On Tue, Jan 31, 2023 at 05:30:07PM +0100, Daniel Bristot de Oliveira wrote: > diff --git a/Documentation/tools/rtla/rtla-hwnoise.rst b/Documentation/tools/rtla/rtla-hwnoise.rst > new file mode 100644 > index 000000000000..fb1c52bbc00b > --- /dev/null > +++ b/Documentation/tools/rtla/rtla-hwnoise.rst > @@ -0,0 +1,107 @@ > +.. 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@xxxxxxxxxx> > + > +.. include:: common_appendix.rst LGTM, thanks! Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> -- An old man doll... just what I always wanted! - Clara
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