From: Peter Zijlstra <peterz@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.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: Sat, 9 Apr 2016 18:02:28 +0200 [thread overview]
Message-ID: <20160409160228.GW3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160408201135.GO24661@htj.duckdns.org>
On Fri, Apr 08, 2016 at 04:11:35PM -0400, Tejun Heo wrote:
> > Yes, I'm familiar with the problem; but simply mandating leaf only nodes
> > is not a solution, for the very simple fact that there are tasks in the
> > root cgroup that cannot ever be moved out, so we _must_ be able to deal
> > with !leaf nodes containing tasks.
>
> As Johannes already pointed out, the root cgroup has always been
> special.
The root of the tree isn't special except for 2 properties.
- it _is_ a root; iow, it doesn't have any incoming edges.
This also means it doesn't have a parent; nor can have a weight,
since that is an edge propery, not a node property.
- it always exists; for without a root there is no tree.
Making it _more_ special is silly.
> > Maybe, but so far I've only heard people complain this v2 thing didn't
> > work for them, and as far as I can see the whole v2 model is internally
> > inconsistent and impossible to implement.
>
> I suppose we live in different bubbles. Can you please elaborate
> which parts of cgroup v2 model are internally inconsistent and
> impossible to implement? I'd be happy to rectify the situation.
The fact that we have to deal with tasks in the root cgroup while not
allowing tasks in any other node is internally inconsistent.
If I can deal with tasks in one node (root) I can equally deal with
tasks in any other node in exactly the same manner.
Making it different is actually _more_ code.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org,
pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-team-b10kYP2dOMg@public.gmane.org
Subject: Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP
Date: Sat, 9 Apr 2016 18:02:28 +0200 [thread overview]
Message-ID: <20160409160228.GW3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160408201135.GO24661-piEFEHQLUPpN0TnZuCh8vA@public.gmane.org>
On Fri, Apr 08, 2016 at 04:11:35PM -0400, Tejun Heo wrote:
> > Yes, I'm familiar with the problem; but simply mandating leaf only nodes
> > is not a solution, for the very simple fact that there are tasks in the
> > root cgroup that cannot ever be moved out, so we _must_ be able to deal
> > with !leaf nodes containing tasks.
>
> As Johannes already pointed out, the root cgroup has always been
> special.
The root of the tree isn't special except for 2 properties.
- it _is_ a root; iow, it doesn't have any incoming edges.
This also means it doesn't have a parent; nor can have a weight,
since that is an edge propery, not a node property.
- it always exists; for without a root there is no tree.
Making it _more_ special is silly.
> > Maybe, but so far I've only heard people complain this v2 thing didn't
> > work for them, and as far as I can see the whole v2 model is internally
> > inconsistent and impossible to implement.
>
> I suppose we live in different bubbles. Can you please elaborate
> which parts of cgroup v2 model are internally inconsistent and
> impossible to implement? I'd be happy to rectify the situation.
The fact that we have to deal with tasks in the root cgroup while not
allowing tasks in any other node is internally inconsistent.
If I can deal with tasks in one node (root) I can equally deal with
tasks in any other node in exactly the same manner.
Making it different is actually _more_ code.
next prev parent reply other threads:[~2016-04-09 16:02 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-11 15:41 [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO_RGRP Tejun Heo
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 ` 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 ` 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 ` 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 ` Tejun Heo
2016-03-11 15:41 ` [PATCH 08/10] cgroup: implement rgroup control mask handling Tejun Heo
2016-03-11 15:41 ` 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 15:41 ` Tejun Heo
2016-03-11 16:05 ` Example program for PRIO_RGRP Tejun Heo
2016-03-11 16:05 ` 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 6:26 ` Mike Galbraith
2016-03-12 17:04 ` Mike Galbraith
2016-03-12 17:04 ` Mike Galbraith
2016-03-12 17:13 ` cgroup NAKs ignored? " Ingo Molnar
2016-03-12 17:13 ` Ingo Molnar
2016-03-13 14:42 ` Tejun Heo
2016-03-13 14:42 ` Tejun Heo
2016-03-13 15:00 ` Tejun Heo
2016-03-13 15:00 ` Tejun Heo
2016-03-13 17:40 ` Mike Galbraith
2016-03-13 17:40 ` Mike Galbraith
2016-04-07 0:00 ` Tejun Heo
2016-04-07 0:00 ` Tejun Heo
2016-04-07 3:26 ` Mike Galbraith
2016-04-07 3:26 ` Mike Galbraith
2016-03-14 2:23 ` Mike Galbraith
2016-03-14 2:23 ` Mike Galbraith
2016-03-14 11:30 ` Peter Zijlstra
2016-03-14 11:30 ` Peter Zijlstra
2016-04-06 15:58 ` Tejun Heo
2016-04-06 15:58 ` Tejun Heo
2016-04-06 15:58 ` Tejun Heo
2016-04-07 6:45 ` Peter Zijlstra
2016-04-07 6:45 ` Peter Zijlstra
2016-04-07 7:35 ` Johannes Weiner
2016-04-07 7:35 ` Johannes Weiner
2016-04-07 8:05 ` Mike Galbraith
2016-04-07 8:05 ` Mike Galbraith
2016-04-07 8:08 ` Peter Zijlstra
2016-04-07 8:08 ` Peter Zijlstra
2016-04-07 9:28 ` Johannes Weiner
2016-04-07 9:28 ` Johannes Weiner
2016-04-07 10:42 ` Peter Zijlstra
2016-04-07 10:42 ` Peter Zijlstra
2016-04-07 19:45 ` Tejun Heo
2016-04-07 19:45 ` Tejun Heo
2016-04-07 20:25 ` Peter Zijlstra
2016-04-07 20:25 ` Peter Zijlstra
2016-04-08 20:11 ` Tejun Heo
2016-04-08 20:11 ` Tejun Heo
2016-04-09 6:16 ` Mike Galbraith
2016-04-09 6:16 ` Mike Galbraith
2016-04-09 13:39 ` Peter Zijlstra
2016-04-09 13:39 ` Peter Zijlstra
2016-04-12 22:29 ` Tejun Heo
2016-04-12 22:29 ` Tejun Heo
2016-04-13 7:43 ` Mike Galbraith
2016-04-13 7:43 ` Mike Galbraith
2016-04-13 15:59 ` Tejun Heo
2016-04-13 19:15 ` Mike Galbraith
2016-04-13 19:15 ` Mike Galbraith
2016-04-14 6:07 ` Mike Galbraith
2016-04-14 19:57 ` Tejun Heo
2016-04-14 19:57 ` Tejun Heo
2016-04-15 2:42 ` Mike Galbraith
2016-04-15 2:42 ` Mike Galbraith
2016-04-09 16:02 ` Peter Zijlstra [this message]
2016-04-09 16:02 ` Peter Zijlstra
2016-04-07 8:28 ` Peter Zijlstra
2016-04-07 8:28 ` Peter Zijlstra
2016-04-07 19:04 ` Johannes Weiner
2016-04-07 19:04 ` Johannes Weiner
2016-04-07 19:31 ` Peter Zijlstra
2016-04-07 19:31 ` Peter Zijlstra
2016-04-07 20:23 ` Johannes Weiner
2016-04-07 20:23 ` Johannes Weiner
2016-04-08 3:13 ` Mike Galbraith
2016-04-08 3:13 ` Mike Galbraith
2016-03-15 17:21 ` Michal Hocko
2016-03-15 17:21 ` Michal Hocko
2016-04-06 21:53 ` Tejun Heo
2016-04-06 21:53 ` Tejun Heo
2016-04-07 6:40 ` Peter Zijlstra
2016-04-07 6:40 ` Peter Zijlstra
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