Process Management - Information Technology - Lecture Slides, Slides of Information Technology

Download Process Management - Information Technology - Lecture Slides and more Slides Information Technology in PDF only on Docsity!

Topic

:^ Process

Management

Index

Process

Concept

Process

states

Process

Control

Block

Processes

Scheduling

Schedulers Scheduling

Algorithms

Operations

on^ Processes

Process

Creation

Process

Termination

Process

States

^ Contains

information associated

with^ each

process ^ Process

State^ ‐

e.g.^ new, ready,^ running

etc. ^ Process

Number

• Process

ID ^ Program

Counter

‐ address

of^ next instruction

to^ be executed  CPU^ registers

‐^ general purpose

registers,

stack pointer

etc.

Process

Control

Block

Process

Control

Block

(Cont..)

^ CPU scheduling information

‐^ process

priority, pointer  Memory

Management

information

base/limit information  Accounting

information

‐^ time

limits,

process number  I/O^ Status

information

‐^ list

of^ I/O

devices allocated

Schedulers

^ Long

‐term^ scheduler

(or^ job

scheduler)

^ selects

which processes

should

be^ brought

into^ the

ready^

queue. ^ invoked

very^ infrequently

(seconds,

minutes);

may^ be

slow. ^ controls

the^ degree

of^ multiprogramming

^ Short

term^

scheduler

(or^ CPU

scheduler)

^ selects

which

process

should

execute

next

and^ allocates

CPU.

^ invoked

very^ frequently

(milliseconds)

must^ be

very^ fast ^ Medium

Term Scheduler ^ swaps

out^ process

temporarily

^ balances

load^ for

better

throughput

Schedulers

(Cont..)

Scheduling Criteria(Cont..)  Waiting time

— It is define as the time spent by the process in the ready queue .waiting timeshould be small.  Response time

— It is define as the time when the first response start coming. It should also beas small as possible.

Scheduling Criteria(Cont..)^ ^ Max

CPU^ utilization

^ Max

throughput

^ Min^

turnaround

time

^ Min^

waiting

time

^ Min^

Response

time

Types

of^ CPU

Scheduling

(cont..)

^ A scheduling discipline is

non‐

preemptive

if, once a process has been given the CPU, theCPU cannot be taken away from that process.  In^ nonpreemptive

system, ‐^ short

jobs^ are

made^ to

wait^ by

longer^

jobs^ but

the

overall^

treatment

of^ all^ processes

is^ fair.

‐a^ scheduler

executes

jobs^ in

the^ following

two

situations.^ ^ When

a^ process

switches

from^ running

state^ to

the

waiting

state. ^ When

a^ process

terminates.

Types

of^ CPU

Scheduling

(cont..)

^ A^ scheduling

discipline

is^ preemptive

if,

once^ a

process

has^ been

given

the^ CPU

can

taken^

away.

FCFS

(First

Come

First

Serve

^ Implementation:^ ^ As

each^ process

becomes

ready,

it^ joins

the

ready^ queue.  When

the^ current

process

finishes

the^ oldest

process

is^ selected

next.

^ Characteristics:^ ^ Simple

to^ implement ^ Nonpreemptive

FCFS

^ EXAMPLE :

Process

Burst Time

P^

8

P^

4

P^

9

P^

5

0

8

12

21

26

Average

wait^ =(0+8+12+21)/

=^ 10.

P^

P^

P^

P