linux-kernel - Re: [PATCH 2/4] memcg: enable accounting for kernfs nodes and iattrs

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Message-Id: <20220520011233.fxbqxcljfcrjk44n@google.com>
Date:   Fri, 20 May 2022 01:12:33 +0000
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Vasily Averin <vvs@...nvz.org>
Cc:     Roman Gushchin <roman.gushchin@...ux.dev>,
        "Michal Koutný" <mkoutny@...e.com>,
        kernel@...nvz.org, linux-kernel@...r.kernel.org,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>, cgroups@...r.kernel.org
Subject: Re: [PATCH 2/4] memcg: enable accounting for kernfs nodes and iattrs

On Fri, May 13, 2022 at 06:51:55PM +0300, Vasily Averin wrote:
> kernfs nodes are quite small kernel objects, however there are few
> scenarios where it consumes significant piece of all allocated memory:
> 
> 1) creating a new netdevice allocates ~50Kb of memory, where ~10Kb
>    was allocated for 80+ kernfs nodes.
> 
> 2) cgroupv2 mkdir allocates ~60Kb of memory, ~10Kb of them are kernfs
>    structures.
> 
> 3) Shakeel Butt reports that Google has workloads which create 100s
>    of subcontainers and they have observed high system overhead
>    without memcg accounting of kernfs.
> 
> It makes sense to enable accounting for kernfs objects, otherwise its
> misuse inside memcg-limited can lead to global memory shortage,
> OOM and random kills of host processes.
> 
> Signed-off-by: Vasily Averin <vvs@...nvz.org>

Acked-by: Shakeel Butt <shakeelb@...gle.com>

You can keep the ack if you decide to include simple_xattr_alloc() in
following version or different patch.