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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47ee28144aasm16156295e9.11.2026.01.14.01.56.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jan 2026 01:56:21 -0800 (PST) Date: Wed, 14 Jan 2026 10:56:19 +0100 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Yafang Shao Cc: roman.gushchin@linux.dev, inwardvessel@gmail.com, shakeel.butt@linux.dev, akpm@linux-foundation.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yu.c.chen@intel.com, zhao1.liu@intel.com, bpf@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH bpf-next 2/3] mm: add support for bpf based numa balancing Message-ID: References: <20260113121238.11300-1-laoar.shao@gmail.com> <20260113121238.11300-3-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="hlubd5uybwds24at" Content-Disposition: inline In-Reply-To: <20260113121238.11300-3-laoar.shao@gmail.com> X-Stat-Signature: duacppi4b7cs3138rsw3weftbbtz8h3h X-Rspamd-Queue-Id: A195740007 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1768384583-212651 X-HE-Meta: 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 /DAKXPnT TU5YgCwUU3GcqszfzJhMGoE2Gb/uTJ3snG1+YcJXswWduCpicFb5KfwAE//NWjjnE3RoDhruo67kGDUyxR0te8vorQAaCexA22bDVWHhX1oko9NHueEIguu71jSjc4WidpXaNwcf1Ut7QtO7pKlQoCEN71Mf9WSRorEwgHk8wkOGwVFQ/j+4ktgSXHgIfXZ+Y4evilC1zyMXaBPbNygieqWUi+NG0FG6z7dBX/2noQck2ZfjvpmaTWh6ocrILGNp/m5yv4MyIN8sA6Mwx9+Gb6Jc+NCAQrd6gcZBI3xxknlV9SxWSP/8I6Qr6IrHSZMM5t0DQVI9TEGq1oQgzc9fn3p5O0/brbnBYGZNYAa61tnmvfmc9kg8/YY6yb4QYLfx1l6iWk2wMdqQ7BzyXY8mfwhHhti2z5YEFIDHtXqcMagLtkHWPxmdLHhLhzeaaSw0nVBLIJSbPcVe4WtuY6GfVJM2BnhsoGyVdZYLP6/sqWfBRm0+aQ4TqPogfYtFJt/NJDPOsLP1av3BDhN5kPad3wXGXwA== 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: --hlubd5uybwds24at Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [RFC PATCH bpf-next 2/3] mm: add support for bpf based numa balancing MIME-Version: 1.0 On Tue, Jan 13, 2026 at 08:12:37PM +0800, Yafang Shao wrote: > bpf_numab_ops enables NUMA balancing for tasks within a specific memcg, > even when global NUMA balancing is disabled. This allows selective NUMA > optimization for workloads that benefit from it, while avoiding potential > latency spikes for other workloads. >=20 > The policy must be attached to a leaf memory cgroup. Why this restriction? Do you envision how these extensions would apply hierarchically? Regardless of that, being a "leaf memcg" is not a stationary condition (mkdirs, writes to `cgroup.subtree_control`) so it should also be prepared for that. Also, I think (please correct me) that NUMA balancing doesn't need memory controller (in contrast with OOM), so the attachment shouldn't be through struct mem_cgroup but plain struct cgroup::bpf. If you could consider this or add some details about this decision, it'd be great. Thanks, Michal > To reduce lookup > overhead, we can cache memcg::bpf_numab in the mm_struct of tasks within > the memcg when it becomes a performance bottleneck. >=20 > The cgroup ID is embedded in bpf_numab_ops as a compile-time constant, > which restricts each instance to a single cgroup and prevents attachment > to multiple cgroups. Roman is working on a solution to remove this > limitation, after which we can migrate to the new approach. >=20 > Currently only the normal mode is supported. >=20 > Signed-off-by: Yafang Shao --hlubd5uybwds24at Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCaWdoORsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMSwyLDIACgkQfj0C55Tb+AiIeAEAyE9SkoPTsyFkBRkyPBoC pzkAGjkincYpSGguv87R/CYA/AjBG2txgb/mG2NlcFAsgUWYMsnoFANpNYkc1sUa 9lcE =vIqs -----END PGP SIGNATURE----- --hlubd5uybwds24at--