Real-Time Scheduling Author: Peter van der Stok CTT-DRTS-WS - PowerPoint PPT Presentation

1 Real-Time Scheduling Real-Time Scheduling Author: Peter van der Stok CTT-DRTS-WS Scheduling dd 5-1-2001 Phi l i ps Res ear ch

2 Real-Time Scheduling Overview • Three examples – water vessel – avionics – multimedia streaming

3 Real-Time Scheduling Example of RT system: Problem • Water vessel problem – Requirements • Water should not overflow • Pump should not run dry – Properties: • Positive but limited influx of water when pump is off • Positive but limited outflux of water when pump is on • Sensors are placed ∆ h from critical levels • d time units needed for level change ∆ h ∆ h water high sensor -- o water low sensor --o ∆ h pump

4 Real-Time Scheduling Example of RT system: Solution – Critical conditions should not exist longer than d without response • critical conditions C : water above/below sensor – Periodic task is released with period T and satisfy deadline D within this period. • If water at low sensor: Task stops pump • If water at high sensor: Task starts pump – Schedulability conditions: T + D < d • If the task finishes within the period ( D = T ) : 2. T < d D T d ¬ C C t

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6 Real-Time Scheduling Avionics functions • Control and check airplane – Navigation – Communication – Recording – Steering • Specific requirements for IMA – auto check – maintenance checks • cost effective !! – reliable • one hour < 10 -9 • last fault to maintenance > 200h

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8 Real-Time Scheduling • LRM: line replacable modules

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15 Real-Time Scheduling Video streaming over network into terminal

16 Real-Time Scheduling Terminology Stream Composite stream Task Buffer User application Terminal application

17 Real-Time Scheduling audio audio rend dec. read dmux DVD sharp dec. enh. main: scalabale mixer digit scaler digitizer: non-scalable pip: scalable mixer : non-scalable buffer hw enc. enc. writer task enc. scaler data transfer disk : non-scalable dec scalable task hierarchical task connection to HW IO

18 Real-Time Scheduling Application mode Mode parameters Stream modes Application graph

19 Real-Time Scheduling Load changes in MPEG decoding load structural load running average temporal load time

20 Real-Time Scheduling Control architecture in terminal Application Manager 1a Set up session 1a 1b Monitor / Alarm / Notify event 1b 2a Select and Set mode Mode Manager 2b Monitor / Alarm / Notify event 2a 2b 3a Set mode and quality level Quality Manager 3b Monitor / Alarm / Notify event 3a 3b 4a Set local parameters 4b Monitor Alarm / Notify event RCE control 5a Select and Set resource contract 4a 4b 5b Monitor resource usage RCE operation 5c 5a 5b 5c Monitor resource usage 6 Resource usage Contract-based Resource Manager

21 Real-Time Scheduling Layered view of Integrated framework Network and terminal Application Manager Mode Manager Terminal QM Subnet QM RCE NCE Terminal RM Subnet RM Terminal Subnet

22 Real-Time Scheduling RCE A2 Application A2 audio audio rend dec. tuner dmux sharp dec. enh. mixer Terminal T1 Subnet S1 RCE A3 digit scaler rend Terminal T2

23 Real-Time Scheduling RCE A2 audio audio rend dec. tuner dmux sharp dec. enh. RCE A3, 1 mixer router scaler Terminal T1 NCE A3 Stream transfer Subnet S1 RCE A3,1 digit router Terminal T2