From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zefan Li Subject: Re: [PATCH] sched: Relax a restriction in sched_rt_can_attach() Date: Mon, 4 May 2015 12:39:39 +0800 Message-ID: <5546F80B.3070802@huawei.com> References: <5546C34C.7050202@huawei.com> <1430709236.3129.42.camel@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1430709236.3129.42.camel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Mike Galbraith Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , LKML , Cgroups On 2015/5/4 11:13, Mike Galbraith wrote: > On Mon, 2015-05-04 at 08:54 +0800, Zefan Li wrote: >> It's allowed to promote a task from normal to realtime after it has been >> attached to a non-root cgroup, but it will fail if the attaching happens >> after it has become realtime. I don't see how this restriction is useful. > > In the CONFIG_RT_GROUP_SCHED case, promotion will fail is there is no > bandwidth allocated. > Right. I forgot to mention this patch affects !CONFIG_RT_GROUP_SCHED only, though it should be obvious by reading the change. >> We are moving toward unified hierarchy where all the cgroup controllers >> are bound together, so it would make cgroups easier to use if we have less >> restrictions on attaching tasks between cgroups. > > Forcing group scheduling overhead on users if they want cpuset or memory > cgroup functionality would be far from wonderful. Am I interpreting the > implications of this unification/binding properly? > > (I hope not, surely the plan is not to utterly _destroy_ cgroup utility) > 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)