tài liệu hệ Điều hành tiếng việt
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Tài Liệu Hệ Điều Hành Tiếng Việt online từ cơ bản đến nâng caoTRANSCRIPT
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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
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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
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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
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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
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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.
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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.
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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:
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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:
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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.
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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).
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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)
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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:
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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.
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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
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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.
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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:
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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
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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
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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:
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Tin
trnh
Thi gian ch: thi gian phc v - thi gian n
P0 9 - 0 = 9
P1 6 - 1 = 5
P2 14 - 2 = 12
P3 0 - 0 = 0
Thi gian ch trung bnh: (9+5+12+0) / 4 = 6.5
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:
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Tin
trnh
Thi gian ch: thi gian phc v - thi gian n
P0 (0-0) + (12-3) = 9
P1 (3-1) = 2
P2 (6-2) + (14-9) + (20-17) = 12
P3 (9-3) + (17-12) = 11
Thi gian ch trung bnh: (9+2+12+11) / 4 = 8.5
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
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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
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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
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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
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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 .
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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
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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.
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Biu di l cu trc bng trang:
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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.
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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.
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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.
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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:
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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.
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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
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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.
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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.
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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.
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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
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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.
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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
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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.
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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
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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