Oai?ey iia?aoeeiiiuo nenoai
Aaaaeaiea. Iniiaiua iiiyoey e ii?aaeaeaiey.
Iia?aoeeiiiay nenoaia – yoi i?ia?aiia, eioi?ay auiieiyao ooieoeee
iin?aaeieea iaaeaeo iieueciaaoaeai e eiiiuethoa?ii.
IN, auiieiyy ?ieue iin?aaeieea, neoaeeo aeaoi oeaeyi:
yooaeoeaii eniieueciaaoue eiiiuethoa?iua ?ano?nu.
nicaeaaaoue oneiaey aeey yooaeoeaiie ?aaiou iieueciaaoaey
A ea/anoaa ?ano?nia eiiiuethoa?a iau/ii ?anniao?eaatho:
a?aiy ?aaiou i?ioeanni?a
aae?aniia i?ino?ainoai iniiaiie iaiyoe
iai?oaeiaaiea aaiaea – auaiaea
oaeeu, o?aiyueany ai aiaoiae iaiyoe
Ia ?enoiea i?eaaaeaiu iniiaiua eiiiiiaiou IN eae nenoaiu ?acaeaeaiey
?ano?nia.
Oaeei ia?acii, iniiaiua eiiiiiaiou IN:
oi?aaeaiea i?ioeannaie (?ani?aaeaeyao ?ano?n — i?ioeanni?iia a?aiy);
oi?aaeaiea iaiyoueth (?ani?aaeaeyao ?ano?n — aae?aniia i?ino?ainoai
iniiaiie iaiyoe);
oi?aaeaiea ono?ienoaaie (?ani?aaeaeyao ?ano?nu) — iai?oaeiaaiea
aaiaea – auaiaea;
oi?aaeaiea aeaiiuie (?ani?aaeaeyao ?ano?n — aeaiiua eee oaeeu).
Ooieoeeiie?iaaiea eiiiuethoa?a iinea aeeth/aiey ieoaiey ia/eiaaony n
caionea i?ia?aiiu ia?aiia/aeueiie caa?ocee — Boot Track. I?ia?aiia Boot
Track eieoeeaeece?oao iniiaiua aiia?aoiua aeiee eiiiuethoa?a e ?aaeno?u
i?ioeanni?a (CPU), iaeiieoaeue iaiyoe, eiio?ieea?u ia?eoa?eeiiai
iai?oaeiaaiey. Caoai caa?oaeaaony yae?i IN, oi aeoue Operating System
Kernel. Aeaeueiaeoaa ooieoeeiie?iaaiea IN inouanoaeyaony eae ?aaeoeey ia
niauoey, i?ienoiaeyuea a eiiiuethoa?a. Ianooieaiea oiai eee eiiai
niauoey neaiaeece?oaony i?a?uaaieyie – Interrupt. Enoi/ieeaie i?a?uaaiee
iiaoo auoue eae aiia?aoo?a (HardWare), oae e i?ia?aiiu (SoftWare).
Aiia?aoo?a “niiauaao” i i?a?uaaiee aneio?iiii (a ethaie iiiaio a?aiaie)
iooai ia?anueee a CPU /a?ac iauoth oeio neaiaeia i?a?uaaiee. I?ia?aiia
“niiauaao” i i?a?uaaiee iooai auiieiaiey iia?aoeee System Call. I?eia?u
niauoee, aucuaathueo i?a?uaaiey:
iiiuoea aeaeaiey ia 0
cai?in ia nenoaiiia ianeoaeeaaiea
caaa?oaiea iia?aoeee aaiaea – auaiaea
iai?aaeeueiia ia?auaiea e iaiyoe
Eaaeaeia i?a?uaaiea ia?aaaouaaaony niioaaonoaaiii ia?aaio/eeii
i?a?uaaiee (Interrupt handler), aoiaeyuei a ninoaa IN.
Aeaaiua ooieoeee iaoaiecia i?a?uaaiee — yoi:
?aniiciaaaiea eee eeanneoeeaoeey i?a?uaaiee
ia?aaea/a oi?aaeaiey niioaaonoaaiii ia?aaio/eeo i?a?uaaiee
ei??aeoiia aica?auaiea e i?a?aaiiie i?ia?aiia
Ia?aoiae io i?a?uaaaiie i?ia?aiiu e ia?aaio/eeo e ia?aoii aeieaeai
auiieiyoueny eae iiaeii auno?ae. Iaeiei ec auno?uo iaoiaeia yaeyaony
eniieueciaaiea oaaeeoeu, niaea?aeauae ia?a/aiue anao aeiionoeiuo aeey
eiiiuethoa?a i?a?uaaiee e aae?ana niioaaonoaothueo ia?aaio/eeia. Oaeay
oaaeeoea iacuaaaony aaeoi?ii i?a?uaaiee (Interrupt vector) e o?aieony a
ia/aea aae?aniiai i?ino?ainoaa iniiaiie iaiyoe (UNIX/MS DOS).
Aeey ei??aeoiiai aica?auaiey e i?a?aaiiie i?ia?aiia ia?aae ia?aaea/ae
oi?aaeaiey ia?aaio/eeo i?a?uaaiee, niaea?aeeiia ?aaeno?ia i?ioeanni?a
caiiieiaaony eeai a iaiyoe n i?yiui aeinooiii eeai a nenoaiiii noaea —
System Stack.
Iau/ii cai?auathony i?a?uaaiey ia?aaio/eea i?a?uaaiee. Iaeiaei, a
iaeioi?uo IN i?a?uaaiey niaaaeathony i?ei?eoaoaie, oi anoue ?aaioa
ia?aaio/eea i?a?uaaiey n aieaa ieceei i?ei?eoaoii iiaeao auoue i?a?aaia,
anee i?iecioei i?a?uaaiea n aieaa aunieei i?ei?eoaoii.
1. Oi?aaeaiea i?ioeannaie.
I?ioeann — yoi i?ia?aiiiue iiaeoeue, auiieiyaiue a CPU. Iia?aoeeiiiay
nenoaia eiio?iee?oao neaaeothuoth aeayoaeueiinoue, naycaiioth n
i?ioeannaie:
nicaeaiea e oaeaeaiea i?ioeannia
ieaie?iaaiea i?ioeannia
neio?iiecaoeey i?ioeannia
eiiioieeaoeey i?ioeannia
?ac?aoaiea ooieeiauo neooaoeee
1.1 Iiiyoea I?ioeann. Ninoiyiey i?ioeanna
Ia neaaeoao niaoeaaoue iiiyoey i?ioeann e i?ia?aiia. I?ia?aiia — yoi
ieai aeaenoaee, a i?ioeann — yoi naii aeaenoaea. Iiiyoea i?ioeann
aeeth/aao:
i?ia?aiiiue eiae
aeaiiua
niaea?aeeiia noaea
niaea?aeeiia aae?aniiai e ae?oaeo ?aaeno?ia CPU.
Oaeei ia?acii, aeey iaeiie i?ia?aiiu iiaoo auoue nicaeaiu ianeieueei
i?ioeannia, a oii neo/aa, anee n iiiiuueth iaeiie i?ia?aiiu a
eiiiuethoa?a auiieiyaony ianeieueei ianiaiaaeathueo
iineaaeiaaoaeueiinoae eiiaiae. Ca a?aiy nouanoaiaaiey i?ioeann
iiiaie?aoii eciaiyao naia ninoiyiea.
?acee/atho neaaeothuea ninoiyiey i?ioeanna:
iiaue (new, i?ioeann oieueei /oi nicaeai)
auiieiyaiue (running, eiiaiaeu i?ia?aiiu auiieiythony a CPU)
iaeeaeathuee (waiting, i?ioeann iaeeaeaao caaa?oaiey iaeioi?iai niauoey,
/aua anaai iia?aoeee aaiaea – auaiaea)
aioiaue (ready, i?ioeann iaeeaeaao inaiaiaeaeaiey CPU)
caaa?oaiiue (terminated, i?ioeann caaa?oee naith ?aaioo)
Ia?aoiae ec iaeiiai ninoiyiey a ae?oaia ia iiaeao auiieiyoueny
i?iecaieueiui ia?acii. Ia ?enoiea i?eaaaeaia oeiiaay aeeaa?aiia
ia?aoiaeia aeey ninoiyiee i?ioeanni?a.
Eaaeaeue i?ioeann i?aaenoaaeai a iia?aoeeiiiie nenoaia iaai?ii aeaiiuo,
iacuaaaiuo process control block . A process control block i?ioeann
iienuaaaony iaai?ii cia/aiee, ia?aiao?ia, oa?aeoa?ecothueo aai oaeouaa
ninoiyiea e eniieuecoaiuo iia?aoeeiiiie nenoaiie aeey oi?aaeaiey
i?ioiaeaeaieai i?ioeanna /a?ac eiiiuethoa?.
Ia ?enoiea noaiaoe/anee iieacaii, eaeei ia?acii iia?aoeeiiiay nenoaia
eniieuecoao process control block aeey ia?aeeth/aiey i?ioeanni?a n
iaeiiai i?ioeanna ia ae?oaie.
time
1.2. Ieaie?iaaiea i?ioeannia. Iiiyoea i/a?aaee.
Nenoaia oi?aaeaiey i?ioeannaie iaania/eaaao i?ioiaeaeaiea i?ioeanna
/a?ac eiiiuethoa?. A caaeneiinoe io ninoiyiey i?ioeanna aio aeieaeai
auoue i?aaeinoaaeoue oio eee eiie ?ano?n. Iai?eia?, iiaue i?ioeann
iaiaoiaeeii ?acianoeoue a iniiaiie iaiyoe, neaaeiaaoaeueii, aio
iaiaoiaeeii auaeaeeoue /anoue aae?aniiai i?ino?ainoaa. I?ioeanno a
ninoiyiee aioiaue aeieaeii auoue i?aaeinoaaeaii i?ioeanni?iia a?aiy.
Auiieiyaiue i?ioeann iiaeao iio?aaiaaoue iai?oaeiaaiea aaiaea – auaiaea
e aeinooi e oaeeo.
I/a?aaeue e
ia?aue
PCB5
oa?ieiaeo
? 1
iineaaeiee
?ani?aaeaeaiea i?ioeannia iaaeaeo eiathueieny ?ano?naie iineo iacaaiea
ieaie?iaaiea i?ioeannia. Iaeiei ec iaoiaeii ieaie?iaaiey i?ioeannia,
i?eaioe?iaaiiuo ia yooaeoeaioth caa?oceo ?ano?nia, yaeyaony iaoiae
i/a?aaeae ?ano?nia. Iiaua i?ioeannu iaoiaeyony ai aoiaeiie i/a?aaee,
/anoi iacuaaaiie i/a?aaeueth ?aaio – caaeaiee (job queue).
Aoiaeiay i/a?aaeue ?aniieaaaaony ai aiaoiae iaiyoe, ai aoiaeiie
i/a?aaee i?ioeannu iaeeaeatho inaiaiaeaeaiey ?ano?na — aae?aniiai
i?ino?ainoaa iniiaiie iaiyoe.
Aioiaua e auiieiaieth i?ioeannu ?aniieaaathony a iniiaiie iaiyoe e
naycaiu i/a?aaeueth aioiauo i?ioeannia eee ready queue. I?ioeannu a yoie
i/a?aaee iaeeaeatho inaiaiaeaeaiey ?ano?na i?ioeanni?iia a?aiy.
I?ioeann a ninoiyiee iaeeaeaiey caaa?oaiey iia?aoeee aaiaea – auaiaea
iaoiaeeony a iaeiie ec i/a?aaeae e iai?oaeiaaieth aaiaea – auaiaea,
eioi?ay iineo iacaaiea devices queue.
I?e i?ioiaeaeaiee /a?ac eiiiuethoa? i?ioeann iea?e?oao iaaeaeo
?acee/iuie i/a?aaeyie iiae oi?aaeaieai i?ia?aiiu, eioi?ay iacuaaaony
ieaie?iauee. (scheduler) Iia?aoeeiiiay nenoaia, iaania/eaathuay ?aaeei
ioeueoei?ia?aiie?iaaiey, iau/ii aeeth/aao aeaa ieaie?iaueea —
aeieain?i/iue (long term scheduler) e e?aoein?i/iue (short term
scheduler/CPU scheduler).
Iniiaiia ioee/ea iaaeaeo aeieain?i/iui e e?aoein?i/iui ieaie?iaueeaie
caeeth/aaony a /anoioa caionea, iai?eia?: e?aoein?i/iue ieaie?iauee
iiaeao caioneaoueny eaaeaeua 100 in, aeieain?i/iue — iaeei ?ac ca
ianeieueei ieioo.
Aeieain?i/iue ieaie?iauee ?aoaao, eaeie ec i?ioeannia, iaoiaeyueony ai
aoiaeiie i/a?aaee, aeieaeai auoue ia?aaaaeai a i/a?aaeue aioiauo
i?ioeannia a neo/aa inaiaiaeaeaiey ?ano?nia iaiyoe.
Aeieain?i/iue ieaie?iauee auae?aao i?ioeann ec aoiaeiie i/a?aaee n
oeaeueth nicaeaiey iaiaeii?iaeiie ioeueoei?ia?aiiiie niane. Yoi
icia/aao, /oi a i/a?aaee aioiauo i?ioeannia aeieaeiu iaoiaeeoueny a
?aciie i?iii?oeee eae i?ioeannu, i?eaioe?iaaiiua ia aaiae – auaiae, oae
e i?ioeannu, i?eaioe?iaaiiua ia i?aeiouanoaaiioth ?aaioo n CPU.
E?aoein?i/iue ieaie?iauee ?aoaao, eaeie ec i?ioeannia, iaoiaeyueony a
i/a?aaee aioiauo i?ioeannia, aeieaeai auoue ia?aaeai ia auiieiaiea a
CPU. A iaeioi?uo iia?aoeeiiiuo nenoaiao aeieain?i/iue ieaie?iauee iiaeao
ionoonoaiaaoue. Iai?eia?, a nenoaiao ?acaeaeaiey a?aiaie (time sharing
system), eaaeaeue iiaue i?ioeann n?aco aea iiiauaaony a iniiaioth
iaiyoue.
1.3. Acaeiiaeaenoaea i?ioeannia. Iieueciaaoaeueneee o?iaaiue.
Niaianoii auiieiyaiua i?ioeannu iiaoo auoue eeai iacaaeneiuie
(independed processes), eeai acaeiiaeaenoaothueie (cooperating
processes). Acaeiiaeaenoaea i?ioeannia /anoi iiieiaaony a niunea
acaeiiiai iaiaia aeaiiuie /a?ac iauee aooa? aeaiiuo.
Acaeiiaeaenoaea i?ioeannia oaeiaii ?anniao?eaaoue a noaia
i?iecaiaeeoaeue – iio?aaeoaeue (produces – consumer). Iai?eia?,
i?ia?aiia auaiaea ia ia/aoue i?iecaiaeeo iineaaeiaaoaeueiinoue neiaieia,
eioi?ua iio?aaeythony ae?aeaa?ii i?eioa?a eee eiiieeyoi? i?iecaiaeeo
annaiaea?iue oaeno, eioi?ue caoai iio?aaeyaony annaiaea?ii.
Aeey oiai, /oiau i?ioeann – i?iecaiaeeoaeue e i?ioeann – iio?aaeoaeue
iiaee caiieiyoue niaianoii iaiaoiaeeiue aooa?, caiieiyaiue i?ioeannii –
i?iecaiaeeoaeai e iio?aaeyaiui i?ioeannii – iio?aaeoaeai.
Aooa? eiaao oeene?iaaiiua ?acia?u, e neaaeiaaoaeueii i?ioeannu iiaoo
iaoiaeeoueny a ninoiyiee iaeeaeaiey, eiaaea:
aooa? caiieiai; iaeeaeaao i?ioeann – i?iecaiaeeoaeue
aooa? iono; iaeeaeaao i?ioeann – iio?aaeoaeue
Aooa? iiaeao i?aaeinoaaeyoueny e iiaeaea?aeeaaoueny naiie IN, iai?eia?
n iiiiuueth n?aaenoa eiiioieeaoeee i?ioeannia (IPC — Inter Process
Communication), eeai i?aaieciaaoue i?eeeaaeiui i?ia?aiienoii. I?e yoii
iaa i?ioeanna eniieuecotho iauee o/anoie iaiyoe, iai?eia? i?ioeann –
i?iecaiaeeoaeue e i?ioeann – iio?aaeoaeue iiaoo eniieueciaaoue
neaaeothuea ia?aiaiiua:
Var n;
type item=…;
Var buffer:array[0..n-1] of item;
in, out:0..n-1;, aaea n – eiee/anoai aae?anoaiuo yeaiaioia aooa?a, Item
– eiy oeia yeaiaioia aooa?a, in, out – oeacaoaee, oa?aeoa?ecothuea
caiieiaiea aooa?a.
Aooa? i?aaenoaaeai a aeaea oeeeee/anee naycaiiiai ianneaa aae?anoaiuo
yeaiaioia n aeaoiy oeacaoaeyie – in, out. Oeacaoaeue in niaea?aeeo iiia?
ia?aiai naiaiaeiiai yeaiaioa aooa?a, a out – ia?aiai caiyoiai yeaiaioa
aooa?a.
0 1 2 3 4 5
n-1
Iono. in=out. I/aaeaeii, /oi aooa? iono a oii neo/aa, anee auiieiyaony
yoi oneiaea.
Aooa? aoaeao iieiinoueth caiieiai, anee auiieiyaony oneiaea
(in+1) mod n = out
I?ioeann – i?iecaiaeeoaeue aeieaeai auiieiyoue i?ioeaaeo?o caiene a
aooa? oeia
Repeat
…
i?iaeooee?oaony i/a?aaeiie yeaiaio a Next p
…
while (in+1) mod n = out do no_op;
buffer (in):=next p;
in:=(in+1) mod n;
until false
aaea Next p – eieaeueiay ia?aiaiiay i?ioeanna – i?iecaiaeeoaey, a
eioi?ie o?aieony i/a?aaeiie i?iaeooee?oaiue yeaiaio
no_op – ionoie iia?aoi?
I?ioeann – iio?aaeoaeue aeieaeai auiieiyoue i?ioeaaeo?o /oaiey ec aooa?a
oeia
Repeat
while in out do no_op;
next p := buffer (out);
out:=(out+1) mod n;
…
iio?aaeyaony i/a?aaeiie yeaiaio ec Next n
…
until false
2. Ieaie?iaaiea i?ioeanni?a.
E?aoein?i/iue ieaie?iauee auae?aao i?ioeannu ec i/a?aaee aioiauo
i?ioeannia e ia?aaeaao eo ia auiieiaiea a CPU. Nouanoaotho ?acee/iu
aeai?eoiu eee no?aoaaee ?aoaiey yoie caaea/e, ioee/athueany ioiioaieai e
e?eoa?eyi ieaie?iaaiey.
2.1. E?eoa?ee ieaie?iaaiey i?ioeanni?a.
Eniieuecothony neaaeothuea e?eoa?ee, iicaieythuea n?aaieaaoue aeai?eoiu
e?aoein?i/iuo ieaie?iaueeia:
ooeeecaoeey CPU (eniieueciaaiea) CPU utilization. ooeeecaoeey CPU
oai?aoe/anee iiaeao iaoiaeeoueny i?aaeaeao io 0 aei 100%. A ?aaeueiuo
nenoaiao ooeeecaoeey CPU eieaaeaony a i?aaeaeao 40% aeey eaaei
caa?oaeaiiiai CPU, 90% aeey oyaeaei caa?oaeaiiiai CPU.
i?iioneiay niiniaiinoue CPU throughput. I?iioneiay niiniaiinoue CPU
iiaeao ecia?youeny eiee/anoaii i?ioeannia, eioi?ua auiieiythony a
aaeeieoeo a?aiaie.
a?aiy iai?ioa (turnaround time) aeey iaeioi?uo i?ioeannia aaaeiui
e?eoa?eai yaeyaony iieiia a?aiy auiieiaiey, oi anoue eioa?aae io iiiaioa
iiyaeaiey i?ioeanna ai aoiaeiie i/a?aaee aei iiiaioa aai caaa?oaiey. Yoi
a?aiy iacaaii a?aiaiai iai?ioa e aeeth/aao a?aiy iaeeaeaiey ai aoiaeiie
i/a?aaee, a?aiy iaeeaeaiey a i/a?aaee aioiauo i?ioeannia, a?aiy
iaeeaeaiey a i/a?aaeyo e iai?oaeiaaieth, a?aiy auiieiaiey a i?ioeanni?a
e a?aiy aaiaea – auaiaea.
a?aiy iaeeaeaiey (waiting time). iiae a?aiaiai iaeeaeaiey iiieiaaony
noiia?iia a?aiy iaoiaeaeaiey i?ioeanna a i/a?aaee aioiauo i?ioeannia.
a?aiy ioeeeea (response time) aeey noaoai eioa?aeoeaiuo i?ia?aii aaaeiui
iieacaoaeai yaeyaony a?aiy ioeeeea eee a?aiy, i?ioaaeoaa io iiiaioa
iiiaaeaiey i?ioeanna ai aoiaeioth i/a?aaeue aei iiiaioa ia?aiai
ia?auaiey e oa?ieiaeo.
I/aaeaeii, /oi i?inoaeoay no?aoaaey e?aoein?i/iiai ieaie?iaueea
aeieaeia auoue iai?aaeaia ia iaeneiecaoeeth n?aaeieo cia/aiee
caa?oaeaiiinoe e i?iioneiie niiniaiinoe, a?aiaie iaeeaeaiey e a?aiaie
ioeeeea.
A ?yaea neo/aaa eniieuecothony neiaeiua e?eoa?ee, iai?eia? oae
iacuaaaiue ieieiaeniue e?eoa?ee, oi anoue aianoi i?inoiai e?eoa?ey
ieieioi n?aaeiaai a?aiaie ioeeeea eniieuecoaony neaaeothuee — ieieioi
iaeneiaeueiiai a?aiaie ioeeeea.
2.2. No?aoaaee ieaie?iaaiey i?ioeanni?a.
2.2.1.Ia?aue i?eoae — ia?aue ianeoaeeaaaony FIFO. first come — first
served (FCFS).
FCFS yaeyaony iaeaieaa i?inoie no?aoaaeae ieaie?iaaiey i?ioeannia e
caeeth/aaony a oii, /oi i?ioeanni? ia?aaeaaony oiio i?ioeanno, eioi?ue
?aiueoa anao ae?oaeo aai cai?inee.
Eiaaea i?ioeann iiiaaeaao a i/a?aaeue aioiauo i?ioeannia, process
control block i?eniaaeeiyaony e oainoo i/a?aaee.
N?aaeiaa a?aiy iaeeaeaiey aeey no?aoaaee FCFS /anoi aanueia aaeeei e
caaeneo io ii?yaeea iinooieaiey i?ioeannia a i/a?aaeue aioiauo
i?ioeannia.
I?eia? ? 1
Ionoue o?e i?ioeanna iiiaaeatho a i/a?aaeue iaeiia?aiaiii a iiiaio 0 e
eiatho neaaeothuea cia/aiey a?aiaie iineaaeothuaai ianeoaeeaaiey a CPU.
aa?eaio 1:
I1(24 in)
I2(3 in)
I3(3 in)
aa?eaio 2:
I2(3 in)
I3(3 in)
I1(24 in)
Ia ?enoiea i?eaaaeaiu aeeaa?aiiu Aaiaa i/a?aaee aioiauo i?ioeannia
aa?eaio 1:
I1 I2 I3 WT=17 in
WT1=0 in WT2=24 in WT3=27 in
aa?eaio 2:
I2 I3 I1 WT=3 in
WT2=0 in WT3=3 in WT1=6 in
No?aoaaee FCFS i?enou oae iacuaaaiue “yooaeo eiiaiy”. A oii neo/aa,
eiaaea a eiiiuethoa?a eiaaony iaeei aieueoie i?ioeann e ianeieueei
iaeuo, oi ana i?ioeannu niae?athony a ia/aea i/a?aaee aioiauo
i?ioeannia, a caoai a i/a?aaee e iai?oaeiaaieth. Oaeei ia?acii, “yooaeo
eiiaiy” i?eaiaeeo e nieaeaieth caa?oaeaiiinoe eae i?ioeanni?a, oae e
ia?eoa?eeiiai iai?oaeiaaiey.
2.2.2. No?aoaaey iaeaieaa ei?ioeay ?aaioa — aia?aae e iiaaaea eiiioiecia
! SJF
SJF — Shortest Job First. Iaeiei ec iaoiaeia ai?ueau n “yooaeoii
eiiaiy” yaeyaony no?aoaaey, iicaieythuay i?ioeanno ec i/a?aaee
auiieiyoueny ia?aui.
I?eia? ? 2
Ionoue /aou?a i?ioeanna iaeiia?aiaiii iiiaaeatho a i/a?aaeue aioiauo
i?ioeannia e eiatho neaaeothuea cia/aiey a?aiaie iineaaeothuaai
ianeoaeeaaiey
I1(6 in)
I2(8 in)
I3(7 in)
I4(3 in)
Ia ?enoiea i?eaaaeaia aeeaa?aiia Aaiaa, iino?iaiiay a niioaaonoaee ni
no?aoaaeae SJF.
I4 I1 I3 I2 WT=7 in
WT4=0 in WT1=3 in WT3=9 in WT2=16 in
Eaaei iin/eoaoue, /oi i?e eniieueciaaiee FCFS – no?aoaaee n?aaeiaa
a?aiy iaeeaeaiey aeey oao aea i?ioeannia ?aaii 10.25 in, oaeei ia?acii
no?aoaaey SJF nieaeaao a?aiy iaeeaeaiey i/a?aaee. Iaeaieueoay
o?oaeiinoue a i?aeoe/aneie ?aaeecaoeee SJF caeeth/aaony a iaaiciiaeiinoe
ca?aiaa ii?aaeaeeoue aaee/eio a?aiaie iineaaeothuaai ianeoaeeaaiey.
Iiyoiio no?aoaaey SJF /anoi i?eiaiyaony a aeieain?i/iuo ieaie?iaueeao,
ianeoaeeaathueo iaeaoiue ?aaeei. A yoii neo/aa aianoi aaee/eiu a?aiaie
iineaaeothuaai ianeoaeeaaiey eniieuecoaony aeiionoeiia iaeneiaeueiia
a?aiy auiieiaiey caaeaiey, eioi?ia i?ia?aiieno aeieaeai
niaoeeoeoee?iaaoue ia?aae ioi?aaeie caaeaiey a iaeao.
2.2.3. I?ei?eoaoiia ieaie?iaaiea.
Iienaiiua ?aiaa no?aoaaee iiaoo ?anniao?eaaoueny eae /anoiua neo/ae
no?aoaaee i?ei?eoaoiiai ieaie?iaaiey. Yoa no?aoaaey i?aaeiieaaaao, /oi
eaaeaeiio i?ioeanno i?eienuaaaony i?ei?eoao, ii?aaeaeythuee
i/a?aaeiinoue i?aaeinoaaeaiey aio CPU. Iai?eia?, no?aoaaey FCFS
i?aaeiieaaaao, /oi ana i?ioeannu i?aaeiieaaaao, /oi ana i?ioeannu eiatho
iaeeiaeiaua i?ei?eoaou, a no?aoaaey SJF i?aaeiieaaaao, /oi i?ei?eoao
anoue aaee/eia, ia?aoiay a?aiaie iineaaeothuaai ianeoaeeaaiey.
I?ei?eoao — yoi oeaeia iieiaeeoaeueiia /enei, iaoiaeyuaany a iaeioi?ii
aeeaiaciia, iai?eia? io 0 aei 7, io 0 aei 4095. Aoaeai n/eoaoue, /oi /ai
iaiueoa cia/aiea /enea, oai auoa i?ei?eoao i?ioeanna.
I?eia? ?3. i?ei?eoao
I1(10 in) 3
I2(1 in) 1
I3(2 in) 3
I4(1 in) 4
I5(5 in) 2
Ia ?enoiea i?eaaaeaia aeeaa?aiia Aaiaa, ?aniieaaathuay i?ioeannu a
i/a?aaee a niioaaonoaee ni no?aoaaeae i?ei?eoaoiiai ieaie?iaaiey
I2 I5 I1 I3 I4
WT2=0 in WT5=1 in WT1=6 in WT3=16 in WT4=18 in
I?ei?eoaou ii?aaeaeythony enoiaey ec niaieoiiinoe aioo?aiieo e aiaoieo
ii ioiioaieth e iia?aoeeiiiie nenoaia oaeoi?ia.
Aioo?aiiea oaeoi?u:
o?aaiaaiey e iaiyoe
eiee/anoai ioe?uouo oaeeia
ioiioaiea n?aaeiaai a?aiaie aaiaea – auaiaea e n?aaeiaio a?aiaie CPU e
oae aeaeaa
Aiaoiea oaeoi?u:
aaaeiinoue i?ioeanna
oei e aaee/eia oaeeia, eniieuecoaiuo aeey iieaou
ioaeaeaiea, auiieiythuaa ?aaiou e oae aeaeaa
Aioo?aiiea oaeoi?u iiaoo eniieueciaaoueny aeey aaoiiaoe/aneiai
iacia/aiey i?ei?eoaoia naiie iia?aoeeiiiie nenoaiie, a aiaoiea aeey
i?eioaeeoaeueiiai, n iiiiuueth iia?aoi?a.
Aeaaiue iaaeinoaoie i?ei?eoaoiiai ieaie?iaaiey caeeth/aaony a
aiciiaeiinoe aeiee?iaaiey ia iaii?aaeaeaiii aeieaia a?aiy
ieceii?ei?eoaoiuo i?ioeannia.
Ecaanoai neo/ae, eiaaea a 1973 aiaeo a Ianna/onaoneii oaoiieiae/aneii
einoeoooa MIT i?e inoaiiaea eiiiuethoa?a IBM 7094 a i/a?aaee aioiauo
i?ioeannia auee iaia?oaeaiu i?ioeannu, i?aaenoaaeaiiua a 1967 e ana aua
ia auiieiaiiua.
Aeey ono?aiaiey ioia/aiiiai iaaeinoaoea eniieuecothony neaaeothuea
iaoiaeu: i?ioeannu, a?aiy iaeeaeaiey eioi?uo i?aauoaao oeene?iaaiioth
aaee/eio, iai?eia? 15 ieioo, aaoiiaoe/anee iieo/atho aaeeie/iia
i?e?auaiea i?ei?eoaoa.
2.2.4. “Ea?onaeueiay” no?aoaaey ieaie?iaaiey.
RR-Round Robin
Round Robin no?aoaaey i?eiaiyaony a nenoaiao ?acaeaeaiey a?aiaie.
Ii?aaeaeyaony iaaieueoie io?acie a?aiaie, iacaaiiue eaaioii a?aiaie
(10..100 in). I/a?aaeue aioiauo i?ioeannia ?anniao?eaaaony eae
eieueoeaaay. I?ioeannu oeeeee/anee ia?aiauathony ii i/a?aaee, iieo/ay
CPU ia a?aiy, ?aaiia iaeiiio eaaioo. Iiaue i?ioeann aeiaaaeyaony a oaino
i/a?aaee. Anee i?ioeann ia caaa?oeeny a i?aaeaeao auaeaeaiiiai aio
eaaioa a?aiaie, aai ?aaioa i?eioaeeoaeueii i?a?uaaaony, e ii
ia?aiauaaony a oaino i/a?aaee.
I?eia? 4
I1(24 in)
I2(3 in)
I3(3 in)
q=4 in.
Aeeaa?aiia Aaiaa niioaaonoaaiii Round Robin no?aoaaee aeey yoiai neo/ay
eiaao aeae:
I1 I2 I3 I1 I1 I1 I1 I1
WT1=0 in 7 10 14 18 22 26 30
Naienoaa Round Robin no?aoaaee neeueii caaenyo io aaee/eiu a?aiaiiiai
eaaioa q. *ai aieueoa a?aiaiiie eaaio, oai aeieueoa Round Robin
no?aoaaey i?eaeeaeaaony e FCFS no?aoaaee. (aeey ?anniio?aiiiai i?eia?a,
anee q>24 in, oi -> FCFS.) I?e i/aiue iaeuo cia/aieyo a?aiaiiiai eaaioa
Round Robin no?aoaaey iacuaatho ?acaeaeaieai i?ioeanni?a — processor
sharing. Oai?aoe/anee yoi icia/aao, /oi eaaeaeue ec N i?ioeannia
?aaioaao ni naiei nianoaaiiui i?ioeanni?ii, i?iecaiaeeoaeueiinoue
i?ioeanni?a ?aaia 1/N io i?iecaiaeeoaeueiinoe oece/aneiai i?ioeanni?a.
2.2.5. IEAIE?IAAIEA n eniieueciaaieai iiiaio?iaiaaie
i/a?aaee.(Multilevel queue scheduling)
Yoa no?aoaaey ?ac?aaioaia aeey neooaoeee, eiaaea i?ioeannu iiaoo auoue
eaaei eeanneoeoee?iaaiu ia ianeieueei a?oii, iai?eia?, /anoi i?ioeannu
?acaeaeytho ia aeaa a?oiiu: eioa?aeoeaiua (i?ioeannu ia?aaeiaai ieaia) e
iaeaoiua (oiiiaua).
Eioa?aeoeaiua e iaeaoiua i?ioeannu eiatho ?acee/iua o?aaiaaiey e
e?aoein?i/iiio ieaie?iaueeo, iai?eia? ii ioiioaieth ei a?aiaie ioeeeea.
No?aoaaey iiiaio?iaiaaie i/a?aaee ?acaeaeyao i/a?aaeue aioiauo
i?ioeannia ia ianeieueei i/a?aaeae, a eaaeaeie ec eioi?uo iaoiaeyony
i?ioeannu n iaeeiaeiauie naienoaaie, e eaaeaeue ec eioi?uo iiaeao
ieaie?iaaoueny eiaeeaeaeoaeueiie no?aoaaeae, iai?eia? Round Robin
no?aoaaey aeey eioa?aeoeaiuo i?ioeannia e FCFS aeey iaeaoiuo i?ioeannia.
Acaeiiaeaenoaea i/a?aaeae inouanoaeyaony ii neaaeothuei i?aaeeai: ie
iaeei i?ioeann n aieaa ieceei i?ei?eoaoii ia iiaeao auoue caiouai, iiea
ia auiieiyony i?ioeannu ai anao i/a?aaeyo n aieaa aunieei i?ei?eoaoii.
?aaioa i?ioeanna ec i/a?aaee n aieaa ieceei i?ei?eoaoii iiaeao auoue
i?einoaiiaeaia, anee a iaeiie ec i/a?aaeae n aieaa aunieei i?ei?eoaoii
iiyaeeny i?ioeann.
2.2.6. I?ia?aiie?iaaiea n eniieueciaaieai iiiaio?iaiaaie i/a?aaee n
ia?aoiuie naycyie (multilevel feedback queue sheduling)
Iau/iay iiiaio?iaiaaay i/a?aaeue ia aeiioneaao ia?aiauaiey i?ioeannia
iaaeaeo i/a?aaeyie. Iiiaio?iaiaaay i/a?aaeue n ia?aoiuie naycyie
i?aaeiieaaaao, /oi i?ioeannu i?e ii?aaeaeaiiuo oneiaeyo iiaoo
ia?aiauaoueny iaaeaeo i/a?aaeyie.
I?ioeannu ia?aiia/aeueii iiiaaeatho a i/a?aaeue 0, aaea eaaeaeiio ec
ieo i?aaeinoaaeyaony eaaio a?aiaie, ?aaiue 8 in. Oa i?ioeannu, eioi?ua
ia oniaee auiieieoueny a oa/aiea yoiai a?aiaie, ia?aiauathony a
i/a?aaeue 1. I?ioeannu ec i/a?aaee 1 ia/eiatho ia?aaaouaaoueny oieueei
oiaaea, eiaaea i/a?aaeue 0 noaiiaeoueny ionoie. Oa i?ioeannu, eioi?ua ia
auiieieeenue a i/a?aaee 1 (q=16 in) ia?aiauathony a i/a?aaeue 2.
I?ioeannu ec i/a?aaee 2 aoaeoo ia?aaaouaaoueny oieueei a oii neo/aa,
anee noaiiayony ionouie i/a?aaee 0 e 1.
?anniio?aiiay no?aoaaey yaeyaony iaeaieaa oieaa?naeueiie e ni/aoaao a
naaa naienoaa anao ?anniio?aiiuo ?aiueoa no?aoaaee.
FCFS
SJF
i?ei?eoaoiay
Round Robin
iiiaio?iaiaaay i/a?aaeue
3. Oi?aaeaiea iaae?ooaeueiie iaiyoueth.
3.1. Naiiieia. (swapping)
Naiiieiaii iacuaaaony iaoiae oi?aaeaiey iaiyoueth, iniiaaiiue ia oii,
/oi ana i?ioeannu, o/anoaothuea a ioeueoei?ia?aiiiie ia?aaioea, o?aiyony
ai aiaoiae iaiyoe.
I?ioeann, eioi?iio auaeaeai CPU, a?aiaiii ia?aiauaaony a iniiaioth
iaiyoue (swap in/roll in).
A neo/aa i?a?uaaiey ?aaiou i?ioeanna ii ia?aiauaaony ia?aoii ai
aiaoithth iaiyoue (swap out/roll out).
Caia/aiea: i?e naiiieiaa ec iniiaiie iaiyoe ai aiaoithth (e ia?aoii)
ia?aiauaaony any i?ia?aiia, a ia a? ioaeaeueiay /anoue.
Naiiieia eiiaaea eniieuecotho i?e i?ei?eoaoiii ieaie?iaaiee CPU. A yoii
neo/aa n oeaeueth inaiaiaeaeaiey iaiyoe aeey aunieii?ei?eoaoiuo
i?ioeannia, ieceii?ei?eoaoiua i?ioeannu ia?aiauathony ai aiaoithth
iaiyoue.
Iniiaiia i?eiaiaiea naiiieia iaoiaeeo a nenoaiao ?acaeaeaiey a?aiaie,
aaea ii eniieuecoaony iaeiia?aiaiii n Round Robin no?aoaaeae
ieaie?iaaiey CPU.
A ia/aea eaaeaeiai a?aiaiiiai eaaioa aeie oi?aaeaiey iaiyoueth
aua?oaeaao ec iniiaiie iaiyoe i?ioeann, ?aaioa eioi?iai auea oieueei /oi
i?a?aaia, e caa?oaeaao i/a?aaeiie auiieiaiiue i?ioeann.
Iaoiae naiiieiaa aeeyao ia aaee/eio a?aiaiiiai eaaioa Round Robin
no?aoaaee.
I?eia?.
ionoue i/a?aaeiie caa?oaeaaiue a iaiyoue i?ioeann eiaao ?acia? 100Ea.
aeene iicaieyao /eoaoue aeaiiua ni nei?inoueth 1 Ia a naeoiaeo
neaaeiaaoaeueii, 100 Ea iiaoo auoue caa?oaeaiu ca 100 in.
aoaeai n/eoaoue, /oi aeey ia?aiia/aeueiiai iiaeaiaea aieiaee /oaiey –
caiene iio?aaoaony 8 in
oaeei ia?acii, iia?aoeey naiiieia caeiao 108 in, a iauaa a?aiy naiiieiaa
– 216 in.
Aeey yooaeoeaiie caa?oaeaiiinoe i?ioeanni?a a?aiy naiiieiaa aeieaeii
auoue nouanoaaiii iaiueoa a?aiaie n/aoa. Neaaeiaaoaeueii, aeey
?anniio?aiiiai i?eia?a eaaio a?aiaie aeieaeai auoue nouanoaaiii aieueoa,
/ai 216 in. ssnii, /oi yoi /enei cia/eoaeueii oaaee/eony, anee
ia?aiauaaiue i?ioeann eiaao ?acia?, iai?eia?, 1 Ia.
Iaaeinoaoie “/enoiai” naiiieiaa a aieueoeo iioa?yo a?aiaie ia caa?oceo
eee aua?oceo i?ioeannia. Iiyoiio a nia?aiaiiuo iia?aoeeiiiuo nenoaiao
eniieuecoaony iiaeeoeoee?iaaiiua aa?eaiou naiiieiaa.
Oae, iai?eia?, ai iiiaeo aa?neyo iia?aoeeiiiie nenoaiu UNIX naiiieia
aeeth/aaony oieueei a oii neo/aa, eiaaea eiee/anoai i?ioeannia a iaiyoe
noaiiaeony neeoeii aieueoei.
3.2. Niaaeiia ?aciauaiea i?ioeannia.
Iaoiaeu ?aciauaiey i?ioeannia a iniiaiie iaiyoe ii ioiioaieth e
?aniieiaeaieth o/anoeia iaiyoe, auaeaeaiiuo aeey iaeiie e oie aea
i?ia?aiiu aeaeyo ia aeaa eeanna. Ia?aue — iaoiae niaaeiiai ?aciauaiey, a
aoi?ie — iaoiae ianiaaeiiai ?aciauaiey.
Niaaeiia ?aciauaiea yaeyaony i?inoaeoei e i?aaeiieaaaao, /oi a iaiyoe,
ia/eiay n iaeioi?iai ia/aeueiiai aae?ana auaeaeyaony iaeei iai?a?uaiue
o/anoie aae?aniiai i?ino?ainoaa.
i?e ianiaaeiii ?aciauaiee i?ia?aiia ?acaeaaaony ia iiiaeanoai /anoae,
eioi?ua ?aniieaaathony a ?acee/iuo, iaiaycaoaeueii niaaeiuo o/anoeao
aae?aniiai i?ino?ainoaa.
3.2.1. Iaeiii?ia?aiiiue ?aaeei.
?enoiie eeethno?e?oao niaaeiia ?aciauaiea (contiguous allocation)
iaeiie i?ia?aiiu a iniiaiie iaiyoe.
I?e niaaeiii ?aciauaiee ?acia? caa?oaeaaiie i?ia?aiiu ia?aie/eaaaony
?acia?ii iaeiieoaey. Aeey oiai, /oiau i?e niaaeiii ?aciauaiee
caa?oaeaoue i?ia?aiiu, ?acia?u eioi?uo i?aauoatho ?acia?u iaeiieoaey,
eniieuecotho iaoiae iaa?eaeiuo naaiaioia (overlay segments).
A i?ia?aiia, eiathuae ae?aaiaeaeioth no?oeoo?o, iiaeoee aoi?iai o?iaiy
?aaioatho noaoai iineaaeiaaoaeueii, iiyoiio a iaiyoe iiaeao iaoiaeeoueny
oieueei iaeei ec ieo.
Iaa?eaeioth no?oeoo?o i?ia?aiiu e iineaaeiaaoaeueiinoue caa?ocee
iaa?eaeiuo naaiaioia ieaie?oao nai i?ia?aiieno.
A i?ioeanna auiieiaiey i?ia?aiiu ana a? aae?ana ia aeieaeiu auoue
iaiueoa /enea a. A i?ioeaiii neo/aa aiciiaeia caienue eaeiai-eeai
?acoeueoaoa ?aaiou i?ia?aiiu (iiaa?o iia?aoeeiiiie nenoaiu) e
oie/oiaeaiea iaeioi?uo a? /anoae. Caueoo iia?aoeeiiiie nenoaiu a neo/aa
niaaeiiai ?aciauaiey i?e iaeiii?ia?aiiiii ?aaeeia iiaeii inouanoaeoue n
iiiiuueth ?aaeno?a a?aieoeu.
Ai a?aiy ?aaiou i?eeeaaeiie i?ia?aiiu ana aae?ana, aaia?e?oaiua CPU,
n?aaieaathony n niaea?aeeiui ?aaeno?a a?aieoeu. Anee aaia?e?oaony aae?an
iaiueoa /enea a, ?aaioa i?ia?aiiu i?a?uaaaony.
3.2.2 Ioeueoei?ia?aiiiue ?aaeei n OEENE?IAAIIUIE a?aieoeaie.
Ioeueoei?ia?aiie?iaaiea n oeene?iaaiiuie ?acaeaeaie (Multiprogramming
with a fixed number of tasks) i?aaeiieaaaao ?acaeaeaiea aae?aniiai
i?ino?ainoaa ia ?yae ?acaeaeia oeene?iaaiiiai ?acaeaea. A eaaeaeii
?acaeaea ?aciauaaony iaeei i?ioeann.
Iaeaieaa i?inoie e iaeiaiaa yooaeoeaiue ?aaeei MFT niioaaonoaoao
neo/ath, eiaaea o?aineyoeey i?ia?aii inouanoaeyaony a aaniethoiuo
aae?anao aeey niioaaonoaothuaai ?acaeaea.
A yoii neo/aa, anee niioaaonoaothuee ?acaeae caiyo, oi i?ioeann
inoaaony a i/a?aaee ai aiaoiae iaiyoe aeaaea a oii neo/aa, eiaaea
ae?oaea ?acaeaeu naiaiaeiu.
Oiaiueoeoue o?aaiaioaoeeth i?e ioeueoei?ia?aiie?iaaiee n oeene?iaaiiuie
?acaeaeaie iiaeii, anee caa?oci/iua iiaeoee iieo/aoue a ia?aiauaaiuo
aae?anao. Oaeie iiaeoeue iiaeao auoue caa?oaeai a ethaie naiaiaeiue
?acaeae iinea niioaaonoaothuae iano?ieee.
I?e ioeueoei?ia?aiie?iaaiee n o?aineyoeeae a ia?aiauaaiuo aae?anao
eiathony aeaa i?e/eiu o?aaiaioaoeee. Ia?aay — ?acia? caa?oaeaiiiai
i?ioeanna iaiueoa ?acia?a, caieiaaiiai ?acaeaeii (aioo?aiiyy
o?aaiaioaoeey), aoi?ay — ?acia? i?ioeanna a i/a?aaee aieueoa ?acia?a
naiaiaeiiai ?acaeaea, e yoio ?acaeae inoaaony naiaiaeiui (aiaoiyy
o?aaiaioaoeey).
Aeey caueou iaiyoe i?e ioeueoei?ia?aiie?iaaiee n oeene?iaaiiui
?acaeaeaie iaiaoiaeeiu aeaa ?aaeno?a. Ia?aue — ?aaeno? aa?oiae a?aieoeu
(iaeiaiueoee aae?an), aoi?ie — ?aaeno? ieaeiae a?aieoeu (iaeaieueoee
aae?an).
I?aaeaea /ai i?ia?aiia a ?acaeaea N ia/iao auiieiyoueny, aa a?aie/iua
aae?ana caa?oaeathony a niioaaonoaothuea ?aaeno?u. A i?ioeanna ?aaiou
i?ia?aiiu ana oi?ie?oaiua ath aae?ana eiio?iee?othony ia oaeiaeaoai?aiea
ia?aaainoaa
a
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