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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47787e85a94sm37157975e9.13.2025.11.12.06.02.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Nov 2025 06:02:09 -0800 (PST) Date: Wed, 12 Nov 2025 15:02:08 +0100 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Michal Hocko Cc: Waiman Long , Leon Huang Fu , linux-mm@kvack.org, tj@kernel.org, hannes@cmpxchg.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, joel.granados@kernel.org, jack@suse.cz, laoar.shao@gmail.com, mclapinski@google.com, kyle.meyer@hpe.com, corbet@lwn.net, lance.yang@linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH mm-new v3] mm/memcontrol: Add memory.stat_refresh for on-demand stats flushing Message-ID: References: <20251110101948.19277-1-leon.huangfu@shopee.com> <9a9a2ede-af6e-413a-97a0-800993072b22@redhat.com> <061cdd9e-a70b-4d45-909a-6d50f4da8ef3@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="jtcwccftag6wk3eh" Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 854A5180021 X-Rspamd-Server: rspam07 X-Stat-Signature: 15sre6zc8gkzbskcdznnpmhfare3gxtd X-Rspam-User: X-HE-Tag: 1762956133-309981 X-HE-Meta: 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 GB+zATmi 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 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: --jtcwccftag6wk3eh Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH mm-new v3] mm/memcontrol: Add memory.stat_refresh for on-demand stats flushing MIME-Version: 1.0 On Tue, Nov 11, 2025 at 10:01:37PM +0100, Michal Hocko wr= ote: > How does that differ from writing a limit that would cause a constant > memory reclaim from a worklad that you craft and cause a constant CPU > activity and even worse lock contention? >=20 > I guess the answer is that you do not let untrusted entities to create > cgroup hierarchies and allow to modify or generally have a write access > to control files. Or am I missing something? This used to apply in cgroup v1 but the v2 controller APIs are meant to be available to anyone (e.g. rootless containers). So yes, if it turns out that the isolation may be substantially bypassed by reclaim, I think it should be solved by some rework. The memory.stat_refresh is different because it doesn't exist yet so its impact on isolation needn't be even potentially solved :-p (not more than memory.stat). --- That's also why memory.stat_refresh is different from one global vm/stat_refresh (easily constrained to root's monitoring tools). And despite this precedent, I don't like the approach of two independent invocations (write(2)+read(2)) when the intention [1] is to obtain precise data (at least) at the time of the read(2). Cheers, Michal [1] I guess. I'd still wait for what the actual usefulness besides fixing LTP here is. --jtcwccftag6wk3eh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCaRSTXRsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMSwyLDIACgkQfj0C55Tb+AgYtAD/c+S8KG22icAY+D5u/Hw+ IaaTSOoxlnotS8mWtF9Q37kA/Rx/AJ5T2cm0Z5vyBpqCrcQhSgksn4AhdUXvWv8t O8AL =ff7K -----END PGP SIGNATURE----- --jtcwccftag6wk3eh--