1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ============ 3 ============
4 rtla-hwnoise 4 rtla-hwnoise
5 ============ 5 ============
6 ------------------------------------------ 6 ------------------------------------------
7 Detect and quantify hardware-related noise 7 Detect and quantify hardware-related noise
8 ------------------------------------------ 8 ------------------------------------------
9 9
10 :Manual section: 1 10 :Manual section: 1
11 11
12 SYNOPSIS 12 SYNOPSIS
13 ======== 13 ========
14 14
15 **rtla hwnoise** [*OPTIONS*] 15 **rtla hwnoise** [*OPTIONS*]
16 16
17 DESCRIPTION 17 DESCRIPTION
18 =========== 18 ===========
19 19
20 **rtla hwnoise** collects the periodic summary 20 **rtla hwnoise** collects the periodic summary from the *osnoise* tracer
21 running with *interrupts disabled*. By disabli 21 running with *interrupts disabled*. By disabling interrupts, and the scheduling
22 of threads as a consequence, only non-maskable 22 of threads as a consequence, only non-maskable interrupts and hardware-related
23 noise is allowed. 23 noise is allowed.
24 24
25 The tool also allows the configurations of the 25 The tool also allows the configurations of the *osnoise* tracer and the
26 collection of the tracer output. 26 collection of the tracer output.
27 27
28 OPTIONS 28 OPTIONS
29 ======= 29 =======
30 .. include:: common_osnoise_options.rst 30 .. include:: common_osnoise_options.rst
31 31
32 .. include:: common_top_options.rst 32 .. include:: common_top_options.rst
33 33
34 .. include:: common_options.rst 34 .. include:: common_options.rst
35 35
36 EXAMPLE 36 EXAMPLE
37 ======= 37 =======
38 In the example below, the **rtla hwnoise** too 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 39 on a system with 8 cores/16 threads with hyper-threading enabled.
40 40
41 The tool is set to detect any noise higher tha 41 The tool is set to detect any noise higher than *one microsecond*,
42 to run for *ten minutes*, displaying a summary 42 to run for *ten minutes*, displaying a summary of the report at the
43 end of the session:: 43 end of the session::
44 44
45 # rtla hwnoise -c 1-7 -T 1 -d 10m -q 45 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
46 Hard 46 Hardware-related Noise
47 duration: 0 00:10:00 | time is in us 47 duration: 0 00:10:00 | time is in us
48 CPU Period Runtime Noise % CPU 48 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
49 1 #599 599000000 138 99. 49 1 #599 599000000 138 99.99997 3 3 4 74
50 2 #599 599000000 85 99. 50 2 #599 599000000 85 99.99998 3 3 4 75
51 3 #599 599000000 86 99. 51 3 #599 599000000 86 99.99998 4 3 6 75
52 4 #599 599000000 81 99. 52 4 #599 599000000 81 99.99998 4 4 2 75
53 5 #599 599000000 85 99. 53 5 #599 599000000 85 99.99998 2 2 2 75
54 6 #599 599000000 76 99. 54 6 #599 599000000 76 99.99998 2 2 0 75
55 7 #599 599000000 77 99. 55 7 #599 599000000 77 99.99998 3 3 0 75
56 56
57 57
58 The first column shows the *CPU*, and the seco 58 The first column shows the *CPU*, and the second column shows how many
59 *Periods* the tool ran during the session. The 59 *Periods* the tool ran during the session. The *Runtime* is the time
60 the tool effectively runs on the CPU. The *Noi 60 the tool effectively runs on the CPU. The *Noise* column is the sum of
61 all noise that the tool observed, and the *% C 61 all noise that the tool observed, and the *% CPU Aval* is the relation
62 between the *Runtime* and *Noise*. 62 between the *Runtime* and *Noise*.
63 63
64 The *Max Noise* column is the maximum hardware 64 The *Max Noise* column is the maximum hardware noise the tool detected in a
65 single period, and the *Max Single* is the max 65 single period, and the *Max Single* is the maximum single noise seen.
66 66
67 The *HW* and *NMI* columns show the total numb 67 The *HW* and *NMI* columns show the total number of *hardware* and *NMI* noise
68 occurrence observed by the tool. 68 occurrence observed by the tool.
69 69
70 For example, *CPU 3* ran *599* periods of *1 s 70 For example, *CPU 3* ran *599* periods of *1 second Runtime*. The CPU received
71 *86 us* of noise during the entire execution, 71 *86 us* of noise during the entire execution, leaving *99.99997 %* of CPU time
72 for the application. In the worst single perio 72 for the application. In the worst single period, the CPU caused *4 us* of
73 noise to the application, but it was certainly 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* 74 noise, as the *Max Single* noise was of *3 us*. The CPU has *HW noise,* at a
75 rate of *six occurrences*/*ten minutes*. The C 75 rate of *six occurrences*/*ten minutes*. The CPU also has *NMIs*, at a higher
76 frequency: around *seven per second*. 76 frequency: around *seven per second*.
77 77
78 The tool should report *0* hardware-related no 78 The tool should report *0* hardware-related noise in the ideal situation.
79 For example, by disabling hyper-threading to r 79 For example, by disabling hyper-threading to remove the hardware noise,
80 and disabling the TSC watchdog to remove the N 80 and disabling the TSC watchdog to remove the NMI (it is possible to identify
81 this using tracing options of **rtla hwnoise** 81 this using tracing options of **rtla hwnoise**), it was possible to reach
82 the ideal situation in the same hardware:: 82 the ideal situation in the same hardware::
83 83
84 # rtla hwnoise -c 1-7 -T 1 -d 10m -q 84 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
85 Hard 85 Hardware-related Noise
86 duration: 0 00:10:00 | time is in us 86 duration: 0 00:10:00 | time is in us
87 CPU Period Runtime Noise % CPU 87 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
88 1 #599 599000000 0 100. 88 1 #599 599000000 0 100.00000 0 0 0 0
89 2 #599 599000000 0 100. 89 2 #599 599000000 0 100.00000 0 0 0 0
90 3 #599 599000000 0 100. 90 3 #599 599000000 0 100.00000 0 0 0 0
91 4 #599 599000000 0 100. 91 4 #599 599000000 0 100.00000 0 0 0 0
92 5 #599 599000000 0 100. 92 5 #599 599000000 0 100.00000 0 0 0 0
93 6 #599 599000000 0 100. 93 6 #599 599000000 0 100.00000 0 0 0 0
94 7 #599 599000000 0 100. 94 7 #599 599000000 0 100.00000 0 0 0 0
95 95
96 SEE ALSO 96 SEE ALSO
97 ======== 97 ========
98 98
99 **rtla-osnoise**\(1) 99 **rtla-osnoise**\(1)
100 100
101 Osnoise tracer documentation: <https://www.ker 101 Osnoise tracer documentation: <https://www.kernel.org/doc/html/latest/trace/osnoise-tracer.html>
102 102
103 AUTHOR 103 AUTHOR
104 ====== 104 ======
105 Written by Daniel Bristot de Oliveira <bristot@ 105 Written by Daniel Bristot de Oliveira <bristot@kernel.org>
106 106
107 .. include:: common_appendix.rst 107 .. include:: common_appendix.rst
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