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kernel: add OSNOISE_TRACER kernel config option

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This adds the OSNOISE_TRACER kernel configuration option. The osnoise
tracer allows to track interference experienced by an application due to
activities inside the operating system (like NMIs, IRQs ...).

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 16:31:36 +01:00
committed by Hauke Mehrtens
parent 9a584c631e
commit c1c37b40c1
1 changed files with 34 additions and 0 deletions
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config/Config-kernel.in
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@@ -448,6 +448,40 @@ config KERNEL_HWLAT_TRACER
file. Every time a latency is greater than tracing_thresh, it will
be recorded into the ring buffer.
config KERNEL_OSNOISE_TRACER
bool "OS Noise tracer"
depends on KERNEL_FTRACE
help
In the context of high-performance computing (HPC), the Operating
System Noise (osnoise) refers to the interference experienced by an
application due to activities inside the operating system. In the
context of Linux, NMIs, IRQs, SoftIRQs, and any other system thread
can cause noise to the system. Moreover, hardware-related jobs can
also cause noise, for example, via SMIs.
The osnoise tracer leverages the hwlat_detector by running a similar
loop with preemption, SoftIRQs and IRQs enabled, thus allowing all
the sources of osnoise during its execution. The osnoise tracer takes
note of the entry and exit point of any source of interferences,
increasing a per-cpu interference counter. It saves an interference
counter for each source of interference. The interference counter for
NMI, IRQs, SoftIRQs, and threads is increased anytime the tool
observes these interferences' entry events. When a noise happens
without any interference from the operating system level, the
hardware noise counter increases, pointing to a hardware-related
noise. In this way, osnoise can account for any source of
interference. At the end of the period, the osnoise tracer prints
the sum of all noise, the max single noise, the percentage of CPU
available for the thread, and the counters for the noise sources.
In addition to the tracer, a set of tracepoints were added to
facilitate the identification of the osnoise source.
The output will appear in the trace and trace_pipe files.
To enable this tracer, echo in "osnoise" into the current_tracer
file.
config KERNEL_HIST_TRIGGERS
bool "Histogram triggers"
depends on KERNEL_FTRACE