Re: [PATCH 00/10] cgroups: Task counter subsystem v8

[Daniel Lezcano]

On 02/02/2012 03:50 PM, Frederic Weisbecker wrote:
> On Wed, Feb 01, 2012 at 11:51:07AM -0800, Andrew Morton wrote:
> > On Wed, 1 Feb 2012 19:50:01 +0100
> > Frederic Weisbecker<fweisbec@xxxxxxxxx>  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"?
> The reason why I've been working on it is because we need this feature
> (at least) for LXC.

This feature is a recurrent request from the users of LXC. Recently, a 
container administrator complained an user was able to crash the entire 
host from a container.

http://sourceforge.net/mailarchive/message.php?msg_id=28915923

This feature is really useful to make the containers secure.

  -- Daniel

> Two people from our teams have jumped onto the discussion to express
> that they want this feature and why:
>
> https://lkml.org/lkml/2011/12/13/309
> https://lkml.org/lkml/2011/12/13/364
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