lecture3 os support

8/16/2019 Lecture3 Os Support

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CMPT 431

Dr. Alexandra Fedorova

Lecture III: OS Support


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2CMPT 431 © A. Fedorova

Te !ole o" te OS

# Te operat$n% &'&te( need& to prov$de&upport "or $(ple(entat$on o"

d$&tr$)uted &'&te(&# *e +$ll loo, at o+ d$&tr$)uted &'&te(&

&erv$ce& $nteract +$t te operat$n%&'&te(&

# *e +$ll d$&cu&& te &upport tat teoperat$n% &'&te( need& to prov$de


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D$rect Interact$on +$t te OS

OS

Proce&&:a DS

co(ponent

&'&te(call&

• A proce&& d$rectl'$nteract& +$t te OS v$a&'&te( call&

• -xa(ple: a +e) )ro+&era +e) &erver


4/20


Interact$on v$a M$ddle+are La'er

OS

Proce&&:a DS

co(ponent

&'&te(

call&

M$ddle+are

Funct$on call&or IPC

• A proce&& d$rectl'$nteract& +$t te OS v$aa ($ddle+are la'er

• A ($ddle+are la'erd$rectl' $nteract& +$tte OS

• -xa(ple: a peer/to/peer0le &'&te( $(ple(ented

over a d$&tr$)uted a&ta)le


5/20


Interact$on v$a Inclu&$on

OS DSco(ponent

• A DS co(ponent $& a part o" te operat$n% &'&te( $.e.an operat$n% &'&te( daemon

• -xa(ple: et+or, F$le S'&te( 2FS dae(on• !un& a& a ,ernel tread &are& addre&& &pace +$t te

,ernel $nteract& +$t te re&t o" te OS v$a "unct$oncall&

• *' +ould one +ant to )u$ld a DS co(ponent tat$nteract& +$t te OS v$a $nclu&$on


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D$%re&&$on: Protect$on

I(ple(entat$on In te 5ernel# S'&te( call& are expen&$ve

# *' 6 Protect$on do(a$n&

# !e"re& (e(or' protect$on "ro( 'ourOS cla&&

# 7ood t$n%: +e %et (e(or' protect$on

# 8ad t$n%: cro&&$n% protect$on do(a$n&$& expen&$ve. *'

# So $& t$& te )e&t &olut$on


7/207CMPT 431 © A. Fedorova

Alternat$ve: Protect$on 9$a

Lan%ua%e# Sa"et' "eature& are %uaranteed )' lan%ua%erunt$(e

# Co(p$ler cec,& &a"e (e(or' acce&&

# In add$t$on tere are (an$"e&t& +.r.t. +at te

proce&& +$ll and +$ll not do

# T$& +a' 'ou %et protect$on

# And no need "or ard+are protect$on do(a$n& 6ever't$n% can run $n a &$n%le addre&& &pace

# S$n%ular$t': an OS "ro( M$cro&o"t $(ple(ented te&econcept&

# ... -nd d$%re&&$on



In"ra&tructure Prov$ded )' te

OS# et+or,$n%

6 Inter"ace to net+or, dev$ce&

6 I(ple(entat$on o" co((on protocol&: TPC;DP IP

# Proce&&e& and tread&

6 -



Te eed "or 7ood

Proce&&Tread Support

• Man' d$&tr$)uted appl$cat$on& are $(ple(ented u&$n%(ult$ple tread& or proce&&e&

• *'



Mot$vat$on "or Mult$treaded

De&$%n&# Server& prov$de acce&& to lar%e

data &et& 2+e) &erver& e/co((erce &erver&

# -ven $n te pre&ence o" cac$n%

te' o"ten need to do IO 2toacce&& 0le& on d$&, or a net+or,FS

# IO ta,e& (uc lon%er tanco(putat$on

# Overlapp$n% IO +$t co(putat$on

to $(prove re&pon&e t$(e# Tread& (a,e $t ea&' to overlap IO

+$t co(putat$on

# *$le one tread )loc,& on IOanoter can per"or( co(putat$on

Singlethread

Multiple

threads

1request

1.6requests



Proce&& or Tread Scedul$n%

# *$ll u&e >proce&&? and >tread? $ntercan%ea)l'6 A &$n%le/treaded proce&& (ap& to a ,ernel tread

6 -ac tread $n a (ult$treaded proce&& 2u&uall' (ap& to a

,ernel tread# A &ceduler dec$de& +$c tread run& next on te

CP;

# To en&ure %ood &upport "or DS co(ponent& a&ceduler (u&t:

6 8e &cala)le

6 8alance te load +ell

6 -n&ure %ood $nteract$ve re&pon&e

6 5eep context &+$tce& to a ($n$(u( 2+'



Ca&e Stud': Solar$&@ 1 OS

# Solar$& $& o"ten u&ed on &erver &'&te(&

# 5no+n "or $t& %ood &cala)$l$t' %ood load

)alanc$n% and $nteract$ve per"or(ance# *e +$ll loo, at Solar$& runqueues and

o+ te' are (ana%ed

6 A runqueue $& a &cedul$n% Bueue

6 A &tructure conta$n$n% po$nter& to runna)letread& 6 $.e. tread& tat are +a$t$n% "orCP;



!unBueue& $n Solar$&

7lo)al ,ernelpr$or$t' Bueue

kpqueue

;&er pr$or$t'Bueue& "or CP;

disp_q &

;&er pr$or$t'Bueue& "or CP;1

disp_q &

Pri

0

Pri

1

Pri

N

Pri

0

Pri

1

Pri

N

• Tere $& a u&er/level Bueue "or eac pr$or$t' level• A dispatcher run& te tread "ro( te $%e&t/pr$or$t' non/e(pt'

Bueue



Proce&&or Load 8alanc$n%

# Load )alanc$n% en&ure& tat te load $& evenl'd$&tr$)uted a(on% te CP;& on a (ult$proce&&or

# T$& $(prove& te overall re&pon&e t$(e

# Solar$& ,ernel en&ure& tat Bueue& are +ell )alanced+en $t enBueue& a tread $nto a runBueue

/*

* setbackdq() keeps runqs balanced such that the difference in length

* between the chosen runq and the next one is no more than RUNQ!"#$%&&'

* () */

A comment from Solaris source code. Source:ttp:cv&.open&olar$&.or%&ourcexre"onnvonnv/%ateu&r&rcut&co((ond$&pd$&p.c l$ne 1



Tun$n% Tread Pr$or$t$e& For

I(proved !e&pon&e T$(e# I" a tread a& +a$ted too lon% "or a proce&&or $t&

pr$or$t' $& elevated &o no tread $& &tarved

# Tread& old$n% cr$t$cal re&ource& are put to te front o"

te Bueue &o tat te' relea&e to&e re&ource& a&Bu$c,l' a& po&&$)le

/*

* ut the specified thread on the front of the dispatcher

* queue corresponding to its current priorit'

*

* +alled with the thread in transition, onproc or stopped state

* and locked (transition implies locked) and at high spl'* Returns with the thread in -.RUN state and still locked'

*/

A comment on setfrontdq from Solaris source code. Source:ttp:cv&.open&olar$&.or%&ourcexre"onnvonnv/%ateu&r&rcut&co((ond$&pd$&p.c l$ne 13E1



-n&ur$n% 7ood !e&pon&$vene&&

$n T$(e/Sar$n% Sceduler# Solar$&& t$(e/&ar$n% &ceduler 2te de"ault

&ceduler a&&$%n& pr$or$t$e& &o a& to en&ure %ood$nteract$ve per"or(ance

# T$(e&l$ce: te a(ount o" t$(e a tread can run onCP; )e"ore $t $& pre/e(pted

# I" tread T u&ed up $t& ent$re t$(e&l$ce on CP;:6 pr$or$t'2TG t$(e&l$ce2TH

# I" tread T a& %$ven up CP; )e"ore u&$n% up $t&t$(e&l$ce:6 pr$or$t'2T H t$(e&l$ce 2T G

# *' $& t$& done



T$(e/Sar$n% Sceduler:

An&+er&# M$n$($=$n% context &+$tc co&t&:

6 CP;/)ound tread& &ta' on CP; lon%er +$tout a context &+$tc

6 In co(pen&at$on te' are &ceduled le&& o"ten due to decrea&edpr$or$t'

6 !educ$n% te nu()er o" context &+$tce& $(prove& per"or(ance

# -n&ur$n% %ood re&pon&e "or $nteract$ve appl$cat$on&6 Interact$ve appl$cat$on& u&uall' dont u&e up te$r ent$re t$(e&l$ce

6 -xa(ple: proce&& a net+or, (e&&a%e and relea&e te CP; )e"orete t$(e&l$ce exp$re&

6 To&e appl$cat$on& +$ll ave te$r pr$or$t' elevated &o te' +$llre&pond Bu$c,l' +en re&pon&e $& needed 2e.%. te next net+or,pac,et arr$ve&



*at L$($t& Per"or(ance o"

MPMT Appl$cat$on&# Te co&t o" context &+$tc$n% 6 depend& on te

ard+are te OS cannot 0x $t alone

6 Savere&tore te re%$&ter&

6 Flu& te CP; p$pel$ne6 I" &+$tc$n% addre&& &pace&

# Ma' need to Ju& te TL8 2depend& on te proce&&or

# Ma' need to Ju& te cace 2depend& on te proce&&or

# Te co&t o" $nter/proce&& co((un$cat$on2IPC: reBu$re&

context &+$tc$n%# Te co&t o" $nter/tread &'ncron$=at$on 6 )' and lar%e

depend& on te pro%ra( &tructure OS can 0x &o(e o"$t )ut not all



Tread S'ncron$=at$on

I" loc, $& not ava$la)le

tread& +a$t

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