Re: [RFD] cgroup: about multiple hierarchies

[Tejun Heo <tj@kernel.org>]

Hey, Peter.

On Wed, Feb 22, 2012 at 02:30:59PM +0100, Peter Zijlstra wrote:
> FWIW I'm all for ripping the orthogonal hierarchy crap out, I hate it
> just about as much as you do judging from your write-up.

I just don't get why it's there.  Maybe, there can be some remote use
cases where orthogonal hierarchies can be useful but structuring whole
cgroup around that seems really extreme.

> I'm not sure on your process hierarchy pie though, I rather like being
> able to assign tasks to cgroups of my making without having to mirror
> that in the process hierarchy.

The only question is whether we want to allow cgroup hierarchy to be
completely orthogonal from process tree structure, which I don't think
is a good idea.  It shouldn't affect trivial use cases.  If not
explicitly configured, all tasks would live in a single root cgroup -
much like every process would belong to the same session if nobody
does setsid() since boot (or container).

I don't know how the implementation would turn out and it may as well
stay separate as it is now but I still think the topology should match
pstree.

Thanks.

-- 
tejun