CPU scheduling is
to
basis of multiprogrammed operating systems. In a singleprocessor system , only one process can run at...
A process is executed until it must wait
typically for completion of I/O. In a simple
computer system, the CPU then just s...
Whenever the CPU becomes idle, the OS must
select one of the processes in the ready
queue to be executed. This is done by ...






CPU utilization
Throughput
Turn around time
Waiting time
Response time
It is desirable to maximize CPU utilizat...



Preemptive scheduling
Non-preemptive scheduling





First- Come, First –Served Scheduling.
Shortest Job First Scheduling.
Priority Scheduling.
Round Robin Scheduling...


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The process that requests the CPU first is
allocated CPU first.
Simplest of all.
Non-preemptive in nature.



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When the CPU is available , it is assigned to
the process having smallest CPU burst.
SJF is optimal.
Can be preemp...





A priority is associated with each process and
CPU
is allocated to the process having
highest priority.
Can be pre...





Is used in time shared systems.
A small unit of time, called as time quantum
is defined(10-100 ms).
The ready queu...
Scheduling
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Scheduling

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Scheduling

  1. 1. 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.
  2. 2. 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.
  3. 3. 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.
  4. 4.      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.
  5. 5.   Preemptive scheduling Non-preemptive scheduling
  6. 6.     First- Come, First –Served Scheduling. Shortest Job First Scheduling. Priority Scheduling. Round Robin Scheduling.
  7. 7.    The process that requests the CPU first is allocated CPU first. Simplest of all. Non-preemptive in nature.
  8. 8.    When the CPU is available , it is assigned to the process having smallest CPU burst. SJF is optimal. Can be preemptive or non-preemptive.
  9. 9.    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.
  10. 10.    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.

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