Missed Deadlines Should be Considered- Proposals for Modifying Existing Real-Time Disk Scheduling Algorithms
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Abstract
A system is said to be a real time system if it is capable of producing the correct results within a particular time limit. This time limit is called deadline. Real time systems may be hard or soft. A hard real time system may be considered to have failed if it is unable to produce the correct results within its allotted time span. Examples of hard real time systems are pacemakers, anti-lock brakes and aircraft control systems. In soft real time systems, deadline misses are tolerable, but may degrade the system’s quality of service. Scheduling is the basic mechanism adopted by a real time system to meet the deadline. Hence, scheduling algorithms dictate the proper functioning of real time systems. This paper aims to propose modifications to the existing real time disk scheduling algorithms. The modifications were made to include tardiness while assigning priorities to the disk requests. The modified algorithms were then experimentally compared with the existing ones on several parameters like seek time, average waiting time and average turnaround time.
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Keywords: Deadline; hard and soft real time systems; disk scheduling; tardiness; seek time; average waiting time; average turnaround time.
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