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

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Message-ID: <CAG53R5VQrm-c-F8GdqJ9fx4n+=QU5n3gT-9adx4HqRO_R8BOaw@mail.gmail.com>
Date:   Tue, 7 Mar 2017 20:59:39 -0600
From:   Parav Pandit <pandit.parav@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Krzysztof Opasiak <k.opasiak@...sung.com>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Łukasz Stelmach <l.stelmach@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Karol Lewandowski <k.lewandowsk@...sung.com>,
        cgroups@...r.kernel.org
Subject: Re: counting file descriptors with a cgroup controller

Hi,

On Tue, Mar 7, 2017 at 2:48 PM, Tejun Heo <tj@...nel.org> wrote:
>
> Hello,
>
> On Tue, Mar 07, 2017 at 09:06:49PM +0100, Krzysztof Opasiak wrote:
> > Personally, I don't want to use rlimit for this as it ends up returning
> > error code from for example open() when we hit the limit. This may lead to
> > some unpredictable crashes in  services (esp. those poor proprietary binary
> > blobs). Instead of injecting errors to service we would like to just get
> > notification that this service has more opened fds than it should and ask it
> > to restart in a polite way.
> >

How does those poor proprietary binary blobs remain polite after restart?
Do you mean you want to keep restarting them when it reaches the limit?

> > For memory seems to be quite easy to achieve as we can just get eventfd
> > notification when application passes given memory usage using memory cgroup
> > controller. Maybe you know some efficient method to do the same for fds?
>
> So, if all you wanna do is reliably detecting open(2) failures, can't
> you do that with bpf tracing?
>
> Thanks.
>
> --
> tejun
> --
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