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Tue, 24 Feb 2026 08:47:00 -0800 (PST) Date: Tue, 24 Feb 2026 08:47:00 -0800 (PST) From: "Christoph Lameter (Ampere)" To: Ryan Roberts cc: Yang Shi , lsf-pc@lists.linux-foundation.org, Linux MM , dennis@kernel.org, Tejun Heo , urezki@gmail.com, Catalin Marinas , Will Deacon , Yang Shi Subject: Re: [LSF/MM/BPF TOPIC] Improve this_cpu_ops performance for ARM64 (and potentially other architectures) In-Reply-To: Message-ID: <51b8e946-a0f5-7948-c695-98671da4a56a@gentwo.org> References: <5a648f49-97b1-4195-a825-47f3261225eb@arm.com> <32969518-9106-363f-8a89-479b8246e4b1@gentwo.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Stat-Signature: mfe3j5bwtsj9eqjyh5rsp4nodu6f6fpk X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: DC52120003 X-HE-Tag: 1771951621-693433 X-HE-Meta: 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 uf+1Ivkm eWMtbhUMLOVNnpUJPgiGzBtqFH5OUlvtXCc91+JkL8Wfzj/CRejXhGvWoRUGcwDdxQW9x6fp6bH4WI+Ru6nsic+m07Za/BTseISjDMFU8Mfsw4Z59cNj1GGUldfLliS2BcOwfPyzXrrVtbXk8wS7qQ84+qF3WrpQHZd9kM9yrgzVBQpd8b9ZVvu+SPDubWux4G8CfX0fJ65sYXhoB4nuhtr0BvchBVt+yE7H58CHMNMR+a8cLMqRJN8hUAnIdL+p1B3wMvNCa1SfGVBxCuIVIvBocVIYKwyz2S17aqn6+8yO409fOkjSZAAPd7NGOEZud1W0u 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: On Thu, 12 Feb 2026, Ryan Roberts wrote: > > - Kernel text / readonly / readmostly replication for NUMA configurations > > to limit the volume of cacheline transfers across an interconnect. > > I'm aware of Russell King's series to map kernel text locally for each node. I > guess that's the shape of what you're describing here? That is one issue that could be addressed yes. I think it depends on the NUMA architecture and the inter node access cost if this makes sense. The reason that Russell's patch was rejected was because we did not have per cpu page tables. The infrastructure for that will allow a cleaner implementation of Russell's approach and also the other things that I mentioned.