present intro notes-operating systems - cs222

8/20/2019 Present Intro Notes-Operating Systems - CS222

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OPERATING SYSTEMS

Text Book: Operating System Concepts by Silberschatz Gal!in an" Gagne

Reference Books:-• Mo"ern Operating Systems by An"re# S$ Tanenba%m$

• Operating Systems by &$M$'ietel$

• Operating Systems by (illiam Stallings$

Course Description:-

This co%rse pro!i"es st%"ents an %n"erstan"ing o) internal an" e*ternal !ie# o) comp%ter

operating systems+ basic concepts an" terminology processes comm%nication an"

synchronization sche"%ling share" reso%rces reso%rce allocation an" "e,allocation memoryan" )ile management$

Pre- requisite:-

(or-ing -no#le"ge o) 'ata Str%ct%res

Grading Policy:- In Semester E!al%ations. /01

En" Semester E!al%ation. 201

1 3 11



4$4 (hat Operating Systems 'o , 5or 6sers 5or Applications etc$

Figure 11 - !"stract #ie$ of t%e co&ponents of a co&puter syste&

• Comp%ter 7 &( 8 OS 8 Apps 8 6sers

• OS ser!es as inter)ace bet#een &( an" 9 Apps : 6sers ;

• OS pro!i"es ser!ices )or Apps : 6sers

• OS manages reso%rces 9Go!ernment mo"el it "oesn<t pro"%ce anything;

• 'ebates abo%t #hat is incl%"e" in the OS , =%st the -ernel or e!erything the !en"or ships>

9Consi"er the "istinction bet#een system applications an" /r" party or %ser apps;

4$? Comp%ter,System Organization , (hat are all the parts an" ho# "o they )it together>

Figure 1' - ! &odern co&puter syste&

1'1 Co&puter-(yste& )peration• @ootstrap program

• Share" memory bet#een CP6 an" I3O car"s

• Time slicing )or m%lti,process operation

• Interr%pt han"ling , cloc- &( S(

• Implementation o) system calls

Figure 1* - +nterrupt ti&eline for a single process doing output

1'' (torage (tructure• Main memory 9 RAM ;

o Programs m%st be loa"e" into RAM to r%n$

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o Instr%ctions an" "ata )etche" )rom RAM into registers$

o RAM is !olatile

o Me"i%m size an" spee"

• Other electronic 9 !olatile ; memory is )aster smaller an" more e*pensi!e per bit.

o Registers

o CP6 Cache

• Non,!olatile memory 9 permanent storage ; is slo#er larger an" less e*pensi!e per bit.

o Electronic "is-s

o Magnetic "is-s

o Optical "is-s

o Magnetic Tapes

Figure 1, - (torage-de#ice %ierarc%y

1'* +) (tructure• Typical operation in!ol!es I3O reB%ests "irect memory access 9 'MA ; an" interr%pt han"ling$

Figure 1. - /o$ a &odern co&puter syste& $orks

4$/ Comp%ter,System Architect%re , 'i))erent Operating Systems )or 'i))erent in"s o)

Comp%ter En!ironments1*1 (ingle-Processor (yste&s

• One main CP6 #hich manages the comp%ter an" r%ns %ser apps$

• Other specialize" processors 9"is- controllers GP6s etc$; "o not r%n %ser apps$

1*' 0ultiprocessor (yste&s4$ Increase" thro%ghp%t , 5aster e*ec%tion b%t not 4001 linear spee"%p$

?$ Economy o) scale , Peripherals "is-s memory share" among processors$

/$ Increase" reliability

* 3 11



o 5ail%re o) a CP6 slo#s system "oesn<t crash it$

o Re"%n"ant processing pro!i"es system o) chec-s an" balances$ 9 e$g$ NASA ;

Figure 1 - (y&&etric &ultiprocessing arc%itecture

Figure 12 - ! dual-core design $it% t$o cores placed on t%e sa&e c%ip

1** Clustered (yste&s• In"epen"ent systems #ith share" common storage an" connecte" by a high,spee" DAN #or-ing together$

• Special consi"erations )or access to share" storage are reB%ire" 9'istrib%te" loc- management; as are collaboration

protocols$

Figure 13 - General structure of a clustered syste&

4$ Operating,System Str%ct%reTime,sharing 9m%lti,%ser m%lti,tas-ing; OS reB%ires.

• Memory management

• Process management

• =ob sche"%ling

• Reso%rce allocation strategies

• S#ap space 3 !irt%al memory in physical memory

• Interr%pt han"ling

• 5ile system management

• Protection an" sec%rity

• Inter,process comm%nications

, 3 11



Figure 14 - 0e&ory layout for a &ultiprogra&&ing syste&

4$F Operating,System OperationsInterr%pt,"ri!en nat%re o) mo"ern OSes reB%ires that erroneo%s processes not be able to "ist%rb anything

else$

1.1 Dual-0ode and 0ulti&ode )peration• 6ser mo"e #hen e*ec%ting harmless co"e in %ser applications

• ernel mo"e 9 a$-$a$ system mo"e s%per!isor mo"e pri!ilege" mo"e ; #hen e*ec%ting potentially "angero%s co"e

in the system -ernel$

• Certain machine instr%ctions 9 pri!ilege" instr%ctions ; can only be e*ec%te" in -ernel mo"e$

• ernel mo"e can only be entere" by ma-ing system calls$ 6ser co"e cannot )lip the mo"e s#itch$

• Mo"ern comp%ters s%pport "%al,mo"e operation in har"#are an" there)ore most mo"ern OSes s%pport "%al,mo"e

operation$

Figure 115 - Transition fro& user to kernel &ode

• The concept o) mo"es can be e*ten"e" beyon" t#o reB%iring more than a single mo"e bit

• CP6s that s%pport !irt%alization %se one o) these e*tra bits to in"icate #hen the !irt%al machine manager MM is

in control o) the system$ The MM has more pri!ileges than or"inary %ser programs b%t not so many as the )%ll

-ernel$

• System calls are typically implemente" in the )orm o) so)t#are interr%pts #hich ca%ses the har"#are<s interr%pt

han"ler to trans)er control o!er to an appropriate interr%pt han"ler #hich is part o) the operating system s#itching

the mo"e bit to -ernel mo"e in the process$ The interr%pt han"ler chec-s e*actly #hich interr%pt #as generate"

chec-s a""itional parameters 9 generally passe" thro%gh registers ; i) appropriate an" then calls the appropriate

-ernel ser!ice ro%tine to han"le the ser!ice reB%este" by the system call$

• 6ser programs< attempts to e*ec%te illegal instr%ctions 9 pri!ilege" or non,e*istent instr%ctions ; or to access

)orbi""en memory areas also generate so)t#are interr%pts #hich are trappe" by the interr%pt han"ler an" control is

trans)erre" to the OS #hich iss%es an appropriate error message possibly "%mps "ata to a log 9 core ; )ile )or later

analysis an" then terminates the o))en"ing program$

1.' Ti&er• @e)ore the -ernel begins e*ec%ting %ser co"e a timer is set to generate an interr%pt$

• The timer interr%pt han"ler re!erts control bac- to the -ernel$

• This ass%res that no %ser process can ta-e o!er the system$

• Timer control is a pri!ilege" instr%ction 9 reB%iring -ernel mo"e$ ;

4$H Process ManagementAn OS is responsible )or the )ollo#ing tas-s #ith regar"s to process management.

• Creating an" "eleting both %ser an" system processes

• Ens%ring that each process recei!es its necessary reso%rces #itho%t inter)ering #ith other processes$

• S%spen"ing an" res%ming processes

• Process synchronization an" comm%nication

• 'ea"loc- han"ling

. 3 11



4$2 Memory ManagementAn OS is responsible )or the )ollo#ing tas-s #ith regar"s to memory management.

• eeping trac- o) #hich bloc-s o) memory are c%rrently in %se an" by #hich processes$

• 'etermining #hich bloc-s o) co"e an" "ata to mo!e into an" o%t o) memory an" #hen$

• Allocating an" "eallocating memory as nee"e"$ 9 E$g$ ne# malloc ;

4$ Storage Management131 File-(yste& 0anage&entAn OS is responsible )or the )ollo#ing tas-s #ith regar"s to )ilesystem management.

• Creating an" "eleting )iles an" "irectories

• S%pporting primiti!es )or manip%lating )iles an" "irectories$ 9 open )l%sh etc$ ;

• Mapping )iles onto secon"ary storage$

• @ac-ing %p )iles onto stable permanent storage me"ia$

13' 0ass-(torage 0anage&entAn OS is responsible )or the )ollo#ing tas-s #ith regar"s to mass,storage management.

• 5ree "is- space management

• Storage allocation• 'is- sche"%ling

Note the tra"e,o))s regar"ing size spee" longe!ity sec%rity an" re,#ritability bet#een "i))erent mass

storage "e!ices incl%"ing )loppy "is-s har" "is-s tape "ri!es C's ''s etc$

13* Cac%ing• There are many cases in #hich a smaller higher,spee" storage space ser!es as a cache or temporary storage )or

some o) the most )reB%ently nee"e" portions o) larger slo#er storage areas$

• The hierarchy o) memory storage ranges )rom CP6 registers to har" "ri!es an" e*ternal storage$ 9 See table belo#$ ;

• The OS is responsible )or "etermining #hat in)ormation to store in #hat le!el o) cache an" #hen to trans)er "ata

)rom one le!el to another$

• The proper choice o) cache management can ha!e a pro)o%n" impact on system per)ormance$

• 'ata rea" in )rom "is- )ollo#s a migration path )rom the har" "ri!e to main memory then to the CP6 cache an"

)inally to the registers be)ore it can be %se" #hile "ata being #ritten )ollo#s the re!erse path$ Each step 9 other than

the registers ; #ill typically )etch more "ata than is imme"iately nee"e" an" cache the e*cess in or"er to satis)y

)%t%re reB%ests )aster$ 5or #riting small amo%nts o) "ata are )reB%ently b%))ere" %ntil there is eno%gh to )ill an entire

bloc- on the ne*t o%tp%t "e!ice in the chain$

• The iss%es get more complicate" #hen m%ltiple processes 9 or #orse m%ltiple comp%ters ; access common "ata as it

is important to ens%re that e!ery access reaches the most %p,to,"ate copy o) the cache" "ata 9 amongst se!eral copies

in "i))erent cache le!els$ ;

Figure 111 - Perfor&ance of #arious le#els of storage

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Figure 11' - 0igration of integer ! fro& disk to register

13, +) (yste&sThe I3O s%bsystem consists o) se!eral components.

• A memory,management component that incl%"es b%))ering caching an" spooling$

•

A general "e!ice,"ri!er inter)ace$• 'ri!ers )or speci)ic har"#are "e!ices$

• 9 6NIJ implements m%ltiple "e!ice inter)aces )or many types o) "e!ices one )or accessing the "e!ice character by

character an" one )or accessing the "e!ice bloc- by bloc-$ These can be seen by "oing a long listing o) 3"e! an"

loo-ing )or a c or b in the )irst position$ Yo% #ill also note that the size )iel" contains t#o n%mbers -no#n as

the maKor an" minor "e!ice n%mbers instea" o) the normal one$ The maKor n%mber signi)ies #hich "e!ice "ri!er

han"les I3O )or this "e!ice an" the minor n%mber is a parameter passe" to the "ri!er to let it -no# #hich speci)ic

"e!ice is being accesse"$ (here a "e!ice can be accesse" as either a bloc- or character "e!ice the minor n%mbers

)or the t#o options %s%ally "i))er by a single bit$ ;

4$L Protection an" Sec%rity• Protection in!ol!es ens%ring that no process access or inter)ere #ith reso%rces to #hich they are not entitle" either

by "esign or by acci"ent$ 9 E$g$ protection )a%lts #hen pointer !ariables are mis%se"$ ;

• Security in!ol!es protecting the system )rom "eliberate attac-s either )rom legitimate %sers o) the system attempting

to gain %na%thorize" access an" pri!ileges or e*ternal attac-ers attempting to access or "amage the system$

4$40 ernel 'ata Str%ct%res1151 6ists7 (tacks7 and 8ueues

Figure 11* - (ingly linked list

Figure 11, - Dou"ly linked list

Figure 11. - Circularly linked list

115' Trees

Figure 11 - Binary searc% trees

2 3 11



115* /as% Functions and 0aps

Figure 112 - /as% &ap

115, Bit&aps• A string o) 4s an" 0s %se" to -eep trac- o) the boolean state o) a collection o) obKects s%ch as the )ree state o) bloc-s

on a "is- or pages in memory$

4$44 Comp%ting En!ironments1111 Traditional Co&puting

111' 0o"ile Co&puting• Comp%ting on small han"hel" "e!ices s%ch as smart phones or tablets$ 9 As oppose" to laptops #hich still )all %n"er

tra"itional comp%ting$ ;

• May ta-e a"!antage o) a""itional b%ilt,in sensors s%ch as GPS tilt compass an" inertial mo!ement$

• Typically connect to the Internet %sing #ireless net#or-ing 9 IEEE 0?$44 ; or cell%lar telephone technology$

• Dimite" in storage capacity memory capacity an" comp%ting po#er relati!e to a PC$

• Generally %ses slo#er processors that cons%me less battery po#er an" pro"%ce less heat$

• The t#o "ominant OSes to"ay are Google An"roi" an" Apple iOS$

111* Distri"uted (yste&s• 'istrib%te" Systems consist o) m%ltiple possibly heterogeneo%s comp%ters connecte" together !ia a net#or- an"

cooperating in some #ay )orm or )ashion$

• Net#or-s may range )rom small tight DANs to broa" reaching (ANs$

o (AN 7 (i"e Area Net#or- s%ch as an international corporation

o MAN 7Metropolitan Area Net#or- co!ering a region the size o) a city )or e*ample$

o DAN 7Docal Area Net#or- typical o) a home b%siness single,site corporation or %ni!ersity camp%s$

o PAN 7 Personal Area Net#or- s%ch as the bl%etooth connection bet#een yo%r PC phone hea"set car etc$

• Net#or- access spee"s thro%ghp%ts reliabilities are all important iss%es$

• OS !ie# o) the net#or- may range )rom K%st a special )orm o) )ile access to comple* #ell,coor"inate" net#or-

operating systems$

• Share" reso%rces may incl%"e )iles CP6 cycles RAM printers an" other reso%rces$

111, Client-(er#er Co&puting•

A "e)ine" ser!er pro!i"es ser!ices 9 &( or S( ; to other systems #hich ser!e as clients$ 9 Technically clients an"ser!ers are processes not &( an" may co,e*ist on the same physical comp%ter$ ;

• A process may act as both client an" ser!er o) either the same or "i))erent reso%rces$

• Ser!e" reso%rces may incl%"e "is- space CP6 cycles time o) "ay IP name in)ormation graphical "isplays 9 J

Ser!ers ; or other reso%rces$

Figure 113 - General structure of a client-ser#er syste&

111. Peer-to-Peer Co&puting• Any comp%ter or process on the net#or- may pro!i"e ser!ices to any other #hich reB%ests it$ There is no clear

lea"er or o!erall organization$

3 3 11



• May employ a central "irectory ser!er )or loo-ing %p the location o) reso%rces or may %se peer,to,peer searching

to )in" reso%rces$

• E$g$ S-ype %ses a central ser!er to locate a "esire" peer an" then )%rther comm%nication is peer to peer$

Figure 114 - Peer-to-peer syste& $it% no centrali9ed ser#ice

111 irtuali9ation• Allo#s one or more g%est operating systems to r%n on !irt%al machines hoste" by a single physical machine an"

the !irt%al machine manager$

• 6se)%l )or cross,plat)orm "e!elopment an" s%pport$

• 5or e*ample a st%"ent co%l" r%n 6NIJ on a !irt%al machine hoste" by a !irt%al machine manager on a (in"o#s

base" personal comp%ter$ The st%"ent #o%l" ha!e )%ll root access to the !irt%al machine an" i) it crashe" the

%n"erlying (in"o#s machine sho%l" be %na))ecte"$

• System calls ha!e to be ca%ght by the MM an" translate" into 9 "i))erent ; system calls ma"e to the real %n"erlying

OS$• irt%alization can slo# "o#n program that ha!e to r%n thro%gh the MM b%t can also spee" %p some things i)

!irt%al har"#are can be accesse" thro%gh a cache instea" o) a physical "e!ice$

• 'epen"ing on the implementation programs can also r%n sim%ltaneo%sly on the nati!e OS bypassing the !irt%al

machines$

Figure 1'5 - 0;are

• To r%n Din%* on a (in"o#s system %sing M#are )ollo# these steps.

4$ 'o#nloa" the )ree M#are Player tool )rom http.33###$!m#are$com3"o#nloa"3player an" install it on

yo%r system

?$ Choose a Din%* !ersion )rom among h%n"re"s o) !irt%al machine images athttp.33###$!m#are$com3appliances

/$ @oot the !irt%al machine #ithin M#are Player$

1112 Cloud Co&puting• 'eli!ers comp%ting storage an" applications as a ser!ice o!er a net#or-$

• Types o) clo%" comp%ting.

o P%blic clo%" , A!ailable to anyone #illing to pay )or the ser!ice$

o Pri!ate clo%" , R%n by a company )or internal %se only$

o &ybri" clo%" , A clo%" #ith both p%blic an" pri!ate components$

o So)t#are as a Ser!ice , SaaS , Applications s%ch as #or" processors a!ailable !ia the Internet

o Plat)orm as a Ser!ice , PaaS , A so)t#are stac- a!ailable )or application %se s%ch as a "atabase ser!er

o In)rastr%ct%re as a Ser!ice , IaaS , Ser!ers or storage a!ailable on the Internet s%ch as bac-%p ser!ers

photo storage or )ile storage$

o Ser!ice pro!i"ers may pro!i"e more than one type o) ser!ice

4 3 11

http://www.vmware.com/download/player


http://www.vmware.com/appliances





• Clo%"s may contain tho%san"s o) physical comp%ters millions o) !irt%al ones an" petabytes o) total storage$

• (eb hosting ser!ices may o))er 9 one or more ; !irt%al machine9s; to each o) their clients$

Figure 1'1 - Cloud co&puting

1113 Real-Ti&e <&"edded (yste&s• Embe""e" into "e!ices s%ch as a%tomobiles climate control systems process control an" e!en toasters an"

re)rigerators$

• May in!ol!e specialize" chips or generic CP6s applie" to a partic%lar tas-$ 9 Consi"er the c%rrent price o) 0?H or

e!en 0H or 0 chips #hich are still plenty po#er)%l eno%gh )or simple electronic "e!ices s%ch as -i"s toys$ ;

• Process control "e!ices reB%ire real,time 9 interr%pt "ri!en ; OSes$ Response time can be critical )or many s%ch

"e!ices$

4$4? Open,So%rce Operating Systems• 9 5or more in)ormation on the 5lo%rish con)erence hel" at 6IC on the s%bKect o) 5ree Dibre an" Open So%rce

So)t#are !isit http.33###$)lo%rishcon)$com ;

• Open,So%rce so)t#are is p%blishe" 9 sometimes sol" ; #ith the so%rce co"e so that anyone can see an" optionally

mo"i)y the co"e$

• Open,so%rce S( is o)ten "e!elope" an" maintaine" by a small army o) loosely connecte" o)ten %npai"

programmers each #or-ing to#ar"s the common goo"$

• Critics arg%e that open,so%rce S( can be b%ggy b%t proponents co%nter that b%gs are )o%n" an" )i*e" B%ic-ly since

there are so many pairs o) eyes inspecting all the co"e$

• Open,so%rce operating systems are a goo" reso%rce )or st%"ying OS "e!elopment since st%"ents can e*amine the

so%rce co"e an" e!en change it an" re,compile the changes$

11'1 /istory• At one time 9 4LF0s ; a lot o) co"e #as open,so%rce$

• Dater companies trie" to protect the pri!acy o) their co"e partic%larly sensiti!e iss%es s%ch as copyright protection

algorithms$

• In 4L/ Richar" Stallman starte" the GN6 proKect to pro"%ce an open,so%rce 6NIJ$

• &e later p%blishe" the GN6 Mani)esto arg%ing that ADD so)t#are sho%l" be open,so%rce an" )o%n"e" the 5ree

So)t#are 5o%n"ation to promote open,so%rce "e!elopment$

• 5S5 an" GN6 %se the GN6 General P%blic Dicense #hich essentially states that all %sers o) the so)t#are ha!e )%ll

rights to copy an" change the S( ho#e!er they #ish so long as anything they "istrib%te )%rther contain the same

license agreement$ 9 Copyle)ting ;

11'' 6inux• 'e!elope" by Din%s Tor!al"s in 5inlan" in 4LL4 as the )irst )%ll operating system "e!elope" by GN6$

• Many "i))erent "istrib%tions o) Din%* ha!e e!ol!e" )rom Din%s<s original incl%"ing Re"&at S6SE 5e"ora 'ebian

Slac-#are an" 6b%nt% each geare" to#ar" a "i))erent gro%p o) en",%sers an" operating en!ironments$

• To r%n Din%* on a (in"o#s system %sing M#are )ollo# these steps.

15 3 11

http://www.flourishconf.com/



http://www.fsf.org/

http://www.fsf.org/

http://www.fsf.org/

http://www.gnu.org/copyleft/gpl.html



http://www.fsf.org/

http://www.fsf.org/




4$ 'o#nloa" the )ree M#are Player tool )rom http.33###$!m#are$com3"o#nloa"3player an" install it on

yo%r system

?$ Choose a Din%* !ersion )rom among h%n"re"s o) !irt%al machine images at

http.33###$!m#are$com3appliances

/$ @oot the !irt%al machine #ithin M#are Player$

11'* B(D =>+?• 6NIJ #as originally "e!elope" at ATT @ell labs an" the so%rce co"e ma"e a!ailable to comp%ter science st%"ents

at many %ni!ersities incl%"ing the 6ni!ersity o) Cali)ornia at @er-eley 6C@$

• 6C@ st%"ents "e!elope" 6NIJ )%rther an" release" their pro"%ct as @S' 6NIJ in both binary an" so%rce,co"e

)ormat$

• @S' 6NIJ is not open,so%rce ho#e!er beca%se a license is still nee"e" )rom ATT$

• In spite o) !ario%s la#s%its there are no# se!eral !ersions o) @S' 6NIJ incl%"ing 5ree @S' Net@S' Open@S'

an" 'ragon)ly@S'

• The so%rce co"e is locate" in 3%sr3src$

• The core o) the Mac operating system is 'ar#in "eri!e" )rom @S' 6NIJ an" is a!ailable at

http.33"e!eloper$apple$com3openso%rce3in"e*$html

11*, (olaris• Solaris is the 6NIJ operating system )or comp%ters )rom S%n Microsystems$

• Solaris #as originally base" on @S' 6NIJ an" has since migrate" to ATT System as its basis$

• Parts o) Solaris are no# open,so%rce an" some are not beca%se they are still co!ere" by ATT copyrights$

• It is possible to change the open,so%rce components o) Solaris re,compile them an" then lin- them in #ith binary

libraries o) the copyrighte" portions o) Solaris$

• Open Solaris is a!ailable )rom http.33###$opensolaris$org3os3

• Solaris also allo#s !ie#ing o) the so%rce co"e online #itho%t ha!ing to "o#nloa" an" %npac- the entire pac-age$

11*. =tility

• The )ree so)t#are mo!ement is gaining rapi"ly in pop%larity lea"ing to tho%san"s o) ongoing proKects in!ol!ing%ntol" n%mbers o) programmers$

• Sites s%ch as http.33)reshmeat$net3 an" http.33"istro#atch$com3 pro!i"e portals to many o) these proKects$

11 3 11




http://developer.apple.com/opensource/index.html

http://www.opensolaris.org/os/

http://freshmeat.net/



http://distrowatch.com/



http://developer.apple.com/opensource/index.html

http://www.opensolaris.org/os/


http://distrowatch.com/

present intro notes-operating systems - cs222

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