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    SubjectRe: [PATCH 6/6] Makes procs file writable to move all threads by tgid at once
    Quoting Paul Menage (menage@google.com):
    > On Mon, Aug 3, 2009 at 12:45 PM, Serge E. Hallyn<serue@us.ibm.com> wrote:
    > >
    > > This is probably a stupid idea, but...  what about having zero
    > > overhead at clone(), and instead, at cgroup_task_migrate(),
    > > dequeue_task()ing all of the affected threads for the duration of
    > > the migrate?
    > >
    >
    > Or a simpler alternative - rather than taking the thread group
    > leader's rwsem in cgroup_fork(), always take current's rwsem. Then
    > you're always locking a (probably?) local rwsem and minimizing the
    > overhead. So not quite zero overhead in the fork path, but I'd be
    > surprised if it was measurable. In cgroup_attach_proc() you then have
    > to take the rwsem of every thread in the process. Kind of the
    > equivalent of a per-threadgroup big-reader lock.
    >
    > Paul

    Yup I think that would addres my concern (cache-line bouncing in hot
    clone(CLONE_THREAD) case).

    thanks,
    -serge
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