Hierarchical Real-Time Systems for Imprecise Computation Model

Real-Time Systems Laboratory GNU@

Hierarchical Real-Time Systems for Imprecise

Computation Model

The 5th EuroSys Doctoral Workshop (EuroDW 2011)

Guy Martin TchamgoueDepartment of Informatics,

Gyeongsang National University, South Korea

Hierarchical Real-Time Systems for Imprecise Computation Model

Problem

An Application

Proposed Solution

Preliminary Results

Ongoing Work

EuroDW'11 April 10, 2011

2

Agenda


Statement To build large complex real-time systems

from simpler ones Flexibility and Reliability

To handle both hard and soft real-time systems To enhance the resource utilization on system

overload To facilitate the development and deployment

process


3

Problem



4

An Application

Virtual Ma-chine or Par-

tition 1Virtual Ma-

chine or Par-tition 2


tition N


tition N-1

Audio/Video Applications

Multimedia Streaming

Real-TimeImage

TrackingOther

Applications

Operating System

Operating System

Operating System

Operating System

Operating System


Hierarchical resource sharing among components under different scheduling policies

Higher-level schedulers: Consider each component

as a scheduling unit Do not need to know about

the internal complexity of its components

Lower-level schedulers: Focus on local scheduling for a given resource supply


5

Compositional Scheduling Framework

C1 C2

C3 C4

C1 C2


Publications Tchamgoue et al., “Compositional Scheduling Framework for

Imprecise Computation Model”, Work-in-Progress Session, RTAS’10, April 2010

Tchamgoue et al., “Hierarchical Real-Time Scheduling Framework for Imprecise Computations”, 8th IEEE/IFIP EUC, December 2010

System Model Imprecise Computation Tasks: T = {i (pi , mi ,

oi , fi)} pi : period mi : execution time of the mandatory part oi : execution time of the optional part fi : reward function for optional execution


6

Preliminary Results


The Imprecise Resource Model: (, , ) : resource period : resource allocation for mandatory part : resource allocation for optional part (, , ) periodically supplies at least time units and at

most + time units. Example:

The resource supply of (, , )


7

,...2,1,0 re whe,))1(,(supply kkk


The Interface Model Specifying the real-time requirement of a component Interface Model I(P, M, O, F)

P : period M : mandatory part

requirement O : optional part

requirement F : reward function of

optional execution


8

1(40, 5, 3, f1(t)) 2(30, 4, 2, f2(t))

MF-EDF

I1(10, 3, 2, F1(t))

3(50, 4, 2, f3(t)) 4 (25, 3, 3, f4(t))

MF-RM

I2(15, 4, 2, F2(t))

5 (10, 3, 2, F1(t)) 6 (15, 4, 2, F2(t))

MF-EDF

I0 (5, 3, 2, F0(t))

Component C0

Component C1 Component C2

R1=1 (10, 3, 2) R2=2 (15, 4, 2)


Other Results Schedulability Analysis

To guarantee the minimum requirements of a component

Utilization Bound To determine the largest possible utilization bound that

makes a component schedulable Scheduling Algorithm with Guarantee of

Reward To provide a minimum reward guarantee to an upper layer

that provides resources to lower layers


9


Component Interface Generation How to optimally compute the resource and interface

parameters

Component Reward function To derive the reward function for the component’s interface

Optimal scheduling of optional parts To schedule optional parts in order to maximize the total

reward of a component


10

Ongoing Work



11

Thank you for your atten-tion.

EuroDW 2011


Proposed for flexible scheduling of hard deadline tasks

An IC task consists of: A mandatory subtask for an acceptable result, and An optional subtask for

refining the mandatory task result ,and improving the quality of the task according to the amount of

execution time.


12

Imprecise Computation* (IC) Model

* J. W.-S. Liu, K.-J. Lin, W.-K. Shih, A. C.-S. Yu, C. Chung, J. Yao, and W. Zhao, “Algorithms for scheduling imprecise computations,” IEEE Computer, vol. 24, no. 5, pp. 58–68, 1991.

period

time

: Mandatory part : Optional part

Documents

Hierarchical Real-Time Systems for Imprecise Computation Model