CPU Process Scheduler | mysimulator.uk

Scheduling algorithm

Time quantum (RR) 2

Processes 6

Sim speed 1.0×

Avg waiting

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Avg turnaround

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CPU utilization

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Completed

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How it works

Each process arrives at a random tick with a random CPU burst length and priority. Every clock tick the scheduler picks which process gets the CPU next, according to the active algorithm, and the choice is drawn live as a growing Gantt chart. When every process has run to completion, waiting and turnaround time are averaged and a fresh batch of processes arrives.

turnaround(p) = completion(p) − arrival(p)
waiting(p)    = turnaround(p) − burst(p)
RR: each process runs at most `quantum` ticks per turn,
    then is pre-empted and sent to the back of the ready queue.

FCFS — First-Come-First-Served: strictly arrival order, run to completion. Simple, but a long process can block short ones behind it ("convoy effect").
SJF — Shortest-Job-First (non-preemptive): among arrived processes, the one with the smallest burst runs next. Minimizes average waiting time but can starve long processes.
Round Robin — preemptive, fixed time slice per turn. Fair and responsive; a short quantum lowers response time but raises the number of context switches.
Priority — the lowest priority number (highest urgency) runs next, non-preemptive. Realistic for interactive systems, but low-priority processes can starve without aging.

Real-world relevance: every general-purpose OS kernel (Linux's CFS, Windows' multilevel feedback queue) is a refinement of exactly these trade-offs — fairness versus throughput versus responsiveness.

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