On Thu, Apr 19, 2018 at 09:47:02AM -0400, Waiman Long wrote:
> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
> index c970bd7..8d89dc2 100644
> --- a/Documentation/cgroup-v2.txt
> +++ b/Documentation/cgroup-v2.txt
> @@ -1484,6 +1484,31 @@ Cpuset Interface Files
>       a subset of "cpuset.cpus".  Its value will be affected by CPU
>       hotplug events.
>  
> +  cpuset.cpus.isolated
> +     A read-write multiple values file which exists on root cgroup
> +     only.
> +
> +     It lists the CPUs that have been withdrawn from the root cgroup
> +     for load balancing.  These CPUs can still be allocated to child
> +     cpusets with load balancing enabled, if necessary.
> +
> +     If a child cpuset contains only an exclusive set of CPUs that are
> +     a subset of the isolated CPUs and with load balancing enabled,
> +     these CPUs will be load balanced on a separate root domain from
> +     the one in the root cgroup.
> +
> +     Just putting the CPUs into "cpuset.cpus.isolated" will be
> +     enough to disable load balancing on those CPUs as long as they
> +     do not appear in a child cpuset with load balancing enabled.
> +     Fine-grained control of cpu isolation can also be done by
> +     putting these isolated CPUs into child cpusets with load
> +     balancing disabled.
> +
> +     The "cpuset.cpus.isolated" should be set up before child
> +     cpusets are created.  Once child cpusets are present, changes
> +     to "cpuset.cpus.isolated" will not be allowed if the CPUs that
> +     change their states are in any of the child cpusets.
> +

So I see why you did this, but it is _really_ ugly and breaks the
container invariant.

Ideally we'd make the root group less special, not more special.
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