.. 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: AUTHOR ====== Written by Daniel Bristot de Oliveira .. include:: common_appendix.rst