sbc-bench on arm

[sfx2000]

Recommendation - don't change the CPU governors on sbc-bench - can report what's in use, but by changing it, it's hard to tell if exploring this item for a/b testing

echo performance >/sys/devices/system/cpu/cpu${i}/cpufreq/scaling_governor

[ThomasKaiser]

The readme of this project clearly explains the four different usage modes:

• Generate a rough CPU performance assessment for a specific SBC in general (under ideal conditions)
• Show whether an individual SBC is able to perform the same and if not hopefully answering the question 'why?'
• Help software developers and hardware designers to improve 'thermal performance' when using the -t and/or -T switches (details/discussion, another example)
• Provide basic CLI monitoring functionality through the -m switch

The first three usage modes require the cpufreq governor being set to performance to let cpufreq governor not alter performance behavior (and in 'thermal testing' mode allowing the cpufreq to decrease for other reasons than throttling making the whole reporting completely useless).

The last mode is for monitoring and doesn't alter the cpufreq governor.

What you're asking for is an interesting area of investigation: how does the chosen cpufreq settings (governor + other settings like min/max cpufreq or stuff like io_is_busy) negatively affects performance of boards. But unfortunately for this an entirely different set of tests is needed and I don't plan on adding this to this tool anytime soon or at all. Since getting an idea how/why cpufreq governors work requires to dig a lot more deeper than firing up some standard benchmarks and drawing the wrong conclusions.

Examples:

• network performance seems to suck due to inappropriate cpufreq settings
• Tuning cpufreq behavior results in better benchmark numbers but might harm real world performance
• Inappropriate cpufreq settings destroying storage performance

These issues can only be addressed by looking into details (the Active Benchmarking approach) and not by providing a tool that is meant to be operated in fire&forget mode.