Scheduling Algorithms in OS

Imagine you are the conductor of a big orchestra, skillfully organizing and leading a beautiful mix of different instruments. Every musician looks to you for signs when it's their turn to play, so everything happens smoothly, creating an interesting performance. Scheduling algorithms in OS are precisely like this maestro. They guide how processes and threads get executed efficiently, similar to how an orchestra conductor manages musicians playing different instruments during a performance. 

Being someone who loves operating system design, I am excited to guide you into the interesting world of scheduling algorithms in OS. Prepare yourself to learn how your computer works so smoothly. We’ll look at various scheduling algorithms in OS with examples so that you’re not left with any doubts or confusion at all! 

What Are Scheduling Algorithms in OS?

The core part of any operating system consists of scheduling algorithms in OS, which decide how system resources like CPU time and I/O devices are distributed among processes and threads contending for them. These algorithms play a crucial role in deciding which tasks should be executed at what time, for how much duration, and the order they will follow. The main aim is to enhance overall system performance while maximizing the utilization of resources and guaranteeing just handling of all processes.

All in all, the scheduling algorithms in OS are like traffic controllers for the computing world. They handle how execution moves, ensuring every process receives its equal portion of CPU time, and no one process overuses system resources. These algorithms use smart tactics and rules to cut down waiting periods, lower response delays, and stop starving scenarios from happening.

Types Scheduling Algorithms in OS with Examples

In OS, scheduling algorithms for operating systems are used to manage and arrange the running of processes. Let’s look at different types of scheduling algorithms in OS with examples that have been designed to handle various scenarios or requirements. 

Disk Scheduling Algorithms in OS

Disk scheduling algorithms in OS are used to improve the order and timing of disk I/O operations. The goal is to reduce seek time and rotational latency, which has a large impact on the performance of storage systems. A few well-known disk scheduling algorithms are:

1. First In, First Out (FIFO): Requests are handled in the sequence they were made. This method is plain and simple to implement, but it may produce high seek times for certain workload patterns. 
2. Shortest Seek Time First (SSTF): The request that is closest to the current position of the disk head gets served first. This method aims to minimize seek time, but it can result in starvation for some requests.
3. SCAN: The arm of the disk moves in one direction only and serves all requests coming up along its path. When an end is reached, it reverses direction and starts servicing those requests in reverse order too. This method prevents starvation for any request and provides balanced performance. 
   

Round Robin Scheduling Algorithms in OS

The round robin scheduling algorithms in OS is a classic technique for CPU scheduling in operating systems. It works by giving time slices to every process in a cyclic manner, making sure of fairness with the distribution of CPU time. The way it functions can be understood through these steps:

1. A certain time quantum (time slice) is assigned to every process for it to run.
2. When a process uses up its time quantum, it gets preempted, and the CPU is given to the next process in line.
3. The process that got preempted is placed at the tail of the ready queue, waiting for its next turn to come.
4. This cycle continues, giving each process an equal share of CPU time.

The round robin scheduling algorithms in OS is particularly appreciated for their simplicity and justice, which makes it top choice among time-sharing systems.

CPU Scheduling Algorithms in OS

The CPU scheduling algorithms in OS are the ones that decide which process or thread should be next to run on the CPU at each moment. These algorithms have a goal to make sure maximum utilization of the CPU is achieved, response time is kept minimum and fair distribution of resources from it happens. Some popular types of CPU scheduling algorithms are:

1. First-In, First-Out (FIFO): Processes are executed in the same sequence they enter the ready queue. This method for scheduling algorithms in OS is simple to understand and implement, but it can result in a problem known as "starvation" if short processes wait behind long ones.
   

2. Shortest Job First (SJF): The process that has the shortest estimated execution time is scheduled initially. This algorithm gives good results for average waiting time, but it needs exact predictions about how long each task will take.
   

3. Priority Scheduling: Every process gets a priority, and the CPU is given to the process with the highest priority. Priority can be influenced by multiple factors, such as importance, resource needs, or criteria set by the user.
   

4. Multilevel Queue Scheduling: In this method, processes are put into several queues according to their nature, such as foreground or background, system or user, and interactive or batch. Every queue has its personal scheduling algorithm, and the CPU is assigned to queues based on set priorities.

If you want to learn more about CPU scheduling algorithms and how they are put into practice, I suggest checking out the diverse array of courses offered by upGrad. These courses cover both the theoretical and the practical aspects of these concepts, thereby ensuring you come out with a well-rounded understanding! 

Now, let’s look at real time scheduling algorithms in OS.

Real Time Scheduling Algorithms in OS

Real time scheduling algorithms in OS are particularly made to match the strict timing restrictions of real-time systems, where tasks must finish within set deadlines. These algorithms give more importance to predictability and determinism than other factors. A few popular real-time scheduling algorithms are:

1. Rate Monotonic Scheduling (RMS): In this method, tasks are given priority based on their periods. Shorter periods mean higher priority. RMS is best for periodic tasks with fixed execution times.
   

2. Earliest Deadline First (EDF): The EDF method arranges tasks according to their deadlines, with the task with the smallest deadline receiving top priority. This approach is considered optimal for periodic tasks with changing execution durations.
   

3. Least Laxity First (LLF): In LLF, we consider laxity as the gap between a task's deadline and its remaining execution time. This method gives priority to tasks that have the least amount of laxity, emphasizing those with the smallest laxity first.

Real-time scheduling algorithms are vital in fields like aerospace, automotive systems, and industrial control, where meeting deadlines is crucial.

Concluding Remarks

Scheduling algorithms in OS are evidently very important for handling process and thread execution. They make sure that system resources are used effectively, improving overall performance of the computer. The algorithms manage different types of scheduling tasks from disk to CPU and real-time activities too. They use many strategies to solve problems in concurrent or competing tasks situations.

When one starts their learning journey towards becoming an expert in operating system design, it is crucial that they comprehend scheduling algorithms in OS, along with different types like disk scheduling algorithms in OS, round robin scheduling in OS, CPU scheduling algorithms in OS, real time scheduling algorithms in OS, and more. The suitable use of these algorithms in different situations can help establish systems that are flexible, quick to respond, and able to manage a variety of workloads.

For those excited about learning more and investigating the details of operating system design, upGrad's numerous technical courses would be a great recommendation. Whether it is computer science, software engineering, or other similar fields, upGrad has complete educational routes to assist you in understanding this captivating domain of operating systems.

So, embrace the influence of scheduling algorithms in OS and be amazed by the arrangement of processes and threads that maintain our digital world's harmony. Enjoy your scheduling, and may your systems always discover just the right beat!

FAQs

1. What is a scheduling algorithm in OS?

An OS scheduling algorithm is a group of guidelines and steps that decide the sequence and timing for executing a process or thread. Its goal is to improve the system's performance by using resources optimally.

2. What are the primary objectives of scheduling algorithms?

The main goals for scheduling algorithms include maximizing the use of CPU, decreasing response time, fairly distributing resources and fulfilling special needs of the system like real-time limits or user preferences.

3. What are the common scheduling algorithms used in operating systems?

Scheduling algorithms that are normally used in operating systems are First-Come, First-Served (FCFS), Shortest Job First (SJF), Priority Scheduling, Round Robin, Multilevel Queue Scheduling, and real-time scheduling algorithms, including Rate Monotonic Scheduling (RMS) and Earliest Deadline First (EDF).

4. What are the 5 scheduling algorithm types?

The five main scheduling algorithm types are:

• First-Come, First-Served (FCFS)
• Shortest Job First (SJF)
• Priority Scheduling
• Round Robin
• Multilevel Queue Scheduling
  

5. Which scheduling algorithm is best?

The title "best" scheduling algorithm isn't accurate since it relies on the system's particular needs and features. Various algorithms perform well in different situations, like maximizing average wait time, guaranteeing fairness, meeting actual-time limits, or balancing response and throughput.

6. What is the first scheduling algorithm?

The First-Come, First-Served (FCFS) algorithm is frequently known as a basic and easy scheduling method. It handles processes in the sequence they come, with no preemption or priority involved.

7. How do operating systems select the most appropriate scheduling algorithm?

The most suitable scheduling algorithm for operating systems depends on various things like workload type, system purposes, resources that can be used and performance needs. The decision might also relate to what kind of system it is: batch processing system, interactive, or real-time systems.

8. Which is a preemptive scheduling algorithm?

A preemptive scheduling algorithm is a method where the operating system can stop the process or thread from running before it finishes, using particular conditions like priority or time quantum expiration. Examples of preemptive scheduling algorithms are Round Robin, Shortest Remaining Time First (SRTF), and Priority Scheduling with Preemption.