[systemd-devel] What do I need to do to force systemd to create folders in the cgroups tree?

[Barry Scott]

For my application I have three slices. Two of these are working,
onelan.slice and onelan-screen.slice, but onelan-player.slice is
not causing the cgroup folders to come into existence.

I put a dependency on workaround-systemd-cgroup-limitations-onelan-player-
slice.service to cause onelan-player.slice to be created. That slice will
be used later to hold processes create via the dbus start transient interface.

But when that services run I see the following cgroups:

# find /sys/fs/cgroup -name '*.slice' -print
/sys/fs/cgroup/memory/onelan.slice
/sys/fs/cgroup/cpuacct/onelan.slice
/sys/fs/cgroup/cpuacct/onelan.slice/onelan-screen.slice
/sys/fs/cgroup/cpuacct/onelan.slice/onelan-player.slice
/sys/fs/cgroup/cpu/onelan.slice
/sys/fs/cgroup/cpu/onelan.slice/onelan-screen.slice
/sys/fs/cgroup/cpu/onelan.slice/onelan-player.slice
/sys/fs/cgroup/systemd/user.slice
/sys/fs/cgroup/systemd/onelan.slice
/sys/fs/cgroup/systemd/onelan.slice/onelan-screen.slice
/sys/fs/cgroup/systemd/onelan.slice/onelan-player.slice
/sys/fs/cgroup/systemd/system.slice
/sys/fs/cgroup/systemd/system.slice/system-lvm2\x2dpvscan.slice
/sys/fs/cgroup/systemd/system.slice/system-systemd\x2dfsck.slice
/sys/fs/cgroup/systemd/system.slice/system-systemd\x2dbacklight.slice
/sys/fs/cgroup/systemd/system.slice/system-getty.slice

I expect to have /sys/fs/cgroup/memory/onelan.slice/onelan-player.slice
but it does not exist.

What do I need to do to force it to be created?

Here is the content of involved unit files and status from systemd.

# cat /etc/systemd/system/workaround-systemd-cgroup-limitations-onelan-player-
slice.service
[Unit]
Description="workaround systemd cgroup limitations service"

After=workaround-systemd-cgroup-limitations-onelan-slice.service
Requires=workaround-systemd-cgroup-limitations-onelan-slice.service

[Service]
Slice=onelan-player.slice
Type=oneshot
StandardOutput=syslog
ExecStart=/usr/local/onelan/systemd/workaround-systemd-cgroup-limitations 
onelan-player.slice
RemainAfterExit=yes

# cat /usr/local/onelan/systemd/workaround-systemd-cgroup-limitations
#!/bin/bash
#
#   Copyright 2014 (c) ONELAN Ltd. www.onelan.co.uk
#   All rights reserved.
#
#
#   workaround-systemd-cgroup-limitations
#
#   As of systemd 208 it is not possible to setup all
#   the cgroup attributes that we need.
#
#   As soon as systemd aquires a method of doing the
#   additional cgroup setup this module and its .service
#   can be deleted.
#
set -e

function set_attr {
    VALUE=$1
    CGATTR=$2
    echo Info: Set ${VALUE} into ${CGATTR}
    echo ${VALUE} >${CGATTR}
}

case "$1" in
onelan.slice)
    find /sys/fs/cgroup -name '*.slice' -print >/root/onelan.slice.log
    CGROUP=/sys/fs/cgroup/cpu/onelan.slice
    set_attr 1000000000 ${CGROUP}/cpu.rt_period_us
    set_attr  900000000 ${CGROUP}/cpu.rt_runtime_us
    ;;

onelan-player.slice)
    find /sys/fs/cgroup -name '*.slice' -print >/root/onelan-player.slice.log
    CGROUP=/sys/fs/cgroup/memory/onelan.slice/onelan-players.slice

    LINE=$( grep '#SwapMemoryLimit' /etc/onelan/ntb/systemd-player-memory-
limits.include )
    LIMIT=${LINE#*=}

    set_attr ${LIMIT} ${CGROUP}/memory.memsw.limit_in_bytes
    ;;

*)
    exit 1
    ;;
esac


# cat /etc/systemd/system/onelan-players.slice 
[Unit]
Description=ONELAN Players Slice

DefaultDependencies=no
Before=slices.target

Wants=onelan.slice
After=onelan.slice

[Slice]
CPUAccounting=true
MemoryAccounting=true

.include /etc/onelan/ntb/systemd-player-memory-limits.include

# cat /etc/onelan/ntb/systemd-player-memory-limits.include
[Slice]
MemoryLimit=3217719296
#SwapMemoryLimit=5365202944


# systemctl status onelan-player.slice
onelan-player.slice
   Loaded: loaded
   Active: active since Mon 2014-01-27 10:43:20 GMT; 24min ago


Barry