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Another component that is involved in the CPU-scheduling function is the dispatcher, which is the module that gives control of the CPU to the process selected by the short-term scheduler. It receives control in kernel mode as the result of an interrupt or system call. The functions of a dispatcher involve the following:
A process with two threads of execution, running on one processor Program vs. Process vs. Thread Scheduling, Preemption, Context Switching. In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. [1]
Process control information is used by the OS to manage the process itself. This includes: Process scheduling state – The state of the process in terms of "ready", "suspended", etc., and other scheduling information as well, such as priority value, the amount of time elapsed since the process gained control of the CPU or since it was suspended.
In computing environments that support the pipes-and-filters model for interprocess communication, a FIFO is another name for a named pipe.. Disk controllers can use the FIFO as a disk scheduling algorithm to determine the order in which to service disk I/O requests, where it is also known by the same FCFS initialism as for CPU scheduling mentioned before.
Thread scheduling is also a major problem in multithreading. Merging data from two processes can often incur significantly higher costs compared to processing the same data on a single thread, potentially by two or more orders of magnitude due to overheads such as inter-process communication and synchronization. [2] [3] [4]
A "maximum execution time" is also calculated for each process to represent the time the process would have expected to run on an "ideal processor". This is the time the process has been waiting to run, divided by the total number of processes. When the scheduler is invoked to run a new process:
Processor affinity takes advantage of the fact that remnants of a process that was run on a given processor may remain in that processor's state (for example, data in the cache memory) after another process was run on that processor. Scheduling a CPU-intensive process that has few interrupts to execute on the same processor may improve its ...
The process state is changed back to "waiting" when the process no longer needs to wait (in a blocked state). Once the process finishes execution, or is terminated by the operating system, it is no longer needed. The process is removed instantly or is moved to the "terminated" state. When removed, it just waits to be removed from main memory ...