linux-kernel - Re: cgroups(7): documenting cgroups v2 delegation

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Message-ID: <5207cfc8-5525-b932-baee-6b0160886178@gmail.com>
Date:   Wed, 10 Jan 2018 23:24:05 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     mtk.manpages@...il.com, "Serge E. Hallyn" <serge@...lyn.com>,
        linux-man <linux-man@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Roman Gushchin <guro@...com>
Subject: Re: cgroups(7): documenting cgroups v2 delegation

Hello Tejun,

On 01/10/2018 11:14 PM, Tejun Heo wrote:
> Hello, Michael.
> 
> On Wed, Jan 10, 2018 at 11:01:11PM +0100, Michael Kerrisk (man-pages) wrote:
>>>>>> Can you please confirm that it's only necessary to delegate this file
>>>>>> if we are delegating a threaded subtree?
>>>>>
>>>>> Replied on the other thread.  The file isn't delegatable as far as I
>>>>> can tell.
>>>>
>>>> So, following on from the discussion in the other thread, my
>>>> question above still stands.
>>>
>>> Oh, I frankly haven't thought about delegating a threaded subtree.
>>
>> I'm still confused. cgroup-v2.txt documents the possibility. You
>> wrote that text. We just had a conversation in another thread about the
>> fact that cgroup.threads is delegatable. You must have thought at 
>> least a little about this?
> 
> Oh, I'm probably mixing up two things.
> 
> 1. When delegating, cgroup.threads should be delegated.  Doing that
>    selectively doesn't achieve anything meaningful.

Understood. But surely delegating cgroup.threads is effectively
meaningless when delegating a "domain" cgroup tree? (Obviously it's
not harmful to delegate the the cgroup.threads file in this case;
it's just not useful to do so.)

> 2. I haven't thought much about delegating a sub-protion of a threaded
>    subtree.  Everything works the same way.  I just can't think of a
>    use case.

Ahhh -- now I see what you meant before.

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/