Odroid N2 | FIFO and Round Robin CPU scheduling policy not supported

[scetu]

Creating a bug report/issue

Required Information

• DietPi version | cat /boot/dietpi/.version

G_DIETPI_VERSION_CORE=8
G_DIETPI_VERSION_SUB=7
G_DIETPI_VERSION_RC=1
G_GITBRANCH='master'
G_GITOWNER='MichaIng'
G_LIVE_PATCH_STATUS[0]='not applicable'

• Distro version | echo $G_DISTRO_NAME $G_RASPBIAN
bullseye
• Kernel version | uname -a
Linux odroid 5.10.123-meson64 #22.05.3 SMP PREEMPT Wed Jun 22 07:23:04 UTC 2022 aarch64 GNU/Linux
• SBC model | echo $G_HW_MODEL_NAME or (EG: RPi3)
  Odroid N2 (aarch64)
• Power supply used | (EG: 5V 1A RAVpower)
  12V A2
• SD card used | (EG: SanDisk ultra)
  EEMC 64GB

Additional Information (if applicable)

• Software title | (EG: Nextcloud)
  Docker
• Was the software title installed freshly or updated/migrated?
  freshly installed today
• Can this issue be replicated on a fresh installation of DietPi?
  Most probably yes

• Bug report ID | echo $G_HW_UUID

Steps to reproduce

1. Install Docker from dietpi-software
2. Go to dietpi-services and try to apply predefined Highest priority
3. 
4. After service restart services fails to load
   

Expected behaviour

• Service should eb started and preset applied

Actual behaviour

• described in "Steps to reproduce"

Extra details

• This preset is working on RPi 4B, but not on Odroid N2+
• High Priority preset works and service can start
• There were other minor errors which I saw today on Odroid N2+ for the first time after getting it in addition to my Raspberry Pis, also related to Docker, so maybe it is upstream error

[Joulinar]

Can you reboot your system and share following

journalctl -u docker. Service

[scetu]

Highest priority

after reboot...

root@odroid:~# journalctl -u docker
-- Journal begins at Sat 2022-08-20 15:12:30 CEST, ends at Sat 2022-08-20 15:13:02 CEST. --
Aug 20 15:12:38 odroid systemd[2087]: docker.service: Failed to set up CPU scheduling: Operation not permitted
Aug 20 15:12:38 odroid systemd[1]: Started Docker Application Container Engine.
Aug 20 15:12:38 odroid systemd[2087]: docker.service: Failed at step SETSCHEDULER spawning /usr/bin/dockerd: Operation not permitted
Aug 20 15:12:38 odroid systemd[1]: docker.service: Main process exited, code=exited, status=214/SETSCHEDULER
Aug 20 15:12:38 odroid systemd[1]: docker.service: Failed with result 'exit-code'.
Aug 20 15:12:40 odroid systemd[1]: docker.service: Scheduled restart job, restart counter is at 1.
Aug 20 15:12:40 odroid systemd[1]: Stopped Docker Application Container Engine.
Aug 20 15:12:40 odroid systemd[2108]: docker.service: Failed to set up CPU scheduling: Operation not permitted
Aug 20 15:12:40 odroid systemd[2108]: docker.service: Failed at step SETSCHEDULER spawning /usr/bin/dockerd: Operation not permitted
Aug 20 15:12:40 odroid systemd[1]: Started Docker Application Container Engine.
Aug 20 15:12:40 odroid systemd[1]: docker.service: Main process exited, code=exited, status=214/SETSCHEDULER
Aug 20 15:12:40 odroid systemd[1]: docker.service: Failed with result 'exit-code'.
Aug 20 15:12:42 odroid systemd[1]: docker.service: Scheduled restart job, restart counter is at 2.
Aug 20 15:12:42 odroid systemd[1]: Stopped Docker Application Container Engine.
Aug 20 15:12:42 odroid systemd[2111]: docker.service: Failed to set up CPU scheduling: Operation not permitted
Aug 20 15:12:42 odroid systemd[2111]: docker.service: Failed at step SETSCHEDULER spawning /usr/bin/dockerd: Operation not permitted
Aug 20 15:12:42 odroid systemd[1]: Started Docker Application Container Engine.
Aug 20 15:12:42 odroid systemd[1]: docker.service: Main process exited, code=exited, status=214/SETSCHEDULER
Aug 20 15:12:42 odroid systemd[1]: docker.service: Failed with result 'exit-code'.
Aug 20 15:12:44 odroid systemd[1]: docker.service: Scheduled restart job, restart counter is at 3.
Aug 20 15:12:44 odroid systemd[1]: Stopped Docker Application Container Engine.
Aug 20 15:12:44 odroid systemd[1]: docker.service: Start request repeated too quickly.
Aug 20 15:12:44 odroid systemd[1]: docker.service: Failed with result 'exit-code'.
Aug 20 15:12:44 odroid systemd[1]: Failed to start Docker Application Container Engine.

High priority

Aug 20 15:15:58 odroid systemd[1]: Started Docker Application Container Engine.

[Joulinar]

looks like Docker don't like to have CPU scheduling set

Aug 20 15:12:42 odroid systemd[2111]: docker.service: Failed to set up CPU scheduling: Operation not permitted
Aug 20 15:12:42 odroid systemd[2111]: docker.service: Failed at step SETSCHEDULER spawning /usr/bin/dockerd: Operation not permitted

[MichaIng]

I guess it's the CPU scheduling class which is the issue. And to be true, giving the whole Docker engine realtime is probably dangerous, as there are a lot of low priority processes included, the engine itself and the wrapping container system services, like probably logging as such things.

However, it seems to be a kernel flag which causes this in combination with systemd: https://stackoverflow.com/questions/34018956/sched-setscheduler-error-eperm-after-installing-libpam-systemd

We need to replicate this is a simple dummy service.

[MichaIng]

While it is not what I'd recommend, I just tested the highest possible CPU and I/O classes and priorities (as well as the "Highest Priority" preset) on Docker on VM and there it works without issues:

root@VM-Bullseye:~# cat /etc/systemd/system/docker.service.d/dietpi-process_tool.conf
# WARNING: Do not manually edit this file, use "dietpi-services" to adjust values!
[Service]
CPUSchedulingPolicy=fifo
CPUSchedulingPriority=99
IOSchedulingClass=realtime
IOSchedulingPriority=0
...
root@VM-Bullseye:~# cat /etc/systemd/system/docker.service.d/dietpi-process_tool.conf
# WARNING: Do not manually edit this file, use "dietpi-services" to adjust values!
[Service]
CPUSchedulingPolicy=fifo
IOSchedulingClass=realtime
CPUSchedulingPriority=50

Probably a limitation of the Odroid N2 kernel? Needs further testing.

[scetu]

Unfortunately, I have only one Odroid N2 and it is already in production use with "High priority" preset applied. Maybe somebody else could help with testing of these tweaks.

[MichaIng]

Verified: FIFO and Round Robin are both generally not permitted on Odroid N2 for whatever reason. On x86_64 VMs and Raspberry Pi it works without issues:

root@OdroidN2:~# chrt -f --pid 1 5094
chrt: failed to set pid 5094's policy: Operation not permitted
root@OdroidN2:~# chrt -r --pid 1 5094
chrt: failed to set pid 5094's policy: Operation not permitted
root@OdroidN2:~# chrt -o --pid 0 5094
root@OdroidN2:~#

Must be a kernel limitation. I'll test this on some other SBCs tomorrow.