Understanding Polling and Interrupt Handling
Definition
Polling
Polling is a technique where the CPU repeatedly checks the status of a device at regular intervals to see if it needs attention.
Definition
Interrupt Handling
Interrupt Handling involves a device sending a signal to the CPU, causing it to pause its current task and execute a specific routine to address the event.
Polling is like a teacher constantly checking if students have questions, while interrupts are like students raising their hands when they need help.
Factors to Consider
- Event Frequency
- High Frequency: Interrupts are preferred to ensure timely responses.
- Low Frequency: Polling can be sufficient, reducing complexity.
- CPU Processing Overheads
- Interrupts: Introduce overhead by saving and restoring CPU state.
- Polling: Consumes CPU cycles continuously, potentially reducing efficiency.
- Power Source
- Battery-Powered Devices: Interrupts are more efficient, allowing the CPU to enter low-power states.
- Mains-Powered Devices: Polling may be acceptable due to less concern about power consumption.
- Event Predictability
- Predictable Events: Polling can be scheduled efficiently.
- Unpredictable Events: Interrupts ensure immediate response.
- Controlled Latency
- Interrupts: Provide lower and more predictable latency.
- Polling: May introduce variable latency depending on the polling interval.
- Security Concerns
- Interrupts: Can be exploited for denial-of-service attacks if not managed properly.
- Polling: Less susceptible to such attacks but may overlook anomalies if checks are infrequent.
When designing a system, always consider the specific requirements of your application, such as power constraints and latency needs, before choosing between polling and interrupts.
Real-World Scenarios
- Keyboard and Mouse Inputs
- Interrupts: Ensure immediate responsiveness, providing a seamless user experience.
- Polling: Would introduce lag, reducing user satisfaction.
- Network Communications
- Interrupts: Allow timely processing of incoming data, reducing latency.
- Polling: Could delay data handling, especially in high-speed networks.
- Disk Input/Output Operations
- Interrupts: Notify the CPU when operations are complete, freeing it for other tasks.
