An Operating System has many tasks lined up every minute. It is designed to connect all the programs and execute task offers. Process Scheduling is an essential task for an Operating System.
The Operating System Processes different tasks in different states; ready, running and waiting.
The critical reason for process scheduling is it allows the operating system to allocate specific time intervals of the processor for every process. The main task of process scheduling is to keep the processor working seamlessly to experience minimum wait time for all the programs.
There are three process states: Running, Waiting, and Ready. Process scheduling has different queues for different conditions. All the tasks with similar forms are directed to the same line. If any of the tasks’ state is changed, it shifts to the corresponding queue.
There are three categories of queues available for process scheduling. They are the job queue, ready queue, and device queue. The processes of the system are stored in the job queue.
The ready queue lines up all the tasks waiting to be executed, while the Device queue takes care of the peripherals and internal system devices.
- A short-term or CPU scheduler allocates system resources to processes ready to execute. In contrast, a long-term scheduler, also known as a job scheduler, determines which processes should be admitted to the system.
- Short-term scheduler focuses on maximizing CPU utilization and minimizing wait time for processes. In contrast, a long-term scheduler focuses on ensuring the system is manageable with only a few processes simultaneously.
- Short-term and long-term schedulers are important in managing system resources and ensuring efficient performance.
Short Term vs Long Term Scheduler
Short term scheduler selects the process from the ready queue which needs to be executed. The process is sent by the short term scheduler to the CPU. CPU scheduler is another name of short term scheduler. Long term scheduler place the process in the ready queue. Job scheduler is another name of a long term scheduler.
Schedules work in tandem to facilitate process scheduling. Short-term and Long-term Schedulers are the system software that handles the process scheduling effectively.
|Parameter of Comparison||Short–Term Scheduler||Long-Term Scheduler|
|Task||It selects the process from the Ready queue to send to the CPU.||The process is selected from the job pool and passed to the ready queue.|
|Frequency||The frequency of short-term scheduling is more.||The long-term scheduler is not as frequent as a short-term one in scheduling the process.|
|Control of Multi-Programming||Short-term Scheduler has less control over multi-programming.||Long-term Scheduler has control over the multi-programming.|
|Time-Sharing System||Short-term Schedulers have minimal presence in a time-sharing system.||The long-term scheduler is not available in the time-sharing system.|
|Name Alternative||It is otherwise called as CPU Scheduler.||It is otherwise called as Job Scheduler.|
What is Short Term Scheduler?
Short-term Scheduler is system software that selects the processes from the ready queue and sends them to the Processor for execution. Short-term Scheduler is otherwise called as CPU Scheduler.
In the time-sharing system, Short term scheduler is minimally present. The short-term scheduler’s execution happens often and is more frequent than the long-term one.
The degree of multiprogramming is also limited, and has less control over it. A short-term scheduler uses an algorithm that decides which process shall be scheduled for execution.
The execution of the processes takes a few milliseconds, which is one reason why it is more frequent than the long-term scheduler. The algorithm that decides the procedures to be selected is of prime importance as it decides which to go next.
The process with a long waiting time must be selected from the ready queue. That means that once a method is selected, all the other functions shall wait for their turn.
If the short-term scheduler makes a mistake in choosing a process with a long burst time, there will be an error called starvation.
Starvation is a short-term scheduler’s fault in taking the correct process into execution. This can be observed in file opening delays and opening a program asked for.
What is Long Term Scheduler?
The long-term scheduler is system software that selects the process from the job pool and ejects it to the ready queue for further process by the short-term scheduler.
There are many instances where many programs are submitted for execution, and many times, executing all the tasks immediately is not possible.
These tasks are stored in a pool called the job pool. The charges shall be waiting for their turn while the long-term scheduler selects the process with a long wait time and sends it to the ready queue for execution.
The long-term scheduler is otherwise called a Job scheduler. The frequency of the long-term scheduler’s process is less when compared to the short-term scheduler.
Unlike the short-term scheduler, the long-term scheduler manages multi-program versatilely. It is the one that separates the programs as per the timeline and feeds them to the ready queue.
The long-term scheduler is more responsible for selecting the processes and keeping the Input/ Output and the processor-bound tasks in line. This ensures optimum system throughput and proper functionality too.
It is to be understood that the main task of the long-term scheduler is to provide mixed jobs to the ready queue. The short-term scheduler further selects this for its execution.
Main Differences Between Short-Term and Long-Term Schedulers
- The main difference between Short-term Scheduler and Long Term Scheduler is the short-term scheduler selects the processes from the ready queue one by one and feeds them to the CPU for further execution. In contrast, the Long-term scheduler selects the techniques from the mass storage of tasks called job pool and sends it to the ready queue.
- Short-term Scheduler is more frequent in selecting the processes from the ready queue than the long-term scheduler from the job pool.
- A short-term scheduler has less control over multi-programming, whereas a Long-term scheduler controls the degree of multi-programming.
- The short-term scheduler is minimally present in the time-sharing system, whereas the long-term scheduler is not present in the time-sharing system.
- The short-term scheduler allocates the task to the CPU for its process, also called the CPU scheduler. In contrast, the Long-term scheduler allocates the task to the ready queue for further action by the short-term scheduler, called a job scheduler.
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Sandeep Bhandari holds a Bachelor of Engineering in Computers from Thapar University (2006). He has 20 years of experience in the technology field. He has a keen interest in various technical fields, including database systems, computer networks, and programming. You can read more about him on his bio page.