CPU frequency measurements sometimes go below known minimum

[philipandag]

Component

Dasharo firmware

Device

NovaCustom V54 14th Gen

Dasharo version

v0.9.1-rc5

Dasharo Tools Suite version

--

Test case ID

CPF004.005

Brief summary

The CPU frequency sometimes falls below the minimum frequency

How reproducible

5/60 of measurements

How to reproduce

Run CPF test suite or check the clocks manually

Expected behavior

Should be in the documented range of 300-4800 MHz

Actual behavior

Sometimes the clocks fall down to 200MHz

Screenshots

https://github.com/user-attachments/files/16989613/dasharo-performance_log.zip

Additional context

The device was powered via the Wavlink docking station, using an USB-C cable. The CPF test without load passed without issues. In CPF004 we measure the frequencies under load. It seems from the logs that the load stays for only about 1 minute and then the frequencies fall down.

Solutions you've tried

No response

[mkopec]

The 200mhz freq is probably the actual minimum on these processors. You can check by connecting and disconnecting a power supply and watching the frequencies. The CPU will throttle for 3 seconds to the actual minimum frequency achievable

[philipandag]

The 200mhz freq is probably the actual minimum on these processors. You can check by connecting and disconnecting a power supply and watching the frequencies. The CPU will throttle for 3 seconds to the actual minimum frequency achievable

That's interesting then, because on Ubuntu the frequency generally drops only as low as 400MHz but it falls down to 200MHz only during the tests under load. On Windows the frequencies don't drop below 400MHz.

[mkopec]

Could also be a problem with the measurement tool. What does sudo turbostat -s Bzy_MHz -i 0.1 have to say? (you might need to be on kernel 6.8 for this)

[philipandag]

On kernel 6.8.0-44 sudo turbostat -s Bzy_MHz -i 0.1 shows that most of the cores drop to exactly 200MHz the moment I unplug the AC. Some cores fall even a bit below 200MHz for a fraction of a second. After a couple seconds the clocks come back to ~1000-2000MHz

[philipandag]

cpu-frequency.robot_log.zip On battery on Ubuntu with kernel 6.9 the frequencies haven't fell below 400MHz.

The log shows it's a test without load because the load was launched manually. stress-ng --cpu $(nproc) --timeout 60m &> /dev/null & disown

[mkopec]

on Ubuntu 24.10 turbostat shows 200-350 minimum, /proc/cpuinfo shows a pretty constant 400MHz but with some dips below. Not sure if it's an issue with measurement or if the CPU actually clocks down that low