Dietpi: CPU Governor - Permission denied

[bbsixzz]

Creating a bug report/issue

Required Information

DietPi version |
G_DIETPI_VERSION_CORE=6
G_DIETPI_VERSION_SUB=27
G_DIETPI_VERSION_RC=2
G_GITBRANCH='master'
G_GITOWNER='MichaIng'

Distro version | buster 10.2

Kernel version |
Linux DietPi 4.19.75-v7l+ #1270 SMP Tue Sep 24 18:51:41 BST 2019 armv7l GNU/Linux

SBC device | RPi 4 Model B (armv7l)

Power supply used | 3A Official

SDcard used | SanDisk ultra

Extra details

My CPU is locked at 600 MHz with Governor powersave.

I updated EEPROM after updating to DietPi 6.27.2; maybe related?

[EDIT]

-rwxr-xr-x 1 root root 12K Jan 2 04:17 dietpi.txt

[Joulinar]

hi,
as far as I can see some coding changed in /DietPi/dietpi/func/dietpi-set_cpu with new version v6.27.2. So I guess it has noting to do with the EEPROM update and might be a typo/bug in the scripting.

@MichaIng
I guess in section Apply_CPU_Gov the following needs to be changed, line 75. But might be I'm wrong:

from

for i in /sys/devices/system/cpu/cpu[0-9]*/cpufreq/scaling_available_governors

to

for i in /sys/devices/system/cpu/cpu[0-9]*/cpufreq/scaling_governor

[bbsixzz]

That did the trick, cheers!

On a tangent, is it supposed to be 1500 MHz when Governor is ondemand?

There is virtually no load.

[Joulinar]

it should go down after a while

[bbsixzz]

Well maybe this it the culprit?

[ INFO ] DietPi-CPU_info | CPU current frequency, may be affected by this script, due to the processing required to run it.

It still hasn't gone down, did a reboot as well.

[MichaIng]

@bbsixzz
Indeed the script itself should raise the load for a tiny time which is enough to raise frequencies for 1 second (default before or goes down after load) on slower SBCs.

To check with less overhead:

cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq

If this is not available:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq

Ref: https://www.kernel.org/doc/html/v4.19/admin-guide/pm/cpufreq.html#policy-interface-in-sysfs

[bbsixzz]

cpuinfo_cur_freq result: 1500000
scaling_cur_freq result: 600000

I don't think it's a big deal, but it seems locked at 1500 MHz.

Is the RPi4 really so slow that the CPU script throttles all 4 cores like that?

[EDIT]

[EDIT]

I did a test using Governor conservative, I downloaded a large file using SFTP.

It throttled correctly during download and stepped down when idle.

It looks to me like Governor ondemand doesn't work correctly or the settings are bad.

Maybe these two paramaters need adjustment? They are not available for conservative.

Ondemand Sample Rate: [25ms]
Ondemand Down Factor: [80 (2000ms)]

I can run the CPU script all day on Governor conservative and it never throttles to 1500 MHz.

[Joulinar]

For me it looks like using ondemand will look me at 1500 MHz and it's not stepped down. CPU temp is below 40'C. So it's doing nothing.

root@DietPi4:~# cpu

 ─────────────────────────────────────────────────────
 DietPi CPU Info
 Use dietpi-config to change CPU / performance options
 ─────────────────────────────────────────────────────
 Architecture |     armv7l
 Temperature  |     39'C : 102'F (Cool runnings)
 Governor     |     ondemand
 Throttle up  |     50% CPU usage

                 Current Freq    Min Freq   Max Freq
 CPU0         |      1500 MHz      600 MHz    1500 MHz
 CPU1         |      1500 MHz      600 MHz    1500 MHz
 CPU2         |      1500 MHz      600 MHz    1500 MHz
 CPU3         |      1500 MHz      600 MHz    1500 MHz

[ INFO ] DietPi-CPU_info | CPU current frequency, may be affected by this script,
due to the processing required to run it.

While using conservative seems working correctly. It's stepping up if needed and going down once done.

root@DietPi4:~# cpu

 ─────────────────────────────────────────────────────
 DietPi CPU Info
 Use dietpi-config to change CPU / performance options
 ─────────────────────────────────────────────────────
 Architecture |     armv7l
 Temperature  |     50'C : 122'F (Running warm, but safe)
 Governor     |     conservative
 Throttle up  |     50% CPU usage

                 Current Freq    Min Freq   Max Freq
 CPU0         |      1500 MHz      600 MHz    1500 MHz
 CPU1         |      1500 MHz      600 MHz    1500 MHz
 CPU2         |      1500 MHz      600 MHz    1500 MHz
 CPU3         |      1500 MHz      600 MHz    1500 MHz

[ INFO ] DietPi-CPU_info | CPU current frequency, may be affected by this script,
due to the processing required to run it.

root@DietPi4:~#
root@DietPi4:~#
root@DietPi4:~#
root@DietPi4:~# cpu

 ─────────────────────────────────────────────────────
 DietPi CPU Info
 Use dietpi-config to change CPU / performance options
 ─────────────────────────────────────────────────────
 Architecture |     armv7l
 Temperature  |     38'C : 100'F (Cool runnings)
 Governor     |     conservative
 Throttle up  |     50% CPU usage

                 Current Freq    Min Freq   Max Freq
 CPU0         |      600 MHz      600 MHz    1500 MHz
 CPU1         |      600 MHz      600 MHz    1500 MHz
 CPU2         |      600 MHz      600 MHz    1500 MHz
 CPU3         |      600 MHz      600 MHz    1500 MHz

[ INFO ] DietPi-CPU_info | CPU current frequency, may be affected by this script,
due to the processing required to run it.

I used dietpi-config: Stress Test to simulate the load.

[EDIT]
Same seems to be valid for my RPi 3 Model B+ running v6.26.3

[travisboss]

Nevermind, the fix above did work I just had a typo.

[bbsixzz]

@MichaIng just to be clear, you should investigate ondemand as it doesn't seem to be working.

The original bug of "permission denied" is however fixed.

[MichaIng]

@bbsixzz
I am pretty sure that it works fine. Please check the following:

cat /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state

It should show you how long (for current session) the CPU was in which state (only the two 600 and 1500 on RPi).

You can raise the CPU usage on which the freq is raised via up_treshold:

cat /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

Its 50% by default on DietPi. When raising to e.g. 95% it might stay on lower freq during the commands.

echo 95 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

Or via dietpi-config to be persistent.

[bbsixzz]

Alright, after a reboot I got the following numbers which indicate everything works fine!

600000 3509
1500000 5709

Thank you for the education :]

[MichaIng]

v6.28 is out, I mark this issue as closed.