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    SubjectRe: [RFD] Merge task counter into memcg
    From
    2012/4/18 Frederic Weisbecker <fweisbec@gmail.com>:
    > On Tue, Apr 17, 2012 at 08:17:53AM -0700, Tejun Heo wrote:
    >> Hello, Frederic.
    >>
    >> On Thu, Apr 12, 2012 at 06:59:27PM +0200, Frederic Weisbecker wrote:
    >> > I want:
    >> >
    >> > a) to prevent the forkbomb from going far enough to DDOS the machine
    >> > b) to be able to kill that forkbomb once detected, in one go without race
    >> > against concurrent forks.
    >> >
    >> > I think a) can work just fine with kernel stack limiting. I also need
    >> > to be notified about the fact we reached the limit. And b) should
    >> > be feasible with the help of the cgroup freezer.
    >>
    >> kmem allocation fail after reaching the limit which in turn should
    >> fail task creation.  Isn't that the same effect as the task_counter as
    >> implemented?
    >
    > That's it.
    >
    >>
    >> > > Is there anything for which you need to know exactly the number of
    >> > > processes?
    >> >
    >> > No that's really about prevent/kill forkbomb as far as I'm concerned.
    >>
    >> Hmm... so, accounting overhead aside, if the only purpose is
    >> preventing the whole machine being brought down by a fork bomb, kmem
    >> limiting is enough, right?
    >
    > I think so yeah.

    But this needs to be a well defined kind of kmem I think. Relying on
    kernel memory
    alone is too general to just protect against forkbombs. Kernel stack,
    OTOH, should be
    a good criteria.

    But now I'm worrying, do you think this kmem.kernel_stack limitation
    is going to be useful
    for other kind of usecase?
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