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

[Paul Menage]

On Tue, Mar 17, 2009 at 7:39 PM, Li Zefan <lizf at cn.fujitsu.com> wrote:
>>
>> - 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
>>
>
> Then "hierarchy id" is no long a single number..

Correct.

>
>> - 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.
>>
>
> I think it's better to show every subsystems including debug_subsys in
> /proc/cgroups, and show exactly n lines of debug_susys if we have n
> hierarcies with debug_subsys binded, but no header line.

But that gives a contradiction when n == 0 - we can't show exactly 0
lines for an unbound multi subsys, and still show every subsystem.

Does libcgroup actually parse /proc/cgroup? If not, maybe we should
just break the format now and replace it with something more
extensible for future changes.

> And some cgroup test programs, like controller tests in ltp and some
> test programs that I wrote, but they are ok for this change.

Right, changes to test programs aren't a compatibility issue.

Paul
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