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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47be26a81b6sm657711035e9.0.2025.12.30.01.49.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Dec 2025 01:49:28 -0800 (PST) Date: Tue, 30 Dec 2025 10:49:25 +0100 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Hui Zhu Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Peter Zijlstra , Miguel Ojeda , Nathan Chancellor , Kees Cook , Tejun Heo , Jeff Xu , Jan Hendrik Farr , Christian Brauner , Randy Dunlap , Brian Gerst , Masahiro Yamada , davem@davemloft.net, Jakub Kicinski , Jesper Dangaard Brouer , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Hui Zhu Subject: Re: [RFC PATCH v2 0/3] Memory Controller eBPF support Message-ID: References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="nav7xplzwe6tizdp" Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 84406C0007 X-Rspamd-Server: rspam10 X-Stat-Signature: frihemgsx61nhun4rcxkbyb3i7durzmp X-HE-Tag: 1767088170-884942 X-HE-Meta: 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 qLgUf+qs 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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: --nav7xplzwe6tizdp Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [RFC PATCH v2 0/3] Memory Controller eBPF support MIME-Version: 1.0 Hi Hui. On Tue, Dec 30, 2025 at 11:01:58AM +0800, Hui Zhu wrote: > This allows administrators to suppress low-priority cgroups' memory > usage based on custom policies implemented in BPF programs. BTW memory.low was conceived as a work-conserving mechanism for prioritization of different workloads. Have you tried that? No need to go directly to (high) limits. (<- Main question, below are some secondary implementation questions/remarks.) =2E.. > This series introduces a BPF hook that allows reporting > additional "pages over high" for specific cgroups, effectively > increasing memory pressure and throttling for lower-priority > workloads when higher-priority cgroups need resources. Have you considered hooking into calculate_high_delay() instead? (That function has undergone some evolution so it'd seem like the candidate for BPFication.) =2E.. > 3. Cgroup hierarchy management (inheritance during online/offline) I see you're copying the program upon memcg creation. Configuration copies aren't such a good way to properly handle hierarchical behavior. I wonder if this could follow the more generic pattern of how BPF progs are evaluated in hierarchies, see BPF_F_ALLOW_OVERRIDE and BPF_F_ALLOW_MULTI. > Example Results =2E.. > Results show the low-priority cgroup (/sys/fs/cgroup/low) was > significantly throttled: > - High-priority cgroup: 21,033,377 bogo ops at 347,825 ops/s > - Low-priority cgroup: 11,568 bogo ops at 177 ops/s >=20 > The stress-ng process in the low-priority cgroup experienced a > ~99.9% slowdown in memory operations compared to the > high-priority cgroup, demonstrating effective priority > enforcement through BPF-controlled memory pressure. As a demonstrator, it'd be good to compare this with a baseline without any extra progs, e.g. show that high-prio performed better and low-prio wasn't throttled for nothing. Thanks, Michal --nav7xplzwe6tizdp Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCaVOgEhsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMSwyLDIACgkQfj0C55Tb+AjqkwEAsnaDJnUrbpBZvRNgWKP5 6Sa4JrRHis7FmRcVhJPNvUUA/1AnWVzTnXOrXQlAm2C1hsfhl2QuvaTzWc6hD0j/ y5wD =OLWl -----END PGP SIGNATURE----- --nav7xplzwe6tizdp--