An interrupt request (IRQ) is a signal for immediate attention sent from a piece of hardware to a processor. Each device in a system is assigned one or more IRQ numbers, which allow it to send unique interrupts.

When enabled interrupts, processors receiving an interrupt request pause execution of the current application thread to address the interrupt request.

Because an interrupt halts normal operation, high interrupt rates can severely degrade system performance. Reduce interrupt overhead by configuring interrupt affinity or by batching lower-priority interrupts using coalescing.

Interrupt requests have an associated affinity property, smp_affinity, which defines the processors that handle the interrupt request. To improve application performance and enable the specified interrupt and application threads to share cache lines, make the following improvements:

• Assign interrupt affinity.
• Process affinity to either the same processor or processors on the same core.

Modifying smp_affinity on supported systems enables hardware-level interrupt steering. The hardware routes interrupts to specific processors without kernel intervention.