Scheduling -  Who gets to run next

Pre-emptive Scheduling - O.S.. preempts process to put new one in.  (Running to Ready)
Non Preemptive - wait for I/O and put new process in.  (Running to Blocked)

Scheduling Criteria

• Maximize CPU utilization
• CPU as busy as possible    0 - 100%
• 40% is low,  90% is very high
• Maximize Throughput - Number of processes completed over a fixed time.
• e.g. 10 processes / sec.
• Minimize turn around time
• See the real time execution from submission to completion.
• Minimize waiting time
• How long does process sit in ready queue?
• Minimize response time
• Interactive systems:  user interface
• After user hit the ENTER key, user want to see progress immediately.

• First Come First Served
• Short Job First
• Priority
• Round Robin
• Multiple Queues