Tài Liệu Hệ Điều Hành Tiếng Việt

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Mc lc Gii thiu v H iu hnh .................................................................................................... 6

i vi c gi ...................................................................................................................... 6

iu kin tin ................................................................................................................... 6

Tng quan v H iu hnh .................................................................................................. 6

nh ngha ........................................................................................................................ 6

Qun l b nh ................................................................................................................. 7

Qun l b vi x l ............................................................................................................ 8

Qun l thit b .................................................................................................................. 8

Qun l file ........................................................................................................................ 9

Cc hot ng quan trng khc ........................................................................................ 9

Cc kiu H iu hnh .......................................................................................................... 9

H iu hnh Batch ........................................................................................................ 10

H iu hnh Time-sharings ........................................................................................... 10

H iu hnh c phn phi (distributed) ..................................................................... 11

H iu hnh h thng .................................................................................................... 12

H iu hnh thi gian thc (real time) ........................................................................... 12

Cc h thng thi gian thc cng ....................................................................... 13

Cc H iu hnh thi gian thc mm ............................................................... 13

Cc dch v ca H iu hnh ............................................................................................ 13

S thi hnh chng trnh ................................................................................................ 14

Hot ng I/O ................................................................................................................. 14

Thao tc h thng file ...................................................................................................... 15

Giao tip ......................................................................................................................... 15

Kim sot li ................................................................................................................... 16

Qun l ti nguyn .......................................................................................................... 16

Trnh bo mt ................................................................................................................. 16

Cc thuc tnh ca H iu hnh ........................................................................................ 16



Tin trnh x l Batch ...................................................................................................... 17

Cc li th ................................................................................................................ 17

Cc bt li ................................................................................................................ 17

a nhim ........................................................................................................................ 18

a chng trnh ............................................................................................................. 19

Cc li th ................................................................................................................ 20

Cc bt li ................................................................................................................ 20

Kh nng tng tc ........................................................................................................ 20

H thng thi gian thc .................................................................................................. 20

Mi trng c phn phi ............................................................................................ 21

Spooling.......................................................................................................................... 21

Cc li th ................................................................................................................ 22

Cc tin trnh x l trong OS ............................................................................................... 22

Tin trnh x l ................................................................................................................ 22

Chng trnh .................................................................................................................. 23

Cc trng thi tin trnh ................................................................................................... 23

Khi kim sot tin trnh, PCB ......................................................................................... 24

Ghi lch trnh tin trnh trong OS ........................................................................................... 26

nh ngha ...................................................................................................................... 26

Sp hng lch trnh .......................................................................................................... 27

Hai mu trng thi tin trnh ............................................................................................ 28

B lp lch trnh ................................................................................................................ 28

B lp lch trnh thi hn di ............................................................................................ 29

B lch trnh thi hn ngn............................................................................................... 29

B lch trnh thi hn trung............................................................................................... 29

So snh gia cc b lch trnh ......................................................................................... 30

Chuyn bi cnh (context switch) .................................................................................... 31

Cc thut ton lp lch trnh trong OS .................................................................................. 32

Lp lch trnh vo u phc v trc (FCFS) ................................................................... 33



Lp lch trnh cng vic ngn nht phc v trc (SJF) ................................................... 34

Lp lch trnh quyn u tin ............................................................................................. 35

Lp lch trnh Round Robin .............................................................................................. 36

Lp lch trnh a hng ...................................................................................................... 37

Ch a lung (Multi-thread) trong OS ............................................................................. 37

Thread l g? ................................................................................................................... 38

S khc nhau gia Tin trnh v thread .......................................................................... 38

Cc li th ca Thread .................................................................................................... 41

Cc kiu Thread ............................................................................................................. 41

Cc thread mc ngi dng ...................................................................................... 41

Cc li th ................................................................................................................ 42

Cc bt li ................................................................................................................ 42

Cc thread mc Kernel .............................................................................................. 42

Cc li th ................................................................................................................ 43

Cc bt li ................................................................................................................ 43

Cc m hnh a thread ................................................................................................... 43

Ch Many to Many .................................................................................................... 43

Ch Many to One ...................................................................................................... 44

Ch One to One ........................................................................................................ 45

S khc nhau gia ch mc ngi s dng v mc Kernel ........................... 45

Qun l b nh trong OS .................................................................................................... 46

Ti ng (dynamic loading) ............................................................................................. 47

Kt ni ng .................................................................................................................... 48

Khng gian a ch vt l logic ....................................................................................... 48

Swapping........................................................................................................................ 48

S cp pht b nh ........................................................................................................ 49

S phn mnh (Fragmentation) ...................................................................................... 50

K thut nh s trang .................................................................................................... 51

K thut phn on ......................................................................................................... 53



B nh o trong OS ............................................................................................................ 54

K thut nh s trang yu cu (demand paging) ........................................................... 55

Cc li th ................................................................................................................ 58

Cc bt li ................................................................................................................ 58

Thut ton i v tr trang ................................................................................................. 58

Chui tham chiu ............................................................................................................ 59

Thut ton Vo u ra u (First In First Out - FIFO) ....................................................... 59

Thut ton Trang quang hc ........................................................................................... 60

Thut ton c s dng gn y nht (Least Recently Used - LRU) ........................... 60

Thut ton Chuyn hon m trang ............................................................................... 61

Thut ton c s dng thng xuyn t nht (Least frequently Used - LFU) .............. 61

Thut ton c s dng thng xuyn nht (Most Frequently Used MFU) ................. 61

Phn cng Nhp/Xut (IO) trong OS .................................................................................. 62

Tng quan ...................................................................................................................... 62

Chui daisy ..................................................................................................................... 62

B iu khin .................................................................................................................. 62

Cng I/O ......................................................................................................................... 62

Polling ............................................................................................................................. 63

Cc thit b I/O ................................................................................................................ 64

S truy cp b nh trc tip (DMA) ................................................................................ 65

Cc b iu khin thit b ................................................................................................ 67

Phn mm Nhp/Xut (I/O) trong OS ................................................................................. 67

Cc phn mm ngt (interrupts) ...................................................................................... 67

Giao din I/O ng dng .................................................................................................. 68

Cc ng h xung .......................................................................................................... 69

H thng ph Kernel I/O ................................................................................................. 72

B iu khin thit b ....................................................................................................... 73

H thng file trong OS ......................................................................................................... 73

File .................................................................................................................................. 74



Cu trc file ..................................................................................................................... 74

Kiu file ........................................................................................................................... 74

Cc file thng ........................................................................................................ 74

File th mc ............................................................................................................. 74

Cc file c bit ....................................................................................................... 74

K thut truy cp file ........................................................................................................ 75

Truy cp lin tc ...................................................................................................... 75

S truy cp trc tip/ngu nhin .......................................................................... 75

S truy cp lin tc theo ch mc ......................................................................... 75

S cp pht khng gian .................................................................................................. 76

S cp pht lin tc ................................................................................................ 76

S cp pht theo kt ni........................................................................................ 76

S cp pht theo ch mc...................................................................................... 76

Bo mt trong OS ............................................................................................................... 77

S xc minh ................................................................................................................... 77

Cc mt khu Mt ln ..................................................................................................... 78

Cc s e da ti chng trnh ...................................................................................... 78

Cc mi e da ti h thng ........................................................................................... 79

Cc phn hng bo v my tnh ..................................................................................... 79

H iu hnh Linux ............................................................................................................. 80

Cc thnh phn ca h thng Linux ................................................................................ 81

Ch kernel v ch ngi dng .............................................................................. 81

Cc c im c bn ...................................................................................................... 82

Cu trc .......................................................................................................................... 83

Ti liu tham kho v OS .................................................................................................... 83

Cc ng link hu ch v H iu hnh ........................................................................ 84



Gii thiu v H iu hnh Mt H iu hnh (OS) l mt tp hp phn mm m qun l ngun ti nguyn phn cng ca

my tnh v cung cp cc dch v ph bin cho cc chng trnh my tnh. H iu hnh l mt b

phn mang tnh sng cn ca phn mm h thng trong h thng my tnh.

Phn hng dn ny s a bn tng bc tip cn vi cc khi nim ca OS.

Lot bi hng dn ca chng ti da trn ngun ti liu ca: Tutorialspoint

i vi c gi Bi tham kho ny gip cho cc sinh vin khoa hc my tnh c s hiu bit c bn v cc khi

nim tin tin lin quan n H iu hnh.

iu kin tin Trc khi bt u tin hnh nghin cu phn hng dn ny, ti gi s rng bn c s hiu

bit v cc khi nim my tnh c bn nh bn phm, chut, mn hnh, thit b u vo, b nh s

cp v b nh th cp. Nu bn cha thc s nm vng cc khi nim ny, th ti xin ngh

bn nghin cu qua phn hng dn ca chng ti v Cc khi nim c s v my tnh (Computer

Fundermentals).

Tng quan v H iu hnh Mt H iu hnh l mt trung gian kt ni gia ngi s dng v phn cng my tnh. N cung

cp cho ngi s dng mt mi trng m trong mt ngi s dng c th chy cc chng

trnh mt cch thun li v hiu qu.

Theo ngn ng k thut, n l mt phn mm m qun l iu hnh phn cng. Mt H iu hnh

iu khin s cp pht ca cc ti nguyn v dch v nh b nh, cc b x l, cc thit b v

thng tin.

nh ngha Mt H iu hnh l mt chng trnh m hot ng nh mt giao din gia ngi s dng v

phn cng my tnh v iu khin s thc hin ca tt c cc loi chng trnh.



Di y l mt vi cc chc nng quan trng ca mt H iu hnh:

Qun l b nh;

Qun l b vi x l;

Qun l thit b;

Qun l file;

Bo mt;

Kim sot hiu nng h thng;

Job accounting (Thng k k ton);

Gip tm ra li;

Kt ni gia cc phn mm v ngi s dng.

Qun l b nh L s qun l v b nh s cp hay l b nh chnh. B nh chnh l mt mng rng ca cc t

hoc cc byte, m ti ni mi t hoc byte c mt a ch ring.



B nh chnh cung cp mt kho lu nhanh m c th c truy cp trc tip bi CPU. Do

mt chng trnh c th chy c, n phi trong b nh chnh. H iu hnh thc hin cc hot

ng sau cho Qun l b nh:

Theo di b nh chnh, v d nh phn no ang s dng bi ai , phn no khng s

dng.

Trong ch a chng trnh, OS quyt nh tin trnh no chn b nh khi no v bao

nhiu.

Cp pht b nh khi mt tin trnh yu cu.

Tr li b nh khi tin trnh khng cn na hoc kt thc.

Qun l b vi x l Trong mi trng a chng trnh, OS quyt nh tin trnh no nhn b vi x l khi no v bao

lu. Chc nng ny c gi l bn danh biu (lch trnh) ca tin trnh. OS thc hin cc hot

ng sau qun l b vi x l:

Theo di b vi x l v trng thi ca tin trnh. Chng trnh chu trch nhim cho nhim

v ny c bit n vi tn gi iu khin lung tn hiu.

Cp pht b vi x l (CPU) ti mt tin trnh.

Tr li cp pht b vi x l khi tin trnh khng cn na.

Qun l thit b OS qun l giao tip thit b thng qua cc chng trnh iu khin tng ng ca n. H iu

hnh thc hin cc hot ng sau qun l thit b:

Theo di tt c cc thit b. Chng trnh chu trch nhim thc hin nhim v ny c

bit n vi tn gi l Kim sot I/O.

Quyt nh tin trnh no nhn thit b khi no v trong bao lu;

Cp pht thit b theo cch hiu qu nht.

Tr li cp pht thit b.



Qun l file Mt h thng file thng c t chc trong cc th mc d dng cho vic iu hng v s

dng. Nhng th mc ny c th cha cc file v cc th mc khc. H iu hnh thc hin cc

hot ng sau qun l file:

Kim tra thng tin, v tr, trng thi. Cc phng tin thu thp ny thng c bit nh

l h thng file.

Quyt nh ai nhn ngun ti nguyn no;

Cp pht ngun ti nguyn;

Tr li cp pht ngun ti nguyn.

Cc hot ng quan trng khc Di y l mt vi cc hot ng quan trng m H iu hnh thc hin.

Bo mt -- Vi mt khu v cc cng c khc, ngn chn cc s truy cp khng c cp

pht quyn ti chng trnh v d liu.

Kim sot hiu nng h thng -- Ghi chp li thi gian tr hon gia yu cu cho mt dch

v v s phn ng li t h thng.

Job accounting -- Theo di thi gian v ngun ti nguyn c s dng bi cc cng vic

v ngi s dng khc nhau.

Gip pht hin ra li -- Thng bo v pht hin cc li.

Kt ni gia ngi s dng v phn mm -- S kt ni v ch nh ca trnh bin dch,

phin dch, b bin m v phn mm khc ti cc ngi s dng khc nhau ca h thng

my tnh.

Cc kiu H iu hnh H iu hnh c t th h my tnh u tin. H iu hnh tip tc pht trin theo thi gian. Di

y l mt s loi H iu hnh m c s dng ph bin nht.



H iu hnh Batch Nhng ngi s dng H iu hnh Batch khng tng tc vi my tnh mt cch trc tip. Mi

ngi s dng chun b phn vic ca h trn mt thit b off-line nh cc th c l (punch cards)

v trnh n ti ngi iu hnh my tnh. tng tc x l, cc phn vic vi cc yu cu

tng t nhau c kt t li vi nhau v chy nh l mt nhm. Do , cc nh lp trnh bung

chng trnh ca h cho ngi iu hnh. Sau ngi iu hnh sp xp cc chng trnh vo

cc t vi cc yu cu tng t nhau.

Tuy nhin c nhng vn m xy ra vi H iu hnh Batch nh sau:

Thiu s tng tc (hay giao din tng tc) gia ngi s dng v phn vic ca h.

CPU thng khng lm g, bi v tc ca cc thit b I/O l chm hn CPU.

Rt kh cung cp quyn u tin nh mun.

H iu hnh Time-sharings Time-sharings l mt k thut m cho php nhiu ngi, ti cc terminal khc nhau, kh nng s

dng mt H iu hnh ring bit ti cng mt thi im. Thi gian ca b vi x l ng thi c

chia s bi nhng ngi s dng. im khc nhau chnh gia H iu hnh a chng trnh

Batch v H iu hnh a nhim: mc tiu ca H iu hnh Batch l ti a ha s s dng ca

b x l, trong khi mc tiu ca H iu hnh a nhim l ti thiu thi gian phn hi.

Nhiu chng trnh c chy bi CPU bng cch chuyn mch gia chng, nhng s chuyn

mch xy ra thng xuyn. Do , ngi s dng c th nhn s phn hi ngay lp tc. V d,

trong mt tin trnh truyn ti, b x l chy mi chng trnh ngi s dng mt xung ngn ca

my tnh ha. l nu n ngi ang s dng hin ti, mi ngi dng c th nhn xung thi

gian. Khi ngi s dng trnh lnh, thi gian phn hi ch l trong vi giy ngn.

H iu hnh s dng a chng trnh v biu lp chng trnh CPU cung cp cho mi

ngi s dng vi mt phn nh ca thi gian. Cc h thng my tnh m c thit k u tin

nh H iu hnh Batch c chnh sa thnh dng H iu hnh chia s thi gian.

Cc li th ca H iu hnh Time-sharings nh sau:

Li th ca s phn hi nhanh.

Trnh c s sao nhn ca phn mm.



Gim thi gian CPU khng lm vic.

Bt li ca H iu hnh ny l:

Vn ca s ng tin cy.

QVn bo mt v tnh nguyn vn ca cc chng trnh v d liu ca ngi s dng

c t du hi.

Vn v s trao i d liu.

H iu hnh c phn phi (distributed) H iu hnh ny s dng nhiu b x l trung tm phc v nhiu ng dng v nhiu ngi s

dng. Cc chng trnh x l d liu c phn phi bn trong cc b x l mt cch ph hp m

mi chng trnh c th thc hin mt cng vic mt cch hiu qu nht.

Cc b x l giao tip vi nhau thng qua cc ng kt ni a dng (nh cc cng bus tc

cao hoc cc ng dy in thoi). Nhng ci ny c gi nh l cc h thng b ghp mt

cch lng lo hoc cc h thng c phn phi. Cc b x l trong h thng ny c th a dng

c v kch c v chc nng. Nhng b x l c gi nh cc site, cc nt, cc my tnh.

Cc li th ca H iu hnh c phn phi l:

Vi ngun ti nguyn d dng chia s, ngi s dng ti cng mt site c th s dng

cc ti nguyn c sn ti site khc.

Tng tc trao i d liu vi nhau thng qua mail in t.

Nu mt site b li trong h thng phn phi, th cc site cn li c th c kh nng tip tc

hot ng.

Cht lng phc v tt hn i vi khch hng.

Gim thiu lng ti trn my host.

Gim thiu s tr hon trong qu trnh x l d liu.



H iu hnh h thng Network Operating System chy trn mt server v cung cp cho server kh nng qun l d

liu, cc ngi s dng, cc nhm, s bo mt, cc chng trnh ng dng v cc chc nng h

thng khc. Mc ch u tin ca H iu hnh ny l cho php cc file c chia s v vic

truy cp vo my in trong nhiu my tnh trong mt h thng, c bit nh trong h thng mng

LAN, h thng mng c nhn hoc cc h thng khc. Cc v d ca mng h thng l Microsoft

Windows Server 2003, Microsoft Windows Server 2008, Unix, Linux, Mac OS X, Novell NetWare,

v BSD.

Cc li th ca H iu hnh h thng l:

Server trung tm mang tnh n nh cao.

S bo mt l c qun l.

Vic nng cp vi cng ngh v phn cng mi c th d dng c tch hp vo trong h

thng.

C th truy cp t xa ti server t cc my ni b v cc kiu h thng khc nhau.

S bt li ca loi H iu hnh ny l:

Chi ph cao mua sm v chy mt server;

Ph thuc vo mt v tr server trung tm cho hu ht cc hot ng;

Lun yu cu c duy tr v cp nht;

H iu hnh thi gian thc (real time) H iu hnh thi gian thc l mt nh ngha nh l h thng x l d liu m trong khon thi

gian cn thit x l v phn hi ti cc d liu u vo l ngn m n kim sot mi trng.

Tin trnh x l thi gian thc thng l trc tuyn trong khi h thng trc tuyn khng cn thit

phi l thi gian thc. Thi gian tn bi h thng phn hi ti mi d liu u vo v hin th

thng tin c cp nht theo yu cu c gi l thi gian phn hi. V th trong phng thc ny

thi gian phn hi l t hn khi so snh vi tin trnh x l trc tuyn.

H iu hnh thi gian thc c s dng khi c cc yu cu thi gian cng nhc trn mt hot

ng ca mt b x l hoc lung d liu v cc h thng thi gian thc c th c s dng nh



l mt thit b iu khin. H iu hnh ny c xc nh r, rng buc v thi gian c b tr,

nu khng th h thng s gp s c. V d, cc th nghim khoa hc, cc h thng nh y t, h

thng v kh, robot, h thng qun l lung bay.

C hai kiu H iu hnh thi gian thc:

Cc h thng thi gian thc cng

Cc h thng ny m bo rng cc nhim v quan trng c hon thnh ng thi gian. Trong

h thng thi gian thc cng, kho lu th cp c hn ch hoc b qun vi d liu c lu

trong ROM. Trong cc h thng ny, b nh o thng khng bao gi c tm thy.

Cc H iu hnh thi gian thc mm

Cc h thng ny th t c s gii hn hn. Cc nhim v quan trng nhn quyn u tin thc hin

so vi cc nhim v khc v tr li quyn u tin ti khi n hon thnh. H iu hnh ny c cc

tin ch b gii hn hn cc h thng thi gian thc cng. V d, a phng tin, cc d n khoa

hc tin tin nh tham d y bin, thm d khng gian.

Cc dch v ca H iu hnh Mt H iu hnh cung cp cc dch v ti c ngi s dng v ti cc chng trnh:

N cung cp cc chng trnh mt mi trng chy;

N cung cp cho ngi s dng cc dch v thc hin cc chng trnh theo cch tin

li nht.

Di y l mt vi dch v ph bin c cung cp bi cc H iu hnh:

S thi hnh chng trnh

Cc hot ng I/O

Thao tc h thng file

Giao tip

Thm tra li

Cp pht ti nguyn



Bo v

S thi hnh chng trnh H iu hnh vn dng nhiu loi hot ng t cc chng trnh ngi dng n cc chng trnh

h thng nh Spooler, tn server, file server. Mi mt hot ng c ng gi nh l mt tin

trnh.

Mt tin trnh bao gm mt dy thi hnh y (m chy, d liu thao tc, ng k, ngun

OS s dng). Di y l cc hot ng chnh ca mt H iu hnh lin quan ti qun l

chng trnh:

Ti mt chng trnh vo trong b nh.

Chy chng trnh .

iu khin s thi hnh ca chng trnh.

Cung cp mt k thut cho s ng b tin trnh x l.

Cung cp mt k thut cho giao tip tin trnh.

Cung cp mt k thut cho vic x l cc s b tc.

Hot ng I/O H thng ph I/O bao gm cc thit b I/O v phn mm iu khin (drivers) tng ng. Cc b

iu khin n nhng nt c th ca cc thit b phn cng c th t ngi s dng.

H iu hnh qun l giao tip gia ngi dng v cc thit b drivers. Di y l cc hot ng

chnh ca mt H iu hnh lin quan ti hot ng I/O:

Hot ng I/O ngha l hot ng c hoc vit bt k file no hoc bt k thit b I/O c th

no.

Chng trnh c th yu cu bt c thit b I/O no trong khi chy.

H iu hnh cung cp s truy cp ti cc thit b I/O khi c yu cu.



Thao tc h thng file File i din cho mt tp hp cc thng tin lin quan c thu thp. My tnh c th lu file trn

cng (kho lu th cp), cho mc ch lu trong thi gian di. Mt vi v d ca phng tin lu gi

l cc bng t, a t v cc a quang nh CD, DVD. Mi mt phng tin c cc thuc tnh ring

ca n nh tc , dung lng, t l trao i d liu v cc phng thc truy cp d liu.

Mt h thng file thng c t chc vo trong cc th mc s dng v iu hng d dng.

Nhng th mc ny c th cha cc file v cc th mc khc. Di y l cc hot ng chnh

ca mt H iu hnh lin quan ti qun l file:

Chng trnh cn c hoc vit mt file.

H iu hnh cung cp s cho php ti chng trnh thc hin hot ng trn cc file.

S cho php a dng t ch c (read-only), c-vit,

H iu hnh cung cp mt giao din ti ngi s dng to/xa cc file.

H iu hnh cung cp mt giao din ti ngi s dng to/xa cc th mc.

H iu hnh cung cp mt giao din ti ngi s dng to bn d phng (cc bn sao)

ca h thng file.

Giao tip Trong h thng c phn phi m l mt tp hp ca cc b x l khng chia s b nh, cc

thit b ngoi vi, hoc ng h xung th H iu hnh ny qun l s truyn thng tin gia cc tin

trnh x l. Nhiu tin trnh x l vi trao i thng tin vi nhau thng qua cc ng dn thng tin

trong mng h thng.

H iu hnh kim sot chin lc kt ni v tuyn ng, v cc vn v cc s xung t v

bo mt. Di y l cc hot ng chnh ca mt H iu hnh lin quan ti trao i thng tin:

Hai tin trnh thng yu cu d liu c truyn ti gia chng;

C hai tin trnh c th trn mt my tnh hoc trn hai my tnh khc nhau nhng c kt

ni vi nhau thng qua mng h thng my tnh.

Giao tip c th c thc hin theo hai phng thc: bi B nh c chia s hoc bi

thng bo trao i.



Kim sot li Cc li hay trc trc c th xy ra bt c lc no v bt c u. Li c th xy ra trong CPU, trong

cc thit b I/O hoc trong b nh cng. Di y l cc hot ng chnh ca mt H iu hnh

lin quan ti kim sot li:

H iu hnh lin tc nhn bit cc li c th nhn bit.

H iu hnh thc hin cc hnh ng ph hp chnh sa cc li.

Qun l ti nguyn Trong mi trng a nhim hoc nhiu ngi s dng, cc ngun ti nguyn nh b nh chnh,

CPU, v vic lu gi file c cp pht ti mi ngi s dng hoc mi cng vic. Di y l

cc hot ng chnh ca mt H iu hnh lin quan ti qun l ti nguyn:

H iu hnh qun l tt c ngun ti nguyn bng vic s dng cc bng biu lch trnh.

Gii thut lch trnh CPU c s dng mang li s tin ch ha ln nht ca CPU.

Trnh bo mt Gi s rng mt h thng ang c nhiu ngi s dng ang chy ng thi nhiu tin trnh, th

khi mi tin trnh khc nhau phi c bo v t cc hot ng ca n.

Trnh bo mt ny lin quan ti k thut hoc phng thc kim sot s truy cp vo cc

chng trnh, cc b x l, hoc ngi s dng ti cc ngun ti nguyn c xc nh r bi h

thng my tnh. Di y l cc hot ng chnh ca H iu hnh lin quan ti trnh bo mt:

OS m bo rng tt c cc s truy cp ti ti nguyn h thng c kim sot.

OS bo m rng cc thit b ngoi vi c bo v t cc c gng truy cp khng c cp

php.

OS cung cp tnh nng xc minh cho mi ngi s dng (gi l mt khu).

Cc thuc tnh ca H iu hnh Di y l cc nhim v quan trng m H iu hnh kim sot:



Tin trnh x l Batch Tin trnh x l Batch l mt k thut trong H iu hnh thu thp cc chng trnh v d liu

vi nhau trong mt batch trc khi bt u tin trnh x l. H iu hnh thc hin cc hot ng

sau lin quan ti tin trnh x l batch:

OS xc nh r mt cng vic m sp hng trc theo th t cc lnh, cc chng trnh v

d liu nh l mt n v n l.

OS gi s hiu ca cc cng vic trong b nh v thc hin chng m khng cn bt c

thng tin nhn hiu.

Cc cng vic c x l theo th t trnh, v d: s hiu u tin th x l u tin.

Khi cng vic kt thc, b nh ca n c gii phng v kt qu u ra cho cng vic

c sao vo trong spool u ra cho tin trnh x l hoc tin trnh in sau .

Cc li th

Tin trnh x l batch thc hin nhiu cng vic ca ngi iu hnh ti my tnh.

Tng hiu sut: mt cng vic mi c bt u ngay sau khi cng vic trc kt thc m

khng cn bt c s xen vo no ca ngi iu khin.

Cc bt li

Kh g li (debug) chng trnh.

Mt cng vic c th nhp mt vng lp v hn.



Do thiu lch trnh bo mt, mt Batch c th nh hng n cc cng vic ang trong

qung thi gian ch x l.

a nhim a nhim lin quan ti khi nim trong nhiu cng vic c thc hin lin tc bi CPU bng

cch chuyn i gia chng. Trnh chuyn i ny xy ra lin tc ngi s dng c th tng

tc vi mi chng trnh trong khi n ang chy. H iu hnh thc hin cc hot ng sau lin

quan n a nhim:

Ngi s dng cung cp ch dn ti H iu hnh hoc ti chng trnh mt cch trc tip,

v nhn phn hi ngay lp tc.

H iu hnh iu khin a nhim theo cch m n c th kim sot nhiu hot ng/thc

hin nhiu chng trnh cng mt lc.

H iu hnh a nhim cng cn c bit l H iu hnh Time-Sharing.

H iu hnh a nhim c pht trin cung cp giao din s dng ca mt h thng

my tnh mt mc chi ph hp l.

H iu hnh time-sharings s dng khi nim lch trnh v ch a chng trnh CPU

cung cp cho mi ngi s dng m phn nh ca mt CPU c chia s phin s dng.

Mi ngi s dng c t nht mt chng trnh ring trong b nh.

Mt chng trnh c ti vo trong b nh v ang thc hin mt tin trnh ph bin.



Khi mt tin trnh thc hin, n chy ch trong mt thi gian ngn trc khi n kt thc hoc

cn thc hin I/O.

Khi I/O tng tc chy, n tn mt thi gian kh di kt thc. Trong sut thi gian ny,

mt CPU c th c tin ch ha (trng dng s dng) bi mt chng trnh khc.

H iu hnh cho php nhng ngi s dng chia s my tnh mt cch lin tc. Khi mi

hot ng hoc lnh trong h thng time-sharing d nh hot ng trong mt thi gian

ngn, th ch mt phn nh thi gian CPU c cn cho mi ngi s dng.

Khi h thng chuyn i CPU mt cch nhanh chng t mt ngi s dng/mt chng

trnh ti k tip, mi ngi s dng c cung cp mt khong CPU ring cho mnh, trong

khi m mt CPU thc s ang c chia s bn trong nhng ngi s dng.

a chng trnh Khi hai hoc nhiu chng trnh ang trong b nh ti cng mt thi im, th b x l c

chia s ti a chng trnh. a chng trnh gi nh mt b x l c chia s. a chng trnh

lm tng tin ch ha CPU bng vic t chc cc cng vic m CPU lun lun thc hin mt

cng vic.

Hnh di biu th b nh cho h thng a chng trnh.



H iu hnh thc hin cc hot ng sau lin quan ti a chng trnh:

Gi mt s cng vic trong b nh ti cng mt thi im.

B tng hp ph lch trnh cng vic c gi trong khu vc cng vic.

a chng trnh chn v bt u chy mt cng vic trong b nh.

a chng trnh gim st trng thi ca tt c cc chng trnh ang hot ng v ngun

ti nguyn h thng s dng chng trnh qun l b nh m bo rng CPU khng

bao gi rng ri tr khi khng c cng vic no c trnh.

Cc li th

Ti a s dng CPU tc cao v hiu qu.

Ngi s dng cm nhn rng nhiu chng trnh c cp pht CPU mt cch lin tc.

Cc bt li

Lch trnh CPU c yu cu.

dn xp ch cho nhiu cng vic trong b nh, chng trnh qun l b nh c yu

cu.

Kh nng tng tc Khi nim ny l mt ngi s dng c kh nng tng tc vi h thng my tnh. H iu hnh

thc hin cc hot ng lin quan ti kh nng tng tc nh sau:

OS cung cp ngi s dng mt giao din tng tc vi h thng.

OS qun l cc thit b u vo nhn d liu u vo t ngi s dng. V d: bn

phm.

OS qun l cc thit b u ra hin th kt qu u ra ti ngi s dng. V d: mn hnh.

Thi gian phn hi h thng cn ngn t lc ngi s dng trnh v ch i kt qu.

H thng thi gian thc H thng thi gian thc thng l cc h thng c nhng. H iu hnh thc hin cc hot

ng sau lin quan ti h thng thi gian thc.



Trong nhng h thng ny, H iu hnh mt cch c trng c v phn ng li cc d

liu nhy.

H iu hnh phi bo m s phn hi ti cc s kin trong mt thi gian c chnh

trc m bo vic thc hin chnh xc.

Mi trng c phn phi Mi trng c phn phi lin quan ti nhiu CPU hoc b x l c lp trong h thng my tnh.

H iu hnh thc hin cc hot ng sau lin quan ti mi trng c phn phi:

OS phn phi cc logic k thut tnh ton trong cc b x l vt l.

Cc b x l khng chia s b nh v mt ng h xung.

Thay vo , mi b x l c mt b nh ni b ring.

OS qun l trao i thng tin gia cc b x l. Chng trao i thng tin vi nhau thng qua

cc ng dn trao i a dng.

Spooling Spooling l t vit tt cho cc hot ng ngoi vi ng thi trn ng dy dn. Spooling cp

n vic t d liu ca cc cng vic I/O a dng vo trong mt b m. B m ny l mt khu

vc c bit trong b nh hoc cng m c th truy cp ti cc thit b I/O. H iu hnh thc

hin cc hot ng lin quan n mi trng c phn phi nh sau:

OS kim sot vic spooling cc d liu thit b I/O khi cc thit b c cc t l truy cp d liu

khc nhau.

OS duy tr b m spooling m cung cp mt ga ch, ti ni ny d liu c th ch i

trong khi cc thit b chm hn bt kp n.

OS duy tr k thut tnh ton song song bi v tin trnh spooling khi mt my tnh thc hin

I/O trong fashing song song. N c th c d liu t bng, ghi d liu vo a v vit ra

mt bng in khc trong khi n ang thc hin cng vic tnh ton.



Cc li th

Hot ng spooling s dng mt a cng nh l b m ln.

Spooling c kh nng chng cc hot ng I/O cho mt cng vic vi cc hot ng b x

l cho cng vic khc.

Cc tin trnh x l trong OS Tin trnh x l Tin trnh x l l mt chng trnh ang thc hin. Vic thi hnh mt tin trnh phi c pht

trin mt cch tun t. S nh ngha ca tin trnh x l nh sau:

Tin trnh c xc nh r nh l mt thc th m tng trng cho n v c bn ca

cng vic c thc hin trong h thng.

Cc thnh phn ca tin trnh nh sau:

STT Thnh phn & Miu t

1 Chng trnh i tng

M c chy

2 D liu

D liu c s dng cho chy chng trnh.



3 Ngun ti nguyn

Trong khi chy chng trnh, n c th yu cu mt s ngun ti

nguyn

4 Trng thi

Xc nh trng thi vic thc hin tin trnh. Mt tin trnh x l c th

chy ti khi hon thnh ch khi tt c cc ngun ti nguyn c yu

cu c cp pht ti n. Hai hoc nhiu tin trnh x l c th

c thi hnh cng mt chng trnh, mi trong s chng s dng

d liu v ngun ti nguyn ring.

Chng trnh Mt chng trnh chnh n khng phi l mt tin trnh x l. N l mt thc th tnh trong khi tin

trnh x l l mt thc th ng.

Mt chng trnh ly khong khng gian trong b nh chnh v tip tc ti v tr . Mt chng

trnh khng thc hin bt c hot ng no bi chnh n.

Cc trng thi tin trnh Khi mt tin trnh x l thc hin, n thay i cc trng thi. Trng thi ca tin trnh c xc nh

r nh l hot ng hin ti ca tin trnh.

Tin trnh x l c th c mt trong 5 trng thi sau ti mt thi im:

STT Trng thi & Miu t

1 Mi (New)

Tin trnh mi c to

2 Sn sng (Ready)

Tin trnh ang i c ch nh ti mt b x l. Hay l cc tin

trnh ang trong trng thi sn sng ang i c mt b x l

c cp pht cho ti chng bi H iu hnh m chng c th



chy.

3 ang chy (Running)

Cc ch dn tin trnh va c thc hin (v d: tin trnh ang thc

hin).

4 ang ch (Waiting)

Tin trnh ang ch cho mt s s kin xy ra (nh s hon thnh

ca mt hot ng I/O).

5 Hon thnh (Terminate)

Tin trnh kt thc vic thc hin.

Khi kim sot tin trnh, PCB Mi tin trnh c biu din trong mt H iu hnh bi mt khi kim sot (PCB), m cng c

gi l khi iu khin nhim v. PCB l mt cu trc d liu c s dng bi H iu hnh. H

iu hnh nhm tt c thng tin m cn cho nhng tin trnh c th.

PCB cha nhiu phn thng tin lin kt vi mt tin trnh c th m c miu t trong bng di

y:



STT Thng tin & Miu t

1 Con tr

Ch ti khi iu khin tin trnh khc. Con tr c s dng duy

tr bng biu ca chng trnh.

2 Trng thi tin trnh

C th l mi, sn sng, ang chy, ang i, .

3 B m chng trnh

Ch a ch ca ch lnh tip theo c thc hin cho tin trnh

ny.

4 Thanh ghi CPU

Bao gm cc thanh ghi mang mc ch chung, cc con tr stack, cc

thanh ghi ch s, S lng v kiu ca thanh ghi nhn chung ph

thuc vo kin trc my tnh.

5 Thng tin qun l b nh

Thng tin ny c th bao gm gi tr ca cc thanh ghi c s v gii

hn, trang bng, hoc bng phn on ph thuc vo h thng b

nh c s dng bi H iu hnh. Thng tin ny l hu ch cho

vic tr li cp pht b nh khi tin trnh hon thnh.

6 Thng tin k ton (thng k)

Bao gm dung lng CPU v thi gian thc c s dng, thi gian

gii hn, s hiu cng vic hoc tin trnh, tng s.



Khi iu khin tin trnh (PCU) gm bng lch trnh CPU, qun l ngun ti nguyn I/O, thng tin

qun l file. PCB phc v kho lu cho bt k thng tin no m c th a dng t tin trnh n

tin trnh. B ti/b kt ni thit lp cc c hiu v cc thanh ghi khi mt tin trnh c to. Nu

mt tin trnh khng c nh, ni dung ca thanh ghi c lu trn mt stack v con tr ti khung

stack c th c lu trong PCB. Nhng k thut ny, trng thi phn cng c th c lu li

m tin trnh c th c ghi vo lch trnh chy li.

Ghi lch trnh tin trnh trong OS nh ngha Ghi lch trnh tin trnh l mt hot ng ca b qun l tin trnh m iu khin s di chuyn ca

tin trnh ang chy t CPU v vic la chn ca tin trnh khc trn c s ca mt chin lc c

th.

Ghi lch trnh tin trnh l mt phn tt yu ca H iu hnh a chng trnh. Nhng H iu hnh

nh vy cho php nhiu hn mt tin trnh c ti vo trong b nh c th chy ti mt thi im

v ti tin trnh chia s CPU s dng vic dn thi gian (time multiplexing).



Sp hng lch trnh Sp hng lch trnh lin quan ti cc hng ca cc tin trnh hoc thit b. Khi tin trnh nhp vo

trong h thng, th tin trnh ny c t vo trong mt hng cng vic. Hng ny bao gm tt c

cc tin trnh trong h thng. H iu hnh cng duy tr cc hng khc nh hng thit b. Hng thit

b l mt hng cho nhiu tin trnh m ang i cho mt thit b I/O c th. Mi thit b c mt hng

thit b ring ca n.

Di y ch s ca ghi lch trnh tin trnh:

Hng tng trng bi mt hp ch nht.

Cc vng i din cho cc ngun ti nguyn m phc v cho cc hng.

Mi tn ch lung tin trnh trong h thng.

C hai loi sp hng:

Hng sn sng (ready queue)

Hng thit b (device queue)



Mt tin trnh mi c n c t trong mt hng sn sng. Cc tin trnh i trong hng sn

sng ch cp pht CPU. Mt khi CPU c ch nh ti mt tin trnh, th tin trnh s chy.

Trong khi chy chng trnh, bt k mt s kin no sau y c th xy ra.

Tin trnh c th thng bo mt yu cu I/O v sau n c th c t vo trong mt

hng I/O.

Tin trnh c th to mt tin trnh ph mi v s i cho n kt thc.

Tin trnh c th b mnh m di chuyn t CPU, do s ngt tn hiu v quay tr li hng sn

sng.

Hai mu trng thi tin trnh L hai trng thi ang chy v khng ang chy m c miu t nh di y:

STT Trng thi & Miu t

1 ang chy (Running)

Khi mt tin trnh mi c to bi H iu hnh m nhp vo trong

h thng th trng thi l ang chy.

2 Khng ang chy (Not Running)

Cc tin trnh khng trong trng thi ang chy c gi trong hng,

ch cho n lt thc hin. Mi tin trnh nhp vo trong hng l

mt con tr ti mt tin trnh c th. Hng c thc hin bng vic

s dng danh sch kt ni. S dng b phn gi i nh sau. Khi mt

tin trnh b ngt, tin trnh c gi vo trong hng i. Nu tin

trnh hon thnh hoc b ngng, tin trnh c loi b. Trong

trng hp cn li, b phn gi sau chn mt tin trnh t hng

chy.

B lp lch trnh Cc b lp lch trnh l cc phn mm h thng c bit m iu khin lch trnh tin trnh theo cc

cch khc nhau. Nhim v chnh ca n l chn cc cng vic c trnh vo trong h

thng v quyt nh tin trnh no chy. Cc b lp tin trnh c ba loi:



B lp lch trnh thi hn di.

B lp lch trnh thi hn ngn.

B lp lch trnh thi hn trung.

B lp lch trnh thi hn di N cng c gi b lp chng trnh cng vic. B lp ny quyt nh cc chng trnh c

chp nhn ti h thng x l. B lp chng trnh cng vic chn tin trnh t hng v ti chng

vo trong b nh thi hnh. Tin trnh ti vo trong b nh cho vic ghi lch trnh CPU. i tng

u tin ca b lp chng trnh cng vic l cung cp mt s ho trn cn bng ca cc cng

vic, nh ng bin I/O v ng bin b x l tin trnh. N cng iu khin mc ca a

chng trnh. Nu mc l n nh, th khi t l trung bnh ca vic to ra tin trnh phi c

cn bng ti t l xut pht trung bnh ca vic cc tin trnh ri h thng.

Trn mt s h thng, bng lch trnh thi hn di c th khng c sn hoc l ti thiu. H iu

hnh chia phin khng c b lch trnh thi hn di. Khi tin trnh thay i trng thi t mi sang

sn sng, th sau n s dng b lch trnh thi hn di.

B lch trnh thi hn ngn N cng c gi l b lch trnh CPU. i tng chnh l lm tng hiu sut h thng trong s

ph hp vi cc b tiu ch c chn. N thay i t trng thi sn sng sang trng thi chy ca

tin trnh. B lch trnh CPU chn tin trnh trong cc tin trnh m sn sng thc hin v cp

pht CPU cho mt trong s chng.

B lch trnh thi hn ngn cng c bit nh b gi i, thc hin mt cch lin tc v iu khin

lung khuynh hng ca tin trnh chy k tip. B lch trnh thi hn ngn th nhanh hn b lch

trnh thi hn di.

B lch trnh thi hn trung L mt phn ca vic trao i (swapping). N g b tin trnh t b nh. N gim mc ca a

chng trnh. B lch trnh ny ph trch x l cc tin trnh c chuyn i.



Tin trnh ang chy c th tr thnh khng c nh nu n to mt yu cu I/O. Tin trnh khng

c nh khng th lm cho vic tin hnh ti khi hon thin. Trong tnh hung ny, g b tin

trnh t b nh v to khng gian cho cc tin trnh khc, tin trnh khng c nh c di chuyn

ti kho lu th cp. Tin trnh ny c gi l swapping. Swapping c th cn thit ci thin

vic trn tin trnh.

So snh gia cc b lch trnh

STT B lch trnh thi

hn di

B lch trnh thi

hn ngn

B lch trnh thi hn

trung

1 L mt b lch trnh

cng vic

L mt b lch

trnh CPU

L mt b lch trnh

swapping tin trnh

2 Tc chm hn b

lch trnh thi hn

ngn

Tc nhanh hn

hai b cn li

Tc trong khong

gia hai b cn li

3 iu khin mc

ca a chng trnh

N cung cp iu

khin t hn qua

mc ca a

chng trnh

N gim mc ca a

chng trnh



4 N hu nh vng

mt hoc xut hin

nh nht trong h

thng Time-Sharing

Tng t. N l mt phn ca h

thng Time-Sharing

5 N chn cc tin

trnh t pool v ti

chng vo trong b

nh thc hin

N chn cc tin

trnh m sn sng

thc hin

N c th gii thiu li

tin trnh vo trong b

nh v vic thc hin c

th c tip tc

Chuyn bi cnh (context switch) Mt context switch l mt k thut lu v lu li trng thi hoc bi cnh ca mt CPU trong

khi iu khin tin trnh PCB m mt s thi hnh tin trnh c th c hi phc li cng thi

im vo thi gian sau. S dng k thut ny mt context switch cho nhiu tin trnh kh nng

chia s mt CPU n. Context switch l mt phn thit yu ca cc tnh nng ca H iu hnh a

nhim.

Khi b lch trnh chuyn CPU t ch ang chy mt tin trnh ti thc hin mt tin trnh khc,

b chuyn bi cnh lu ni dung ca tt c cc thanh ghi x l co tin trnh c g b t CPU,

trong du hiu nhn din tin trnh ca n. Bi cnh ca mt tin trnh c i din trong khi

iu khin tin trnh ca n.

Thi gian chuyn bi cnh l khng tinh khit. Chuyn bi cnh c th nh hng mt cch mnh

m ti hiu sut khi cc my tnh hin i c nhiu thanh ghi trng thi v chung c lu. Thi

gian chuyn i l ph thuc nhiu vo s h tr ca phn cng. Chuyn i bi cnh yu cu

(n+m)bxk n v thi gian lu trng thi ca b x l vi n thanh ghi chung, gi s b l cc hot

ng lu c yu cu lu n v m thanh ghi ca hai khi iu khin tin trnh v mi vic ch

lnh lu yu cu k thi gian n v.



Mt vi h thng phn cng dng hai hoc nhiu b cc thanh ghi x l gim lng thi gian

chuyn i bi cnh. Khi mt tin trnh c chuyn i, thng tin sau c lu:

B m chng trnh

Thng tin lch trnh

Gi tr thanh ghi c s v gii hn

Thanh ghi c s dng hin ti

Trng thi thay i

Trng thi I/O

Thng tin thng k

Cc thut ton lp lch trnh trong OS Chng ta s bn lun 5 thut ton lp lch trnh chnh y:



Lp lch trnh vo u phc v trc (First Come First Serve FCFS)

Lp lch trnh cng vic ngn nht phc v trc (Shortest-Job-First SJF)

Lp lch trnh quyn u tin

Lp lch trnh Round Robin (RR)

Lp lch trnh nhiu hng mc (multilevel queue)

Lp lch trnh vo u phc v trc (FCFS) Cc cng vic c chy trn ch vo u phc v u

D hiu v thc hin

Hiu sut thp khi thi gian ch i trung bnh l cao

Thi gian i ca mi tin trnh nh sau:

Tin

trnh

Thi gian i: thi gian phc v - thi gian n

P0 0 - 0 = 0



P1 5 - 1 = 4

P2 8 - 2 = 6

P3 16 - 3 = 13

Thi gian trung bnh: (0+4+6+13) / 4 = 5.55

Lp lch trnh cng vic ngn nht phc v trc (SJF) Cch tip cn tt nht gim thiu ti a thi gian i

Khng d dng thc hin

Cc b x l nn bit trc khong thi gian m tin trnh s tn

Thi gian i ca mi tin trnh nh sau:

Tin

trnh

Thi gian ch: thi gian phc v - thi gian n



P0 3 - 0 = 3

P1 0 - 0 = 0

P2 16 - 2 = 14

P3 8 - 3 = 5

Thi gian ch trung bnh: (3+0+14+5) / 4 = 5.50

Lp lch trnh quyn u tin Mi tin trnh c ch nh mt quyn u tin. Tin trnh c quyn u tin cao nht c

thc hin u tin v tip tc vi phng thc tng t.

Cc tin trnh vi quyn u tin nh nhau c thc hin theo th t nhp u th phc v

u.

Quyn u tin c th c quyt nh da trn cc yu cu ca b nh, thi gian hoc bt

k yu cu ngun ti nguyn khc.

Thi gian ch ca mi tin trnh nh sau:



Tin

trnh


P0 9 - 0 = 9

P1 6 - 1 = 5

P2 14 - 2 = 12

P3 0 - 0 = 0


Lp lch trnh Round Robin Mi tin trnh c cung cp mt thi gian c nh thc hin c gi l quantum (hn

ngch thi gian)

Mt khi mt tin trnh c chy trong mt qung thi gian cho trc. Tin trnh c

u tin v tin trnh khc c thc hin trong qung thi gian cho trc.

Vic chuyn i bi cnh c s dng lu trng thi ca cc tin trnh c u tin.

Thi gian ch ca mi tin trnh nh sau:



Tin

trnh


P0 (0-0) + (12-3) = 9

P1 (3-1) = 2

P2 (6-2) + (14-9) + (20-17) = 12

P3 (9-3) + (17-12) = 11


Lp lch trnh a hng Ch nhiu hng c duy tr cho cc tin trnh.

Mi hng c th c thut ton lp lch trnh ring ca n.

Cc quyn u tin c ch nh ti mi hng.

Ch a lung (Multi-thread) trong OS



Thread l g? Mt thread l mt dng ca vic thi hnh thng qua m tin trnh, vi b m chng trnh ring,

cc thanh ghi h thng v stack ca n. Mt thread cng c gi l mt tin trnh nh. Cc thread

cung cp mt cch ci thin hiu sut ng dng thng qua quan h song song. Cc thread i

din cho mt cch tip cn phn mm ci thin hiu sut ca H iu hnh bng vic gim tng

ph lung bng vi mt tin trnh c in.

Mi thread s hu chnh xc mt tin trnh v khng thread no c th tn ti bn ngoi mt tin

trnh. Mi thread i din cho mt lung iu khin. Cc thread c s dng mt cch thnh cng

trong vic thc hin cc server h thng v cc server web. Chng cng cung cp mt nn tng

ph hp cho s thi hnh song song ca ng dng trn nhiu b x l b nh c chia s. Di

y l hnh nh ch s lm vic ca cc tin trnh n v a.

S khc nhau gia Tin trnh v thread

STT Tin trnh Thread

1 Tin trnh l nng v nhy vi ngun ti nguyn Thread

th nh



hn v

yu

cu t

ti

nguyn

hn

tin

trnh

2 Chuyn i tin trnh cn s tng tc vi H iu hnh Chuyn

i

thread

khng

cn

tng

tc vi

H iu

hnh

3 Trong mi trng a tin trnh, mi tin trnh chy vi cng

mt m nhng c b nh v ngun file ring cho tng tin

trnh.

Tt c

thread

c th

chia s

cng

mt b

thit

lp cc

file m,

cc tin

trnh

con.

4 Nu mt tin trnh c ng khi th khi khng tin trnh

no khc c th chy ti khi tin trnh u tin c m

Trong

khi mt

thread



khi. c

ng

khi v

ang

i,

tin

trnh

th hai

trong

cng

mt

nhim

v c

th

chy.

5 Nhiu tin trnh khng s dng thread th dng nhiu ti

nguyn hn.

Nhiu

tin

trnh

c

thread

s

dng t

ti

nguyn

hn.

6 Trong mi trng a tin trnh, mi tin trnh hot ng mt

cch c lp vi tin trnh khc.

Mt

thread

c th

c,

vit

hoc

thay

i d



liu ca

mt

thread

khc.

Cc li th ca Thread Thread ti thiu ha thi gian chuyn i bi cnh.

S s dng cc thread cung cp s ng thi trong mt tin trnh.

Giao tip hiu qu.

Tnh kinh t - n l mang tnh kinh t hn khi to v chuyn i bi cnh cc thread.

Tin ch ha cc cu trc b vi x l hiu qu hn.

Cc kiu Thread Cc thread c thc hin theo hai cch sau:

Cc thread mc ngi dng -- ngi s dng qun l cc thread.

Cc thread mc ht nhn (kernel) -- H iu hnh qun l cc thread hot ng trn

kernel, mt b nh li H iu hnh..

Cc thread mc ngi dng Trong trng hp ny, ng dng qun l thread khng nhn thc c s tn ti ca cc thread.

Th vin thread cha m to v hy cc thread, chuyn thng bo v d liu gia cc

thread, thc hin lp lch trnh thread v lu v khi phc cc bi cnh thread. ng dng bt

u vi mt thread n v bt u chy trong thread .



Cc li th

Chuyn thread khng yu cu c quyn ch Kernel.

Thread mc ngi s dng c th chy trn bt k H iu hnh no.

Lp lch trnh c th l ng dng ring trong thread mc ngi s dng.

Thread mc ngi s dng l nhanh hn trong vic to v qun l.

Cc bt li

Trong mt H iu hnh c bit, hu ht vic gi h thng l ng khi.

ng dng a thread khng th c li th ca ch a tin trnh.

Cc thread mc Kernel Trong tnh hung ny, vic qun l thread c thc hin bi Kernel. Khng c m qun l thread

trong khu vc ng dng. Cc thread ht nhn c h tr mt cch trc tip bi H iu hnh.

Bt k ng dng no c th c chng trnh ha c a thread. Tt c cc thread trong

mt ng dng c h tr trong mt tin trnh n.

Kernel duy tr thng tin bi cnh cho tin trnh cho mt thread tng th v cho cc thread n trong

tin trnh. Lp lch trnh bi Kernel c thc hin trn mt thread c bn. Kernel thc hin vic



to thread, lp lch trnh v qun l trong khng gian Kernel. Cc thread ht nhn thng thng

chm hn cc thread ngi s dng trong vic to v qun l.

Cc li th

Kernel c th lp lch trnh lin tc nhiu thread t cng mt tin trnh trn nhiu cc tin

trnh.

Nu mt thread trong mt tin trnh c ng khi, Kernel c th lp lch trnh thread khc

ca cng mt tin trnh.

Cc chng trnh Kernel chnh n c th l a thread.

Cc bt li

Cc thread ht nhn thng chm hn cc thread ngi s dng trong vic to v qun l.

Vic chuyn i ca iu khin t mt thread ti mt thread khc trong cng mt chng

trnh yu cu mt ch chuyn i ti Kernel.

Cc m hnh a thread Mt s H iu hnh cung cp mt thread mc ngi dng c kt ni v phng tin thread

mc Kernel. Solaris l mt v d ca s tip cn c kt ni ny. Trong mt h thng kt ni,

nhiu thread trong cng ng dng c th chy song song trn nhiu b x l v mt s gi h

thng ng khi khng cn ng khi ton b tin trnh. Cc m hnh a thread c 3 kiu:

Nhiu ti nhiu mi quan h (many to many relationship)

Nhiu ti mt mi quan h (many to one)

Mt ti mt mi quan h (one to one)

Ch Many to Many Trong ch ny, nhiu thread mc ngi s dng kt hp ti s thread ht nhn nh hn

hoc bng. S lng ca thread ht nhn c th c th ti hoc mt ng dng ring hoc mt thit

b ring.

Hnh di y ch ch Many to Many. Trong ch ny, cc nh pht trin c th to nhiu

thread ngi s dng khi cn thit v cc thread Kernel tng ng c th chy song song trn mt

b vi x l.



Ch Many to One Ch ny lp bn nhiu thread mc ngi s dng ti mt thread mc Kernel. Qun l

thread c thc hin trong khng gian ngi s dng. Khi thread to mt vic gi h thng ng

khi, ton b tin trnh s l cc khi. Ch khi mt thread c th truy cp Kernel ti mt thi im, v

th nhiu thread l khng th chy song song trn ch b vi x l.

Nu cc th vin thread mc ngi s dng c thc hin trong mt H iu hnh theo cch

m h thng khng h tr chng khi cc thread ht nhn s dng ch Many to One.



Ch One to One C mt mi quan h mt i mt ca thread mc ngi dng ti thread mc Kernel. Ch

cung cp ng thi hn ch Many to One. N cng gi thread khc chy khi mt thread to

vic gi h thng ng khi. N h tr nhiu thread thc hin song song trn cc b vi x l.

S bt li ca ch ny l to ra thread ngi s dng yu cu thread ht nhn tng ng.

OS/2, Windows NT v Windows 2000 s dng ch One to One.

S khc nhau gia ch mc ngi s dng v mc Kernel

STT Ch mc ngi

dng

Ch mc Kernel

1 Cc thread mc ngi

dng l nhanh hn khi to

v qun l.

Cc thread mc Kernel l chm

hn khi to v qun l.

2 Vic thc hin bi mt th

vin thread ti ch mc

ngi dng.

H iu hnh h tr vic to cc

thread ht nhn.



3 Thread mc ngi dng

mang tnh chung v c th

chy trn bt k H iu

hnh no.

Cc thread mc Kernel l c trng

ti H iu hnh.

4 ng dng a thread khng

th nhn c li th ca

a tin trnh.

Cc chng trnh Kernel chnh n c

th l a thread.

Qun l b nh trong OS Qun l b nh l tnh nng ca mt H iu hnh m iu khin hoc qun l b nh s cp.

Qun l b nh theo di mi v mi v tr b nh cho d n c hay khng c cp pht ti mt vi

b x l hoc n l ri. N kim tra bao nhiu b nh c cp pht ti cc tin trnh. N quyt

nh tin trnh no s nhn b nh ti thi im no. N theo di bt c khi no mt vi phn b

nh l ri hoc khng c cp pht v tng ng n cp nht trng thi.

Qun l b nh cung cp s bo v bi vic s dng hai thanh ghi, mt thanh ghi c s v mt

thanh ghi gii hn. Thanh ghi c s gi a ch b nh vt l nh nht v thanh ghi gii hn xc

nh kch c ca dy. V d, nu mt thanh ghi c s gi 300000 v thanh ghi gii hn l 1209000,

th khi chng trnh c th truy cp tt c cc a ch t 300000 ti 411999.



Cc ch lnh v d liu ti cc a ch b nh c th c thc hin theo cc cch sau:

Thi gian bin dch -- Khi n c bit ti thi gian bin dch, ti ni cc tin trnh s li,

vic rng buc thi gian bin dch c s dng to m tuyt i.

Thi gian ti -- Khi n khng c bit ti thi gian bin dch, ti ni tin trnh li trong

b nh, sau b bin dch to m c th t li v tr.

Thi gian chy -- Nu mt tin trnh c th c di chuyn trong sut thi gian chy ca

n t mt phn on b nh ti phn on khc, th khi vic rng buc phi b tr hon

c thc hin ti thi gian chy.

Ti ng (dynamic loading) Trong Dynamic Loading, mt on chng trnh khng c ti ti khi n c gi bi mt

chng trnh. Tt c cc on c gi trn a trong nh dng ti c th t li v tr. Chng

trnh chnh c ti vo trong b nh v c thc hin. Cc phng thc on hoc mdun

khc c ti theo yu cu. Dynamic loading to s tin ch ha khng gian b nh tt hn v cc

on chng trnh khng s dng th khng bao gi c ti.



Kt ni ng Vic kt ni l tin trnh ca vic thu thp v kt ni cc module a dng ca m v d liu vo

trong mt file c th chy m c th c ti vo trong b nh v thc hin. H iu hnh c th

kt ni cc th vin h thng ti mt chng trnh. Khi n kt ni cc th vin ti thi gian ti, vic

kt ni c gi l kt ni tnh v khi vic kt ni ny c thc hin ti thi im ca vic thc

hin, n c gi l kt ni ng.

Trong kt ni tnh, cc th vin kt ni ti thi gian bin dch, v th c m chng trnh tr ln ln

hn. Trong khi kt ni ng, cc th vin kt ni ti thi gian chy c m chng trnh tr ln

nh hn.

Khng gian a ch vt l logic Mt a ch to bi mt CPU l mt a ch logic trong khi a ch thc s c sn trn n v b nh

l mt a ch vt l. a ch logic cng cn c bit nh l mt a ch o.

Cc a ch o v vt l l cng trong gin rng buc a ch thi gian bin dch v thi gian ti.

Cc a ch ny khc nhau trong biu rng buc a ch thi gian thc hin.

Tp hp ca tt c cc a ch logic to bi mt chng trnh lin quan ti khng gian a ch logic.

Tp hp ca tt c cc a ch vt l tng ng ti cc a ch logic lin quan ti khng gian a ch

vt l.

Biu thi gian chy t b nh o ti vt l c thc hin bi n v qun l b nh (MMU) m

l mt thit b phn cng. MMU s dng k thut sau chuyn i a ch o thnh a ch vt l:

Gi tr ca mt thanh ghi c s c thm vo ti mi a ch c to ra bi mt tin trnh

ngi s dng m c i x nh l offset ti thi im n c gi ti b nh. V d,

nu gi tr thanh ghi c s l 10000, th mt s th bi ngi dng s dng cc v tr

a ch 100 s c cp pht li ti v tr 10000.

Chng trnh ngi s dng ch thc hin vi cc a ch o. N khng bao gi quan st

cc a ch vt l.

Swapping Swapping l mt k thut trong mt tin trnh c th c trao i mt cch lin tc bn ngoi

b nh ti mt kho lu sau (backing store), v sau mang li sau vo trong b nh tip tc

chy.



Kho lu sau thng l mt thit b a cng hoc bt c mt kho lu th cp khc m nhanh trong

truy cp v ln t v tr cc bn sao ca tt c nh b nh cho tt c ngi dng. N phi

c kh nng cung cp s truy cp trc tip ti cc nh b nh ny.

Phn ln thi gian ca swapping l thi gian trao i. Tng thi gian trao i l trc tip t l thun

vi lng b nh c trao i. Gi s rng tin trnh s dng l 100KB v kho lu sau l mt a

cng tiu chun vi t l trao i l 1MB/giy. Th thi gian thc s trao i ca tin trnh 100KB

ti hoc t b nh s l:

100KB / 1000KB mi giy

= 1/10 giy

= 100 mini giy

S cp pht b nh B nh chnh thng c hai ngn:

Low Memory -- H iu hnh trong b nh ny



High Memory -- Cc tin trnh s dng c gi trong b nh ny.

H iu hnh s dng cc k thut cp pht b nh sau:

STT S cp pht b nh Miu t

1 S cp pht ngn n Trong kiu cp pht ny, gin thanh ghi

t li v tr c s dng bo v cc

tin trnh ngi dng t cc tin trnh ngi

dng khc, v t vic thay i m H iu

hnh v d liu. Thanh ghi t li v tr

cha gi tr cc a ch a ch vt l nh

nht, nu khng thanh ghi gii hn cha

dy cc a ch logic. Mi a ch logic phi

nh hn thanh ghi gii hn.

2 S cp pht a ngn Trong kiu cp pht ny, b nh chnh

c phn chia nh thnh cc ngn c c

c nh, ti ni ny mi ngn nn ch cha

mt tin trnh. Khi mt ngn l ri, mt tin

trnh c chn t hng u vo v c

ti vo trong ngn ri . Khi tin trnh hon

thnh, ngn ny li sn sng cho tin trnh

khc.

S phn mnh (Fragmentation) Khi cc tin trnh c ti v c g b t b nh, phn khng gian b nh ri c chia nh

thnh nhiu phn. Vic chia nh xy ra sau mt vi ln khi m cc tin trnh khng c cp pht

ti khi b nh vi vic gi s rng kch c ca chng l nh v cc khi b nh vn cha c

s dng. Vn ny c bit nh l s phn mnh (Fragmentation).

C hai kiu Fragmentation:

STT Fragmentation Miu t



1 S phn mnh ngoi vi Tng khng gian b nh l tha

mn mt yu cu hoc c tr mt tin

trnh trong , nhng n khng k nhau

n c th c s dng.

2 S phn mnh ni vi Khi b nh c ch nh cho tin trnh l

ln hn. Mt vi phn ca b nh s tr

nn khng c s dng khi n khng th

c s dng bi tin trnh khc ( ch

nh cho tin trnh trc).

S phn mnh ngoi vi c th gim bng cch nn hoc trn cc ni dung b nh ngu nhin

t tt c cc phn b nh ri trong mt khi ln hn. lm cho vic nn tr nn d dng, s t

li v tr nn trng thi ng.

K thut nh s trang S phn mnh ngoi vi c trnh bi k thut nh s trang. Trong k thut ny th b nh vt l

c chia nh thnh cc khi cng kch thc c gi l cc trang (kch thc l 2, gia 512

byte v 8192 byte). Khi mt tin trnh c thc hin, cc trang tng ng ca n c ti vo

trong bt k mt khung b nh c sn no.

Khng gian a ch logic ca mt tin trnh c th khng lin k v mt tin trnh c cp pht b

nh vt l bt c khi no khung b nh ri c sn. H iu hnh theo di tt c cc khung b nh

ri. H iu hnh cn n khung ri chy mt chng trnh vi kch c l n trang.

ac ch to bi CPU c phn chia thnh:

S trang (p) -- c s dng nh l mt danh mc trong mt bng trang m cha a ch

c s ca mi trang trong b nh vt l.

Offset trang (d) -- c kt ni vi a ch c bn xc nh r a ch b nh vt l.



Biu di l cu trc bng trang:



K thut phn on S phn on l mt k thut phn chia b nh thnh cc phn logic nh ti mi phn i

din cho mt nhm thng tin lin quan vi nhau. V d, cc phn on d liu hoc phn on m

cho mi tin trnh, phn on d liu cho H iu hnh S phn on c th c thc hin vi

vic s dng hoc khng s dng k thut nh s trang.

Khng ging k thut nh s trang, phn on l c nhiu kch c v nh vy n kh s phn

mnh ni vi. S phn mnh ngoi vi vn tn ti nhng vi phm vi nh hn.

a ch c to ra bi CPU c phn chia thnh:

S phn on (s) -- c s dng nh l mt ch mc trong bng phn on m cha a

ch c bn ca mi phn on trong b nh vt l v gii hn ca phn on.

Offset phn on (o) -- c kim tra u tin so snh vi gii hn v sau c kt

ni vi a ch c s xc nh r a ch b nh vt l.



B nh o trong OS B nh o l mt k thut m cho php vic thc hin cc tin trnh m khng hon ton c sn

trong b nh. Li th thy r chnh ca gin ny l chng trnh c th ln hn b nh vt

l. B nh o l phn ring bit ca b nh logic ngi dng t b nh vt l.

Phn ring bit ny cho php mt b nh o ln c cung cp cho cc ngi lp chng trnh

khi m ch c b nh vt l nh hn l c sn. Di y l cc tnh hung, khi ton b chng

trnh l khng c yu cu ti ton b trong b nh chnh:

Cc on chng trnh kim sot li c vit bi ngi dng ch c s dng khi mt li

xy ra trong d liu hoc trong tnh ton.

Cc chc nng v tnh nng no ca chng trnh him khi c s dng.

Nhiu bng c ch nh mt s lng c nh khng gian a ch ngay c khi ch c mt

s lng bng thc s c s dng.

Kh nng chy mt chng trnh m ch mt phn trong b nh s em li nhiu li ch.

S lng t cc I/O cn ti hoc trao i mi chng trnh ngi dng trong b nh.



Mt chng trnh c th khng b hn ch bi s lng b nh vt l c sn.

Mi chng trnh ngi dng c th dng t b nh vt l hn, nhiu chng trnh c th

chy cng mt thi im, vi s tng ln tng ng ca vic tin ch ha CPU.

B nh o thng c thc hin bi k thut nh s trang yu cu. N cng c th c thc

hin trong h thng phn on. S phn on yu cu c th cng c s dng cung cp b

nh o.

K thut nh s trang yu cu (demand paging) H thng nh s trang yu cu l kh ging vi h thng nh s trang vi vic swapping. Khi

chng ta mun thc hin mt chng trnh, chng ta trao i n vo trong b nh. Thay v vic

trao i ton b tin trnh vo trong b nh, chng ta s dng mt my nhn tin pager.

Khi mt tin trnh c trao i, pager d on cc trang no s c s dng trc khi tin trnh

c trao i li ra ngoi. Thay v trao i trong mt tng th chng trnh, pager ch mang nhng

trang cn thit vo trong b nh. V th, n trnh c cc trang b nh m s khng c s

dng, gim c thi gian trao i v lng b nh vt l cn thit.



S h tr phn cng l cn thit phn bit gia cc trang m trong b nh vi cc trang trong

phn cng. Ti ni cc trang c hiu lc v khng c hiu lc c th c kim tra bi vic kim

tra bit. nh du mt trang s khng hiu qu nu tin trnh khng bao gi th truy cp vo trang.

Trong khi tin trnh thc hin v truy cp vo trang m trong b nh, s thc hin c tin

hnh bnh thng.

Truy cp ti mt trang c nh du l khng hiu lc v mt by trang li (page-fault trap). By

ny l kt qu ca li h thng mang cc trang yu cu vo trong b nh. Nhng li trang c

th c gii quyt nh sau:



Bc Miu t

Bc 1 Kim tra mt bng ni vi cho tin trnh ny, xc nh s

lin h l hiu lc hay khng hoc n l mt s truy cp b

nh khng hiu lc.

Bc 2 Nu s lin h l khng hiu lc, kt thc tin trnh. Nu n

l hiu lc, nhng trang vn cha c mang vo, trang

th t sau.

Bc 3 Tm mt khung ri.

Bc 4 Lp gin mt hot ng a c trang yu cu vo

trong khung c cp pht mi nht.



Bc 5 Khi c a kt thc, chnh sa bng ni vi c gi cng

vi tin trnh v bng trang ch dn rng trang by gi

trong b nh.

Bc 6 Bt u li ch lnh m b ngt bi by a ch khng hp

l. Tin trnh by gi c th truy cp vo trang. Bi vy, H

iu hnh c cc trang yu cu vo trong b nh v bt

u li tin trnh khi m trang lun lun trong b nh.

Cc li th

Di y l cc li th ca nh s trang yu cu:

B nh o ln.

Hiu qu hn trong vic s dng b nh.

a chng trnh khng b g b. Khng c gii hn v mc a chng trnh.

Cc bt li

Di y l cc bt li ca nh s trang yu cu:

S lng cc bng v lng b x l vt qu gii quyt vic ngt trang l ln hn

trong trng hp cc k thut qun l nh trang n.

Do thiu mt s rng buc r rng trn mt kch c khng gian a ch cng vic.

Thut ton i v tr trang Thut ton i v tr trang l cc k thut s dng m H iu hnh quyt nh cc trang b nh

no c trao i, vit vo a khi mt trang ca b nh cn c cp pht. nh s trang xy ra

bt c khi no mt li trang xy ra v mt trang ri khng th c s dng cho mc ch cp

pht, l do m cc trang khng c sn hoc s trang ri l t hn cc trang yu cu.

Khi trang m c chn i v tr v c nh trang, c lin h li th khi n phi c t

a, v yu cu ny cho s kt thc I/O. Tin trnh ny quyt nh loi thut ton i v tr trang:

thi gian i trang vo t hn, th thut ton l tt hn. Mt thut ton i v tr trang quan st

thng tin b gii hn v vic truy cp vo cc trang c cung cp bi phn cng, v c gng

chn cc trang no nn c i v tr ti thiu ha tng lng trang b qun, trong khi vic cn



bng n vi ph tn ca kho lu s cp v thi gian b x l ca chnh thut ton. C nhiu thut

ton i v tr trang khc nhau. Chng ta tnh ton mt thut ton bng vic chy n trn mt chui

c th ca b nh tham chiu v tnh ton lng trang li.

Chui tham chiu Chui tham chiu c to ra mt cch gi to hoc bng cch ln theo mt h thng cho v

ghi li a ch ca mi tham chiu b nh. S chn sau to mt s ln d liu, ti ni ny chng ta

vit hai th sau:

Vi mt c trang cho chng ta cn suy xt ch s trang, khng phi ton b a ch.

Nu chng ta c mt s tham chiu ti mt trang, th khi bt k cc tham chiu sau ngay

lp tc ti trang p s khng bao gi gy ra li trang. Trang p s trong b nh sau tham

chiu u tin; cc tham chiu sau ngay lp tc s li.

V d, gi s c dy cc a ch lin tc sau: 123,215,600,1234,76,96.

Nu c trang l 100 th khi chui tham chiu l 1,2,6,12,0,0.

Thut ton Vo u ra u (First In First Out - FIFO) Cc trang vo u tin trong b nh l mt trang c chn i v tr.

D dng thc hin, gi mt danh sch, i cc trang t ui v thm cc trang mi ti

u.



Thut ton Trang quang hc Thut ton i v tr trang quang hc c t l trang li t nht trong tt c cc thut ton. Mt

thut ton i v tr quang hc tn ti v c gi l OPT hoc MIN.

i v tr trang m khng c s dng cho thi gian di nht. S dng thi gian khi mt

trang c s dng.

Thut ton c s dng gn y nht (Least Recently Used - LRU)

Trang m khng c s dng cho thi gian di nht trong b nh chnh l mt trang c

chn i v tr.

D dng thc hin, gi mt danh sch, i cc trang bi vic quan st cc ln nhp

trang sau.



Thut ton Chuyn hon m trang bt u tin trnh mt cch nhanh chng, gi mt pool ca cc khung ri.

Trn trang li, chn mt trang c i v tr.

Vit trang mi trong khung ri, nh du bng trang v bt u li tin trnh.

By gi vit trang li ra a v t v tr khung gi trang i v tr trong khu vc ri.

Thut ton c s dng thng xuyn t nht (Least frequently Used - LFU)

Trang vi lng tnh nh nht l mt trang c chn i v tr.

Thut ton ny c s dng nhiu trong giai on u ca tin trnh, nhng sau n

khng bao gi c s dng li.

Thut ton c s dng thng xuyn nht (Most Frequently Used MFU)

Thut ton ny trn c s trang vi tnh ton trang nh nht l c th c mang vo trong

v cha c s dng.



Phn cng Nhp/Xut (IO) trong OS Tng quan My tnh hot ng trn nhiu loi thit b. Cc loi chung bao gm cc thit b lu tr (cc a, cc

bng), cc thit b trao i (cc th mng h thng, cc modem) v cc thit b giao din ngi

dng (mn hnh, bn phm, chut). Cc thit b khc th c bit hn. Mt thit b giao tip vi h

thng my tnh bng vic gi cc tn hiu thng qua mt cp hoc thng qua khng kh.

Thit b giao tip vi my mc thng qua mt im kt ni t trong mt cng (port) (v d: mt

serial port). Nu mt hoc nhiu thit b s dng mt b dy wire chung, s kt ni ny c gi l

bus. Mt bus l mt b thit lp ca cc wire v mt giao thc c xc nh r mt cch cng

nhc m xc nh mt b thit lp cc thng bo c th c gi trn cc wire.

Chui daisy Khi thit b A c mt cp m cm vo trong thit b B, v thit b B c mt cp cm vo thit b C, v

thit b C cm vo trong mt port trn my tnh, s sp xp ny c gi l daisy chain. N thng

t chc nh l mt bus.

B iu khin L mt tp hp cc thit b in t m c th iu hnh mt port, mt bus, hoc mt thit b. Mt

b iu khin serial port l mt v d ca mt b iu khin thit b n. y l mt chip trong my

tnh m iu khin cc tn hiu trn cc wire ca mt serial port.

B iu khin SCSI bus thng c thc hin nh l mt bng mch ring m cm vo trong

my tnh. N cha mt b x l, vi ct, v mt vi b nh t nhn cho n kh nng x l cc

thng bo giao thc SCSI. Mt vi thit b c cc b iu khin ring c xy dng trong n.

Cng I/O Mt cch c trng th I/O port cha 4 thanh ghi c gi l cc thanh ghi trng thi, iu khin,

d liu nhp v d liu ra:

STT Thanh ghi & Miu t

1 Thanh ghi trng thi

Cha cc bit m c th sn sng bi host. Nhng bit ny ch trng



thi m c hay khng cc lnh hin ti hon thnh, c hay khng

mt byte l c sn c c t thanh ghi u vo, v c hay

khng c mt thit b b li.

2 Thanh ghi iu khin

Thanh ghi iu khin ny c th c vit bi host bt u mt

lnh hoc thay i ch ca mt thit b. V d, mt bit ngu

nhin trong thanh ghi iu khin ca mt serial port chn gia s giao

tip full-duplex v half-duplex, ci khc cho kh nng ngang bc kim

sot, mt bit th ba thit lp di t t 7-8 bit, cc bit khc chn

mt trong nhng tc c h tr bi serial port.

3 Thanh ghi d liu nhp

Thanh ghi d liu nhp c c bi host nhn d liu u vo.

4 Thanh ghi d liu ra

Thanh ghi d liu ra c vit bi host gi kt qu u ra.

Polling Polling l mt tin trnh bi n m mt host i cho b iu khin phn hi. N l mt tin trnh lp,

c trng thi thanh ghi thng qua cc bit bn ca thanh trng thi n ht. B iu khin s

dng/thit lp bit bn khi n ang lm vic trn mt lnh, v lm sch cc bit bn khi n l sn

sng chp nhn lnh tip. Host bo hiu iu n mun thng qua bit lnh-sn sng trong thanh

lnh. Host thit lp bit ny khi mt lnh l c sn cho b iu khin thc hin.

Trong v d sau, host vit kt qu u ra thng qua mt port, m kt ni vi b iu khin:

Host lp i lp li c bit bn ti khi bit tr nn rng.

Host thit lp bit vit trong thanh lnh v vit mt byte vo trong thanh d liu u ra.

Host thit lp bit lnh-sn sng.

Khi b iu khin thng bo rng bit lnh-sn sng c thit lp, n thit lp bit bn.



B iu khin c thanh lnh v quan st lnh write.

N c thanh d liu u ra nhn cc byte, v thc hin I/O ti thit b.

B iu khin dn sch bit lnh-sn sng, dn sch bit li trong thanh trng thi ch rng

cc thit b I/O thc hin thnh cng, v dn sch bit bn ch rng n hon thnh.

Cc thit b I/O Cc thit b I/O c th c phn thnh cc loi sau:

STT Loi & Miu t

1 Ngi dng c th c

Cc thit b ngi dng c th c ph hp cho giao tip vi ngi

s dng my tnh. Cc v d l my in, video, bn phm

2 My mc c th c

Cc thit b my mc c th c ph hp cho giao tip vi cc thit b

in t. Cc v d l cc a, bng, b iu khin.

2 Giao tip

Cc thit b trao i thng tin ph hp cho giao tip vi cc thit b

iu khin. Cc v d l cc ng dy dn k thut v cc modem.

Di y l s khc nhau gia cc thit b I/O:

STT Tiu chun & Miu t

1 T l d liu

C th c s khc bit v cc bc cng gia cc t l truyn ti

d liu.

2 ng dng



Cc thit b khc nhau c s s dng khc nhau trong h thng.

3 Tnh phc tp ca iu khin

Mt a th phc tp hn trong khi my in yu cu giao thc tng

tc iu khin n.

4 n v truyn ti

D liu c th c truyn ti nh l mt lung cc byte hoc cc k

t hoc trong cc khi ln hn.

5 S i din (m ha) cho d liu

Cc gin m ha d liu khc nhau c s dng cho cc thit b

khc nhau.

6 Cc iu kin li

Khc nhau mt cch rng ri cho tng thit b.

S truy cp b nh trc tip (DMA) Nhiu my tnh trnh gnh nng ca CPU chnh vi I/O c chng trnh ha bi vic dng ti

mt vi cng vic ti b x l mc ch c bit. Kiu ny ca b x l c gi l mt b iu

khin truy cp b nh trc tip. Mt n v iu khin c bit c s dng truyn ti khi d

liu mt cch trc tip gia cc thit b ngoi vi v b nh chnh, m khng cn s can thip ca

b x l. Hng tip cn ny c gi l Direct Memory Access (DMA).

DMA c th c s dng vi phn mm polling hoc phn mm ngt. DMA l c bit hu ch

trn cc thit b nh cc a, ni m rt nhiu byte thng tin c th c truyn ti trong cc hot

ng I/O n. Khi s dng vi mt phn mm ngt, CPU c thng bo ch sau khi c khi ca

d liu c truyn ti. i vi mi byte hoc t c truyn ti, n phi cung cp a ch b

nh v tt cc tn hiu bus iu khin vic truyn ti d liu. Tng tc vi b iu khin thit b

c qun l thng qua mt driver thit b.

Handshaking l mt tin trnh gia b iu khin DMA v b iu khin thit b. N c thc hin

thng qua cc wire bng s dng cc mc yu cu DMA v s cng nhn DMA.



Bc Miu t

1 Driver thit b c ch dn truyn ti d liu t a ti mt b

m a ch X.

2 Driver thit b sau ch dn b iu khin a truyn ti d liu

ti b m.

3 B iu khin a bt u truyn ti DMA.

4 B iu khin a gi tng byte ti b iu khin DMA.

5 B iu khin DMA truyn ti cc byte ti b m, lm tng a ch



b nh, gim b m t C ti 0.

6 Khi C tr v 0, DMA ngt CPU gi tn hiu vic hon thnh

truyn ti.

Cc b iu khin thit b Mt h thng my tnh cha nhiu kiu thit b I/O v cc b iu khin ring phn.

Th h thng

u c ha (graphics adapter)

B iu khin a

B iu khin DVD-ROM

Serial port

USB

Th m thanh

Phn mm Nhp/Xut (I/O) trong OS Cc phn mm ngt (interrupts) Phn cng CPU s dng mt ng wire yu cu ngt m gip CPU cm nhn sau khi thc hin

mi ch lnh. Khi CPU kim tra rng mt b iu khin t mt tn hiu trn dy yu cu ngt,

CPU lu trng thi, nh gi tr hin ti ca im con tr ch lnh, v nhy ti on kim sot ngt

ti mt a ch c nh. Phn kim sot ngt quyt nh vic gy ra ngt, thc hin tin trnh cn

thit v chy mt ch lnh ngt tr li ti CPU v trng thi thc hin ca n.

K thut ngt c bn cho CPU kh nng phn hi ti mt s kin khng ng b, nh khi mt

b iu khin thit b tr ln sn sng phc v. Hu ht CPU c hai ng dy yu cu ngt:

Ngt khng che du

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