On Tue, Jun 26, 2012 at 12:56 AM, Michal Hocko [off-list ref] 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:
[...]

quoted

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?

quoted

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

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