimuli and responses for a burglar alarm system Stimulus Response Clear alarms Switch off all active alarms; switch off all lights that have been switched on. Console panic button positive Initiate alarm; turn on lights around console; call police. Power supply failure Call service technician. Sensor failure Call service technician. Single sensor positive Initiate alarm; turn on lights around site of positive sensor.

Two or more sensors positive Initiate alarm; turn on lights around sites of positive sensors; call police with location of suspected break-in. Real-time Software Engineering 10 Real-time Software Engineering 11 Real-time Software Engineering 12 Real-time Software Engineering 13 Real-time Software Engineering 14 May buffer information collected in response to a sensor stimulus. Real-time Software Engineering 15 Real-time Software Engineering 16 Real-time Software Engineering 17 Consumer processes take data from the buffer and make elements available.

Real-time Software Engineering 18 Real-time Software Engineering 19 Real-time Software Engineering 20 Real-time Software Engineering 21 Real-time Software Engineering 22 The loss of performance may make it impossible to meet real-time deadlines. Real-time Software Engineering 23 Real-time Software Engineering 24 If an error occurs in a soft real-time system, the computation is rolled back to a previously established checkpoint to initiate a recovery action.

A hard real-time system must execute a set of concurrent real-time tasks in a such a way that all time-critical tasks meet their specified deadlines. Every task needs computational and data resources to complete the job.

The scheduling problem is concerned with the allocation of the resources to satisfy the timing constraints. Figure 2 given below represents a taxonomy of real-time scheduling algorithms. Real-Time scheduling can be categorized into hard vs soft. Hard real-time scheduling can be used for soft real-time scheduling. Some of the research on QoS [ Klara95 ] addresses this problem in detail and is not covered here.

The present paper focuses on scheduling algorithms for hard real-time. Hard real-time scheduling can be broadly classifies into two types: static and dynamic.

In static scheduling, the scheduling decisions are made at compile time. A run-time schedule is generated off-line based on the prior knowledge of task-set parameters, e. So run-time overhead is small. More details on static scheduling can be found in [ Xu90 ]. On the otherhand, dynamic scheduling makes its scheduling decisions at run time, selecting one out of the current set of ready tasks.

Dynamic schedulers are flexible and adaptive. But they can incur significant overheads because of run-time processing. Preemptive or nonpreemptive scheduling of tasks is possible with static and dynamic scheduling. In preemptive scheduling, the currently executing task will be preempted upon arrival of a higher priority task. In nonpreemptive scheduling, the currently executing task will not be preempted until completion.

Schedulability test often used by dynamic schedulers to determine whether a given set of ready tasks can be scheduled to meet their deadlines. Different scheduling algorithms and their schedulability criteria is explained below. Rate monotonic algorithm [ Lui94 ] is a dynamic preemptive algorithm based on static priorities. The rate monotonic algorithm assigns static priorities based on task periods. Here task period is the time after which the tasks repeats and inverse of period is task arrival rate.

For example, a task with a period of 10ms repeats itself after every 10ms. The task with the shortest period gets the highest priority, and the task with the longest period gets the lowest static priority. At run time, the dispatcher selects the task with the highest priority for execution. According to RMA a set of periodic, independent task can be scheduled to meet their deadlines, if the sum of their utilization factors of the n tasks is given as below.

EDF algorithm is an optimal dynamic preemptive algorithm based on dynamic priorities. In this after any significant event, the task with the earliest deadline is assigned the highest dynamic priority.

A significant event in a system can be blocking of a task, invocation of a task, completion of a task etc.

Real-time executive components RTE process management Timing requirements Process architecture A temperature control system Reactor flux monitoring A ring buffer Java implementation of a ring buffer 1 Java implementation of a ring buffer 2 Total views 15, On Slideshare 0. From embeds 0. Number of embeds Downloads Shares 0.

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