Re: [PATCH] sched: Relax a restriction in sched_rt_can_attach()

From: Tejun Heo <tj@kernel.org>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Zefan Li <lizefan@huawei.com>, Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH] sched: Relax a restriction in sched_rt_can_attach()
Date: Tue, 5 May 2015 10:09:12 -0400	[thread overview]
Message-ID: <20150505140912.GQ1971@htj.duckdns.org> (raw)
In-Reply-To: <1430717964.3129.62.camel@gmail.com>

Hello, Mike.

On Mon, May 04, 2015 at 07:39:24AM +0200, Mike Galbraith wrote:
> > > Some degree of flexibility is provided so that you may disable some controllers
> > > in a subtree. For example:
> > > 
> > > root                  ---> child1
> > > (cpuset,memory,cpu)        (cpuset,memory)
> > >                       \
> > >                        \-> child2
> > >                            (cpu)
> > 
> > Whew, that's a relief.  Thanks.
> 
> But somehow I'm not feeling a whole lot better.
> 
> "May" means if you don't explicitly take some action to disable group
> scheduling, you get it (I don't care if I have an off button), but that

In the new interface, hierarchy setup and controller configuration are
two separate steps.  Creating subhierarchy doesn't enable controller
automatically and as long as specific controllers are concerned
nothing changes when subhierarchy is created and processes are moved
inbetween them.  If control over specific resources is necessary in a
given hierarchy, the matching controllers should be enabled
explicitly.

Thanks.

-- 
tejun