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SubjectRe: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP
On Thu, Apr 07, 2016 at 05:28:24AM -0400, Johannes Weiner wrote:
> Hm? The root group can always contain tasks. It's not the only thing
> the root is exempt from, it can't control any resources either:

it does in fact control resouces; the hierarchy directly affects the
proportional distribution of time.

> sched_group_set_shares():
>
> /*
> * We can't change the weight of the root cgroup.
> */
> if (!tg->se[0])
> return -EINVAL;

The root has, per definition, no siblings, so setting a weight is
entirely pointless.

> tg_set_cfs_bandwidth():
>
> if (tg == &root_task_group)
> return -EINVAL;
>

We have had patches to implement this, but have so far held off because
they add a bunch of cycles to some really hot paths and we'd rather not
do that. Its not impossible, or unthinkable to do this otherwise.

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