1.. SPDX-License-Identifier: GPL-2.0 2 3.. |tool| replace:: hwnoise 4 5============ 6rtla-hwnoise 7============ 8------------------------------------------ 9Detect and quantify hardware-related noise 10------------------------------------------ 11 12:Manual section: 1 13 14SYNOPSIS 15======== 16 17**rtla hwnoise** [*OPTIONS*] 18 19DESCRIPTION 20=========== 21 22**rtla hwnoise** collects the periodic summary from the *osnoise* tracer 23running with *interrupts disabled*. By disabling interrupts, and the scheduling 24of threads as a consequence, only non-maskable interrupts and hardware-related 25noise is allowed. 26 27The tool also allows the configurations of the *osnoise* tracer and the 28collection of the tracer output. 29 30OPTIONS 31======= 32.. include:: common_osnoise_options.rst 33 34.. include:: common_top_options.rst 35 36.. include:: common_options.rst 37 38EXAMPLE 39======= 40In the example below, the **rtla hwnoise** tool is set to run on CPUs *1-7* 41on a system with 8 cores/16 threads with hyper-threading enabled. 42 43The tool is set to detect any noise higher than *one microsecond*, 44to run for *ten minutes*, displaying a summary of the report at the 45end of the session:: 46 47 # rtla hwnoise -c 1-7 -T 1 -d 10m -q 48 Hardware-related Noise 49 duration: 0 00:10:00 | time is in us 50 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI 51 1 #599 599000000 138 99.99997 3 3 4 74 52 2 #599 599000000 85 99.99998 3 3 4 75 53 3 #599 599000000 86 99.99998 4 3 6 75 54 4 #599 599000000 81 99.99998 4 4 2 75 55 5 #599 599000000 85 99.99998 2 2 2 75 56 6 #599 599000000 76 99.99998 2 2 0 75 57 7 #599 599000000 77 99.99998 3 3 0 75 58 59 60The first column shows the *CPU*, and the second column shows how many 61*Periods* the tool ran during the session. The *Runtime* is the time 62the tool effectively runs on the CPU. The *Noise* column is the sum of 63all noise that the tool observed, and the *% CPU Aval* is the relation 64between the *Runtime* and *Noise*. 65 66The *Max Noise* column is the maximum hardware noise the tool detected in a 67single period, and the *Max Single* is the maximum single noise seen. 68 69The *HW* and *NMI* columns show the total number of *hardware* and *NMI* noise 70occurrence observed by the tool. 71 72For example, *CPU 3* ran *599* periods of *1 second Runtime*. The CPU received 73*86 us* of noise during the entire execution, leaving *99.99997 %* of CPU time 74for the application. In the worst single period, the CPU caused *4 us* of 75noise to the application, but it was certainly caused by more than one single 76noise, as the *Max Single* noise was of *3 us*. The CPU has *HW noise,* at a 77rate of *six occurrences*/*ten minutes*. The CPU also has *NMIs*, at a higher 78frequency: around *seven per second*. 79 80The tool should report *0* hardware-related noise in the ideal situation. 81For example, by disabling hyper-threading to remove the hardware noise, 82and disabling the TSC watchdog to remove the NMI (it is possible to identify 83this using tracing options of **rtla hwnoise**), it was possible to reach 84the ideal situation in the same hardware:: 85 86 # rtla hwnoise -c 1-7 -T 1 -d 10m -q 87 Hardware-related Noise 88 duration: 0 00:10:00 | time is in us 89 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI 90 1 #599 599000000 0 100.00000 0 0 0 0 91 2 #599 599000000 0 100.00000 0 0 0 0 92 3 #599 599000000 0 100.00000 0 0 0 0 93 4 #599 599000000 0 100.00000 0 0 0 0 94 5 #599 599000000 0 100.00000 0 0 0 0 95 6 #599 599000000 0 100.00000 0 0 0 0 96 7 #599 599000000 0 100.00000 0 0 0 0 97 98SEE ALSO 99======== 100 101**rtla-osnoise**\(1) 102 103Osnoise tracer documentation: <https://www.kernel.org/doc/html/latest/trace/osnoise-tracer.html> 104 105AUTHOR 106====== 107Written by Daniel Bristot de Oliveira <bristot@kernel.org> 108 109.. include:: common_appendix.rst 110