On Fri, Jun 06, 2025 at 09:40:05AM +0530, Vishal Chourasia wrote: > Add "Availability" section to Control Group v2 docs. It describes the > meaning of a controller being available in a cgroup, complementing the > existing "Enabling and Disabling" section. > > This update improves the clarity of cgroup controller management by > explicitly distinguishing between: > > 1. Availability – when a controller is supported by the kernel and > listed in "cgroup.controllers", making its interface files accessible > in the cgroup's directory. > 2. Enabling – when a controller is enabled via explicitly writing the > name of the controller to "cgroup.subtree_control" to control > distribution of resource across the cgroup's immediate children. > > As an example, consider > > /sys/fs/cgroup # cat cgroup.controllers > cpuset cpu io memory hugetlb pids misc > /sys/fs/cgroup # cat cgroup.subtree_control # No controllers enabled by default > /sys/fs/cgroup # echo +cpu +memory > cgroup.subtree_control # enabling "cpu" and "memory" > /sys/fs/cgroup # cat cgroup.subtree_control > cpu memory # cpu and memory enabled in /sys/fs/cgroup > /sys/fs/cgroup # mkdir foo_cgrp > /sys/fs/cgroup # cd foo_cgrp/ > /sys/fs/cgroup/foo_cgrp # cat cgroup.controllers > cpu memory # cpu and memory available in 'foo_cgrp' > /sys/fs/cgroup/foo_cgrp # cat cgroup.subtree_control # empty by default > /sys/fs/cgroup/foo_cgrp # ls > cgroup.controllers cpu.max.burst memory.numa_stat > cgroup.events cpu.pressure memory.oom.group > cgroup.freeze cpu.stat memory.peak > cgroup.kill cpu.stat.local memory.pressure > cgroup.max.depth cpu.weight memory.reclaim > cgroup.max.descendants cpu.weight.nice memory.stat > cgroup.pressure io.pressure memory.swap.current > cgroup.procs memory.current memory.swap.events > cgroup.stat memory.events memory.swap.high > cgroup.subtree_control memory.events.local memory.swap.max > cgroup.threads memory.high memory.swap.peak > cgroup.type memory.low memory.zswap.current > cpu.idle memory.max memory.zswap.max > cpu.max memory.min memory.zswap.writeback > > In this example, "cpu" and "memory" are enabled in the root cgroup, > making them available in "foo_cgrp". This exposes the corresponding > interface files in "foo_cgrp/", allowing resource control of processes > in that cgroup. However, these controllers are not yet enabled in > "foo_cgrp" itself. > > Once a controller is available in a cgroup it can be used to resource > control processes of the cgroup. > > Acked-by: Michal Koutný <mkoutny@xxxxxxxx> > Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> > Signed-off-by: Vishal Chourasia <vishalc@xxxxxxxxxxxxx> Applied to cgroup/for-6.17. Thanks. -- tejun
