Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1.. SPDX-License-Identifier: GPL-2.0
2
3.. |tool| replace:: hwnoise
4
5============
6rtla-hwnoise
7============
8------------------------------------------
9Detect and quantify hardware-related noise
10------------------------------------------
11
12:Manual section: 1
13
14SYNOPSIS
15========
16
17**rtla hwnoise** [*OPTIONS*]
18
19DESCRIPTION
20===========
21
22**rtla hwnoise** collects the periodic summary from the *osnoise* tracer
23running with *interrupts disabled*. By disabling interrupts, and the scheduling
24of threads as a consequence, only non-maskable interrupts and hardware-related
25noise is allowed.
26
27The tool also allows the configurations of the *osnoise* tracer and the
28collection of the tracer output.
29
30OPTIONS
31=======
32.. include:: common_osnoise_options.txt
33
34.. include:: common_top_options.txt
35
36.. include:: common_options.txt
37
38EXAMPLE
39=======
40In the example below, the **rtla hwnoise** tool is set to run on CPUs *1-7*
41on a system with 8 cores/16 threads with hyper-threading enabled.
42
43The tool is set to detect any noise higher than *one microsecond*,
44to run for *ten minutes*, displaying a summary of the report at the
45end of the session::
46
47 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
48 Hardware-related Noise
49 duration: 0 00:10:00 | time is in us
50 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
51 1 #599 599000000 138 99.99997 3 3 4 74
52 2 #599 599000000 85 99.99998 3 3 4 75
53 3 #599 599000000 86 99.99998 4 3 6 75
54 4 #599 599000000 81 99.99998 4 4 2 75
55 5 #599 599000000 85 99.99998 2 2 2 75
56 6 #599 599000000 76 99.99998 2 2 0 75
57 7 #599 599000000 77 99.99998 3 3 0 75
58
59
60The first column shows the *CPU*, and the second column shows how many
61*Periods* the tool ran during the session. The *Runtime* is the time
62the tool effectively runs on the CPU. The *Noise* column is the sum of
63all noise that the tool observed, and the *% CPU Aval* is the relation
64between the *Runtime* and *Noise*.
65
66The *Max Noise* column is the maximum hardware noise the tool detected in a
67single period, and the *Max Single* is the maximum single noise seen.
68
69The *HW* and *NMI* columns show the total number of *hardware* and *NMI* noise
70occurrence observed by the tool.
71
72For example, *CPU 3* ran *599* periods of *1 second Runtime*. The CPU received
73*86 us* of noise during the entire execution, leaving *99.99997 %* of CPU time
74for the application. In the worst single period, the CPU caused *4 us* of
75noise to the application, but it was certainly caused by more than one single
76noise, as the *Max Single* noise was of *3 us*. The CPU has *HW noise,* at a
77rate of *six occurrences*/*ten minutes*. The CPU also has *NMIs*, at a higher
78frequency: around *seven per second*.
79
80The tool should report *0* hardware-related noise in the ideal situation.
81For example, by disabling hyper-threading to remove the hardware noise,
82and disabling the TSC watchdog to remove the NMI (it is possible to identify
83this using tracing options of **rtla hwnoise**), it was possible to reach
84the ideal situation in the same hardware::
85
86 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
87 Hardware-related Noise
88 duration: 0 00:10:00 | time is in us
89 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
90 1 #599 599000000 0 100.00000 0 0 0 0
91 2 #599 599000000 0 100.00000 0 0 0 0
92 3 #599 599000000 0 100.00000 0 0 0 0
93 4 #599 599000000 0 100.00000 0 0 0 0
94 5 #599 599000000 0 100.00000 0 0 0 0
95 6 #599 599000000 0 100.00000 0 0 0 0
96 7 #599 599000000 0 100.00000 0 0 0 0
97
98SEE ALSO
99========
100
101**rtla-osnoise**\(1)
102
103`Osnoise tracer <https://docs.kernel.org/trace/osnoise-tracer.html>`__
104
105AUTHOR
106======
107Written by Daniel Bristot de Oliveira <bristot@kernel.org>
108
109.. include:: common_appendix.txt