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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b79c4534b3sm2409107f8f.47.2025.07.31.06.38.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Jul 2025 06:38:59 -0700 (PDT) Date: Thu, 31 Jul 2025 15:38:57 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Kuniyuki Iwashima Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Neal Cardwell , Paolo Abeni , Willem de Bruijn , Matthieu Baerts , Mat Martineau , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton , Simon Horman , Geliang Tang , Muchun Song , Kuniyuki Iwashima , netdev@vger.kernel.org, mptcp@lists.linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v1 net-next 13/13] net-memcg: Allow decoupling memcg from global protocol memory accounting. Message-ID: References: <20250721203624.3807041-1-kuniyu@google.com> <20250721203624.3807041-14-kuniyu@google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="2gxvsfqre7jriys5" Content-Disposition: inline In-Reply-To: <20250721203624.3807041-14-kuniyu@google.com> X-Rspamd-Queue-Id: BB2261C000C X-Stat-Signature: 4uio3dpz9z568ieyege5y5ub6rag1dcr X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1753969141-293382 X-HE-Meta: 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 WdS4cPQx q1S4hZgXf4K3UsPZINUGiFsXYDzIZb8V/s+MXSrNR/DnXCHV0xavO3Lik7D0EoZ0S10CaNLUZUEGLtPfS8ssfT+rnAFm82PGGsIkmj8NdFMtPUjTziQX6nQv2Q4/EvKajM2ORmDzh9fiIKMlRpIl3ZnrUoUcAAQuyzI/LHMxtXOcD7qo7eYSuha5X0VOtrIElyO0qJPkVMS3NtNxJGudQkNWewYxKyqhTR9ne3DYxqjbi0BbKIjWHvAGEUVhLV9cevGVamyn01Uir2AgoC8jS3v8OfjOkV3gJ7Kq+HTGjQSuOKmzF3v9DZ7y/JnN0Gu5KrwUTWKqA01Wi1HRtBa6oPxl1DZdtcl1L0aboU9mqmDuByw6axYzKf3gykXXyk3iOeYs8Pkw6GXWsxTKtu1oWzG5dB82tpjCqxvOn+4GIJx+7RO2ehi1BGUhTzZjYkf1QSeVWNBWKVIH2NoA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --2gxvsfqre7jriys5 Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v1 net-next 13/13] net-memcg: Allow decoupling memcg from global protocol memory accounting. MIME-Version: 1.0 On Mon, Jul 21, 2025 at 08:35:32PM +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. >=20 > When running under a non-root cgroup, this memory is also charged to the > memcg as sock in memory.stat. >=20 > Even when memory usage is controlled by memcg, sockets using such protoco= ls > are still subject to global limits (e.g., /proc/sys/net/ipv4/tcp_mem). IIUC the envisioned use case is that some cgroups feed from global resource and some from their own limit. It means the admin knows both: a) how to configure individual cgroup, b) how to configure global limit (for the rest). So why cannot they stick to a single model only? > This makes it difficult to accurately estimate and configure appropriate > global limits, especially in multi-tenant environments. >=20 > 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. >=20 > In reality, this assumption does not always hold, and a single workload > that opts out of memcg can consume memory up to the global limit, > becoming a noisy neighbour. That doesn't like a good idea to remove limits from possibly noisy units. > Let's decouple memcg from the global per-protocol memory accounting. >=20 > This simplifies memcg configuration while keeping the global limits > within a reasonable range. I think this is a configuration issue only, i.e. instead of preserving the global limit because of _some_ memcgs, the configuration management could have a default memcg limit that is substituted to those memcgs so that there's no risk of runaways even in absence of global limit. Regards, Michal --2gxvsfqre7jriys5 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCaItx7wAKCRB+PQLnlNv4 COjkAP0UcZBWkhc+vB0FfA1p+pH/BzzZDKA27tR3sA4T4P3PBQEAyknqdHl6GIJ5 yIxBX8DBx92ijoCOGSF1vaocgD203AQ= =iTKX -----END PGP SIGNATURE----- --2gxvsfqre7jriys5--