[Devel] Re: [PATCH 4/5] Setup the control group

[Paul Menage]

On 10/1/07, Balbir Singh <balbir at linux.vnet.ibm.com> wrote:
>
> Excellent, I prefer the later as well, but it would mean overheads
> for controllers not using the hierarchy.

I don't think it would have to with the ideas I've been thinking about
- each task would still have a set of pointers to subsystems which
could be dereferenced just as quickly. The complexity comes in trying
to map a task to its actual cgroup object in a given hierarchy - this
would involve a bit more work on the part of the cgroup framework, but
wouldn't be a fast path operation.

See my mail last week titled "Thoughts on virtualizing task containers".

> a design such that parents<->children can effectively share resources,
> track them and do so recursively, that would be really nice.

I think the recursive tracking would probably need to be supplied by
the subsystem rather than by the framework. But there's no reason that
multiple subsystems couldn't re-use the same hierarchy code via e.g.
resource counters. So when you initialize a resource counter you'd
tell it about its parent resource counter, and it would handle the
recursion automatically in charge/uncharge.

Paul