Using the kernel function tracing system

Recent versions of the Linux kernel contain a set of tracers that, by instrumenting the kernel, allow you to analyze different areas like:

• Interrupt latency

• Preemption latency

• Scheduling latency

• Process context switches

• Event tracing

• Syscalls

• Maximum stack

• Block layer

• Functions

The tracers have no performance overhead when not enabled.

Getting ready...

The tracing system can be used in a wide variety of debugging scenarios, but one of the most common tracers used is the function tracer. It instruments every kernel function with a NOP call that is replaced and used to trace the kernel functions when a trace point is enabled.

To enable the function tracer in the kernel, use the CONFIG_FUNCTION_TRACER and CONFIG_FUNCTION_GRAPH_TRACER configuration variables.

The kernel tracing system is controlled via a tracing file in the debug filesystem, which is mounted by default on Yocto's default images. If not, you can mount it with:

$ mount -t debugfs nodev /sys/kernel/debug...