2. CPU scheduling is
to
basis of multiprogrammed operating systems. In a singleprocessor system , only one process can run at a
time until the CPU is free and can be
rescheduled.The objective of multiprogramming
is to have some process running at all times. To
maximum CPU utilization.
3. A process is executed until it must wait
typically for completion of I/O. In a simple
computer system, the CPU then just sits idle.
All the waiting time is wasted as no useful
work is done. With multiprogramming we try
to use
this time productivity. Several
processes are kept in the memory at one
time. When one process has to wait . The
operating system takes away CPU and give it
to another one.
4. Whenever the CPU becomes idle, the OS must
select one of the processes in the ready
queue to be executed. This is done by short
term scheduler. Scheduler uses various
scheduling algorithms, To select process
from ready queue and let it to be executed.
5.
CPU utilization
Throughput
Turn around time
Waiting time
Response time
It is desirable to maximize CPU utilization
and throughput and to minimize turnaround
time, waiting time and response time.
7.
First- Come, First –Served Scheduling.
Shortest Job First Scheduling.
Priority Scheduling.
Round Robin Scheduling.
8.
The process that requests the CPU first is
allocated CPU first.
Simplest of all.
Non-preemptive in nature.
9.
When the CPU is available , it is assigned to
the process having smallest CPU burst.
SJF is optimal.
Can be preemptive or non-preemptive.
10.
A priority is associated with each process and
CPU
is allocated to the process having
highest priority.
Can be preemptive or non-preemptive.
Suffers from problem of starvation.
11.
Is used in time shared systems.
A small unit of time, called as time quantum
is defined(10-100 ms).
The ready queue is treated as circular queue
and CPU scheduler goes around it ,allocating
CPU to each process for a tome interval upto
one quantum.
