netdev - Re: [PATCH v1 net-next 00/13] net-memcg: Allow decoupling memcg from sk->sk_prot->memory

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

Message-ID: <vokpyz3p5pbv7ja4ltipxapq4xjemqmv26gayezeekcyq7llyq@6kahz7tldhfz>
Date: Tue, 22 Jul 2025 08:04:13 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Neal Cardwell <ncardwell@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	Willem de Bruijn <willemb@...gle.com>, Matthieu Baerts <matttbe@...nel.org>, 
	Mat Martineau <martineau@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Andrew Morton <akpm@...ux-foundation.org>, Simon Horman <horms@...nel.org>, 
	Geliang Tang <geliang@...nel.org>, Muchun Song <muchun.song@...ux.dev>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, mptcp@...ts.linux.dev, 
	cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 net-next 00/13] net-memcg: Allow decoupling memcg from
 sk->sk_prot->memory_allocated.

On Mon, Jul 21, 2025 at 08:35:19PM +0000, Kuniyuki Iwashima wrote:
> Some protocols (e.g., TCP, UDP) has their own memory accounting for
> socket buffers and charge memory to global per-protocol counters such
> as /proc/net/ipv4/tcp_mem.
> 
> When running under a non-root cgroup, this memory is also charged to
> the memcg as sock in memory.stat.
> 
> Sockets using such protocols are still subject to the global limits,
> thus affected by a noisy neighbour outside cgroup.
> 
> This makes it difficult to accurately estimate and configure appropriate
> global limits.
> 
> If all workloads were guaranteed to be controlled under memcg, the issue
> can be worked around by setting tcp_mem[0~2] to UINT_MAX.
> 
> However, this assumption does not always hold, and a single workload that
> opts out of memcg can consume memory up to the global limit, which is
> problematic.
> 
> This series introduces a new per-memcg know to allow decoupling memcg
> from the global memory accounting, which simplifies the memcg
> configuration while keeping the global limits within a reasonable range.

Sorry, the above para is confusing. What is per-memcg know? Or maybe it
is knob. Also please go a bit in more detail how decoupling helps the
global limits within a reasonable range?