--- name: "rtla-hwnoise" section: "1" platform: "linux" package: "rtla" version: "6.12.107-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/rtla-hwnoise" --- # rtla-hwnoise(1) Detect and quantify hardware-related noise ## NAME rtla-hwnoise - Detect and quantify hardware-related noise ## 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 - **-a**, **--auto** *us* Set the automatic trace mode. This mode sets some commonly used options while debugging the system. It is equivalent to use **-s** *us* **-T 1 -t**. - **-p**, **--period** *us* Set the *osnoise* tracer period in microseconds. - **-r**, **--runtime** *us* Set the *osnoise* tracer runtime in microseconds. - **-s**, **--stop** *us* Stop the trace if a single sample is higher than the argument in microseconds. If **-T** is set, it will also save the trace to the output. - **-S**, **--stop-total** *us* Stop the trace if the total sample is higher than the argument in microseconds. If **-T** is set, it will also save the trace to the output. - **-T**, **--threshold** *us* Specify the minimum delta between two time reads to be considered noise. The default threshold is *5 us*. - **-t**, **--trace** \[*file*\] Save the stopped trace to \[*file\|osnoise\_trace.txt*\]. - **-q**, **--quiet** Print only a summary at the end of the session. - **-c**, **--cpus** *cpu-list* Set the osnoise tracer to run the sample threads in the cpu-list. - **-H**, **--house-keeping** *cpu-list* Run rtla control threads only on the given cpu-list. - **-d**, **--duration** *time\[s\|m\|h\|d\]* Set the duration of the session. - **-D**, **--debug** Print debug info. - **-e**, **--event** *sys:event* Enable an event in the trace (**-t**) session. The argument can be a specific event, e.g., **-e** *sched:sched\_switch*, or all events of a system group, e.g., **-e** *sched*. Multiple **-e** are allowed. It is only active when **-t** or **-a** are set. - **--filter** *\* Filter the previous **-e** *sys:event* event with *\*. For further information about event filtering see \ . - **--trigger *\*** Enable a trace event trigger to the previous **-e** *sys:event*. If the *hist:* trigger is activated, the output histogram will be automatically saved to a file named *system\_event\_hist.txt*. For example, the command: rtla \ \ -t -e osnoise:irq\_noise --trigger="hist:key=desc,duration/1000:sort=desc,duration/1000:vals=hitcount" Will automatically save the content of the histogram associated to *osnoise:irq\_noise* event in *osnoise\_irq\_noise\_hist.txt*. For further information about event trigger see \ . - **-P**, **--priority** *o:prio\|r:prio\|f:prio\|d:runtime:period* Set scheduling parameters to the osnoise tracer threads, the format to set the priority are: - • *o:prio* - use SCHED\_OTHER with *prio*; - • *r:prio* - use SCHED\_RR with *prio*; - • *f:prio* - use SCHED\_FIFO with *prio*; - • *d:runtime\[us\|ms\|s\]:period\[us\|ms\|s\]* - use SCHED\_DEADLINE with *runtime* and *period* in nanoseconds. - **-C**, **--cgroup**\[*=cgroup*\] Set a *cgroup* to the tracer's threads. If the **-C** option is passed without arguments, the tracer's thread will inherit **rtla**'s *cgroup*. Otherwise, the threads will be placed on the *cgroup* passed to the option. - **--warm-up** *s* After starting the workload, let it run for *s* seconds before starting collecting the data, allowing the system to warm-up. Statistical data generated during warm-up is discarded. - **--trace-buffer-size *kB*** Set the per-cpu trace buffer size in kB for the tracing output. - **-h**, **--help** Print help menu. ## 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)](/rtla-osnoise/1.md) Osnoise tracer documentation: \< \ \> ## AUTHOR Written by Daniel Bristot de Oliveira \< \ \> ## REPORTING BUGS Report bugs to \< \ \> and \< \ \> ## LICENSE **rtla** is Free Software licensed under the GNU GPLv2 ## COPYING Copyright (C) 2021 Red Hat, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).