Is Your Linux Version Hiding Interrupt CPU Usage From You?

TL;DR: Some Linux distros and even different kernel versions within a distro have disabled IRQ time accounting. In such case, your monitoring tools will report zero time spent in hardware interrupt handlers (shown as %hi, %irq, hiq, etc). It’s easy to check how your kernel is behaving by looking at /proc/stat and you can still measure interrupt CPU usage using perf and a little creativity.
Index Index Problem Explanation Kernel configuration options Measuring IRQ time with perf Different distros and kernel versions Summary Here’s a reminder that your Linux kernel may be not breaking down hardware interrupt CPU usage separately in its /proc/stat CPU time reporting, depending on the kernel’s compile-time settings.