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    SubjectRe: [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status
    On Tue, 29 Nov 2011 23:12:54 +0400
    Cyrill Gorcunov <gorcunov@openvz.org> wrote:

    > From: Pavel Emelyanov <xemul@parallels.com>
    >
    > There is no easy way to make a reverse parent->children chain
    > from the task status, in turn children->parent provided with "PPid"
    > field.
    >
    > So instead of walking over all pids in system to figure out what
    > children the task have -- we add explicit "Children" member to
    > /proc/<pid>/status since kernel already knows this kind of information
    > but it was not yet exported.
    >
    > Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
    > Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
    > Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

    I may be too pessimistic but what amount of overhead will this add to
    ps -elf/ top ? Assuming an environment 'ps -elf' is called once per a sec,
    if there are 2000 processes, task_list lock is taken 2000 times by this patch.

    Isn't it better to add /proc/<pid>/children file or dir (as task)?

    Thanks,
    -Kame



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