Process Scheduling
- Job queue – set of all processes in the system
- Ready queue – set of all processes residing in main memory, ready and waiting to execute
- Device queues – set of processes waiting for an I/O device
- Processes migrate among the various queues
Representation of Process Scheduling
Schedulers
- Sometimes the only scheduler in a system
Schedulers (Cont.)
- I/O-bound process – spends more time doing I/O than computations, many short CPU bursts
- CPU-bound process – spends more time doing computations; few very long CPU bursts
Addition of Medium Term Scheduling
Context Switch
- The more complex the OS and the PCB -> longer the context switch
- Some hardware provides multiple sets of registers per CPU -> multiple contexts loaded at once