CPU Scheduling
• General rule
— keep the CPU busy; an idle CPU is a
wasted CPU
• Major source of CPU idleness: I/O (or waiting for it)
• Many programs have a characteristic CPU–I/O burst
cycle
— alternating phases of CPU activity and I/O
inactivity
CPU-bound programs have fewer, longer CPU bursts
I/O-bound programs have more, shorter CPU bursts
