Function check_cgroup_support 

pub(crate) fn check_cgroup_support(
    requested: bool,
    kernel_support: bool,
    cpu_max: bool,
)

Tell whether cgroup scheduling can do what the options ask for: warn when it was asked for and the kernel or the cgroup setup leaves nothing to hook into, and when a cpu.weight or a cpu.max somebody set is ignored because the feature that reads it is off.