Message-ID: <4966EEDD.5070204@cn.fujitsu.com>
Date: Fri, 09 Jan 2009 14:29:49 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: Paul Menage <menage@google.com>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [RFC][PATCH] NOOP cgroup subsystem
References: <20090109143226.b79d21b4.kamezawa.hiroyu@jp.fujitsu.com> <6599ad830901082226h6d47053cp801dafb67b6e2bc9@mail.gmail.com>
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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;
	...
}

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