On 17/05/18 16:55, Waiman Long wrote:

[...]

> +     A parent cgroup cannot distribute all its CPUs to child
> +     scheduling domain cgroups unless its load balancing flag is
> +     turned off.
> +
> +  cpuset.sched.load_balance
> +     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 a non-zero value (on).  This flag is set
> +     by the parent and is not delegatable.
> +
> +     When it is on, tasks within this cpuset will be load-balanced
> +     by the kernel scheduler.  Tasks will be moved from CPUs with
> +     high load to other CPUs within the same cpuset with less load
> +     periodically.
> +
> +     When it is off, there will be no load balancing among CPUs on
> +     this cgroup.  Tasks will stay in the CPUs they are running on
> +     and will not be moved to other CPUs.
> +
> +     The initial value of this flag is "1".  This flag is then
> +     inherited by child cgroups with cpuset enabled.  Its state
> +     can only be changed on a scheduling domain cgroup with no
> +     cpuset-enabled children.

[...]

> +     /*
> +      * On default hierachy, a load balance flag change is only allowed
> +      * in a scheduling domain with no child cpuset.
> +      */
> +     if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) && balance_flag_changed &&
> +        (!is_sched_domain(cs) || css_has_online_children(&cs->css))) {
> +             err = -EINVAL;
> +             goto out;
> +     }

The rule is actually

 - no child cpuset
 - and it must be a scheduling domain

Right?
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