Powersave governor by default making config.txt overclocking difficult

[m3adow]

On a newly installed Hypriot "Hector" 0.6, the default governor is powersave. To quote kernel.org:

2.2 Powersave
The CPUfreq governor "powersave" sets the CPU statically to the
lowest frequency within the borders of scaling_min_freq and
scaling_max_freq.

This effectively makes overclocking with config.txt impossible without changing the governor via startup script. I can't confirm it's the same for 0.61, but the kernel configs seem to imply that.

Of course I may be in the wrong, but I doubt this is intended. I'd recommend setting it either to ondemand or conservative.

[MathiasRenner]

@m3adow Thanks for filing this, I will have a look at it! We did not discuss this issue for the very latest release since we wanted to release it in time for the DockerCon :-)

[MathiasRenner]

Hmm, I tested a fresh HypriotOS 0.6.1 and saw the CPU frequency immediately switching from 600 to 900 Mhz when stress --cpu 4 is executed.

sudo cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq 
900000

Also, the governor by default is ondemand, even if the script suggests that powersafe is default.

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ondemand

A few lines below the powersafe default option, ondemand is in general enabled:
https://github.com/hypriot/rpi-kernel/blob/master/kernel_configs/rpi2_docker_kernel_config#L522-L526

So it seems that onemdand works fine. Could you please double check this with the latest image on your site?

Finally I created a /boot/config.txt - it did not seem to change anything. What do you expect to happen with these lines from your comment in Gitter?

arm_freq=900
core_freq=333
sdram_freq=450
over_voltage=2

[m3adow]

So it seems that onemdand works fine. Could you please double check this with the latest image on your site?

No sorry, I can't reflash my Pis for a couple of weeks at least, so I'm still running on 0.6. It seems the bug is fixed in 0.61 then.

Finally I created a /boot/config.txt - it did not seem to change anything. What do you expect to happen with these lines from your comment in Gitter?

arm_freq=900
core_freq=333
sdram_freq=450
over_voltage=2

I don't think I understand the intention of your question, but I'll try answering it.
I expect exactly what is documented (https://www.raspberrypi.org/documentation/configuration/config-txt.md). I'm using additional values, specifically smaller min values for less power consumption, I just removed those as it wasn't important. arm_min_freq values work as well with a proper governor.

[MathiasRenner]

Still, thanks for your feedback. This would have definitely been a bug.

I intended to know what the parameters in /boot/config.txt do. Thanks for the link, this is what I was looking for.

I tried some kind of undervoltage and set arm_freq, sdram-freq and similar parameters to about half of the default value, but I only saved about 0.2 Watts. Do you gain more saving effects?

[m3adow]

I can't say how much I got exactly as I only have the result of a calculation I made over one year ago. Back then my Pis were idle for 90% of the time and I underclocked them heavily (I think to 100MHz or something like that) which according to my calculation saved me ~15€/year. Not a lot, but why pay for something I don't use?

Nevertheless, this is more a topic for Gitter and not for an issue tracker. As the problem doesn't seem to exist on 0.61 anymore, I consider this done. Should probably still be changed here for improved clarity.