How to move already running processes to different `cgroup` with systemd?

Mikko Rantalainen

3/28/24, 8:37 AM

I'm using Ubuntu 20.04 LTS with MATE desktop which doesn't natively support launching desktop UI and window manager in a separate cgroup from the other applications.

Is it possible to run some systemd specific commands via .xsessionrc to create nested cgroup as child of user@${UID}.service and move selected processes there? I'd prefer something that doesn't require sudo or root so that the required commands could be safely executed by the respective user account (with the effective user id $UID).

Basically I'm looking for real world replacements for following imaginary commands

systemd-cgroup-create --parent "user@${UID}.service" "gui-desktop@${UID}.slice"
systemd-cgroup-move-process --to "gui-desktop@${UID}.slice" $(pgrep --uid $UID marco) $(pgrep --uid $UID mate-panel) $(pgrep --uid $UID mate-session)
systemd-cgroup-modify --set "MemoryMin=1G" --set "IOWeight=1000" "gui-desktop@${UID}.slice"

All I can see is systemd-run but that only supports starting a single process instead of manipulating already existing processes.

I know that cgclassify and similar old tools can technically do this given root acces but systemd expects that it's the sole source of modifications to the cgroup hierarchy so this would need to be done via systemd specific commands.

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cgroup

systemd

resource-limiting

20.04

Elon Musk

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EN: How to move already running processes to different `cgroup` with systemd?

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