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From: Peter Zijlstra <peterz@infradead.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	mingo@redhat.com, lizefan@huawei.com, pjt@google.com,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-api@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP
Date: Thu, 7 Apr 2016 12:42:59 +0200	[thread overview]
Message-ID: <20160407104259.GQ3430@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160407092824.GA13839@cmpxchg.org>

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.

  reply	other threads:[~2016-04-07 10:43 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-11 15:41 Tejun Heo
2016-03-11 15:41 ` [PATCH 01/10] cgroup: introduce cgroup_[un]lock() Tejun Heo
2016-03-11 15:41 ` [PATCH 02/10] cgroup: un-inline cgroup_path() and friends Tejun Heo
2016-03-11 15:41 ` [PATCH 03/10] cgroup: introduce CGRP_MIGRATE_* flags Tejun Heo
2016-03-11 15:41 ` [PATCH 04/10] signal: make put_signal_struct() public Tejun Heo
2016-03-11 15:41 ` [PATCH 05/10] cgroup, fork: add @new_rgrp_cset[p] and @clone_flags to cgroup fork callbacks Tejun Heo
2016-03-11 15:41 ` [PATCH 06/10] cgroup, fork: add @child and @clone_flags to threadgroup_change_begin/end() Tejun Heo
2016-03-11 15:41 ` [PATCH 07/10] cgroup: introduce resource group Tejun Heo
2016-03-11 15:41 ` [PATCH 08/10] cgroup: implement rgroup control mask handling Tejun Heo
2016-03-11 15:41 ` [PATCH 09/10] cgroup: implement rgroup subtree migration Tejun Heo
2016-03-11 15:41 ` [PATCH 10/10] cgroup, sched: implement PRIO_RGRP for {set|get}priority() Tejun Heo
2016-03-11 16:05 ` Example program for PRIO_RGRP Tejun Heo
2016-03-12  6:26 ` [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP Mike Galbraith
2016-03-12 17:04   ` Mike Galbraith
2016-03-12 17:13     ` cgroup NAKs ignored? " Ingo Molnar
2016-03-13 14:42       ` Tejun Heo
2016-03-13 15:00   ` Tejun Heo
2016-03-13 17:40     ` Mike Galbraith
2016-04-07  0:00       ` Tejun Heo
2016-04-07  3:26         ` Mike Galbraith
2016-03-14  2:23     ` Mike Galbraith
2016-03-14 11:30 ` Peter Zijlstra
2016-04-06 15:58   ` Tejun Heo
2016-04-07  6:45     ` Peter Zijlstra
2016-04-07  7:35       ` Johannes Weiner
2016-04-07  8:05         ` Mike Galbraith
2016-04-07  8:08         ` Peter Zijlstra
2016-04-07  9:28           ` Johannes Weiner
2016-04-07 10:42             ` Peter Zijlstra [this message]
2016-04-07 19:45           ` Tejun Heo
2016-04-07 20:25             ` Peter Zijlstra
2016-04-08 20:11               ` Tejun Heo
2016-04-09  6:16                 ` Mike Galbraith
2016-04-09 13:39                 ` Peter Zijlstra
2016-04-12 22:29                   ` Tejun Heo
2016-04-13  7:43                     ` Mike Galbraith
2016-04-13 15:59                       ` Tejun Heo
2016-04-13 19:15                         ` Mike Galbraith
2016-04-14  6:07                         ` Mike Galbraith
2016-04-14 19:57                           ` Tejun Heo
2016-04-15  2:42                             ` Mike Galbraith
2016-04-09 16:02                 ` Peter Zijlstra
2016-04-07  8:28         ` Peter Zijlstra
2016-04-07 19:04           ` Johannes Weiner
2016-04-07 19:31             ` Peter Zijlstra
2016-04-07 20:23               ` Johannes Weiner
2016-04-08  3:13                 ` Mike Galbraith
2016-03-15 17:21 ` Michal Hocko
2016-04-06 21:53   ` Tejun Heo
2016-04-07  6:40     ` Peter Zijlstra

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