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Date: Thu, 3 Nov 2011 17:49:21 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Glauber Costa <glommer@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Tim Hockin <thockin@hockin.org>,
        LKML <linux-kernel@vger.kernel.org>, Paul Menage <paul@paulmenage.org>,
        Li Zefan <lizf@cn.fujitsu.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Aditya Kali <adityakali@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Kay Sievers <kay.sievers@vrfy.org>, Tejun Heo <tj@kernel.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Containers <containers@lists.linux-foundation.org>,
        Glauber Costa <glommer@parallels.com>
Subject: Re: [PATCH 00/10] cgroups: Task counter subsystem v6
Message-ID: <20111103164917.GF8198@somewhere.redhat.com>
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On Sat, Oct 29, 2011 at 11:38:25AM +0200, Glauber Costa wrote:
> On Sat, Oct 29, 2011 at 1:30 AM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Tue, 25 Oct 2011 13:06:35 -0700
> > Tim Hockin <thockin@hockin.org> wrote:
> >
> >> On Tue, Oct 4, 2011 at 3:01 PM, Andrew Morton <akpm00@gmail.com> wrote:
> >> > On Mon, __3 Oct 2011 21:07:02 +0200
> >> > Frederic Weisbecker <fweisbec@gmail.com> wrote:
> >> >
> >> >> Hi Andrew,
> >> >>
> >> >> This contains minor changes, mostly documentation and changelog
> >> >> updates, off-case build fix, and a code optimization in
> >> >> res_counter_common_ancestor().
> >> >
> >> > I'd normally duck a patch series like this when we're at -rc8 and ask
> >> > for it to be resent late in -rc1. __But I was feeling frisky so I
> >> > grabbed this lot for a bit of testing and will sit on it until -rc1.
> >> >
> >> > I'm still not convinced that the kernel has a burning need for a "task
> >> > counter subsystem". __Someone convince me that we should merge this!
> >>
> >> We have real (accidental) DoS situations which happen because we don't
> >> have this.  It usually takes the form of some library no re-joining
> >> threads.  We end up deploying a few apps linked against this library,
> >> and suddenly we're in trouble on a machine.  Except, this being
> >> Google, we're in trouble on a lot of machines.
> >
> > This is a bit foggy.  I think you mean that machines are experiencing
> > accidental forkbombs?
> >
> >> There may be other ways to cobble this sort of safety together, but
> >> they are less appealing for various reasons.  cgroups are how we
> >> control groups of related pids.
> >>
> 
> In the end of the day, all cgroups are just a group of tasks. So I don't really
> get the need to have a cgroup to control the number of tasks in the system.
> 
> Why don't we just allow all cgroups to have a limit on the number of
> tasks it can hold?

Not sure what you mean. You would prefer to have this as a core feature in
cgroups rather than a subsystem?