tools/rtla/rtla-hwnoise.rst

1 .. SPDX-License-Identifier: GPL-2.0
4 rtla-hwnoise
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7 Detect and quantify hardware-related noise
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22 of threads as a consequence, only non-maskable interrupts and hardware-related
23 noise is allowed.
38 In the example below, the **rtla hwnoise** tool is set to run on CPUs *1-7*
39 on a system with 8 cores/16 threads with hyper-threading enabled.
41 The tool is set to detect any noise higher than *one microsecond*,
45   # rtla hwnoise -c 1-7 -T 1 -d 10m -q
46                                           Hardware-related Noise
48 …CPU Period       Runtime        Noise  % CPU Aval   Max Noise   Max Single          HW          NMI
60 the tool effectively runs on the CPU. The *Noise* column is the sum of
61 all noise that the tool observed, and the *% CPU Aval* is the relation
62 between the *Runtime* and *Noise*.
64 The *Max Noise* column is the maximum hardware noise the tool detected in a
65 single period, and the *Max Single* is the maximum single noise seen.
67 The *HW* and *NMI* columns show the total number of *hardware* and *NMI* noise
71 *86 us* of noise during the entire execution, leaving *99.99997 %* of CPU time
73 noise to the application, but it was certainly caused by more than one single
74 noise, as the *Max Single* noise was of *3 us*. The CPU has *HW noise,* at a
78 The tool should report *0* hardware-related noise in the ideal situation.
79 For example, by disabling hyper-threading to remove the hardware noise,
84   # rtla hwnoise -c 1-7 -T 1 -d 10m -q
85                                           Hardware-related Noise
87 …CPU Period       Runtime        Noise  % CPU Aval   Max Noise   Max Single          HW          NMI
99 **rtla-osnoise**\(1)
101 Osnoise tracer documentation: <https://www.kernel.org/doc/html/latest/trace/osnoise-tracer.html>
105 Written by Daniel Bristot de Oliveira <bristot@kernel.org>