Vahid Salmani and Saman Taghavi Zargar and Mahmoud Naghibzadeh A Modified Maximum Urgency First Scheduling Algorithm for RealTime Tasks
2814 - 2818
2007
1
9
International Journal of Computer, Electrical, Automation, Control and Information Engineering http://waset.org/publications/8174
http://waset.org/publications/9
World Academy of Science, Engineering and Technology
This paper presents a modified version of the
maximum urgency first scheduling algorithm. The maximum
urgency algorithm combines the advantages of fixed and dynamic
scheduling to provide the dynamically changing systems with
flexible scheduling. This algorithm, however, has a major
shortcoming due to its scheduling mechanism which may cause a
critical task to fail. The modified maximum urgency first scheduling
algorithm resolves the mentioned problem. In this paper, we propose
two possible implementations for this algorithm by using either
earliest deadline first or modified least laxity first algorithms for
calculating the dynamic priorities. These two approaches are
compared together by simulating the two algorithms. The earliest
deadline first algorithm as the preferred implementation is then
recommended. Afterwards, we make a comparison between our
proposed algorithm and maximum urgency first algorithm using
simulation and results are presented. It is shown that modified
maximum urgency first is superior to maximum urgency first, since it
usually has less task preemption and hence, less related overhead. It
also leads to less failed noncritical tasks in overloaded situations.
International Science Index 9, 2007