Research Of A Timing Predictable Real-Time Scheduler

As aviation industry,industrial control,telecommunication systems and military man-ufacture develop,correct results are not the most important. What matters much is the reliability and real-time capacity of operationg systems.Real-Time operating systems become the trend of the development of manufacturing industry gradually.Real-time systems lay claim to real-time capability.In other words,the real-time performance depends on whether a task could accurate calculation and return results within the strict time constraints or not.Commonly,a deadline miss will result in a system error or a invalidation.Taken in memory,time and processors,task scheduling decides the execution order in multi-tasking systems.Task scheduling offers the capacity of the al-location of resources and is a significant effect on real-time capacity.Recently,although some high-performance architectures such as processor pipelines and memory hierar-chies make operating systems work efficiency,they increase the difficulty on analysis of a task execution.Operating systems Timing predictability is influenced by applications and finish timing behaviour.Hence real-time system must give a guarantee to timing predictability which is the same as the read-time performance.Besides,resource compe-tition is another area of concern.To avoid priority inversion,There should be a resource access control mechanisms.This thesis do a research and analysis on the three aspects of scheduling above,the main research and implement work to achieve real-time capacity and timing predictabil-ity includes the following issues:(1)This thesis analysed the advantages of SEFM on timing predictability between SEFM and traditional real-time operating systems with as-pect of task model,commucation mechanisms,time constraints etc.A task consists of se-rial cooperating services.The message pushing mechanism avoids intercourse of tasks’ commucation by guiding servant-execution flow within serial services,and therefore re-duces commucating delays.(2)EDF is the optimal scheduling algorithm on unique-core systems. Accordingly,this project upgraded the scheduler of MiniCore based on EDF and SEFM.The improvment includes ready queue,task management and task model,API and data structures,algorithms,time constraints and resource access control mechanisms.(3)This thesis discussed task’s finish time predictability issue and defines virtual dead-line regulation based on SEFM and a timing predictable EDZL algorithm.Then This project upgrades the real-time scheduler with some timing predictability improvments based on the regulation, message pushing mechanism and task-service model of SEFM. Moreover,This thesis provided a proof and a scheduling experiment of predictability of the scheduler.The experimental result shows a demonstration that the upgraded sched- uler results in a promotion of28.5%on timing predictability and save67%runtime overhead on task’s turnaround time.(4)Resource competition within system increases the waiting delay time because of blocked tasks and produces priority inversion and deadlock aporias.This thesis proposed and implementated the PreCP resource access protocol on the scheduler to obtain a low context switch and scheduling overhead.This diploma thesis proposed a design and implement of a timing predictable and real-time scheduler in MiniCore operating system.Timing predictable real-time sched-uler in MiniCore reduces the turnaround time and enhances timing predictability at the same time.