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The scheduler is an operating system module that selects the next jobs to be admitted into the system and the next process to run. Operating systems may feature up to three distinct scheduler types: a long-term scheduler (also known as an admission scheduler or high-level scheduler), a mid-term or medium-term scheduler, and a short-term scheduler.
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]
time (Unix) - can be used to determine the run time of a program, separately counting user time vs. system time, and CPU time vs. clock time. [1] timem (Unix) - can be used to determine the wall-clock time, CPU time, and CPU utilization similar to time (Unix) but supports numerous extensions.
The criteria of a real-time can be classified as hard, firm or soft.The scheduler set the algorithms for executing tasks according to a specified order. [4] There are multiple mathematical models to represent a scheduling System, most implementations of real-time scheduling algorithm are modeled for the implementation of uniprocessors or multiprocessors configurations.
However, on modern hardware, especially multi-core, other tasks in the system will impact the WCET of a given task if they share cache, memory lines and other hardware features. Further, task scheduling events such as blocking or to be interruptions should be considered in WCET analysis if they can occur in a particular system. Therefore, it is ...
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.
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.
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: