Scheduler in operating system

Schedulers play an important role in operating systems. They are responsible for managing system resources and ensuring that processes are executed efficiently. A scheduler is a software component that is responsible for allocating system resources to processes. In this article, we will discuss the types of schedulers, their advantages, and disadvantages.

Types of Schedulers

Schedulers can be divided into three types:

1. Long-Term Scheduler
2. Medium-Term Scheduler
3. Short-Term Scheduler

Long-Term Scheduler

The long-term scheduler is also known as the job scheduler. It is responsible for selecting which processes should be admitted to the system for processing. This scheduler selects processes from the pool of waiting processes and assigns them to the short-term scheduler. The long-term scheduler is responsible for maintaining a balance between CPU utilization and I/O device utilization. It determines which processes should be placed in the ready queue for execution.

Advantages of Long-Term Scheduler:

• It maintains a balance between CPU utilization and I/O device utilization.
• It ensures that the system is not overloaded with too many processes.
• It ensures that the system is not underutilized with too few processes.

Disadvantages of Long-Term Scheduler:

• It can cause delays in process execution as processes have to wait to be admitted to the system.
• It can lead to the creation of long queues of processes waiting to be admitted to the system.

Medium-Term Scheduler

The medium-term scheduler is responsible for managing the degree of multiprogramming. This scheduler determines which processes should be swapped out of main memory to secondary memory to free up space for other processes. It also determines which processes should be swapped in from secondary memory to main memory. The medium-term scheduler is responsible for controlling the degree of multiprogramming to optimize the use of system resources.

Advantages of Medium-Term Scheduler:

• It optimizes the use of system resources.
• It reduces the chances of memory overflow.

Disadvantages of Medium-Term Scheduler:

• It can cause delays in process execution as processes have to wait to be swapped in or out of main memory.
• It can lead to an increase in the overhead associated with swapping processes in and out of main memory.

Short-Term Scheduler

The short-term scheduler is responsible for selecting which process should be executed next. This scheduler selects processes from the ready queue and assigns them to the CPU for execution. The short-term scheduler is responsible for maintaining a balance between CPU-bound and I/O-bound processes.

Advantages of Short-Term Scheduler:

• It ensures that processes are executed efficiently.
• It maintains a balance between CPU-bound and I/O-bound processes.

Disadvantages of Short-Term Scheduler:

• It can cause delays in process execution as processes have to wait to be assigned to the CPU.
• It can lead to a decrease in the overall system performance due to the overhead associated with context switching.

Advantages of Schedulers

Schedulers play an important role in operating systems, and they offer several advantages:

1. Optimized Resource Utilization: Schedulers ensure that system resources are used efficiently, and there is no wastage of resources.

2. Process Prioritization: Schedulers assign priorities to processes, which ensures that critical processes are executed first.

3. System Stability: Schedulers ensure that the system remains stable by managing system resources and preventing processes from causing system crashes.

4. Multitasking: Schedulers allow the system to perform multiple tasks simultaneously, which increases productivity.

Disadvantages of Schedulers

Schedulers also have some disadvantages:

1. Overhead: Schedulers incur overhead due to context switching, which can reduce system performance.

2. Complexity: Schedulers are complex software components that require significant resources to develop and maintain.

3. Latency: Schedulers can cause delays in process execution, which can lead to increased latency and decreased system performance.

4. Fairness: Schedulers may not always be fair in assigning resources to processes, which can lead to some processes receiving more resources than others.

5. Unpredictability: The behavior of schedulers can be unpredictable, which can make it difficult to determine how the system will respond to different loads.

Conclusion

Schedulers play an important role in operating systems by managing system resources and ensuring that processes are executed efficiently. There are three types of schedulers: long-term, medium-term, and short-term, each with its own advantages and disadvantages. Schedulers offer several advantages, including optimized resource utilization, process prioritization, system stability, and multitasking. However, they also have some disadvantages, including overhead, complexity, latency, fairness, and unpredictability. Overall, schedulers are an essential component of operating systems, and their benefits outweigh their drawbacks.