CPU Scheduling

• CPU scheduler selects a process from “Ready to run” queue
  • Scheduling decision
• Allocates CPU to this process.
  • Dispatch
    • Context switching
• Queue is maintained by PCB pointers
• Pre-emptive scheduling
  • When a running process may be removed and put back in the “ready to run” queue.

When to Have CPU Scheduling

• Process moves from running state to waiting state
  • Due to an I/O request
  • Due to a call to wait
• Upon Process Termination
• Expiration of time quota (preemptive)
• Upon any other time when OS is called
  • Interrupts, System Calls