netdev - Re: [PATCH v5 bpf-next/net 4/5] net-memcg: Allow decoupling memcg from global protocol memory accounting.

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Message-ID: <CAAVpQUA+rVJKMXQFATfxT=uX3QaLrCtCG_wtiGF_kt-_KrMRBQ@mail.gmail.com>
Date: Thu, 4 Sep 2025 13:21:47 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: 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>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	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 v5 bpf-next/net 4/5] net-memcg: Allow decoupling memcg
 from global protocol memory accounting.

On Wed, Sep 3, 2025 at 11:35 PM Johannes Weiner <hannes@...xchg.org> wrote:
>
> On Wed, Sep 03, 2025 at 07:02:03PM +0000, Kuniyuki Iwashima wrote:
> > If all workloads were guaranteed to be controlled under memcg, the issue
> > could be worked around by setting tcp_mem[0~2] to UINT_MAX.
> >
> > In reality, this assumption does not always hold, and processes not
> > controlled by memcg lose the seatbelt and can consume memory up to
> > the global limit, becoming noisy neighbour.
>
> It's been repeatedly pointed out to you that this container
> configuration is not, and cannot be, supported. Processes not
> controlled by memcg have many avenues to become noisy neighbors in a
> multi-tenant system.
>
> So my NAK still applies. Please carry this forward in all future patch
> submissions even if your implementation changes.

I see.

I'm waiting for Shakeel's response as he agreed on decoupling
memcg and tcp_mem and suggested the bpf approach.