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systemd : How to move all realtime(RT) processes to "root cgroup"?

Linux Kernel, Network, and Services configuration.
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hopperman
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Joined: 2021-09-25 19:00
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systemd : How to move all realtime(RT) processes to "root cgroup"?

#1 Post by hopperman »

I have a problem adding cpu controller since command gives error :

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 sudo echo "+cpu" >> cgroup.subtree_control 
 bash: cgroup.subtree_control: Access Denied.
 

Therefore, I have found a solution is that I have to move all realtime(RT) processes to root cgroup as explained in cgroupv2 documents (revealed in similar problem's solution which reference to https://www.kernel.org/doc/Documentation/cgroup-v2.txt).
WARNING: cgroup2 doesn't yet support control of realtime processes and
the cpu controller can only be enabled when all RT processes are in
the root cgroup. Be aware that system management software may already
have placed RT processes into nonroot cgroups during the system boot
process, and these processes may need to be moved to the root cgroup
before the cpu controller can be enabled.

When I used

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 ps ax -L -o 'pid tid cls rtprio comm' | grep RR 

command, I obtained 5 different processes :

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 1220    1229  RR     20 pipewire
 1221    1342  RR      5 alsa-sink-ALC88
 1221    1343  RR      5 alsa-source-ALC
 1246    1250  RR     20 pipewire-media-
 7771    7773  RR     99 rtkit-daemon

As I understood from internet, pipewire and pipewire-media are RT "streaming services". I tried to move one of them to root cgroup by using :

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 echo "1220" > /sys/fs/cgroup/cgroup.procs

but it gives the same error, the most probabily since they are still active and system does not allow to change their group. So how can I move those processes to root cgroup? I tried to kill them before moving and activating CPU and CPUSet controllers but no success, since all RT processes restarted immediately after I kill them again! What can I do?

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