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Shortest job next being executed. Shortest job next (SJN), also known as shortest job first (SJF) or shortest process next (SPN), is a scheduling policy that selects for execution the waiting process with the smallest execution time. [1] SJN is a non-preemptive algorithm. Shortest remaining time is a preemptive variant of SJN.
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.
Shortest remaining time being executed. Shortest remaining time, also known as shortest remaining time first (SRTF), is a scheduling method that is a preemptive version of shortest job next scheduling. In this scheduling algorithm, the process with the smallest amount of time remaining until completion is selected to execute. Since the ...
LST scheduling is most useful in systems comprising mainly aperiodic tasks, because no prior assumptions are made on the events' rate of occurrence. The main weakness of LST is that it does not look ahead, and works only on the current system state. Thus, during a brief overload of system resources, LST can be suboptimal.
There are many different types of queues, and the ways they operate may be totally different. Operating systems use First-Come, First-Served queues, Shortest remaining time, Fixed-priority pre-emptive scheduling, round-robin scheduling and multilevel queue scheduling. Network devices use First-In-First-Out queue, Weighted fair queue, Priority ...
Earliest deadline first (EDF) or least time to go is a dynamic priority scheduling algorithm used in real-time operating systems to place processes in a priority queue. Whenever a scheduling event occurs (task finishes, new task released, etc.) the queue will be searched for the process closest to its deadline.
Fair-share scheduling is a scheduling algorithm for computer operating systems in which the CPU usage is equally distributed among system users or groups, as opposed to equal distribution of resources among processes. [1]
It uses notions of virtual time, eligible time, virtual requests and virtual deadlines for determining scheduling priority. [1] It has the property that when a job keeps requesting service, the amount of service obtained is always within the maximum quantum size of what it is entitled.