CPU Scheduling Concepts

Flashcards covering key vocabulary terms and concepts related to CPU scheduling from the Operating System Concepts lecture.

CPU Utilization

The percentage of time the CPU is actively working.

Throughput

The number of processes that complete their execution per time unit.

Turnaround Time

The total time taken to execute a particular process.

Waiting Time

The time a process has been in the ready queue waiting to execute.

Response Time

The time it takes from when a request was submitted until the first response is produced.

CPU–I/O Burst Cycle

A pattern of execution that consists of alternating periods of CPU execution and I/O wait.

Preemptive Scheduling

A scheduling scheme where a process can be interrupted and moved to the ready state.

Nonpreemptive Scheduling

A scheduling policy where a process keeps the CPU until it voluntarily releases it.

FCFS Scheduling

First-Come, First-Served; a scheduling algorithm where the first process in the ready queue is the first to execute.

SJF Scheduling

Shortest Job First; schedules the next process with the shortest next CPU burst.

Round Robin Scheduling

Each process gets a fixed time slice (quantum) to execute, after which it is returned to the ready queue.

Priority Scheduling

Assigns priority to processes and allocates the CPU to the process with the highest priority.

Aging

A technique to prevent starvation by gradually increasing the priority of waiting processes.

Virtual CPU

Illusion created by the operating system to allow multiple processes to appear to run simultaneously.

Dispatcher

The module that gives control of the CPU to the chosen process, switching context as necessary.

Preemptive version of SJF

Shortest Remaining Time First; preempts the running process if a new process arrives with a shorter CPU burst.

Gantt Chart

A visual representation of the scheduling of processes over time.

Quantum

The fixed time period allocated to each process in Round Robin scheduling.

Dispatch Latency

The time it takes for the dispatcher to stop one process and start another.

Soft Real-Time Systems

Systems where critical tasks have priority but there is no guarantee of execution time.

Hard Real-Time Systems

Systems that require tasks to be completed by strict deadlines.

Multilevel Queue Scheduling

A scheduling scheme that manages multiple queues, each with its own scheduling algorithm.

Multilevel Feedback Queue

A scheduling scheme that allows processes to move between multiple queues based on their behavior.

Processor Affinity

Preference for a process to run on the same processor due to better cache performance.

Symmetric Multiprocessing (SMP)

Performance architecture where each processor self-schedules tasks.

Load Balancing

The process of distributing workloads evenly across multiple processors.

Interrupt Latency

The time from the arrival of an interrupt to the start of servicing the interrupt request.

Little's Law

A formula that relates average queue length, arrival rate and waiting time; n = λ x W.

Deterministic Modeling

An evaluation method that uses predetermined workloads to analyze performance of scheduling algorithms.

CPU burst duration

The amount of time a process is engaged in CPU activity before performing I/O.

Critical Section Problem

A situation in concurrent programming where two or more processes access shared resources concurrently.

Timer Interrupt

A signal that interrupts the CPU to allow scheduling of the next process.

Convoy Effect

Occurs when a short process is waiting for a long process, delaying its execution.

Exponential Averaging

A method for predicting CPU bursts that weights recent history more heavily.

Starvation

A situation where a process never gets the resources it needs because of indefinite postponement.