Process Scheduling II(5.3)

CPE 261403 - Operating Systemshttp://www.e-cpe.org/moodle

Scheduling Criteria (5.2)

CPU Utilization

Throughput

Turnaround time

Waiting time

Response time

Scheduling Algorithms (5.3)

FCFS SJF (non-preemptive / preemptive) Priority Scheduling Round-Robin Scheduling Multilevel Queue Scheduling Multilevel Feedback-Queue Scheduling

Priority Scheduling

Defining Priorities Internally Defined Priorities

External priorities

Starvation

IBM 7094 at MIT

When closing down in 1973, found a process submitted in 1967 (Myth)

Round Robin Scheduling

Preemptive by Nature

Defines a Time Quantum

Time Quantum >> Context Switch Time

Multilevel Queue Scheduling

Scheduling within & among queues Use simple priority or CPU time slice (quota)

Multilevel Feedback Queue

Example: Q1=RR, Q2=RR, Q3=FCFS

Multilevel Feedback Queue

Parameters: Number of queues

Scheduling algorithms for each queue

When to upgrade a process

When to downgrade a process

Which queue should a new process enter