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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]
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.
The separation of mechanism and policy [1] is a design principle in computer science.It states that mechanisms (those parts of a system implementation that control the authorization of operations and the allocation of resources) should not dictate (or overly restrict) the policies according to which decisions are made about which operations to authorize, and which resources to allocate.
An RTOS is an operating system in which the time taken to process an input stimulus is less than the time lapsed until the next input stimulus of the same type. The most common designs are: Event-driven – switches tasks only when an event of higher priority needs servicing; called preemptive priority , or priority scheduling.
Although the two-state process management model is a perfectly valid design for an operating system, the absence of a BLOCKED state means that the processor lies idle when the active process changes from CPU cycles to I/O cycles. This design does not make efficient use of the processor.
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 ...