Re: [RFC][PATCH] NOOP cgroup subsystem

[Li Zefan <lizf@cn.fujitsu.com>]

Paul Menage wrote:
> On Thu, Jan 8, 2009 at 9:32 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>> Motivation: Simply classify Applications by cgroup
>>  When using cgroup for classifying applications, some kind of "control" or
>>  "account" subsys must be used. For flexible use of cgroup's nature of
>>  classifying applications, NOOP is useful. It can be used regardless of
>>  resource accounting unit or name spaces or some controls.
>>  IOW, NOOP cgroup allows users to tie PIDs with some nickname.
> 
> I agree that the idea is useful. But to me it seems to a bit
> artificial that you still have to mount some kind of subsystem purely
> to get the grouping, and that you can only have one such grouping.
> 
> I think I'd prefer the ability to mount a cgroups hierarchy without
> *any* subsystems (maybe with "-o none"?) which would give you a
> similar effect, but without you needing to know about a special no-op
> subsystem, and would allow you to have multiple "no-op" groupings.
> 

Agreed, but it can't work by just removing the checking in cgroup mount option,
I just tried it:

static int parse_cgroupfs_options(char *data,
				     struct cgroup_sb_opts *opts)
{
	...
-	if (!opts->subsys_bits)
-		return -EINVAL;
	...
}