Cpu scheduling
- 1. Morta, Cathrina B. BSIT 2A scheduler also must ensure that processes can meet deadlines; this is crucial for Scheduling (computing) keeping the system stable. Scheduled tasks are sent to mobile devices and managed In computer science, scheduling is the through an administrative back end. method by which threads, processes or data flows are given access to system resources First-Come-First-Served (FCFS) (e.g. processor time, communications Scheduling bandwidth). This is usually done to load balance a system effectively or achieve a Other names of this algorithm are: target quality of service. The need for a First-In-First-Out (FIFO) scheduling algorithm arises from the Run-to-Completion requirement for most modern systems to Run-Until-Done perform multitasking (execute more than one process at a time) and multiplexing Perhaps, First-Come-First-Served algorithm (transmit multiple flows simultaneously). is the simplest scheduling algorithm is the The scheduler is concerned mainly with: simplest scheduling algorithm. Processes are dispatched according to their arrival time on Throughput - number of processes the ready queue. Being a nonpreemptive that complete their execution per time discipline, once a process has a CPU, it runs unit. to completion. Latency, specifically: o Turnaround - total time The FCFS scheduling is fair in the formal between submission of a sense or human sense of fairness but it is process and its completion. unfair in the sense that long jobs make short o Response time - amount of time jobs wait and unimportant jobs make it takes from when a request important jobs wait. was submitted until the first response is produced. Fairness / Waiting Time - Equal CPU FCFS is more predictable than most of other time to each process (or more schemes since it offers time. FCFS scheme generally appropriate times according is not useful in scheduling interactive users to each process' priority). because it cannot guarantee good response time. The code for FCFS scheduling is In practice, these goals often conflict (e.g. simple to write and understand. One of the throughput versus latency), thus a scheduler will implement a suitable compromise. major drawback of this scheme is that the Preference is given to any one of the above average time is often quite long. mentioned concerns depending upon the user's needs and objectives. The First-Come-First-Served algorithm is rarely used as a master scheme in modern In real-time environments, such as operating systems but it is often embedded embedded systems for automatic control in industry (for example robotics), the within other schemes.