Dynamic Scheduling in Real Time for Resource Optimization

Abstract

Scheduling is a decision making process which deals with the allocation of resources to tasks over given time periods. Scheduling means how the processes can be assigned on the available CPU. It is a key feature in multitasking, multiprocessing and real-time operating system design. Scheduling is done by scheduler and dispatcher. A scheduler is a person or machine that organizes or maintains schedules. A dispatcher is a module which gives control of CPU to the process selected by the scheduler. Scheduling problem involves jobs that must schedule on machines subject to certain constraints to optimize some objective functions. In real time systems the correctness of the results depends not only on the logical computations but also on the time at which results are produced. In real time environments, scheduler needs to ensure that processes meet the deadlines that are crucial for keeping the system safe. The tasks which result in catastrophic conditions on missing the deadline are the hard real time tasks and the tasks whose results are useful even after missing the deadline are known as soft real time systems. In real time system, processes can dynamically increase or decrease in priority depending on whether it has been serviced already, or it is waiting extensively. The priority assignment schemes assign priorities to different tasks which can be static or dynamic. The study of various scheduling algorithms along with the comparison between different real time scheduling algorithms has been done in the thesis. Resource optimization is of main concern in case of scheduling in real time. Shortest path algorithms achieve resource optimization between different nodes by finding the shortest path using dynamic scheduling. Shortest distance between the nodes results in resource optimization and the tasks are scheduled through that optimized path in order to achieve feasible and efficient schedule. The shortest paths between all the nodes along with the calculation of probability of error in all the paths have been evaluated using dynamic scheduling by considering two cases: (i) when node N4 is failed (ii) when node N12 is failed. From the above two cases it has been observed that the probability of failure comes out to be the upmost for nodes N13, N12 and B.