Date:   Wed, 1 Feb 2023 16:10:55 +0700
From:   Bagas Sanjaya <bagasdotme@gmail.com>
To:     Daniel Bristot de Oliveira <bristot@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Jonathan Corbet <corbet@lwn.net>
Cc:     Juri Lelli <juri.lelli@redhat.com>,
        Clark Williams <williams@redhat.com>,
        linux-trace-devel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 6/6] Documentation/rtla: Add hwnoise man page
Message-ID: <Y9osn4sEj7F+Uwhd@debian.me>
References: <cover.1675181734.git.bristot@kernel.org>
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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/to=
ols/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
> +
> +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> +rtla-hwnoise
> +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> +------------------------------------------
> +Detect and quantify hardware-related noise
> +------------------------------------------
> +
> +:Manual section: 1
> +
> +SYNOPSIS
> +=3D=3D=3D=3D=3D=3D=3D=3D
> +
> +**rtla hwnoise** [*OPTIONS*]
> +
> +DESCRIPTION
> +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> +
> +**rtla hwnoise** collects the periodic summary from the *osnoise* tracer
> +running with *interrupts disabled*. By disabling interrupts, and the sch=
eduling
> +of threads as a consequence, only non-maskable interrupts and hardware-r=
elated
> +noise is allowed.
> +
> +The tool also allows the configurations of the *osnoise* tracer and the
> +collection of the tracer output.
> +
> +OPTIONS
> +=3D=3D=3D=3D=3D=3D=3D
> +.. include:: common_osnoise_options.rst
> +
> +.. include:: common_top_options.rst
> +
> +.. include:: common_options.rst
> +
> +EXAMPLE
> +=3D=3D=3D=3D=3D=3D=3D
> +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 Si=
ngle          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 i=
n 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 re=
ceived
> +*86 us* of noise during the entire execution, leaving *99.99997 %* of CP=
U 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 s=
ingle
> +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 h=
igher
> +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 iden=
tify
> +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 Si=
ngle          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
> +=3D=3D=3D=3D=3D=3D=3D=3D
> +
> +**rtla-osnoise**\(1)
> +
> +Osnoise tracer documentation: <https://www.kernel.org/doc/html/latest/tr=
ace/osnoise-tracer.html>
> +
> +AUTHOR
> +=3D=3D=3D=3D=3D=3D
> +Written by Daniel Bristot de Oliveira <bristot@kernel.org>
> +
> +.. include:: common_appendix.rst
=20
LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>

--=20
An old man doll... just what I always wanted! - Clara

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