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- .. SPDX-License-Identifier: GPL-2.0
- ============
- rtla-hwnoise
- ============
- ------------------------------------------
- Detect and quantify hardware-related noise
- ------------------------------------------
- :Manual section: 1
- SYNOPSIS
- ========
- **rtla hwnoise** [*OPTIONS*]
- DESCRIPTION
- ===========
- **rtla hwnoise** collects the periodic summary from the *osnoise* tracer
- running with *interrupts disabled*. By disabling interrupts, and the scheduling
- of threads as a consequence, only non-maskable interrupts and hardware-related
- noise is allowed.
- The tool also allows the configurations of the *osnoise* tracer and the
- collection of the tracer output.
- OPTIONS
- =======
- .. include:: common_osnoise_options.rst
- .. include:: common_top_options.rst
- .. include:: common_options.rst
- EXAMPLE
- =======
- In the example below, the **rtla hwnoise** tool is set to run on CPUs *1-7*
- on a system with 8 cores/16 threads with hyper-threading enabled.
- The tool is set to detect any noise higher than *one microsecond*,
- to run for *ten minutes*, displaying a summary of the report at the
- end of the session::
- # rtla hwnoise -c 1-7 -T 1 -d 10m -q
- Hardware-related Noise
- duration: 0 00:10:00 | time is in us
- CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
- 1 #599 599000000 138 99.99997 3 3 4 74
- 2 #599 599000000 85 99.99998 3 3 4 75
- 3 #599 599000000 86 99.99998 4 3 6 75
- 4 #599 599000000 81 99.99998 4 4 2 75
- 5 #599 599000000 85 99.99998 2 2 2 75
- 6 #599 599000000 76 99.99998 2 2 0 75
- 7 #599 599000000 77 99.99998 3 3 0 75
- The first column shows the *CPU*, and the second column shows how many
- *Periods* the tool ran during the session. The *Runtime* is the time
- the tool effectively runs on the CPU. The *Noise* column is the sum of
- all noise that the tool observed, and the *% CPU Aval* is the relation
- between the *Runtime* and *Noise*.
- The *Max Noise* column is the maximum hardware noise the tool detected in a
- single period, and the *Max Single* is the maximum single noise seen.
- The *HW* and *NMI* columns show the total number of *hardware* and *NMI* noise
- occurrence observed by the tool.
- For example, *CPU 3* ran *599* periods of *1 second Runtime*. The CPU received
- *86 us* of noise during the entire execution, leaving *99.99997 %* of CPU time
- for the application. In the worst single period, the CPU caused *4 us* of
- noise to the application, but it was certainly caused by more than one single
- noise, as the *Max Single* noise was of *3 us*. The CPU has *HW noise,* at a
- rate of *six occurrences*/*ten minutes*. The CPU also has *NMIs*, at a higher
- frequency: around *seven per second*.
- The tool should report *0* hardware-related noise in the ideal situation.
- For example, by disabling hyper-threading to remove the hardware noise,
- and disabling the TSC watchdog to remove the NMI (it is possible to identify
- this using tracing options of **rtla hwnoise**), it was possible to reach
- the ideal situation in the same hardware::
- # rtla hwnoise -c 1-7 -T 1 -d 10m -q
- Hardware-related Noise
- duration: 0 00:10:00 | time is in us
- CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
- 1 #599 599000000 0 100.00000 0 0 0 0
- 2 #599 599000000 0 100.00000 0 0 0 0
- 3 #599 599000000 0 100.00000 0 0 0 0
- 4 #599 599000000 0 100.00000 0 0 0 0
- 5 #599 599000000 0 100.00000 0 0 0 0
- 6 #599 599000000 0 100.00000 0 0 0 0
- 7 #599 599000000 0 100.00000 0 0 0 0
- SEE ALSO
- ========
- **rtla-osnoise**\(1)
- Osnoise tracer documentation: <https://www.kernel.org/doc/html/latest/trace/osnoise-tracer.html>
- AUTHOR
- ======
- Written by Daniel Bristot de Oliveira <bristot@kernel.org>
- .. include:: common_appendix.rst
|
