PPT Slide
Scheduling in Real Operating Systems
- UNIX SVR4
- 160 Priority levels
- 0-59: timesharing/interactive
- 60-99: system processes
- 100-159: processes running in kernel mode
- Highest priority runs first; ties are “Round Robined”.
- Timesharing priorities goes down if it chews up entire time quantum; can go back up if it blocks on an event or waits in the ready queue for a long time.
- Time quanta range from 100 milliseconds (priority 0) to 10 milliseconds (priority 159?)