Re: [PATCH v4 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs

[Tejun Heo <tj@kernel.org>]

On Tue, Aug 10, 2021 at 11:06:05PM -0400, Waiman Long wrote:
> Currently, a parent partition root cannot distribute all its CPUs to
> child partition roots with no CPUs left. However in some use cases,
> a management application may want to create a parent partition root as
> a management unit with no task associated with it and has all its CPUs
> distributed to various child partition roots dynamically according to
> their needs. Leaving a cpu in the parent partition root in such a case is
> now a waste.
> 
> To accommodate such use cases, a parent partition root can now have
> all its CPUs distributed to its child partition roots as long as:
>  1) it is not the top cpuset; and

>  2) there is no task directly associated with the parent.
> 
> Once an empty parent partition root is formed, no new task can be moved
> into it.

The above are already enforced by cgroup2 core, right? No intermediate
cgroup with controllers enabled can have processes. From controllers' POV,
only leaves can have processes.

Thanks.

-- 
tejun