| .. 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 |
