[PATCH 6/7] [RFC] Support multiply-bindable cgroup subsystems

[Paul Menage]

On Tue, Mar 17, 2009 at 7:09 PM, Li Zefan <lizf at cn.fujitsu.com> wrote:
>
> Ah, I just notice debug_subsys will never be in rootnode.

Right - this is the first of the "Open Issues" that I mentioned in the
patch. The question is how to display the multiply-bindable subsystems
in /proc/cgroup in a way that won't break backward-compatibility.
Options include:

- always display one line for each subsystem; if a subsystem is
multiply-bindable then the "hierarchy id" and "num cgroups" columns
may be empty or have multiple (comma or slash-separated?) values

- for a multiply-bindable subsystem, have a header line to indicate
that the subsystem exists, and then a separate line for each bound
instance of the subsystem.

Either of these could confuse existing userspace parsers, but I'm not
sure that any exist other than libcgroup, and I don't think it's in
wide use yet.

Paul