EC503 –

OPERATING

SYSTEM

4.0 RESOURCE MANAGEMENT

Explain how the queuing

routine and the scheduler work

together to load application

programs.

Pn. Nin Hayati binti

Mohd Yusoff

Processor Management Processor management is responsible

for managing the processor’s time efficiently

Multiprogramming

Time-Sharing

Scheduling and Queuing

Spooling

Deadlock

When one job needs to wait for I/O, the processor switches to

another job.

Maximize the throughput (run time divided by elapsed time)

and minimize turnaround time (the time between job

submission and job completion).

When multiple users access the system through terminals, the processor’s time needs to be shared among them. - fair to every one

Minimize the response time to each user. - interactive processing

Most time-sharing systems use roll -in/roll-out memory technique to manage memory

Dispatching

Time-slicing (A program is set to wait state if it uses up its time slice which is perhaps 0.001 second.)

Polling (based on a round-robin table, or some priority algorithms)

Processor management is concerned with the internal

priorities of programs already in memory.

A program's internal priority is a dif ferent issue.

As one program finishes processing and space

becomes available , which program is loaded into memory

next?

This decision typically involves two separate modules, a

queuing routine and a scheduler .

As programs enter the system they are placed on a queue by

the queuing routine (Figure below). When space becomes

available, the scheduler selects a program from the queue

and loads it into memory.

Queuing

routine Job

Queue

Programs

A. When a program first enters a

multiprogramming system, a queuing

routine copies to queue.

Scheduling

routine Job

Queue Program partition

Program partition

B. later, when space becomes available,

the scheduling routine loads a program

from the queue into memory

Generally, the first program on the queue is loaded

first, but more sophisticated priority rules can be used.

Sometimes, more than one queue is maintained.

Often, a program is placed on a particular queue based on its

resource needs; for example, programs requiring magnetic

tape or special printer forms can be separated from those

calling for more normal setup. Grouping programs with

similar resource needs simplifies scheduling.