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CONFIG_TIMERLAT_TRACER: Timerlat tracer

General informations

The Linux kernel configuration item CONFIG_TIMERLAT_TRACER:

Help text

The timerlat tracer aims to help the preemptive kernel developers to find sources of wakeup latencies of real-time threads.

The tracer creates a per-cpu kernel thread with real-time priority. The tracer thread sets a periodic timer to wakeup itself, and goes to sleep waiting for the timer to fire. At the wakeup, the thread then computes a wakeup latency value as the difference between the current time and the absolute time that the timer was set to expire.

The tracer prints two lines at every activation. The first is the timer latency observed at the hardirq context before the activation of the thread. The second is the timer latency observed by the thread, which is the same level that cyclictest reports. The ACTIVATION ID field serves to relate the irq execution to its respective thread execution.

The tracer is build on top of osnoise tracer, and the osnoise: events can be used to trace the source of interference from NMI, IRQs and other threads. It also enables the capture of the stacktrace at the IRQ context, which helps to identify the code path that can cause thread delay.

Hardware

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Automatically generated (in year 2021). See also LKDDb sources on GitLab