Basic Concepts

• CPU-I/O Burst Cycle
  • Process execution consistes of a cycle of CPU execution and I/O wait
  • CPU burst followd by I/O burst

CPU Scheduler and Dispatcher

• CPU scheduler
  • selects the process in ready queue, allocates the cpu to one of them
• Dispacher module
  • gives control of the cpu to the process selected by short-term scheduler
  • switching context
  • switching to user mode
  • jump to the porper location in the user program to restart that program

Scheduling Criteria

• Max CPU utilization -- keep busy asap
• Max Throughput --complete their execution per time unit
• Min Turnaround time -- amount of time to execute a particular process
• Min Waiting time -- time of process been waiting in the ready queue
• Min Response time - time is takes from when a request was submitted until the first response in produced, not output (for tim-sharing environment)

Scheduling Algorithms

• First-Come,First-Served(FCFS) Scheduling
• Shortest-Job-First(SJF) Scheduling