Experiences with CPUFREQ / powersaving

[specs]

I believe the standard Ubuntu version on the distributed media with the N2 come with the setting:
CPU 0-1 667-1900MHz / governor "intermediate"
CPU 2-5 667-1800MHz / governor "intermediate"

When testing I found a workable solution with
CPU 0-1 250-1900MHz / governor "intermediate"
CPU 2-5 250-1800MHz / governor "intermediate"

When switching to "ondemand" or a lower limit of 100MHz I find the N2 unstable (not response, sometimes requiring a reboot).
While "intermediate" results in a responsive system it might not be the most efficient governor.

Are there other experiences with a powersave setting which does lead to a non-responsive system?
What powersave settings do you recommend?
Is disabling cores really helping in powersaving or is it just limiting the system?

I believe the simple accessories I use to check the power use might not be reliable for a good comparison when running behind a AC-DC convertor. But then again I'm no electrician. After the testing period the system should work from battery power, were the measurement should be easier.

Thanks in advance.

[vjoel]

On my N2, "intermediate" is not listed by cpufreq-info:

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  available cpufreq governors: ondemand, powersave, userspace, conservative, interactive, performance, schedutil

I'm using ondemand with 100MHz min and 1.9/1.8 GHz max. I have not noticed a hang/reboot problem, except possibly once during a long-running build using all 6 cores, That has not happened again, but I've only done a few other builds.

[odroid]

As far as I remember, the difference of idle power consumption between 100Mhz and 667Mhz was very negligible.
So 667Mhz minimal clock will give you much better responsiveness with slightly higher electric cost.
Also note that, 100Mhz is not sufficient to handle some sudden heavy tasks.
It seems to be mains reason why x86 and other famous ARM boards set the minimal clock at higher than 500Mhz.

BTW, we've used Performance governor only.

[specs]

@vjoel
Clearly my mistake, the governor used was off course "interactive"
The problems with "ondemand" and with the lower limit of "100MHz" is not so much instability, but more "not waking up" after a period of inactivity.

Also, when reading about governors I found some lines specifying that when used on battery, "conservative" might be better than "ondemand".
Only reason I can think of is that the power peaks are having a negative influence on the complete system.

Since my system should be used on battery power (something like 2*100 Ah) with some other power users, the difference between "conservative" and "ondemand" might be neglectable.

[specs]

@odroid
I think interactive is the standard of the Ubuntu distro shipped with your eMMC. I never used "interactive" before so it was like, "oh, did that also exist".

I thought that the main reason for ARM instead of x86 was that ARM can be powered back more, like completely switching off a core.
Normally a clocked down core can still be expected to use power, i.e. some kind of power leakage due to not completely disconnecting the power supply.
I hoped someone had made some measurements with the difference of switching a core off instead of clocking it down.

One part of the question is, does the next line make sence:
echo 0 > /sys/devices/system/cpu/cpu5/online

Or is it just some cosmetic change in the system, limiting the performance while not preserving power.

[mad_ady]

The hotplug governor should take cores offline when idle. You can also use odroid-cpu-control to set governor/min/max frequency.

In terms of power performance - this depends on too many variables and it's best to measure consumption over time with different governors.

[rooted]

I don't believe you really gain any power savings by setting the minimum CPU speed to below 400mhz, as it can do minimal work without spinning up. Lower than this the CPU will randomly spin up causing spikes in power usage if a process needs a bit of CPU time.

[specs]

The hotplug governor should take cores offline when idle. You can also use odroid-cpu-control to set governor/min/max frequency.

In terms of power performance - this depends on too many variables and it's best to measure consumption over time with different governors.

Based on you mentioning the hotplug driver I found some overview for different governors. Governors for Android to be exact, but it I think the difference between Linux and Android here is most likely the availability of most governors.
https://androidmodguide.blogspot.com/p/blog-page.html

For my purpose:
- ondemand is not worth looking into (too much jumping speeds)
- conservative is same as hotplug but more gradually increasing and decreasing of speeds
- interactive might be an option, but is is explained as conservative + jumping to max frequency when turning on the monitor
- hotplug is ondemand + shutting of cores (and therefore same problems as ondemand)
- ConservativeX is conservative + shutting of core #1, and core #1 would be the A53 which should be the lowpower core.

Even without considering that hotplug and ConservativeX are not available in the standard kernel, they do not look so inviting to me.
Guess I will start with conservative and interactive, since they look the most promising.

As for the hotplugging:
I think I will play with it in a later stage. It might work shutting of some cores manually and testing the system.
I guess the system should work with 2 A53 cores (normally) or A73 cores for testing purposes, which would allow for some testing with a limited setup.
If I could use some powerbank the power usage should be easier to monitor than working on the standard batteries.

I still have to work out if I can assign some logging and background data sharing to a specific core (whether A73 or A53).
In a later stadium I could add a switch based on switching off cores based on input voltage (i.e. recharging or battery power).

Can't wait for the season were I can test in the field to begin.

[mad_ady]

Note that some irqs are pinned to specific big cores (usb, network) so you may not be able to power off some cores.

[rooted]

Install:

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sudo apt install util-linux

Then you can use taskset to launch applications pinned to the desired core. I add this to my ~/.bash_aliases then run a task like "big htop" to run on the fast cores.

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alias big='taskset -c 0-1 $f'
alias little='taskset -c 2-5 $f'

Run

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source ~/.bashrc

This will allow the commands to work right away without rebooting, they will work afterwards regardless.

Example of difference:

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rooted@cloudshell2:~#  big speedtest --server 16618
Retrieving speedtest.net configuration...
Testing from Cox Communications (70.191.xxx.xxx)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Cox - New Orleans (New Orleans, LA) [283.85 km]: 18.149 ms
Testing download speed................................................................................
Download: 520.13 Mbit/s

rooted@cloudshell2:~# little speedtest --server 16618
Retrieving speedtest.net configuration...
Testing from Cox Communications (70.191.xxx.xxx)...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by Cox - New Orleans (New Orleans, LA) [283.85 km]: 21.898 ms
Testing download speed................................................................................
Download: 296.53 Mbit/s

[mad_ady]

Nice alias trick. Didn't know about $f.

[rooted]

Nice alias trick. Didn't know about $f.

That's the great thing about knowledge, no matter how much we have there are always useful little tidbits we gather in our day to day lives. In Linux there is always something to learn, after using it for nearly 25 years I still learn new stuff daily (or relearn things I've forgotten).

It's funny how often I search how to do something that leads me to an old post of my own, I'm so forgetful.

[thatsaltydude]

How do you set the 4 Cortex-A73 to 1800MHz? I can only manage to get them to 1700MHz using cpufreq-set.

[specs]

I don't really understand you question.

All speed settings are visible using cpufreq-info.
Core #0 and #1 are both A53 and the speed settings are coupled.
Idem for core #2 to #5, but these are A73.
667MHz - 1.8GHz is the standard setting with Ubuntu 18.04 as shipping with for the A73 with the N2.

Changing the speed can be done with:

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root@odroid:~# cpufreq-set -c 5 -u 1512000
root@odroid:~# cpufreq-info | tail -13
analyzing CPU 5:
  driver: arm-big-little
  CPUs which run at the same hardware frequency: 2 3 4 5
  CPUs which need to have their frequency coordinated by software: 2 3 4 5
  maximum transition latency: 50.0 us.
  hardware limits: 100.0 MHz - 1.80 GHz
  available frequency steps: 100.0 MHz, 250 MHz, 500 MHz, 667 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz, 1.51 GHz, 1.61 GHz, 1.70 GHz, 1.80 GHz
  available cpufreq governors: conservative, powersave, performance, schedutil
  current policy: frequency should be within 250 MHz and 1.51 GHz.
                  The governor "conservative" may decide which speed to use
                  within this range.
  current CPU frequency is 250 MHz (asserted by call to hardware).
  cpufreq stats: 100.0 MHz:0.00%, 250 MHz:78.38%, 500 MHz:0.73%, 667 MHz:0.47%, 1000 MHz:0.22%, 1.20 GHz:0.10%, 1.40 GHz:0.08%, 1.51 GHz:0.04%, 1.61 GHz:0.03%, 1.70 GHz:0.02%, 1.80 GHz:19.93%  (6897)
root@odroid:~# cpufreq-set -c 5 -u 1800000
root@odroid:~# cpufreq-info | tail -13
analyzing CPU 5:
  driver: arm-big-little
  CPUs which run at the same hardware frequency: 2 3 4 5
  CPUs which need to have their frequency coordinated by software: 2 3 4 5
  maximum transition latency: 50.0 us.
  hardware limits: 100.0 MHz - 1.80 GHz
  available frequency steps: 100.0 MHz, 250 MHz, 500 MHz, 667 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz, 1.51 GHz, 1.61 GHz, 1.70 GHz, 1.80 GHz
  available cpufreq governors: conservative, powersave, performance, schedutil
  current policy: frequency should be within 250 MHz and 1.80 GHz.
                  The governor "conservative" may decide which speed to use
                  within this range.
  current CPU frequency is 250 MHz (asserted by call to hardware).
  cpufreq stats: 100.0 MHz:0.00%, 250 MHz:78.38%, 500 MHz:0.73%, 667 MHz:0.47%, 1000 MHz:0.22%, 1.20 GHz:0.10%, 1.40 GHz:0.08%, 1.51 GHz:0.04%, 1.61 GHz:0.03%, 1.70 GHz:0.02%, 1.80 GHz:19.93%  (6897)

As normal user you might want to add "sudo".
With "-c1", "-c0" or without specification the A53 will be changed (but not to 1800000, since that setting is not available for the A53).

If the available settings are not clear look in /sys:

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~$ cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies 
100000 250000 500000 667000 1000000 1200000 1398000 1512000 1608000 1704000 1896000 
~$ cat /sys/devices/system/cpu/cpufreq/policy2/scaling_available_frequencies 
100000 250000 500000 667000 1000000 1200000 1398000 1512000 1608000 1704000 1800000

Messing around directly in /sys/devices/system/cpu/cpufreq/policyX is of course not a normal user interface.

[joy]

How do you set the 4 Cortex-A73 to 1800MHz? I can only manage to get them to 1700MHz using cpufreq-set.

Hi thatsaltydude,
I'm not sure this is exactly what you're wondering.

Default current freq of A73 is 1800MHz, because default governor of N2 is performance and max freq of A73 is 1800MHz.
If you didn't modify /media/boot/boot.ini, you can confirm the values as following.

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$ cat /sys/devices/system/cpu/cpufreq/policy2/scaling_available_frequencies 
100000 250000 500000 667000 1000000 1200000 1398000 1512000 1608000 1704000 1800000 
$ cat /sys/devices/system/cpu/cpufreq/policy2/scaling_max_freq              
1800000
$ cat /sys/devices/system/cpu/cpufreq/policy2/scaling_governor 
performance
$ cat /sys/devices/system/cpu/cpufreq/policy2/scaling_cur_freq 
1800000

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$ cpufreq-info -o
          minimum CPU frequency  -  maximum CPU frequency  -  governor
CPU  0       667000 kHz ( 35 %)  -    1896000 kHz (100 %)  -  performance
CPU  1       667000 kHz ( 35 %)  -    1896000 kHz (100 %)  -  performance
CPU  2       667000 kHz ( 37 %)  -    1800000 kHz (100 %)  -  performance
CPU  3       667000 kHz ( 37 %)  -    1800000 kHz (100 %)  -  performance
CPU  4       667000 kHz ( 37 %)  -    1800000 kHz (100 %)  -  performance
CPU  5       667000 kHz ( 37 %)  -    1800000 kHz (100 %)  -  performance

[specs]

@joy
Nice, a little off-topic but this lead me to fix another annoyance.

My monitor only went into blanking after a time of inactivity while I expected switching off (powersave standby).

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~# grep -A1 HDMI.PHY /media/boot/boot.ini
# Controls if HDMI PHY should output anything to the monitor
setenv monitor_onoff "true" # true or false

(default setting is of course safe, therefore "false".)

[joy]

My monitor only went into blanking after a time of inactivity while I expected switching off (powersave standby).

@specs,
I've checked the operation again today and screen poweroff works normally by my side.
Can you show me cmdline?

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$ cat /proc/cmdline

[thatsaltydude]

@specs @joy

It seems that Armbian only allows the A73 cores to run at 1.7GHz. Installed Odroid's minimal Ubuntu image, now it shows 1.8GHz. Although, monero mining is actually not faster than before

[specs]

@specs,
I've checked the operation again today and screen poweroff works normally by my side.
Can you show me cmdline?

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$ cat /proc/cmdline

BEFORE the change it read monitor_onoff=false (only change).

AFTER the change in the boot.ini it reads

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root=UUID=xxxxxxxxxxx rootwait rw console=ttyS0,115200n8  no_console_suspend fsck.repair=yes net.ifnames=0 elevator=noop hdmimode=custombuilt cvbsmode=576cvbs max_freq_a53=1896 max_freq_a73=1800 maxcpus=6 voutmode=dvi modeline=1680,1050,119000,64673,60,1680,1728,1760,1840,1050,1053,1059,1080,1,0,1 disablehpd=false cvbscable= overscan=100  monitor_onoff=true logo=osd0,loaded hdmitx=cec3f

And now it works right on my side too.

boot.ini.old and boot.ini.default don't mention monitor_onoff. Perhaps I should put monitor_onoff in /media/boot/boot.ini.default.

[joy]

boot.ini.old and boot.ini.default don't mention monitor_onoff. Perhaps I should put monitor_onoff in /media/boot/boot.ini.default.

Right.
If you use an earlier version than 20190812, monitor_onoff can NOT be in default bootargs.
https://wiki.odroid.com/odroid-n2/os_im ... u/20190812
The option has been added after Jul 24 2019.
https://github.com/mdrjr/n2_bootini/com ... ef84ab9cd1

Or if you didn't include monitor_onoff option in /media/boot/boot.ini.default, same result.
As you mentioned, without monitor_onoff in bootargs, it would not work normally.
So I wanted to check the /proc/cmdline.
You found it already.

[joy]

@specs @joy

It seems that Armbian only allows the A73 cores to run at 1.7GHz. Installed Odroid's minimal Ubuntu image, now it shows 1.8GHz. Although, monero mining is actually not faster than before

Hi thatsaltydude,
As I checked, Armbian supports A73 cores with max 1.8GHz.
I used the latest image from this link.
: Armbian_19.11.3_Odroidn2_bionic_legacy_4.9.196_desktop.img
https://www.armbian.com/odroid-n2/

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# cat /sys/devices/system/cpu/cpufreq/policy2/scaling_available_frequencies
100000 250000 500000 667000 1000000 1200000 1398000 1512000 1608000 1704000 1800000 
# cat /sys/devices/system/cpu/cpufreq/policy2/scaling_max_freq
1800000

Could you check this parameter in cmdline?
max_freq_a73=1800

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# cat /proc/cmdline 
root=UUID=7dcd5b23-4300-46c6-a019-0690fb860e78 rootwait rootflags=data=writeback rw rootfstype=ext4 console=ttyS0,115200n8 console=tty1 loglevel=1  no_console_suspend fsck.repair=yes net.ifnames=0 elevator=noop hdmimode=10 80p60hz cvbsmode=576cvbs max_freq_a53=1896 max_freq_a73=1800 maxcpus=6 voutmode=hdmi  disablehpd=false cvbscable=0 overscan=100 usb-xhci.tablesize=2

And version, too.

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# uname -a
Linux odroidn2 4.9.196-meson64 #20 SMP PREEMPT Mon Nov 18 22:30:06 CET 2019 aarch64 aarch64 aarch64 GNU/Linux

Could you check the image?

[thatsaltydude]

Hi thatsaltydude,
As I checked, Armbian supports A73 cores with max 1.8GHz.
I used the latest image from this link.
: Armbian_19.11.3_Odroidn2_bionic_legacy_4.9.196_desktop.img
https://www.armbian.com/odroid-n2/

Hi, I had an armbian version of balbes150 with kernel 5.4 on my N2 found on his yandex disk, thread: https://forum.freaktab.com/forum/tv-pla ... d-usb-emmc

I can't check that image's properties, as I already moved to odroid's official ubuntu minimal image with legacy kernel 4.9. On that image, my stuff works, so that's it for my concerns

[joy]

Hi, I had an armbian version of balbes150 with kernel 5.4 on my N2 found on his yandex disk, thread: https://forum.freaktab.com/forum/tv-pla ... d-usb-emmc

I can't check that image's properties, as I already moved to odroid's official ubuntu minimal image with legacy kernel 4.9. On that image, my stuff works, so that's it for my concerns

Hi, thatsaltydude.
I see.
I thought your target was unique to Armbian version.
Thanks for sharing your status.