In many real-time systems, external hardware events occur continuously. Sensors, network interfaces, control systems, and measurement devices signal the processor whenever new data is available.

These signals are known as interrupts.

Understanding what an RTOS is and why it matters helps explain why real-time operating systems are essential for many mission-critical applications.

In time-critical applications, how quickly the operating system responds to these interrupts can determine whether the system operates correctly. The delay between the interrupt event and the execution of the interrupt handler is called interrupt latency.

Understanding interrupt latency is essential when designing systems that rely on real-time operating systems (RTOS) or real-time Linux platforms.

What Is an Interrupt?

An interrupt is a signal from hardware or software that requests immediate attention from the processor.

Typical interrupt flow:

Hardware Event → CPU receives interrupt → OS handles interrupt →
Application responds

Interrupts allow systems to respond to events such as:

• Incoming network packets
• Sensor measurements
• Hardware status changes
• Timer events

What Is Interrupt Latency?

Interrupt latency refers to the time between when an interrupt occurs and when the operating system begins executing the interrupt handler.

Interrupt occurs → CPU recognizes interrupt → OS prepares handler →
Interrupt handler executes

In time-critical environments, minimizing this delay is essential.

Sources of Interrupt Latency

Kernel Scheduling

Operating systems may delay interrupt handling while executing other tasks.

Interrupt Masking

Interrupts may be temporarily disabled while executing critical code sections.

CPU Contention

Multiple processes competing for CPU resources can increase latency.

System Load

Heavy workloads can increase scheduling delays.

Interrupt Latency in General-Purpose Operating Systems

In standard operating systems, interrupt latency may vary depending on system activity.

Interrupt occurs → CPU busy running other tasks → Interrupt handled later

These delays can introduce jitter, which is unacceptable for many real-time applications.

Interrupt Latency in Real-Time Systems

Real-time operating systems minimize interrupt latency and ensure predictable response times.

Interrupt occurs → High-priority interrupt handler executes immediately →
Application responds

Techniques for Reducing Interrupt Latency

• Priority-based scheduling
• CPU isolation
• Optimized kernel design
• Interrupt affinity

Real-Time Linux and Interrupt Latency

Real-time Linux platforms modify kernel scheduling and interrupt handling to provide predictable response times.

RedHawk Linux and Low-Latency Performance

RedHawk Linux RTOS is designed for environments where minimizing interrupt latency is critical.

Key capabilities include:

• CPU shielding for isolating real-time tasks
• Real-time scheduling policies
• Optimized interrupt handling