Interrupt-driven i/o

Definition

Interrupt-driven I/O is a method of input and output processing where the CPU is alerted to the availability of data or the need for processing through interrupts, allowing it to efficiently manage multiple tasks without continuous polling. This approach enhances performance by allowing the CPU to execute other tasks while waiting for I/O operations to complete, resulting in more efficient use of system resources. It contrasts with polling methods, where the CPU frequently checks the status of devices.

5 Must Know Facts For Your Next Test

1. Interrupt-driven I/O allows devices to signal the CPU only when they require attention, reducing unnecessary checks and saving processing time.
2. When an interrupt occurs, the CPU temporarily halts its current task and jumps to an interrupt service routine (ISR) to handle the I/O operation.
3. This method is particularly useful in systems where I/O operations can be unpredictable or when devices operate at different speeds.
4. Efficient interrupt handling is crucial for real-time systems, where timely responses are necessary to maintain system performance and reliability.
5. In systems with multiple I/O devices, each device typically has a unique IRQ line to differentiate which device is requesting service.

Review Questions

• How does interrupt-driven I/O improve system efficiency compared to polling?
  • Interrupt-driven I/O improves system efficiency by allowing the CPU to focus on other tasks instead of continuously checking device status. In contrast, polling wastes CPU cycles by making frequent checks, even when no devices need attention. With interrupts, the CPU only reacts when a device signals it needs service, freeing up resources and improving overall system performance.
• Discuss how interrupt requests (IRQs) are utilized in interrupt-driven I/O and their importance in managing multiple devices.
  • Interrupt requests (IRQs) are essential for identifying which device needs the CPU's attention in an interrupt-driven I/O setup. Each device is assigned a unique IRQ line that sends signals to the CPU when it requires processing. This organization allows for efficient management of multiple devices since the CPU can quickly determine which specific device initiated the interrupt and respond accordingly without unnecessary delays or confusion.
• Evaluate the impact of context switching in relation to interrupt-driven I/O and how it affects overall system performance.
  • Context switching plays a crucial role in interrupt-driven I/O as it allows the CPU to pause its current task, manage an incoming interrupt, and then resume its previous operation seamlessly. While context switching introduces some overhead due to state saving and restoring, its benefits in responsiveness and task prioritization outweigh this cost in many applications. This mechanism is especially vital in systems where multiple interrupts may occur simultaneously, ensuring that high-priority tasks receive timely attention without significantly degrading overall system performance.

Related terms

Polling:

A method where the CPU actively checks the status of an I/O device at regular intervals to see if it requires service.

Interrupt Request (IRQ): A hardware signal sent to the CPU indicating that a device needs attention, prompting the CPU to suspend its current activities and execute a specific interrupt handler.

Context Switching:

The process of storing and restoring the state of a CPU so that multiple processes can share a single CPU resource effectively.