[Devel] Re: [PATCH] fix bad behavior in use_hierarchy file

[Ying Han]

On Tue, Jun 26, 2012 at 12:56 AM, Michal Hocko <mhocko at suse.cz> wrote:
> [Adding Ying to CC - they are using hierarchies AFAIU in their workloads]

Sorry for late ( a month late ) to the thread.

Our current production today doesn't support multi-hierarchy setup for
memcg, and all the cgroups are flat under root at least on the memory
resource perspective. However, we do have use_hierarchy set to 1 to
root cgroup upfront.

On the other hand, we started exploring nested cgroup since the flat
configuration doesn't fullfill all our usecases. In that case, we will
have configurations like: root-> A -> B -> C ( not sure about C but at
least level to B). Of course, we will have use_hierarchy set to 1 on
each level, and the mixed setting won't happen AFAIK.

--Ying
>
> On Mon 25-06-12 13:49:08, Tejun Heo wrote:
> [...]
>> A bit of delta but is there any chance we can either deprecate
>> .use_hierarhcy or at least make it global toggle instead of subtree
>> thing?
>
> So what you are proposing is to have all subtrees of the root either
> hierarchical or not, right?
>
>> This seems needlessly complicated. :(
>
> Toggle wouldn't help much I am afraid. We would still have to
> distinguish (non)hierarchical cases. And I am not sure we can make
> everything hierarchical easily.
> Most users (from my experience) ignored use_hierarchy for some reasons
> and the end results might be really unexpected for them if they used
> deeper subtrees (which might be needed due to combination with other
> controller(s)).
> --
> Michal Hocko
> SUSE Labs
> SUSE LINUX s.r.o.
> Lihovarska 1060/12
> 190 00 Praha 9
> Czech Republic