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Subject: Re: [PATCH v4 2/2] net: memcg: late association of sock to memcg
To:     Shakeel Butt <shakeelb@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Roman Gushchin <guro@fb.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "David S . Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        netdev@vger.kernel.org, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200310051606.33121-1-shakeelb@google.com>
 <20200310051606.33121-2-shakeelb@google.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <652106b3-975d-b8bc-ca27-682c0c8d8aa3@gmail.com>
Date:   Tue, 10 Mar 2020 08:53:56 -0700
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On 3/9/20 10:16 PM, Shakeel Butt wrote:
> If a TCP socket is allocated in IRQ context or cloned from unassociated
> (i.e. not associated to a memcg) in IRQ context then it will remain
> unassociated for its whole life. Almost half of the TCPs created on the
> system are created in IRQ context, so, memory used by such sockets will
> not be accounted by the memcg.
> 
> This issue is more widespread in cgroup v1 where network memory
> accounting is opt-in but it can happen in cgroup v2 if the source socket
> for the cloning was created in root memcg.
> 
> To fix the issue, just do the association of the sockets at the accept()
> time in the process context and then force charge the memory buffer
> already used and reserved by the socket.
> 
> Signed-off-by: Shakeel Butt <shakeelb@google.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks !