chapter 1 of Operating system by gagne.ppt

Os slide

1. 1.1 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
th
Edition
Course Introduction
Course Name: Operating Systems
Credit Hours: 3 (2-3)
Contact Hours: 2-3
Pre-requisites: Data Structures
Reference Materials: (or use any other standard and latest books)
1.OperatingSystemsConcepts,9theditionbyAbrahamSilberschatz
2.ModernOperatingSystems,4theditionbyAndrewS.Tanenbaum
3.OperatingSystems,InternalsandDesignPrinciples,9theditionbyWilliam
Stallings

2. 1.2 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Course Learning Outcomes

3. Silberschatz, Galvin and Gagne ©2013Operating System Concepts –9
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Edit9on
Chapter 1: Introduction

4. 1.4 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Chapter 1: Introduction
What Operating Systems Do
Computer-System Organization
Computer-System Architecture
Operating-System Structure
Operating-System Operations
Process Management
Memory Management
Storage Management
Protection and Security
Kernel Data Structures
Computing Environments
Open-Source Operating Systems

5. 1.5 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Objectives
To describe the basic organization of computer systems
To provide a grand tour of the major components of operating systems
To give an overview of the many types of computing environments
To explore several open-source operating systems

6. 1.6 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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What is an Operating System?
Anoperatingsystemmanagesacomputer’shardware.
Italsoprovidesabasisforapplicationprogramsandacts
asanintermediarybetweenthecomputeruserandthe
computerhardware
Operating system goals:
Execute user programs and make solving user problems easier
Make the computer system convenient to use
Use the computer hardware in an efficient manner

7. 1.7 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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What is an Operating System?
Anoperatingsystemislargeandcomplex,itmustbe
createdpiecebypiece.
Eachofthesepiecesshouldbeawell-delineatedportion
ofthesystem,withcarefullydefinedinputs,outputs,and
functions.

8. 1.8 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer System Structure
Computer system can be divided into four components:
1.Hardware –provides basic computing resources
CPU
Memory
I/O devices
2.Operating system
Controls and coordinates use of hardware among
various applications and users

9. 1.9 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer System Structure
3.Application programs –define the ways in which the
system resources are used to solve the computing
problems of the users
–Word processors
–Compilers
–web browsers
–Database systems
–Video games
4.Users
People, machines, other computers

10. 1.10 Silberschatz, Galvin and Gagne ©2013
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Four Components of a Computer System

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What Operating Systems Do: User View
On Personal Computer (PC) Users want
convenience, easeofuse
Don’t care about resourceutilization
Butsharedcomputersuchasmainframeor
minicomputermustkeepallusershappy.The
operatingsysteminsuchcasesisdesignedto
maximizeresourceutilization

12. 1.12 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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What Operating Systems Do: User View
Usersofdedicatesystemssuchasworkstationshave
dedicatedresourcesbutfrequentlyusesharedresources
fromservers.Therefore,theiroperatingsystemis
designedtocompromisebetweenindividualusabilityand
resourceutilization.
Handheldcomputersareresourcepoor,optimizedfor
usabilityandbatterylife
Somecomputershavelittleornouserinterface,suchas
embeddedcomputersindevicesandautomobiles

13. 1.13 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Operating System Definition: System View
OS is a resource allocator
Manages all resources
Decides between conflicting requests for efficient and
fair resource use
OS is a control program
Controls execution of programs to prevent errors and
improper use of the computer

14. 1.14 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Operating System Definition (Cont.)
Nouniversallyaccepteddefinition
“Everythingavendorshipswhenyouorderanoperating
system”isgoodapproximation
Butvarieswildly
“Theoneprogramrunningatalltimesonthecomputer”
isthekernel.Everythingelseiseitherasystemprogram
(shipswiththeoperatingsystem)oranapplication
program.

15. 1.15 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer Startup
bootstrap programis loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known
as firmware
Initializes all aspects of system
Loads operating system kernel and starts execution

16. 1.16 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer System Organization
Computer-system operation
One or more CPUs, device controllers connect through
common bus providing access to shared memory
Concurrent execution of CPUs and devices competing
for memory cycles

17. 1.17 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer-System Operation
I/OdevicesandtheCPUcanexecuteconcurrently
Eachdevicecontrollerisinchargeofaparticular
devicetype
Eachdevicecontrollerhasalocalbuffer

18. 1.18 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer-System Operation
CPU moves data from/to main memory to/from local
buffers
I/O is from the device to local buffer of controller
Device controller informs CPU that it has finished its
operation by causing an interrupt

19. 1.19 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Common Functions of Interrupts
Interrupttransferscontroltotheinterruptserviceroutine
generally,throughtheinterruptvector,whichcontains
theaddressesofalltheserviceroutines
Interruptarchitecturemustsavetheaddressofthe
interruptedinstruction
Atraporexceptionisasoftware-generatedinterrupt
causedeitherbyanerrororauserrequest
Anoperatingsystemisinterruptdriven

20. 1.20 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Interrupt Handling
The operating system preserves the state of the CPU
by storing registers and the program counter
Determines which type of interrupt has occurred:
polling
vectoredinterrupt system
Separate segments of code determine what action
should be taken for each type of interrupt

21. 1.21 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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I/O Structure
AfterI/Ostarts,controlreturnstouserprogramonlyupon
I/Ocompletion
WaitinstructionidlestheCPUuntilthenextinterrupt
Waitloop(contentionformemoryaccess)
AtmostoneI/Orequestisoutstandingatatime,no
simultaneousI/Oprocessing

22. 1.22 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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I/O Structure
AfterI/Ostarts,controlreturnstouserprogramwithout
waitingforI/Ocompletion
Systemcall–requesttotheOStoallowusertowait
forI/Ocompletion
Device-statustablecontainsentryforeachI/O
deviceindicatingitstype,address,andstate
OSindexesintoI/Odevicetabletodeterminedevice
statusandtomodifytableentrytoincludeinterrupt

23. 1.23 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Storage Definitions and Notation Review
Computerstorageisgenerallymeasuredandmanipulated
inbytesandcollectionsofbytes.
1.akilobyte,orKB,is1,024bytes
2.amegabyte,orMB,is1,024
2
bytes
3.agigabyte,orGB,is1,024
3
bytes
4.aterabyte,orTB,is1,024
4
bytes
5.apetabyte,orPB,is1,024
5
bytes

24. 1.24 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Storage Definitions and Notation Review
Thebasicunitofcomputerstorageisthebit.Abitcancontainoneoftwovalues,0and1.
Allotherstorageinacomputerisbasedoncollectionsofbits.Givenenoughbits,itis
amazinghowmanythingsacomputercanrepresent:numbers,letters,images,movies,
sounds,documents,andprograms,tonameafew.Abyteis8bits,andonmostcomputers
itisthesmallestconvenientchunkofstorage.Forexample,mostcomputersdon’thavean
instructiontomoveabitbutdohaveonetomoveabyte.Alesscommontermisword,
whichisagivencomputerarchitecture’snativeunitofdata.Awordismadeupofoneor
morebytes.Forexample,acomputerthathas64-bitregistersand64-bitmemory
addressingtypicallyhas64-bit(8-byte)words.Acomputerexecutesmanyoperationsinits
nativewordsizeratherthanabyteatatime.
Computer storage, along with most computer throughput, is generally measured and
manipulated in bytes and collections of bytes.
A kilobyte, or KB, is 1,024 bytes
a megabyte, or MB, is 1,024
2
bytes
a gigabyte, or GB, is 1,024
3
bytes
a terabyte, or TB, is 1,024
4
bytes
a petabyte, or PB, is 1,024
5
bytes
Computer manufacturers often round off these numbers and say that a megabyte is 1
million bytes and a gigabyte is 1 billion bytes. Networking measurements are an exception
to this general rule; they are given in bits (because networks move data a bit at a time).

25. 1.25 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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25
Metric Units
The metric prefixes

26. 1.26 Silberschatz, Galvin and Gagne ©2013
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Direct Memory Access Structure
Usedforhigh-speedI/Odevicesabletotransmit
informationatclosetomemoryspeeds
Devicecontrollertransfersblocksofdatafrombuffer
storagedirectlytomainmemorywithoutCPUintervention
Onlyoneinterruptisgeneratedperblock,ratherthanthe
oneinterruptperbyte

27. 1.27 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Storage Structure
Main memory –only large storage media that the CPU
can access directly
Randomaccess
Typically volatile
Secondary storage –extension of main memory that
provides large nonvolatilestorage capacity

28. 1.28 Silberschatz, Galvin and Gagne ©2013
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Storage Structure
Magneticdisks–rigidmetalorglassplatterscovered
withmagneticrecordingmaterial
Disksurfaceislogicallydividedintotracks,whichare
subdividedintosectors
Thediskcontrollerdeterminesthelogicalinteractionbetween
thedeviceandthecomputer
Solid-statedisks–fasterthanmagneticdisks,
nonvolatile
Varioustechnologies
Becomingmorepopular

29. 1.29 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Storage Hierarchy
Storage systems organized in hierarchy
Speed
Cost
Volatility
Caching–copyinginformationintofasterstorage
system;mainmemorycanbeviewedasacachefor
secondarystorage
Device Driver for each device controller to manage I/O
Provides uniform interface between controller and kernel

30. 1.30 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Storage-Device Hierarchy

31. 1.31 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Caching
Importantprinciple,performedatmanylevelsina
computer(inhardware,operatingsystem,software)
Informationinusecopiedfromslowertofasterstorage
temporarily
Fasterstorage(cache)checkedfirsttodetermineif
informationisthere
Ifitis,informationuseddirectlyfromthecache(fast)
Ifnot,datacopiedtocacheandusedthere
Cachesmallerthanstoragebeingcached
Cachemanagementimportantdesignproblem
Cachesizeandreplacementpolicy

32. 1.32 Silberschatz, Galvin and Gagne ©2013
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Computer-System Architecture
Mostsystemsuseasinglegeneral-purposeprocessor
Most systems have special-purpose processors as well. Such as
disk, keyboard, and graphics controllers;
Theoperatingsystemcannotcommunicatewiththese
(special-purpose)processors;theydotheirjobs
autonomously

33. 1.33 Silberschatz, Galvin and Gagne ©2013
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Computer-System Architecture
Multiprocessors:Suchsystemshavetwoormore
processorsinclosecommunication,sharingthecomputer
busandsometimestheclock,memory,andperipheral
devices
Multiprocessorsystemsfirstappearedprominently
appearedinserversandhavesincemigratedto
1.Desktop
2.Laptopsystems
3.Mobiledevices
4.SmartphonesandTabletcomputers

34. 1.34 Silberschatz, Galvin and Gagne ©2013
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Computer-System Architecture
Multiprocessorssystems growing in use and importance
Also known as parallel systems, tightly-coupled systems
Advantages include:
1.Increased throughput
2.Economy of scale
3.Increased reliability –graceful degradationor fault
tolerance
Theabilitytocontinueprovidingserviceproportionaltothe
levelofsurvivinghardwareiscalledgraceful
degradation.Somesystemsgobeyondgraceful
degradationandarecalledfaulttolerant,becausethey
cansufferafailureofanysinglecomponentandstill
continueoperation

35. 1.35 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Computer-System Architecture
Multiprocessing systems are of two types:
1.AsymmetricMultiprocessing:therelationship
betweenmulticoreprocessors(heterogeneousor
homogeneous)ofasymmetricmultiprocessingisa
master-slaverelationship
2.SymmetricMultiprocessing:Allprocessorsof
sametype(maybeeitherheterogeneousor
homogeneous)ofsymmetricmultiprocessingare
peers;

36. 1.36 Silberschatz, Galvin and Gagne ©2013
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Computer-System Architecture
Morespecifically,eachCPUinsymmetricmultiprocessing
runsthesamecopyoftheOS,whileinasymmetric
multiprocessing,theysplitresponsibilitiestypically,
thereforeeachmayhavespecialized(different)software
androles.

37. 1.37 Silberschatz, Galvin and Gagne ©2013
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How a Modern Computer Works
A von Neumann architecture

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Multi-chip and Multicore Architecture

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A Dual-Core Design
Uniformmemory access(UMA)isashared
memoryarchitectureusedinparallelcomputers.
AlltheprocessorsintheUMAmodelsharethephysical
memoryuniformly.
InaUMAarchitecture,accesstimetoamemorylocation
isindependentofwhichprocessormakestherequestor
whichmemorychipcontainsthetransferreddata.

40. 1.40 Silberschatz, Galvin and Gagne ©2013
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A Dual-Core Design
Non-uniformmemoryaccess(NUMA)isacomputer
memorydesignusedinmultiprocessing,wherethe
memoryaccesstimedependsonthememorylocation
relativetotheprocessor.
UnderNUMA,aprocessorcanaccessitsownlocal
memoryfasterthannon-localmemory(memorylocalto
anotherprocessorormemorysharedbetween
processors).

41. 1.41 Silberschatz, Galvin and Gagne ©2013
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A Dual-Core Design
NUMA
UMA

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A Dual-Core Design
Systems containing all chips vs. blade servers
Chassis containing multiple separate systems

43. 1.43 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Clustered Systems
They are composed of two or more individual systems—or
nodes—joined together.
Like multiprocessor systems, but multiple systems working
together
Usuallysharingstorageviaastorage-areanetwork(SAN)
Providesahigh-availabilityservicewhichsurvivesfailures
Someclustersareforhigh-performancecomputing(HPC)
Somehavedistributedlockmanager(DLM)toavoidconflicting
operations

44. 1.44 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Clustered Systems

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Operating System Structure
Multiprogrammingisneededforefficiency.
Multiprogrammingisalsotheabilityofanoperating
systemtoexecutemorethanoneprogramonasingle
processormachine.
Morethanonetask/program/job/processcanresideinto
themainmemoryatonepointoftime.
Acomputerrunningexcelandfirefoxbrowser
simultaneouslyisanexampleofmultiprogramming.

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Operating System Structure

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Operating System Structure
Timesharing(multitasking)istheabilityofan
operatingsystemtoexecutemorethanonetask
simultaneouslyonasingleprocessormachine.
Thoughwesaysobutinrealitynotwotasksona
singleprocessormachinecanbeexecutedatthe
sametime.
ActuallyCPUswitchesfromonetasktothenexttask
soquicklythatappearsasifallthetasksare
executingatthesametime.
Morethanonetask/program/job/processcanreside
intothesameCPUatonepointoftime.

48. 1.48 Silberschatz, Galvin and Gagne ©2013
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Memory Layout for Multiprogrammed System

49. 1.49 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Operating System Structure
Multiprocessingistheabilityofanoperatingsystem
toexecutemorethanoneprocesssimultaneouslyon
amultiprocessormachine.Inthis,acomputeruses
morethanoneCPUatatime.

50. 1.50 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Operating-System Operations
Interruptdrivenbyhardware
Softwareerrororrequestcreatesexceptionortrap
Divisionbyzero,requestforoperatingsystem
service,infiniteloop,processesmodifyingeach
otherortheoperatingsystem
Dual-modeoperationallowsOStoprotectitselfand
othersystemcomponents
Usermodeandkernelmode

51. 1.51 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Operating-System Operations
Modebitprovidedbyhardware
Providesabilitytodistinguishwhensystemis
runningusercodeorkernelcode
Someinstructionsdesignatedasprivileged,
onlyexecutableinkernelmode
Systemcallchangesmodetokernel,returnfrom
callresetsittouser

52. 1.52 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Process Management
Aprocessisaprograminexecution.Itisaunitofwork
withinthesystem.Programisapassiveentity,processis
anactiveentity.
Processneedsresourcestoaccomplishitstask
CPU,memory,I/O,files
Initializationdata
Processterminationrequiresreclaimofanyreusable
resources
Single-threadedprocesshasoneprogramcounter
specifyinglocationofnextinstructiontoexecute
Processexecutesinstructionssequentially,oneata
time,untilcompletion

53. 1.53 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts –9
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Process Management
Multi-threadedprocesshasoneprogramcounterper
thread
Typicallysystemhasmanyprocesses,someuser,
someoperatingsystemrunningconcurrentlyononeor
moreCPUs
ConcurrencybymultiplexingtheCPUsamongthe
processes/threads

54. 1.54 Silberschatz, Galvin and Gagne ©2013
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Process Management Activities
Theoperatingsystemisresponsibleforthefollowing
activitiesinconnectionwithprocessmanagement:
1.Creatinganddeletingbothuserandsystemprocesses
2.Suspendingandresumingprocesses
3.Providingmechanismsforprocesssynchronization
4.Providingmechanismsforprocesscommunication
5.Providingmechanismsfordeadlockhandling

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Memory Management
All data in memory before and after processing
All instructions in memory in order to execute
Memory management determines what is in memory
when
Optimizing CPU utilization and computer response to
users

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Memory Management
Memorymanagementactivities
Keepingtrackofwhichpartsofmemoryarecurrently
beingusedandbywhom
Decidingwhichprocesses(orpartsthereof)anddata
tomoveintoandoutofmemory
Allocatinganddeallocatingmemoryspaceas
needed

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Storage Management
File-System management
Files usually organized into directories
Access control on most systems to determine who can
access what
OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media

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Performance of Various Levels of Storage

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Migration of Integer A from Disk to Register
Multitasking environments must be careful to use most recent value, no
matter where it is stored in the storage hierarchy
Multiprocessor environment must provide cache coherency in
hardware such that all CPUs have the most recent value in their cache
Distributed environment situation even more complex
Several copies of a datum can exist
Various solutions covered in Chapter 17

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I/O Subsystem
OnepurposeofOSistohidepeculiaritiesofhardwaredevicesfromthe
user
I/Osubsystemresponsiblefor
MemorymanagementofI/Oincludingbuffering(storingdata
temporarilywhileitisbeingtransferred),caching(storingpartsofdata
infasterstorageforperformance),spooling(theoverlappingofoutput
ofonejobwithinputofotherjobs)
Generaldevice-driverinterface
Driversforspecifichardwaredevices

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Protection and Security
Protection–anymechanismforcontrollingaccessof
processesoruserstoresourcesdefinedbytheOS
Security–defenseofthesystemagainstinternaland
externalattacks
Hugerange,includingdenial-of-service,worms,
viruses,identitytheft,theftofservice

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Writeanswerstoexercisequestionfrom1.1to1.11
Onlyhandwrittenneatandcleanhomeworkwillbe
accepted.
Pagesizeandpagequalitythroughoutthe
courseshouldremainthesame.
Throughoutthiscourse,homeworkshouldbe
submittedtoCRinnextclassaftertheclass
attendance.
Homework

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End of Chapter 1