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kernel: add TIMERLAT_TRACER kernel config option
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This adds the TIMERLAT_TRACER kernel configuration option. The timelat
tracer helps to find sources of wakeup latencies of real-time threads.

Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Link: https://github.com/openwrt/openwrt/pull/21413
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
This commit is contained in:
Thomas Richard 2026-01-05 16:32:44 +01:00 • committed by Hauke Mehrtens
parent c1c37b40c1
commit 3ddee7edc4
1 changed files with 27 additions and 0 deletions
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27
config/Config-kernel.in
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@ -482,6 +482,33 @@ config KERNEL_OSNOISE_TRACER
To enable this tracer, echo in "osnoise" into the current_tracer
file.
config KERNEL_TIMERLAT_TRACER
bool "Timerlat tracer"
depends on KERNEL_FTRACE
help
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.
config KERNEL_HIST_TRIGGERS
bool "Histogram triggers"
depends on KERNEL_FTRACE