MULTIPROCESSOR AND REAL TIME SCHEDULING.ppt

Subject - Operating System Design Principles
Topic - MULTIPROCESSOR AND REAL TIME SCHEDULING

1. MULTIPROCESSOR AND REAL
TIME SCHEDULING
Presentation & Delivery
VEERANAN VEERANAN
I M.Sc. Computer Science
Roll No. P22PCS123
GOVERNMENT ARTS COLLEGE, MELUR
PG. Department of Computer Science

2. Operating System
Multiprocessor
Real Time
Scheduling
Granularity
Design Issues
Process
Scheduling
Thread
Scheduling
Characteristics
of Real Time OS
Real Time
Scheduling
Deadline
Scheduling

3. Multiprocessor
Loosely coupled or distributed multiprocessor,
or cluster
Functionally Specialized Processors
Tightly Coupled Multiprocessor

4. Multiprocessor
Granularity
Independent
Parallelism
Coarse and Very Coarse
Grained Parallelism
Medium Grained
Parallelism
Fine Grained Parallelism

5. Multiprocessor
Design Issues
Assignment of
Processes to
processors
The use of
multiprogramming on
Indirected Processors
Process Dispatching

6. Multiprocessor
Process Scheduling
Assignment of
Processes to
processors
The use of
multiprogramming on
Indirected Processors
Process Dispatching

7. Multiprocessor
Thread Scheduling
Load Sharing
Gang Scheduling
Dedicated Processor
Assignment
Dynamic Scheduling

8. Operating System
Real Time Scheduling
Characteristics of Real Time OS
Real Time Scheduling

10. Real Time Scheduling
Realtimecomputingisbecominganincreasinglyimportant
discipline.
TheOSandinparticularthescheduler,isperhapsthemost
importantcomponentofrealtimesystem.
Examples
Currentapplicationsofrealtimesystemsincludecontrolof
laboratoryexperiments,processcontrolinindustrialplants,
robotics,airtrafficcontrol,telecommunications,andmilitary
commandsandcontrolsystems.
Benefits
Real-timesystemsaredesignedtoperformtasksthatmustbe
executedwithinprecisecycledeadlines(downtomicroseconds).

11. Real Time Scheduling
AHardrealtimetaskisonethatmustmeetitsdeadline;
otherwiseitwillcauseunacceptabledamageorafatal
errortothesystem.
ASoftrealtimetaskhasanassociateddeadlinethatis
desirablebutnotmandatory;itstillmakessenseto
scheduleandcompletethetaskevenifithaspassedits
deadline.

12. Real –Time Operating Systems
Characteristics of Real Time OS
Determinism
Responsiveness
User Control
Reliability
Fail –Soft Operation

13. Real time OS features:
Fastprocessorthreadswitch
Smallsize(withitsassociatedminimalfunctionality)
AbilitytorespondtoexternalInterruptsquickly
Multitaskingwithinterprocesscommunicationtoolssuchas
semaphores,signalsandevents.
Useofspecialsequentialfilesthatcanaccumulatedataatafastrate.
Pre-emptiveschedulingbasedonpriority
MinimizationofintervalsduringwhichInterruptsaredisabled.
Primitivestodelaytasksforaamountoftimeandtopause/resume
tasks
Specialalarmsandtimeout.

14. Real Time Scheduling:
Real time scheduling is one of the most active areas of research in
computer Science.
Whetherasystemperformsscheduleaabilityanalysis
Ifitdoes,whetheritisdonestatisticallyordynamically
Whethertheresultoftheanalysisitselfproducesascheduleorplan
accordingtowhichtasksaredispatchedatruntime

15. Real –Time Operating Systems
Real Time Scheduling
Static Table –Driven Approaches
Static Priority Driven Preemptive
Approaches
Dynamic planning based approaches
Dynamic Best Effort Approaches

17. Static Table –Driven Approaches
Theseperformastaticanalysisoffeasibleschedulesofdispatching.
Theresultoftheanalysisisaschedulethatdetermines,atruntime,
whenataskmustbeginexecution.

18. Static Table –Driven Approaches
Again,astaticanalysisisperformed,butnoscheduleisdrawnback.
Rather,theanalysisisusedtoassignprioritiestotask,sothata
traditionalprioritydrivenpre-emptiveschedulercanbeused.

19. Dynamic planning based approaches
Feasibilityisdeterminedatruntimeratherthanofflinepriortothe
startofexecution(statically).Anarrivingtaskisacceptedfor
executiononlyofitisfeasibletomeetit’stimeconstraints.Oneofthe
resultsofthefeasibilityanalysisisascheduleorplanthatisusedto
decidewhentodispatchthistask.

20. Dynamic Best Effort Approaches
Nofeasibilityanalysisisperformed.Thesystemtriestomeetall
deadlinesandabortsanystatedprocesswhosedeadlineismissed.

21. Thank You
&
Your Opportunity