linux-kernel - Re: [RFC PATCH v2 13/17] cgroup: Allow fine-grained controllers control in cgroup v2

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Message-ID: <20170524175600.GL24798@htj.duckdns.org>
Date:   Wed, 24 May 2017 13:56:00 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, kernel-team@...com, pjt@...gle.com,
        luto@...capital.net, efault@....de
Subject: Re: [RFC PATCH v2 13/17] cgroup: Allow fine-grained controllers
 control in cgroup v2

Hello,

On Wed, May 24, 2017 at 01:49:46PM -0400, Waiman Long wrote:
> What I am saying is as follows:
>     / A
> P - B
>    \ C
> 
> # echo +memory > P/cgroups.subtree_control
> # echo -memory > P/A/cgroup.controllers
> # echo "#memory" > P/B/cgroup.controllers
> 
> The parent grants the memory controller to its children - A, B and C.
> Child A has the memory controller explicitly disabled. Child B has the
> memory controller in pass-through mode, while child C has the memory
> controller enabled by default. "echo +memory > cgroup.controllers" is
> not allowed. There are 2 possible choices with regard to the '-' or '#'
> prefixes. We can allow them before the grant from the parent or only
> after that. In the former case, the state remains dormant until after
> the grant from the parent.

Ah, I see, you want cgroup.controllers to be able to mask available
controllers by the parent.  Can you expand your example with further
nesting and how #memory on cgroup.controllers would affect the nested
descendant?

Thanks.

-- 
tejun