linux-kernel - Re: [PATCH v7 01/10] memcg: enable accounting for mnt

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Date:   Tue, 27 Jul 2021 09:21:00 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, cgroups@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Roman Gushchin <guro@...com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 01/10] memcg: enable accounting for mnt_cache entries

On Tue, Jul 27, 2021 at 08:33:12AM +0300, Vasily Averin wrote:
> The kernel allocates ~400 bytes of 'strcut mount' for any new mount.
> Creating a new mount namespace clones most of the parent mounts,
> and this can be repeated many times. Additionally, each mount allocates
> up to PATH_MAX=4096 bytes for mnt->mnt_devname.
> 
> It makes sense to account for these allocations to restrict the host's
> memory consumption from inside the memcg-limited container.
> 
> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
> ---

Looks good. Thank you!
Acked-by: Christian Brauner <christian.brauner@...ntu.com>

I wonder how much this increases reported memory consumption when you
boot full system containers that run systemd and a bunch of systemd
services that each use a separate mount namespace.