From: Shakeel Butt <shakeelb@google.com>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: "Michal Hocko" <mhocko@suse.com>,
Cgroups <cgroups@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Roman Gushchin" <guro@fb.com>,
"Christian Brauner" <christian.brauner@ubuntu.com>,
"Michal Koutný" <mkoutny@suse.com>,
"Serge Hallyn" <serge@hallyn.com>
Subject: Re: [PATCH v2 1/1] memcg: enable accounting for pids in nested pid namespaces
Date: Mon, 26 Apr 2021 12:39:44 -0700 [thread overview]
Message-ID: <CALvZod5uw+f5dY=dUmHvdRq-4OfJBQ8zqjT5rZzpKtqQoy+28A@mail.gmail.com> (raw)
In-Reply-To: <8b6de616-fd1a-02c6-cbdb-976ecdcfa604@virtuozzo.com>
On Sat, Apr 24, 2021 at 4:54 AM Vasily Averin <vvs@virtuozzo.com> wrote:
>
> Commit 5d097056c9a0 ("kmemcg: account certain kmem allocations to memcg")
> enabled memcg accounting for pids allocated from init_pid_ns.pid_cachep,
> but forgot to adjust the setting for nested pid namespaces.
> As a result, pid memory is not accounted exactly where it is really needed,
> inside memcg-limited containers with their own pid namespaces.
>
> Pid was one the first kernel objects enabled for memcg accounting.
> init_pid_ns.pid_cachep marked by SLAB_ACCOUNT and we can expect that
> any new pids in the system are memcg-accounted.
>
> Though recently I've noticed that it is wrong. nested pid namespaces creates
> own slab caches for pid objects, nested pids have increased size because contain
> id both for all parent and for own pid namespaces. The problem is that these slab
> caches are _NOT_ marked by SLAB_ACCOUNT, as a result any pids allocated in
> nested pid namespaces are not memcg-accounted.
>
> Pid struct in nested pid namespace consumes up to 500 bytes memory,
> 100000 such objects gives us up to ~50Mb unaccounted memory,
> this allow container to exceed assigned memcg limits.
>
> Fixes: 5d097056c9a0 ("kmemcg: account certain kmem allocations to memcg")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> Reviewed-by: Michal Koutný <mkoutny@suse.com>
> Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
> Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
next prev parent reply other threads:[~2021-04-26 19:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <7b777e22-5b0d-7444-343d-92cbfae5f8b4@virtuozzo.com>
2021-04-24 11:54 ` [PATCH v2 0/1] memcg: enable accounting for pids in nested pid namespaces Vasily Averin
2021-04-24 11:54 ` [PATCH v2 1/1] " Vasily Averin
2021-04-26 19:39 ` Shakeel Butt [this message]
2021-07-14 6:31 ` Vasily Averin
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