kernel: add OSNOISE_TRACER kernel config option

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>

1 files changed, 34 insertions, 0 deletions

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 86d99bd49b..cb6e49d393 100644
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -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