netdev - Re: [PATCH v1 net-next 13/13] net-memcg: Allow decoupling memcg from global protocol memory accounting.

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Message-ID: <ekte46qtwawpvdijdmoqhl2pcwtfhxgl6ubxjkgkiitrtfnvpu@5n7kwkj4fs2t>
Date: Fri, 1 Aug 2025 09:00:27 +0200
From: Michal Koutný <mkoutny@...e.com>
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>, 
	Shakeel Butt <shakeel.butt@...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 13/13] net-memcg: Allow decoupling memcg from
 global protocol memory accounting.

On Thu, Jul 31, 2025 at 04:51:43PM -0700, Kuniyuki Iwashima <kuniyu@...gle.com> wrote:
> Doesn't that end up implementing another tcp_mem[] which now
> enforce limits on uncontrolled cgroups (memory.max == max) ?
> Or it will simply end up with the system-wide OOM killer ?

I meant to rely on use the exisiting mem_cgroup_charge_skmem(), i.e.
there'd be always memory.max < max (ensured by the configuring agent).
But you're right the OOM _may_ be global if the limit is too loose.

Actually, as I think about it, another configuration option would be to
reorganize the memcg tree and put all non-isolated memcgs under one
ancestor and set its memory.max limit (so that it's shared among them
like the global limit).

HTH,
Michal

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