What is a Long term Scheduler?

What is a scheduler?

A scheduler is a component of an operating system that determines the order in which processes are executed on the system's resources, such as the CPU, memory, and I/O devices. The scheduler's primary role is to manage and allocate system resources efficiently to ensure that the system is responsive, efficient, and runs smoothly.

There are different types of schedulers in an operating system, including the long-term scheduler, the short-term scheduler, and the medium-term scheduler. Each of these schedulers performs a specific function to ensure that the system runs efficiently and smoothly.

Long term scheduler

A long-term scheduler, also known as a job scheduler or admission scheduler, is a component of an operating system that selects which processes should be admitted into the system for execution from the pool of submitted processes.

The long-term scheduler is responsible for managing the overall system resources and decides which processes are allowed to enter the system based on the available resources, such as memory, CPU, and I/O devices. It determines which processes are important for the system and should be executed, and which ones can be deferred to a later time.

The long-term scheduler helps maintaining a balanced load on the system by controlling the number of processes admitted into the system at a given time. It aims to maximize system throughput and resource utilization while keeping the system responsive and avoiding resource exhaustion.

The long-term scheduler is typically invoked whenever a new process is submitted to the system or when a running process terminates. It evaluates the submitted processes, selects the ones that should be admitted into the system, and assigns them to the appropriate resources, such as memory, CPU, and I/O devices, for execution.

Function of a long term scheduler

The long-term scheduler performs the following functions:

• It determines which processes should be admitted into the system based on the available resources, such as memory, CPU, and I/O devices.
• It balances the load on the system by controlling the number of processes admitted into the system at a given time.
• It maximizes system throughput and resource utilization while keeping the system responsive and avoiding resource exhaustion.
• It assigns the admitted processes to the appropriate resources, such as memory, CPU, and I/O devices, for execution.
• It keeps track of the status of the admitted processes and decides when they should be moved from a blocked state to a ready state for execution.
• It determines when a process should be terminated, either because it has completed its task or because it is no longer needed.

In summary, the long-term scheduler is responsible for ensuring that the system runs efficiently by controlling the number of processes admitted into the system, optimizing resource utilization, and keeping track of the status of the admitted processes.

Why do we use Long term scheduler?

We use a long-term scheduler in an operating system for several reasons:

Resource Management: The long-term scheduler is responsible for managing the system resources by deciding which processes should be admitted into the system for execution. It ensures that the available resources are optimally utilized by selecting only those processes that the system can handle.

Load Balancing: The long-term scheduler helps balance the load on the system by controlling the number of processes admitted into the system at any given time. By keeping the number of processes in check, it ensures that the system runs smoothly and does not become overloaded.

System Throughput: The long-term scheduler maximizes the system throughput by selecting processes that can make the best use of the available resources. By prioritizing the processes that need to be executed first, it ensures that the system is working on the most important tasks.

Prioritization: The long-term scheduler helps prioritize processes by deciding which ones should be admitted into the system first. By selecting the most important processes, it ensures that critical tasks are completed in a timely manner.

Fairness: The long-term scheduler ensures fairness by giving each process an equal chance to be admitted into the system. It does not favour any particular process or user, which helps to ensure that the system is working for the benefit of everyone.

Limitation of long term scheduler

The long-term scheduler, like any component of an operating system, has certain limitations. Some of the limitations of the long-term scheduler include:

• Limited Control: The long-term scheduler has limited control over the system resources, as it only determines which processes are admitted into the system for execution. It does not have control over the actual allocation of resources or the scheduling of processes on those resources.
• Slow Response Time: The long-term scheduler has a slow response time because it decides which processes to admit into the system. It takes time to select processes based on resource availability, which can lead to slow system response times.
• Inefficient Resource Utilization: The long-term scheduler can lead to inefficient resource utilization if it admits too many processes into the system. This can result in resource starvation, where some processes do not get enough resources to execute efficiently.
• Limited Process Prioritization: The long-term scheduler has limited process prioritization capabilities, as it only determines which processes should be admitted into the system. It does not prioritize processes based on their importance or urgency, which can lead to delays in critical processes.
• System Overhead: The long-term scheduler can create system overhead by constantly admitting and terminating processes. This can slow down the system and reduce its overall performance.