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Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP
Date 2016-04-07 12:50 +0200
Message-ID <rlfFE-2v3-15@gated-at.bofh.it> (permalink)
References (2 earlier) <rkY26-68Y-5@gated-at.bofh.it> <rlbVo-8hU-5@gated-at.bofh.it> <rlcHL-pI-1@gated-at.bofh.it> <rldaN-RS-1@gated-at.bofh.it> <rleqf-1G9-23@gated-at.bofh.it>
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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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Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-06 18:00 +0200
  Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 08:50 +0200
    Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Johannes Weiner <hannes@cmpxchg.org> - 2016-04-07 09:40 +0200
      Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 10:10 +0200
        Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Johannes Weiner <hannes@cmpxchg.org> - 2016-04-07 11:30 +0200
          Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 12:50 +0200
        Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-07 21:50 +0200
          Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 22:30 +0200
            Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-08 22:20 +0200
              Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 08:20 +0200
              Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-09 15:40 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-13 00:30 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-13 09:50 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-13 18:10 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-13 21:20 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-14 08:10 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Tejun Heo <tj@kernel.org> - 2016-04-14 22:00 +0200
                Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-15 04:50 +0200
              Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-09 18:10 +0200
      Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-07 10:10 +0200
      Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 10:30 +0200
        Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Johannes Weiner <hannes@cmpxchg.org> - 2016-04-07 21:10 +0200
          Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Peter Zijlstra <peterz@infradead.org> - 2016-04-07 21:40 +0200
            Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Johannes Weiner <hannes@cmpxchg.org> - 2016-04-07 22:30 +0200
              Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource  group and PRIO_RGRP Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-08 05:20 +0200

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