linux-kernel - Re: counting file descriptors with a cgroup controller

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Message-ID: <20170306185820.GA19696@htj.duckdns.org>
Date:   Mon, 6 Mar 2017 13:58:20 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Krzysztof Opasiak <k.opasiak@...sung.com>
Cc:     lizefan@...wei.com, hannes@...xchg.org,
        Łukasz Stelmach <l.stelmach@...sung.com>,
        linux-kernel@...r.kernel.org,
        Karol Lewandowski <k.lewandowsk@...sung.com>,
        cgroups@...r.kernel.org
Subject: Re: counting file descriptors with a cgroup controller

Hello,

On Fri, Feb 17, 2017 at 12:37:11PM +0100, Krzysztof Opasiak wrote:
> > We need to limit and monitor the number of file descriptors processes
> > keep open. If a process exceeds certain limit we'd like to terminate it
> > and restart it or reboot the whole system. Currently the RLIMIT API
> > allows limiting the number of file descriptors but to achieve our goals
> > we'd need to make sure all programmes we run handle EMFILE errno
> > properly. That is why we consider developing a cgroup controller that
> > limits the number of open file descriptors of its members (similar to
> >  memory controler).
> > 
> > Any comments? Is there any alternative that:
> > 
> > + does not require modifications of user-land code,
> > + enables other process (e.g. init) to be notified and apply policy.

Hmm... I'm not quite sure fds qualify as an independent system-wide
resource.  We did that for pids because pids are globally limited and
can run out way earlier than memory backing it.  I don't think we have
similar restructions for fds, do we?

Thanks.

-- 
tejun