Interrupt vs Polling in OS: Key Differences & Performance Impact
Interrupt is an OS mechanism where the CPU pauses its current task to handle urgent device requests. Polling forces the CPU to repeatedly check each device for new data, wasting cycles even when nothing happens.
People confuse the two because both move data between devices and the CPU, but Interrupt feels like a doorbell while Polling feels like knocking every five seconds to see if anyone’s home. One screams when ready; the other keeps asking.
Key Differences
Interrupt triggers only when a device has data, saving power and latency. Polling runs on a fixed loop, consuming CPU even when idle. Interrupt needs hardware support; Polling works everywhere but wastes energy and can miss events under load.
Which One Should You Choose?
Use Interrupt for keyboards, network cards, or battery devices where responsiveness and power matter. Use Polling for legacy hardware or real-time sensors needing predictable timing. Modern OS kernels blend both, starting with Interrupt and switching to Polling only under extreme throughput demands.
Examples and Daily Life
Your phone’s touch screen uses Interrupt; it sleeps until you tap. A cheap game controller on an old console relies on Polling, so missed button presses feel laggy. USB 3.0 hard drives use Interrupt for initial connection, then switch to Polling for bulk transfers to sustain gigabit speeds.
Why does Polling sometimes feel faster?
Because the CPU wastes cycles constantly checking, giving slightly lower latency for extremely high-throughput bursts at the cost of overall efficiency.
Can a device support both methods simultaneously?
Yes. Modern network cards often start with Interrupt for low traffic, then switch to Polling under heavy load to reduce overhead and maximize throughput.