netdev - Re: [PATCH v10 bpf-next/net 2/6] net-memcg: Allow decoupling memcg from global protocol memory accounting.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <f81fa440-4a89-4d80-9707-86db76141969@linux.dev>
Date: Sat, 27 Sep 2025 07:49:45 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>,
 Johannes Weiner <hannes@...xchg.org>, Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 John Fastabend <john.fastabend@...il.com>,
 Stanislav Fomichev <sdf@...ichev.me>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
 Mina Almasry <almasrymina@...gle.com>, Kuniyuki Iwashima
 <kuni1840@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v10 bpf-next/net 2/6] net-memcg: Allow decoupling memcg
 from global protocol memory accounting.

On 9/25/25 3:40 PM, Kuniyuki Iwashima wrote:
> On Fri, Sep 19, 2025 at 10:25 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
>>
>> On Sat, Sep 20, 2025 at 12:07:16AM +0000, Kuniyuki Iwashima wrote:
>>> Some protocols (e.g., TCP, UDP) implement memory accounting for socket
>>> buffers and charge memory to per-protocol global counters pointed to by
>>> sk->sk_proto->memory_allocated.
>>>
>>> If a socket has sk->sk_memcg, this memory is also charged to memcg as
>>> "sock" in memory.stat.
>>>
>>> We do not need to pay costs for two orthogonal memory accounting
>>> mechanisms.  A microbenchmark result is in the subsequent bpf patch.
>>>
>>> Let's decouple sockets under memcg from the global per-protocol memory
>>> accounting if mem_cgroup_sk_exclusive() returns true.
>>>
>>> Note that this does NOT disable memcg, but rather the per-protocol one.
>>>
>>> mem_cgroup_sk_exclusive() starts to return true in the following patches,
>>> and then, the per-protocol memory accounting will be skipped.
>>>
>>> In __inet_accept(), we need to reclaim counts that are already charged
>>> for child sockets because we do not allocate sk->sk_memcg until accept().
>>>
>>> trace_sock_exceed_buf_limit() will always show 0 as accounted for the
>>> memcg-exclusive sockets, but this can be obtained in memory.stat.
>>>
>>> Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
>>> Nacked-by: Johannes Weiner <hannes@...xchg.org>

The patch cannot move on (i.e. land or respin) until the NACK concern is resolved.

>>
>> This looks good to me now, let's ask Johannes to take a look again and if
>> he still has any concerns.
>>
>> Reviewed-by: Shakeel Butt <shakeel.butt@...ux.dev>
> 
> Hi Johannes,
> 
> It would be really appreciated if you have a look again.
> 

Hi Johannes,

Can you take a look if the clarified reason in the commit message has addressed 
the concern ?

Thanks,
Martin