OS 2 - Process & Scheduling

7/31/2019 OS 2 - Process & Scheduling

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TIN TRNH IU PHI TIN TRNH

GV: MAI Xun [email protected]

Khoa Cng NghThng Tin

i HcCng NghipTPHCM

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Khi nim a Nhim v a C hng (1)

V sao mun x l ng thi nhiu cng victrn my tnh ?

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tng hiu sut s dng CPU


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V sao mun x l ng thi nhiu cng victrn my tnh ?

o Job : kq = a*b + c*d;

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tng tc x l


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a nhim (Multitasking): cho php nhiu tc v/cng vic c x l ng thi

o Ngi dng lun mong mun 1 HH a nhimo

Nhng: My tnh thng ch c 1 CPU? a chng (Multiprogramming): cho phpnhiu chng trnh c thc hin ng thi (trn 1 CPU)

o Gi lp nhiuCPU o t 1 CPU tht cho php thihnh nhiu chng trnh ng thi.

o o ho bng cch no ? Xy dng cc thut ton lun chuyn CPU gia cc chng trnh ng dng.

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X l ng hnh (1)

Kh khno Ti nguyn gii hn,ng dng v hn

o Nhiu hot ng anxen

?? Phn chia tinguyn?

?? Chia s ti nguyn??? Bo v?

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HH : Gii quyt nhiu cng vicng thi ? Lm sao y ???


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X l ng hnh (2)

Giiphpo Chia tr, c lp cc hot ngo Mi thi im ch gii quyt1 yu cuo

o ho ti nguyn: bin t thnh nhiu

7HH: Ai cng c phn khi n lt m!


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Tin Trnh

Mt chng trnh ang trong qu trnh thc hinMi tintrnh s hu

o MtCPU (o) ringo Mtkhng gian nh ringo Chim gi1 s ti nguyn ca h thng

Vd: Word chy 2 ln 2 tin trnh khc nhauo Microsoft Word [He_dieu_hanh.doc]o Microsoft Word [Mang_can_ban.doc]

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Chng trnh - Tin trnh

Chng trnh (Program)o Thc th th ng(passive)o Cha cc ch th iu khinmy tnh

Tin trnh (Process)o Thc th hot ng (active)

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Trng thi tin trnh (1)

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Trng thi tin trnh (2)

Sn sng ( ready ) o Tin trnh i gn cho CPU x l

Thc thi ( running ) o Tin trnh ang c CPU thc thi cc lnh

i, B chn (Waiting, blocked ) o Tin trnh i mt s kin no

Xut nhp d liu Mt tintrnh khc to ra

Khi ng (start ) o Tin trnh va c thc hin ngng ( halted )

o Tin trnh kt thc v s ri khi h thng

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Khi qun l tin trnh

PCB (Process Control Block)o nh danh (Process ID)o Trng thi tin trnh (State)o Ng cnh tin trnh (Context)

Trng thi CPU B x l (cho mynhiu CPU) B nhchnh Ti nguyn s dng/to lp

o Thng tin giaotip(Relative) Tintrnh cha, tin trnh con

u tino Thng tinthng k

Thigian s dng CPU Thigian ch

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Cc thao tc trn tin trnh

To lp tin trnhKt thc tin trnhThay i trng thitin trnh :

o Assign()o Block()o Awake()o Suspend()o Resume()

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To lp tin trnh (1)

Cc tnh hung :o Khi ngbatch jobo User logs ono Kchhot 1 dch v (print...)o Tin trnh gihm to mt tintrnh khc

Cc tin trnh c th to tintrnh con, hnhthnh cy tin trnh trongh thngCc tin trnh mi c to c th

o Tha hng ti nguyn t chao c cp ti nguyn mi

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Kt thc tin trnh

Tnh hung :o Tin trnh x l xonglnh cuicng hay giexit ()o Ktthc Batch job, Halt instructiono User logs off o Do li chng trnh

Mt tintrnh c th kt thc 1 tin trnh khcnu c ID(nh danh) ca tin trnh kia.Vd: kill -s SIGKILL 1234Cng vic ca HHkhi kt thc 1 tin trnh?

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M hnh a tin trnh(MultiProcesses)

H thng= mt tp cc tin trnh hot ngng thiCc tin trnh c lp vi nhau khng c s

trao i thng tin a tin trnh: thi hnh ng thi cc chngtrnh, ch th trong my c nhiu CPU

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M hnh a tiu trnh (MultiThreads)

Nhiu tnh hung cn c nhiu dng x l ngthi hot ng trong mt khng gian a ch cng chia s ti nguyn

o Gn nh songsongo Nh cc tin trnh c lp

Tiu trnh (Thread)

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Tiu trnh

Mt n v x l c bn trong h thngMi tiutrnh

o X l tun t on code ca n

o S hu mtcon tr lnh tp cc thanh ghi mtvng nh stack ring

Cc tiu trnh chia s CPU ging nh cch catin trnh

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Tiu trnh & Tin trnh

Tiu trnh : 1 dng x lTin trnh :

o 1 khng gian a ch

o 1 hoc nhiu tiutrnhCc tin trnh l c lpCc tiu trnh trong cng 1tin trnh khng cs bov ln nhau

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Tiu trnh ht nhn (Kernel Thread)

Khi nim tiu trnh(Thread) c xy dngbn trong ht nhn (Kernel)

n v x l l tiu trnh

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Phn chia CPU

1 CPU vt l : lm th no to cm gic mitin trnh s hu CPU ring ca mnh?Lun chuyn CPU gia cc tin trnh

2 thnh phn m nhim vai tr iu phi:o Scheduler chn tintrnho Dispatcher chuyn CPU cho tin trnh c chn

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Danh sch tin trnh

Tng ng vi cc trng thi ca tin trnh

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Scheduler

Nhim v: quyt nh chn mt tin trnh cppht CPU

o ng c vin = {Cctin trnh ready list}o 0 tin trnh: CPUrnh ri(idle)!o 1 tin trnh: hinnhin chno >1: Da vo cc thut ton iu phi

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Dispatcher

Nhim v: Chuyn i ng cnhXt vd

o Tin trnh A ang dng CPU 1lc th b HH thu hiCPU

o HH cpCPU cho B dng 1 lc, HHthu hi liCPUo HH cpCPU tr licho A

Gi tr cc thanh ghi gia nhng ln chuyn iCPU?

Kch bn:o Lu ng cnh tin trnh hin hnho Np ng cnh tin trnh c chn k tip

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H iu hnh & CPU

HH cng l 1 phn mm cn s dng CPUCu hi: Khi tin trnh A ang chim CPU, lmth no HH c th thu hi CPU li c?

o p buc thnh thong trCPU li cho HH?o My tnhphi c 2 CPU, 1 dnh ring cho HH?o HH s dng ngt ng h (ngt iu phi, interrupt)

kim sot h thng Mi khi c ngt ng h, HH kim tra xem c cn thu hi

CPU t 1 tin trnh no li hay khng ? HH ch thu hi CPU khi c ngt ng h pht sinh. Khong thi gian gia 2 ln ngt iu phi gi l chu k

ng h (ti thiu l 18.2 ln/ giy)

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Ngt ng h (1)

C ch

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Interrupt

Trnh x linterrupt


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Ngt ng h (2)

Cc b c x l interrupto H iu hnh chim li quyn thc thio Lu tr trng thi ca qu trnh b ngto Phn tch ngt (dng phn cng)o Thc thi chng trnh x l ngt

Interrupt handler o Chn mt qu trnh tip theo chy

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Ngt ng h (3)

Cc loi interrupto Supervisor call (SVC) interrupt: khi qu trnh yu cu

dch v ca h thngo I/O interrupt: do cc thit b I/O sinh ra khi chuyn

trng thio External interrupt: sinh ra t ng h h thng, bn

phmo Restart interrupt: ngt khi ng li myo

Program check: sinh ra khi chng trnh thc thi lnhb li (chia cho 0, trn s, )o Machine check: do nh sn xut to ra dnh ring

cho vic kim tra phn cng

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Chuyn ng cnh (1)

Chuyn ng cnh (context switching)o Chuyn x l t tin trnh ny sang tin trnh khco Xyra khi c interrupt

Quy trnh:o Lu trng thi ca tin trnh hin hnho Chn tin trnh mi x lo a trng thi ca tin trnh mi vo phn cng x l

Mt ng cnh(context) bao gm:o Tp thanh ghi cha thng tin trng thi tin trnh v trng

thi CPU, b nh ca tintrnh.Program Status Word (PSW)

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Chuyn ng cnh (2)

Cc loiPSW:o Old_PSWo Current _PSWo New_PSW

H thng mt b xl co 1 Current_PSWo 6 New_PSWo 6 Old_PSW (6loi interrupt)

Qu trnh chuyn ng cnh din ra = s thay igia cc PSW trong h thngo Current_PSW Old_PSWo New_PSW Current_PSW

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La chn tin trnh

Tc v ca Scheduler Mctiu?

o S dng CPU hiu quo

m bo tt c cc tin trnh u tin trin x lTiu chun la chn?o Tt c cc tin trnh u nh nhau?o xut mt u tin cho mi tin trnh?

Thi im la chn? (Thi im kch hotScheduler())

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Mc tiu iu phi

Hiu qa (Efficiency)o Thi gian

p ng (Response time ) Hon tt (Turnaround Time = Tquit -Tarrive):

Ch (Waiting Time = T in Ready) :o Thng lng (Throughput = #jobs/s)

Hiu sutTi nguyn Chi ph chuyn i

Cng bng (Fairness ): Tt c cc tin trnh uc c hi nhn CPU

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Thi im quyt nh iu phi

iu phi c quyn (non-preemptive scheduling):o tin trnh c chn c quyn c chim CPUo Cc thi im kch hot Scheduler

Pcur kt thc Pcur: running ->blocked

iu phi khng c quyn (preemptivescheduling):

o tin trnh c chn c th bcp CPU bi tin trnh c u tin cao hn

o Cc thi im kch hot Scheduler Pcur kt thc Pcur: Running -> Blocked Q: Blocked / New -> Ready

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Hai nguyn tc iu phi CPU

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nh gi chin lc iu phi

S dng 2 i lng o :o Turn-around time= Tquit Tarrive: t lc vo HT n

khi hon tto Waiting time= T in Ready

Xt trng hp trung bnho N tin trnho Avg Turn-around time = ( Turn-around timePi)/No Avg Waiting time = ( WaitingtimePi)/N

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Mt s gii thut iu phi

iu phi hn cht(Deadline Scheduling)FCFS (First Come First Served)SJF (Shortest Job First)

SRT (Shortest Remaining Time)RR (Round Robin)

iu phi u tin

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i hi h


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iu phi hn cht(Deadline Scheduling)

iu phi sao cho cc qu trnh c thc thitheo mt bng thi gian xc nh trcMc ch : hon thnh tc v kp lc

ng dng : cng nghip, vinthng, qun sRt phc tpCh c gii thutcho tng h thng c th

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FCFS (First comes first served)

Tin trnh vo RL lu nht c chn trcTheo th t vo RL

c quyn

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FCFSMinh Ha

AvgWT = (23+25)/3 = 16

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FCFSNhn xt

n ginChu ng hin tng tch ly thi gian ch

o Tin trnh c thi gian x l ngn i tin trnh c thigian x ldi

C th xy ra tnh trng c chimCPU

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d b


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Round RobinMinh Ha (1)

Viq=4ms

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R d R bi


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Round RobinMinh Ha (2)

Viq=4ms

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R d R bi


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Round RobinKhi no kt thc lt s dng CPU

Ht thi lng q ms (quantum) cho phpTin trnh kt thcTin trnh b kha

o Ch Rso Ch bin c

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R d R bi


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Round RobinNhn xt

S dng c ch khng c quynMi tin trnh khng phi i qu luLoi b hin tng c chim CPU

Hiu qu?o Ph thuc vo vic chn laquantum q

q qu ln ??? Tng thi gian hi p

Gim tnh tng tc q qu nh ??? Tng chi ph chuyn i ng cnh

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iu phi vi u tin

Phn bit tin trnh quan trng>< tin trnh bnhthng

Tin trnh c u tin cao nht c chn cpCPU trc

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V d: u tin ca HH WinNT

Tin trnhc u tin 0 v 3 1o 0 ( u tin nh nht): dnh ring cho system idle

u tin c phn theo nhm:o

Realtime: (16 - 31) Thch hp cho cc tin trnh thi gian thc Dnh ring cho cc tin trnh ca ngi qun tr h thng

o Dynamic : (0 - 15) Thch hp cho cc tin trnh ca ngi dng thng Chia thnh 3 mc :

high (11 - 15) normal (6 - 10) idle (2 - 6)

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Nguyn tc iu phi

c quyno Lt s dng CPU kt thc khi:

tintrnh kt thc, tintrnh b kha

Khng c quyno Lt s dng CPU kt thc khi:

tintrnh kt thc, tintrnh b kha, C tin trnh vi u tin cao hn voRL

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iu phi u tin


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iu phi u tinNhn xt

Cch tnh u tin ?o H thnggn : CPU timeso Ngi dng gn tng minh

Tnh cht u tin :o Tnho ng

S phn tin trnh c u tin thp ?o Ch lu, lu, lu ...o Tng u tin cho nhng tin trnh ch lu trong

h thng

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Shortest Job First (SJF)

L mt dng u tin c bit vi u tino pi= thi_gian_cn_li(Process i)

C th ci t c quyn hoc khng c quyn

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SJF (c quyn)


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SJF (c quyn)Minh ha (1)

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SJF (khng c quyn)


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SJF (khng c quyn)Minh ha (1)

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SJF (khng c quyn)


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SJF (khng c quyn)Minh ha (2)

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SJF ( nhiu chu k CPU)


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SJF ( nhiu chu k CPU)Minh ha

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SJF


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SJFNhn xt

Ti u thi gian chKhng kh thi

o Lm sao bit CPU burst ?

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iu phi vi nhiu mc u tin


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iu phi vi nhiu mc u tinThc t

T chc N RLng vinhiu mc u tinMiRLi p dng RR

Gia cc RL p dngiu phi theo utin :

o RLi rng mi iu phi

RLi +1

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Khuyt im

iGiiphp Aging

o Ch lu qu : chuynln RLvi u tincao hn

o ChimCPU lu qu :chuyn xung RL vi u tin thp hn

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Tho lun

Cu hi?

kin?

xut?

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Bi Tp

Documents

OS 2 - Process & Scheduling