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    SubjectRe: [RFC][PATCH] NOOP cgroup subsystem
    KAMEZAWA Hiroyuki wrote:
    > How about this idea ? Any comments are welcome.
    >
    > -Kame
    >
    > ==
    > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    >
    > Add an NO OPERATION cgroup subsystem.
    >
    > Cgroup itself is providing a feature to attach a task(PID) to some class.
    > This feature itself is very useful but "no operation" cgroup is not supported
    > now other than debug cgroup. (But debug cgroup should be for DEBUG. distro
    > may not configure it.)
    >

    Then how can we make sure distro will configure this noop subsys. :)

    Or we can make the debug subsys always configured if CONFIG_CGROUP=y ?
    The debug system adds no runtime overhead, and it's about 100 lines
    of code only.

    > 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.
    >
    > After this, application can be checked whether it's still alive or not by
    >
    > mount -t cgroup none /var/apps noop
    > mkdir /var/apps/mydaemon
    > echo 0 > /var/apps/mydaemon
    > /etc/init.d/mydaemon start
    > exit
    >
    > This can be used as the same technique of "recording pid into /var/run/xxx.pid"
    > and not necessary to remove stale files. If mydaemon dies, tasks file will
    > be empty and notify_on_release handler can be used.
    >
    > I myself want to use this for replacement of "ps -elf | grep" if libcgroup supports
    > ps under cgroup.
    >
    > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


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