lecture4-OS-CPU Scheduling

Multiprogramming

The objective is to maximize CPU utilization by selecting and running one process from the ready queue when CPU is available.

CPU-bound process

A process that has a very long CPU burst.

I/O-bound process

A process that has a short CPU burst.

Preemptive scheduling

A scheduling method where a process can be interrupted and moved to the ready state to allow another process to execute.

Non-preemptive scheduling

A scheduling method where once the CPU has been allocated to a process, it will keep the CPU until it finishes or voluntarily releases it.

Dispatcher

The module that transfers control of the CPU to the process selected by the short-term scheduler.

Throughput

The number of processes that complete their execution per time unit; the higher, the better.

Turnaround time

The total time taken from submission to completion of a process; the shorter, the better.

Waiting time

The total time a process spends waiting in the ready queue; the shorter, the better.

Response time

The time from when a request is submitted until the first response is produced; important for time-sharing environments.

Waiting time for FCFS

The average waiting time in a First Come First Served scheduling algorithm that can lead to poor performance.

Shortest Job First (SJF) Scheduling

A scheduling algorithm that selects the process with the shortest CPU burst time.

Aging

A technique used to prevent starvation in scheduling algorithms by gradually increasing the priority of waiting processes.

Round Robin Scheduling

Allocates a small unit of CPU time to each process in a cyclic order; usually used for time-sharing systems.

Multilevel Queue Scheduling

A scheduling approach where the ready queue is partitioned into separate queues, each with its own algorithm.

Completely Fair Scheduler (CFS)

A scheduling algorithm in Linux that allocates CPU time to each task based on its priority, ensuring fair access.

Real-time scheduling

A scheduling requirement where critical tasks must complete within guaranteed time limits.

Simulation in scheduling evaluation

An approach that models the scheduling algorithms using software to evaluate their performance under simulated conditions.

Deterministic model

A scheduling evaluation method that uses a predetermined workload to define the performance of algorithms.

QOS (Quality of Service) guarantees

Commitments made to users about performance, like ensuring a specific amount of CPU time is available.