Re: [PATCH] cgroup_pids: add fork limit

From	Aleksa Sarai <cyphar@cyphar.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] cgroup_pids: add fork limit
Date	2015-11-15 14:40 +0100
Message-ID	<qv5Hd-20o-23@gated-at.bofh.it> (permalink)
References	<qthW9-68s-5@gated-at.bofh.it> <qtj1U-6MH-29@gated-at.bofh.it> <qtjuX-6Yy-37@gated-at.bofh.it> <qtjOj-7kQ-27@gated-at.bofh.it> <qtnfc-Ye-7@gated-at.bofh.it>
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>> If so, could you share little more insight on how that time measure
>> outside of the cpu's cgroup cycles? Just so that its helpful to wider
>> audience.
>
> Well, there are a number of things that I can think of that the kernel does
> on behalf of processes that can consume processor time that isn't trivial to
> account:
>   * Updating timers on behalf of userspace processes (itimers or similar).
>   * Sending certain kernel generated signals to processes (that is, stuff
> generated by the kernel like SIGFPE, SIGSEGV, and so forth).
>   * Queuing events from dnotify/inotify/fanotify.
>   * TLB misses, page faults, and swapping.
>   * Setting up new processes prior to them actually running.
>   * Scheduling.
> All of these are things that fork-bombs can and (other than TLB misses) do
> exploit to bring a system down, and the cpu cgroup is by no means a magic
> bullet to handle this.

I feel like these are backed by different resources, and we should
work on limiting those *at the source* in the context of a controller
rather than just patching up the symptoms (too many forks causing
issues), because these are symptoms of a larger issue IMO.

-- 
Aleksa Sarai (cyphar)
www.cyphar.com
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Thread

[PATCH] cgroup_pids: add fork limit Max Kellermann <mk@cm4all.com> - 2015-11-10 15:20 +0100
  Re: [PATCH] cgroup_pids: add fork limit Tejun Heo <tj@kernel.org> - 2015-11-10 16:20 +0100
    Re: [PATCH] cgroup_pids: add fork limit Max Kellermann <mk@cm4all.com> - 2015-11-10 16:40 +0100
      Re: [PATCH] cgroup_pids: add fork limit Tejun Heo <tj@kernel.org> - 2015-11-10 16:50 +0100
      Re: [PATCH] cgroup_pids: add fork limit Max Kellermann <mk@cm4all.com> - 2015-11-10 18:10 +0100
        Re: [PATCH] cgroup_pids: add fork limit Tejun Heo <tj@kernel.org> - 2015-11-10 18:30 +0100
          Re: [PATCH] cgroup_pids: add fork limit Max Kellermann <mk@cm4all.com> - 2015-11-10 19:00 +0100
  Re: [PATCH] cgroup_pids: add fork limit Aleksa Sarai <cyphar@cyphar.com> - 2015-11-10 16:30 +0100
    Re: [PATCH] cgroup_pids: add fork limit Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-10 17:00 +0100
      Re: [PATCH] cgroup_pids: add fork limit Parav Pandit <pandit.parav@gmail.com> - 2015-11-10 17:20 +0100
        Re: [PATCH] cgroup_pids: add fork limit Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-10 21:00 +0100
          Re: [PATCH] cgroup_pids: add fork limit Aleksa Sarai <cyphar@cyphar.com> - 2015-11-15 14:40 +0100
            Re: [PATCH] cgroup_pids: add fork limit Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-16 18:10 +0100
    Re: [PATCH] cgroup_pids: add fork limit Max Kellermann <mk@cm4all.com> - 2015-11-10 17:10 +0100

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