2004/06/01 1 Issues about Scheduling for Dependent Multimedia Tasks 電機所控制組 R 馮天俊 R 戴兆弘 Adviser ：陳少傑 老師 Date ： 2004/06/01

2004/06/01 2 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 3 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 4 Motivation A popular issue along with the progressive network technology Get the inspiration from the talk introduced by Professor Huang three weeks ago

2004/06/01 5 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 6 What is Multimedia ？ Different kinds of data Combination of two or more continuous media (audio and video)

2004/06/01 7 Characteristics of Multimedia [3: Barroso et al. 1998] The quality of information depends on the time it is presented to the user Soft real-time task Produced and retrieved by periodic processes

2004/06/01 8 Scheduling Problem Addressing [3: Barroso et al. 1998] A labeled, directed, acyclic graph node ： a task link ： a precedence between two tasks Three types of tasks Multimedia Task Graph (MTG) model

2004/06/01 9 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 10 Task Allocation & Scheduling Issue Task allocation ： Task dependence Level dependence Scheduling issue ： Fully Synchronized Pipelining (FSP) Approach Partially Synchronized Pipelining (PSP) Approach

2004/06/01 11 Task Allocation ---Task Dependence [2: Hwang 1994] The scheduling algorithm can be implemented in the following steps ： Step 1 Initiate the ready task set Step 2 Select and schedule a task in the ready task set Step 3 If there are any tasks whose precedence constraints are satisfied due to the execution of Step 2, add it to the ready task set Step 4 Go to Step 2 until all tasks are scheduled 1st round ： T1 T2 T3 2nd round ： T4 T2 T3 3rd round ： T4 T7 T8 …

2004/06/01 12 Task Allocation ---Level Dependence [2: Hwang 1994] The level number of task Ti can be defined as ： where length(Ti)= the longest path among all the paths traversed from the starting nodes to the Ti L=1 ： T1 T2 T3 L=2 ： T4 T5 T6 T7 T8 L=3 ： T9 T10 T11 L=4 ： T12 T13

2004/06/01 13 Scheduling Issue---FSP [2: Hwang 1994] All tasks with same period are scheduled into the same slot of processors Advantage Simplicity Disadvantage Longer response time A task system with tight deadlines may become unschedulable

2004/06/01 14 Scheduling Issue---PSP [2: Hwang 1994] Only the start time of periodic starting tasks is synchronized Advantage Overlap on task’s executions Produce results with shorter response time Disadvantage More complicated Require longer scheduling time

2004/06/01 15 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 16 The Branch and bound Algorithm [2] It is divided two parts Allocation procedure The search tree is extended by considering the allocation of T1 to every processor,denoted by, Ex.Tasks=3, Processors=2 P1P2

2004/06/01 17 The Branch and bound Algorithm (cont ’ d) It is divided two parts Scheduling procedure Branch P1 ： T1  T3 P2 ： T2 P1 P2 P1 choose T1 P1 choose T3 P2 choose T2

2004/06/01 18 The Dependent Earliest-Deadline-First Algorithm A variation of traditional earliest-deadline-first policy Earliest-deadline-first (EDF) algorithm ： [5: Liu & Layland 1973] [6: Krishna & Shin 1997] Higher priority for earlier deadline Dynamic priority scheduling algorithm Schedulable iff

2004/06/01 19 The Dependent Earliest-Deadline-First Algorithm (cont ’ d) Using the task dependence approach Only the tasks in LR can participate in the scheduling selection competition LR ： A list of ready tasks The winner is the one with earliest deadline Schedule the tasks with EDF

2004/06/01 20 The Level Oriented Algorithm [2] The tasks are scheduled level by level The sorting makes the tasks with the smallest period go first The tasks in the same level are allocated in different processors Advantage Can reduce execution time by parallel processing

2004/06/01 21 Comparison of above three algorithms Here, consider two criteria ： The number of processors The execution time of the algorithms Conclusion One compromise can be made with weighting for each Criterion Weighting can be defined case by case B & BDependent EDFLevel Oriented # of processorsFewestMediumMost Execution timeLongestMediumShortest

2004/06/01 22 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 23 Conclusion & Future Work Conclusion A brief study about the problem of dependent real-time multimedia task scheduling A set of scheduling techniques for multimedia tasks on distributed system are investigated Future Work Add more hardware consideration in our project

2004/06/01 24 Outline Motivation Introduction to Multimedia Task Allocation & Scheduling Issue Scheduling Algorithms Conclusion & Future Work References

2004/06/01 25 References [1] Hsing Mei Hwang, ” Scheduling Dependent Real-Time Multimedia Tasks on Distributed Systems,” The 19th Annual International Computer Software & Application Conference, Dallas, USA,1995, pp [2] Hsing Mei Hwang, ” Scheduling Multimedia Tasks on Distributed Systems Based on MTG Model,” Technical Report 94-M001, CSIE Department, Fu Jen Catholic University, Jan [3] Andre Barroso, Andreas Manoli, Michail Petropoulos, “ Issues in Multimedia Task Scheduling,“ Nov.21, 1998 [4] John Regehr, Michael B. Jones, John A. Stankovic, “ Operating System Support for Multimedia: The Programming Model Matters,” Technical Report MSR-TR , Microsoft Corporation, Sep [5] C.L. Liu, J.W. Layland, " Scheduling Algorithms for Multiprogramming in a Hard-real-time Environment," Journal of ACM, Vol. 20, No. 1, pp , Jan [6] Krishna & Shin, “ Real-Time Systems,” 1997

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