linux-kernel - Re: [PATCH v2] fs: fsnotify: account fsnotify metadata to kmemcg

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Message-ID: <CALvZod4r4hC2A47WP1AwwDCkcPSeoV1GBJL2Dr8SC0H9fm8BHA@mail.gmail.com>
Date:   Wed, 24 Jan 2018 18:15:31 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Amir Goldstein <amir73il@...il.com>, Jan Kara <jack@...e.cz>,
        Yang Shi <yang.s@...baba-inc.com>,
        Michal Hocko <mhocko@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] fs: fsnotify: account fsnotify metadata to kmemcg

On Wed, Jan 24, 2018 at 5:54 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Wed, Jan 24, 2018 at 05:08:27PM -0800, Shakeel Butt wrote:
>> First, let me apologize, I think I might have led the discussion in
>> wrong direction by giving one wrong information. The current upstream
>> kernel, from the syscall context, does not invoke oom-killer when a
>> memcg hits its limit and fails to reclaim memory, instead ENOMEM is
>> returned. The memcg oom-killer is only invoked on page faults. However
>> in a separate effort I do plan to converge the behavior, long
>> discussion at <https://patchwork.kernel.org/patch/9988063/>.
>
> Correct me if I'm misinterpreting you, but your rationale in there
> appears to be along the lines of "userland applications might not
> be ready to handle -ENOMEM gracefully, so let's hit them with
> kill -9 instead - that will be handled properly, 'cuz M4G1C!!1!!!!"
>

Nah, the motivation is something like: In the memory overcommitted
system (or memcg) where jobs of different priorities are running, it
is preferable to kill a low priority job than to return an ENOMEM to
high priority job.