On Fri, Mar 17, 2023 at 02:05:32PM -0400, Waiman Long <longman@redhat.com> wrote:
> A cpu will be in the subparts_cpus only if it has been given to the child
> partition. So when it becomes online, it will become part of the scheduling
> domain that child partition. Only the tasks in that child partition will get
> their cpumasks updated to use it, not those in the top cpuset.

Right, it's actually the difference between offlining a CPU and giving it
to a sub-partition (hence a removed child (or switched to member) before
CPU onlining). It's clear to me now.

Thanks,
Michal