Re: [PATCH v2] memcg: first step towards hierarchical controller

Glauber Costa
2012-09-06T12:09:20Z

On 09/06/2012 04:06 PM, Michal Hocko wrote:
> On Wed 05-09-12 13:12:38, Tejun Heo wrote:
>> Hello, Michal.
>>
>> On Wed, Sep 05, 2012 at 04:49:42PM +0200, Michal Hocko wrote:
>>> Can we settle on the following 3 steps?
>>> 1) warn about "flat" hierarchies (give it X releases) - I will push it
>>> to as many Suse code streams as possible (hope other distributions
>>> could do the same)
>>
>> I think I'm just gonna trigger WARN from cgroup core if anyone tries
>> to create hierarchy with a controller which doesn't support full
>> hierarchy. WARN_ON_ONCE() at first and then WARN_ON() on each
>> creation later on.
>
> How do you find out that a controller is not fully hierarchical? Memory
> controller can be both.
>
>>> 2) flip the default on the root cgroup & warn when somebody tries to
>>> change it to 0 (give it another X releases) that the knob will be
>>> removed
>>> 3) remove the knob and the whole nonsese
>>> 4) revert 3 if somebody really objects
>>
>> If we can get to 3, I don't think 4 would be a problem.
>
> Agreed.
>
Just so I understand it:

Michal clearly objected before folding his patch with my Kconfig patch.
But is there still opposition to merge both?

By having it default-n, only people that are either sure that this is
safe for them, or have more clearly defined lifecycles could set it.

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