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Date: Wed, 1 Feb 2012 11:51:07 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tejun Heo <tj@kernel.org>, Li Zefan <lizf@cn.fujitsu.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Paul Menage <paul@paulmenage.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Aditya Kali <adityakali@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Tim Hockin <thockin@hockin.org>,
        Containers <containers@lists.linux-foundation.org>,
        Glauber Costa <glommer@gmail.com>, Cgroups <cgroups@vger.kernel.org>,
        Daniel J Walsh <dwalsh@redhat.com>,
        "Daniel P. Berrange" <berrange@redhat.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Max Kellermann <mk@cm4all.com>,
        Mandeep Singh Baines <msb@chromium.org>
Subject: Re: [PATCH 00/10] cgroups: Task counter subsystem v8
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On Wed, 1 Feb 2012 19:50:01 +0100
Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Wed, Feb 01, 2012 at 08:31:26AM -0800, Tejun Heo wrote:
> > On Wed, Feb 01, 2012 at 04:37:40AM +0100, Frederic Weisbecker wrote:
> > > Changes In this version:
> > > 
> > > - Split 32/64 bits version of res_counter_write_u64() [1/10]
> > >   Courtesy of Kirill A. Shutemov
> > > 
> > > - Added Kirill's ack [8/10]
> > > 
> > > - Added selftests [9/10], [10/10]
> > > 
> > > Please consider for merging. At least two users want this feature:
> > 
> > Has there been further discussion about this approach?  IIRC, we
> > weren't sure whether this should be merged.
> 
> The doubts I have noticed were:
> 
> Q: Can't we rather focus on a global solution to fight forkbombs?
> 
> If we can find a reliable solution that works in any case and that
> prevent from any forkbomb to impact the rest of the system then it
> may be an acceptable solution. But I'm not aware of such feature.
> 
> Besides, another point in having this task counter is that we
> have a per container limit. Assuming all containers are running under
> the same user, we can protect against a container starving all others
> with a massive amount of processes close to the NR_PROC rlimit.
> 
> Q: Can/should we implement a limitation on the number of "fork" as well?
>    (as in https://lkml.org/lkml/2011/11/3/233 )
> 
> I'm still not sure about why such a thing is needed. Is it really something we
> want? Why can't the task counter be used instead?
> 
> I need more details from the author of this patch. But I doubt we can merge
> both subsystems, they have pretty different semantics.

What I struggle with is "is this feature useful enough to warrant
merging it"?