20 Scheduling Algorithms Interview Questions and Answers

Scheduling algorithms are used to determine how best to allocate resources in order to achieve specific goals. In an interview, you may be asked questions about scheduling algorithms in order to gauge your understanding of the subject. Answering these questions correctly can help you demonstrate your skills and knowledge, and land the job you want. In this article, we will review some of the most commonly asked questions about scheduling algorithms.

Scheduling Algorithms Interview Questions and Answers

Here are 20 commonly asked Scheduling Algorithms interview questions and answers to prepare you for your interview:

1. Can you explain the different scheduling algorithms?

There are a few different types of scheduling algorithms. The most common are first come first serve, shortest job first, and priority scheduling. First come first serve is exactly what it sounds like- the first process that arrives is the first one to be scheduled. Shortest job first is similar, but instead of being based on arrival time, it is based on the length of the process. Priority scheduling is a bit more complex- each process is assigned a priority, and the scheduler will run the process with the highest priority first.

2. What’s your understanding of non-preemptive scheduling?

Non-preemptive scheduling is a type of scheduling algorithm where once a process has started, it cannot be interrupted until it has finished. This can be contrasted with preemptive scheduling, where a process can be interrupted at any time.

3. What are some examples of real-world applications that use non-preemptive scheduling?

Non-preemptive scheduling is often used in applications where the order of execution is important, such as in audio or video processing. Another example is when multiple processes are accessing the same resource, like a printer, and it is important to avoid process starvation.

4. What is a context switch and how does it impact performance?

A context switch is the process of storing and restoring the state of a process or thread so that it can be resumed at a later time. Context switches are usually initiated by the kernel when a process or thread needs to be suspended or resumed. Context switches can have a significant impact on performance because they can introduce a significant amount of overhead.

5. How can you determine the processor utilization if all processes have equal priority?

In order to determine the processor utilization if all processes have equal priority, you will need to look at the total amount of time that each process spends running. This can be done by looking at the total amount of time that each process spends in the ready queue, as well as the total amount of time that each process spends running. By adding these two values together, you will be able to get an accurate measure of the processor utilization.

6. What are the goals of process scheduling?

The goals of process scheduling are to ensure that the processes are executed in a timely manner and that the resources of the system are used efficiently.

7. What do you understand about deadlock situations? How can they be avoided?

A deadlock situation is one where two or more processes are waiting on each other to release a resource before they can continue. This can lead to a situation where the processes are effectively frozen, as each is waiting on the other to make a move.

One way to avoid deadlock situations is to use a scheduling algorithm that prevents processes from holding on to resources for too long. Another way to avoid deadlock is to have a process that periodically checks for and releases resources that are no longer being used.

8. Can you give me an example of when an FCFS algorithm would be useful?

FCFS is often used when scheduling processes that have mutually exclusive resources, like a printer. In this case, it is more important to finish the process quickly rather than worry about response time, so FCFS is a good choice.

9. What are some limitations of using an FCFS algorithm?

FCFS can cause starvation if there are processes with very long run times. Additionally, FCFS can lead to convoy effects, where a long process can cause a number of shorter processes to have to wait a long time.

10. What types of resources can cause a deadlock situation?

A deadlock situation can occur when there are two or more processes that are each holding a resource and waiting to acquire a resource that is being held by the other process. This can happen with any type of resource, but is most commonly seen with computer resources like processors, memory, or files.

11. What are the three conditions required for a deadlock to occur?

The three conditions required for a deadlock to occur are:

1. Mutual exclusion: There must be some resource that can only be used by one process at a time.
2. Hold and wait: A process must be holding on to a resource while waiting to acquire another resource.
3. No preemption: A process cannot release a resource voluntarily.
4. Circular wait: There must be a cycle of processes, each holding on to a resource that the next process in the cycle is waiting to acquire.

12. What is starvation in the context of scheduling algorithms?

Starvation is a problem that can occur with scheduling algorithms. It happens when a process is unable to gain access to the CPU because it is continually being preempted by other processes. This can lead to the process never getting a chance to run, and as a result, it can starve to death.

13. What is the best way to avoid starvation?

One of the best ways to avoid starvation is to use a priority-based scheduling algorithm. This type of algorithm ensures that the most important tasks are always given priority, which helps to prevent lower priority tasks from being starved for resources. Another way to avoid starvation is to use a round-robin scheduling algorithm, which ensures that each task is given a fair share of resources.

14. What is preemptive scheduling?

Preemptive scheduling is a type of scheduling algorithm where the scheduler can interrupt a running process in order to run a higher priority process. This can be contrasted with non-preemptive scheduling, where the scheduler will only run processes that are already waiting in the queue.

15. What are the problems with preemptive scheduling?

Preemptive scheduling can lead to issues with program stability and data corruption, as one process can be interrupted at any time by another process with a higher priority. This can cause problems if the first process was in the middle of writing to or reading from a file, for example, as the data may be left in an inconsistent state. Additionally, context switching between processes can be expensive in terms of time and resources, so if processes are being preempted frequently it can lead to performance issues.

16. What do you know about Round Robin scheduling?

Round Robin scheduling is a type of scheduling algorithm where each process is given a set amount of time to run (called a time slice) and then is preempted and added to the end of the queue. This process repeats until all processes have finished. Round Robin is often used in real-time systems where it is important to guarantee that all processes get a fair amount of time to run.

17. Why is round robin scheduling difficult to implement on platforms like Linux?

Round robin scheduling is difficult to implement on Linux because of the way that the Linux kernel is designed. The Linux kernel is a preemptive kernel, meaning that any process can be interrupted at any time by another process with a higher priority. This can cause issues with round robin scheduling, because it is difficult to guarantee that each process will get an equal amount of time if they can be interrupted at any time.

18. What are the advantages of round robin over FIFO scheduling?

Round robin scheduling has a few advantages over FIFO scheduling. First, round robin is more fair, because each process gets a turn in the CPU. Second, round robin is more efficient, because processes that can finish quickly do not have to wait for slower processes to finish. Finally, round robin is more flexible, because it can be adapted to different types of workloads.

19. When should you use SJF as opposed to other scheduling algorithms?

SJF, or Shortest Job First, is a scheduling algorithm that is used when the goal is to minimize the amount of time it takes for all jobs to be completed. This is in contrast to other algorithms, which may prioritize other factors such as fairness or throughput. SJF is most effective when the runtime of each job is known in advance, as this allows for more accurate predictions to be made. If the runtimes are not known, then SJF can still be used, but it may not be as effective.

20. When should you not use SJF?

SJF (Shortest Job First) is an algorithm that schedules jobs based on their estimated run-time. The idea is that the shorter the job, the sooner it should be run. However, there are a few situations where SJF may not be the best choice.

If the run-times of the jobs are not known in advance, then SJF will not work well, since it is basing its decisions on estimates. In addition, SJF can be unfair to longer-running jobs, since they will always be scheduled after shorter jobs, even if they are ready to run sooner. Finally, SJF can be inefficient if the run-times of the jobs vary greatly, since it will often end up rescheduling jobs as new information about their run-times becomes available.