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    SubjectRe: [PATCH v9 2/7] cpuset: Add new v2 cpuset.sched.domain_root flag
    Hi,

    On 29/05/18 09:41, Waiman Long wrote:

    [...]

    > + cpuset.sched.domain_root
    > + A read-write single value file which exists on non-root
    > + cpuset-enabled cgroups. It is a binary value flag that accepts
    > + either "0" (off) or "1" (on). This flag is set by the parent
    > + and is not delegatable.
    > +
    > + If set, it indicates that the current cgroup is the root of a
    > + new scheduling domain or partition that comprises itself and
    > + all its descendants except those that are scheduling domain
    > + roots themselves and their descendants. The root cgroup is
    > + always a scheduling domain root.
    > +
    > + There are constraints on where this flag can be set. It can
    > + only be set in a cgroup if all the following conditions are true.
    > +
    > + 1) The "cpuset.cpus" is not empty and the list of CPUs are
    > + exclusive, i.e. they are not shared by any of its siblings.
    > + 2) The parent cgroup is also a scheduling domain root.
    > + 3) There is no child cgroups with cpuset enabled. This is
    > + for eliminating corner cases that have to be handled if such
    > + a condition is allowed.
    > +
    > + Setting this flag will take the CPUs away from the effective
    > + CPUs of the parent cgroup. Once it is set, this flag cannot
    > + be cleared if there are any child cgroups with cpuset enabled.
    > + Further changes made to "cpuset.cpus" is allowed as long as
    > + the first condition above is still true.

    IIUC, with the configuration below

    cpuset.cpus.effective:6-11
    cgroup.controllers:cpuset
    cpuset.mems.effective:0-1
    cgroup.subtree_control:cpuset
    g1/cpuset.cpus.effective:0-5
    g1/cgroup.controllers:cpuset
    g1/cpuset.sched.load_balance:1
    g1/cpuset.mems.effective:0-1
    g1/cpuset.cpus:0-5
    g1/cpuset.sched.domain_root:1
    user.slice/cpuset.cpus.effective:6-11
    user.slice/cgroup.controllers:cpuset
    user.slice/cpuset.sched.load_balance:1
    user.slice/cpuset.mems.effective:0-1
    user.slice/cpuset.cpus:6-11
    user.slice/cpuset.sched.domain_root:0
    init.scope/cpuset.cpus.effective:6-11
    init.scope/cgroup.controllers:cpuset
    init.scope/cpuset.sched.load_balance:1
    init.scope/cpuset.mems.effective:0-1
    init.scope/cpuset.cpus:6-11
    init.scope/cpuset.sched.domain_root:0
    system.slice/cpuset.cpus.effective:6-11
    system.slice/cgroup.controllers:cpuset
    system.slice/cpuset.sched.load_balance:1
    system.slice/cpuset.mems.effective:0-1
    system.slice/cpuset.cpus:6-11
    system.slice/cpuset.sched.domain_root:0
    machine.slice/cpuset.cpus.effective:6-11
    machine.slice/cgroup.controllers:cpuset
    machine.slice/cpuset.sched.load_balance:1
    machine.slice/cpuset.mems.effective:0-1
    machine.slice/cpuset.cpus:6-11
    machine.slice/cpuset.sched.domain_root:0

    I should be able to

    # echo 0-4 >g1/cpuset.cpus

    ?

    It doesn't let me.

    I'm not sure we actually want to allow that, but that's what would I
    expect as per your text above.

    Thanks,

    - Juri

    BTW: thanks a lot for your prompt feedback and hope it's OK if I keep
    playing and asking questions. :)

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