Minimizing Interrupt Latency via IRQ Affinity Pinning and Core Isolation

Technical Briefing | 7/10/2026

In high-frequency trading and real-time processing environments, generic interrupt handling often leads to cache thrashing and context switching overhead. By default, Linux distributes hardware interrupts across all available CPUs, which can inadvertently wake idle cores and disrupt cache locality for mission-critical threads. Controlling IRQ affinity allows engineers to pin hardware interrupts to specific cores, ensuring that dedicated worker processes remain undisturbed by NIC or storage controller signals.

Isolating Interrupts from Application Cores

To maximize throughput, we must first identify which CPUs are handling the most interrupt traffic and then explicitly disable their automatic rebalancing. By modifying the smp_affinity masks, we redirect incoming hardware requests to a non-application-bound core, thereby preserving the L1 and L2 caches for the application data path.

cat /proc/interrupts | grep eth0
echo 1 > /proc/irq/42/smp_affinity
echo 0 > /proc/irq/default_smp_affinity

• Use /proc/interrupts to identify current IRQ distribution counts.
• Set kernel boot parameters using isolcpus to reserve cores for specific tasks.
• Monitor softirq activity via /proc/softirqs to ensure balance remains optimal.

Achieving deterministic performance requires a holistic approach that pairs interrupt pinning with CPU shielding. Once hardware interrupts are relegated to auxiliary housekeeping cores, the primary processing cores can enter a high-performance state devoid of jitter-inducing kernel overhead, ultimately reducing latency tail distribution in high-load scenarios.