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Date: Tue, 17 Apr 2012 08:17:53 -0700
From: Tejun Heo <tj@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>,
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Subject: Re: [RFD] Merge task counter into memcg
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References: <20120411185715.GA4317@somewhere.redhat.com>
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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?

> > 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?

Thanks.

-- 
tejun