Scheduling policies and priorities

Overview

First come first served scheduling, shortest job first and round robin scheduling.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is first come first served scheduling?

   Model answer

   Processes are given the processor in the order they arrive and run to completion.

2. 2

   Give one disadvantage of first come first served.

   Model answer

   A long job at the front delays every short job behind it, which gives poor average response.

3. 3

   What is shortest job first?

   Model answer

   The process with the smallest estimated runtime is selected next.

4. 4

   Give one advantage and one disadvantage of shortest job first.

   Model answer

   It minimises average waiting time, but a long job may be starved if short ones keep arriving, and runtimes must be estimated in advance.

5. 5

   What is round robin scheduling?

   Model answer

   Each ready process is given the processor for one time slice in turn, returning to the back of the queue if unfinished.

6. 6

   Why is round robin well suited to an interactive system?

   Model answer

   Every process receives the processor regularly, so all users see a response within a predictable time.

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