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

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Message-ID: <20171109135444.znaksm4fucmpuylf@dhcp22.suse.cz>
Date:   Thu, 9 Nov 2017 14:54:44 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Jan Kara <jack@...e.cz>
Cc:     Yang Shi <yang.s@...baba-inc.com>, amir73il@...il.com,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fs: fsnotify: account fsnotify metadata to kmemcg

[Sorry for the late reply]

On Tue 31-10-17 11:12:38, Jan Kara wrote:
> On Tue 31-10-17 00:39:58, Yang Shi wrote:
[...]
> > I do agree it is not fair and not neat to account to producer rather than
> > misbehaving consumer, but current memcg design looks not support such use
> > case. And, the other question is do we know who is the listener if it
> > doesn't read the events?
> 
> So you never know who will read from the notification file descriptor but
> you can simply account that to the process that created the notification
> group and that is IMO the right process to account to.

Yes, if the creator is de-facto owner which defines the lifetime of
those objects then this should be a target of the charge.

> I agree that current SLAB memcg accounting does not allow to account to a
> different memcg than the one of the running process. However I *think* it
> should be possible to add such interface. Michal?

We do have memcg_kmem_charge_memcg but that would require some plumbing
to hook it into the specific allocation path. I suspect it uses kmalloc,
right?
-- 
Michal Hocko
SUSE Labs