netdev - Re: [PATCH v4 2/2] net: memcg: late association of sock to memcg

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Message-ID: <20200310223848.GC96999@carbon.dhcp.thefacebook.com>
Date:   Tue, 10 Mar 2020 15:38:48 -0700
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Eric Dumazet <edumazet@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "David S . Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        <netdev@...r.kernel.org>, <linux-mm@...ck.org>,
        <cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] net: memcg: late association of sock to memcg

On Mon, Mar 09, 2020 at 10:16:06PM -0700, 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@...gle.com>

Reviewed-by: Roman Gushchin <guro@...com>

Thank you!