What is the difference between scheduler and dispatcher

In the operating system, a dispatcher has the following responsibilities:. Suppose four processes, P1, P2, P3, and P4, are in the ready queue. Their arrival times are T1, T2, T3, and T4, respectively. The process P1 arrived first, so the scheduler will decide it is the first process to be executed, and the Dispatcher will remove P1 from the ready queue and give it to the CPU. Then the scheduler will determine process P2 to be the next process that should be executed, so when the Dispatcher returns to the queue for a new process, it will take process P2 and give it to the CPU.

This continues in the same way for process P3 and then P4. The CPU cannot execute all processes residing in the ready queue and waiting for execution simultaneously. So the operating system has to choose a particular process based on the scheduling algorithm, and the scheduler does this procedure of selecting a process among various processes.

Once the scheduler has selected a process from the queue, the Dispatcher takes it from the ready queue and moves it into the running state. Therefore, the scheduler gives the Dispatcher an ordered list of processes which the Dispatcher moves to the CPU over time.

Scheduler and Dispatcher are used in the process scheduling of an operating system, and they both complete the same process or task. Still, the difference between scheduler and Dispatcher is that the scheduler selects a process out of several processes to be executed.

There are some more differences between the scheduler and the Dispatcher in the operating system, such as:. JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services. Please mail your requirement at [email protected] Duration: 1 week to 2 week. OS Tutorial. Next Topic Deadlock vs Starvation. Reinforcement Learning. R Programming.

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This switching of CPU from one process to the other is called as the context switching. A dispatcher performs various tasks including context switching, setting up user registers and memory mapping.

These are necessary for the process to execute and transfer CPU control to that process. When dispatching , the process changes from ready state to running state.

Sometimes, the dispatcher is considered as a part of the short-term scheduler, so the whole unit is called as the short terms scheduler. In this scenario, the task of the short term scheduler is to select a process from ready queue and also to allocate the CPU for that process.

The medium scheduler carries out the swap in, swap out of the process. The dispatcher allocates the CPU to the process selected by the short-term scheduler. Summary — Scheduler vs Dispatcher Scheduler and Dispatcher are used in process scheduling of an operating system.

The difference between scheduler and dispatcher is that the scheduler selects a process out of several processes to be executed while the dispatcher allocates the CPU for the selected process by the scheduler.

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However, a process must be swapped in to run and the memory management will try to avoid swapping out executing processes. Basically,whatever you have known about scheduler and dispatcher is correct.

Sometimes they are referred to as a same unit or scheduler short time in this case contains dispatcher as a single unit and together are responsible for allocating a process to CPU for execution. Sometimes they are referred as two separate units,the scheduler selects a process according to some algorithm and the dispatcher is a software that is responsible for actual context switching.

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