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Miller" , Andreas Larsson , "Matthew Wilcox (Oracle)" , "Mike Rapoport (IBM)" , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Suren Baghdasaryan , Michal Hocko , sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Magnus Lindholm Subject: Re: [PATCH v3 4/4] mm: pass the number of PTEs to move_pte() Date: Wed, 28 Oct 2026 10:16:29 +0100 Message-ID: <20261028091631.8072-1-kaloz@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: <2bc50d2a6829b49ee909e5bb943244859661a40b.1792609488.git.kaloz@kernel.org> <409079fe-ab52-4389-9fe0-d7246eb27bad@kernel.org> <20261027212610.6798-1-kaloz@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4C61E100002 X-Stat-Signature: wcjnw13hggrrb35a8atp3b3iwquudbcm X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793179068-670908 X-HE-Meta: U2FsdGVkX19Kd4m1Wh/M2+0tgewRmWsLp7jqQDFo1UsvaVYgohR4KNbdgJ2Tm0iEwXn8uNsWwhhpqJ3S5QCj4cb7QoYViEvwaJT4jpS/Ljiw5C9gPddDkDaydSRJdSu3JcyJllMA3ihyPTHg5h59HcUcQ9fOVb+7QAoEdfLKaVIu1SM9SZWvLeU2TIQIQatJxtvEZP+Ck3VxEyDHZCY6RZahaio3lEzPF6yJ2juyWO9GzEwfG8PlbmVkwHCU1wZf/3AnLPgKZPfTxC/BQTTPCcUPEQhIfQznlNXOhj9HOk4o5myezjsgCKX5KjPykTY+R8sHfyUmDc3sVM32Qhmi/ylqipwjpd9dWP/SlxTfzuz26vplhvR3zFKsiZsKq8AaCfskdFuG9X3Js5TxMd+vjp3ggFN2pH/t8yMawwra908rqop9t7jqovA1W6tDRrfSMc7GYjBfRwqlusPuix3sdojsefTJM5InDPZrq5488sPAVeYaDgjoadVYEvlFlXT1igjbvs/0yd8ZVO15t2nKqd4gZqH1ge5Bq0UZ/VFlbgIk5MDEmNvmtGtxOzMpRSw+aAy6oqa6xg6ERJS1VGwdH0+ON8FcBw8Zz3AEt4CGyPf7voFkrtmGMDj5T16/PnWfwUI+QypUIM/KgFjgmKCK9Y2uYkhs9bLmoVEWDmlrPGkO+HpPzx+2U1gmkC36IWI68HbWW4DkGDD7ZgenHVGUDU8eEjSOWREgw79MWQ6FdQ+BVkQMMiCd1ZQrkPW2vG3NCaoDE4DSSIOQPPL2ARbwJHtfyDgqddu4h+iLJV05vzIq8G5wyys2ovI7PH2c70jl0fBnzYAQEu/brK5WYOGJoPqgauZDCVtJNapMnlNXRvhIpAG22wVxeKpGuKThw3ZnPvxxTDO+A8NPFIwGYzFwxN3umHhFT1ZcbTDsP90fkBorI1M2krNItmCzy0pbIoTT9xtjCg8YOunflAbk4dj NGAUvpoC ImuLmBS6oIFpdHI5310XJ7FgkLjGLcFGg8eJ5gxP28rftpns6Dv4j6IRkTi4FnQFGYqbXJT0lRgcGkQEo75cjDLgbehKt+C4AJBI1WFu6VUtjqKTsX6HN6BRGIVd8f2h71RSen7pEzhfRwOf4c3FzTPSg0+uXpLE1WleeWSP3dlP5lnDgtX5prLFlw8/9EK/5dFTK2lrKzmxL/Zztex24WbNCx1IbOcCMCYfe4cGiQQbpCUHcJSCJU/QYf48lSIjvDlWY Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi David, On 10/28/26 09:49, David Hildenbrand (Arm) wrote: > But that's too complicated, requiring page table walks .... > People running museum piece hardware and complaining about performance of mremap > or memory reclaim should reconsider life choices. I'm one of the museum folks myself, though more the kind who loves running a modern kernel on old hardware than the kind who complains about it :) A lot of these machines are still doing real work, and these days not everyone can, or wants to, just buy a new computer. Some of us spend our time keeping these platforms working, and I'm not asking anyone else to carry that, which is why I tried to keep all of it in sparc. > So I'd say, make it as slow as you want while reducing core-MM complexity and > not adding more arch complexity. With C, move_pte() and __HAVE_ARCH_MOVE_PTE go away from include/linux/pgtable.h and mm/mremap.c just like with A and B. The walk lives in sparc's own flush_cache_range() and only runs on the CPUs that need it. B would be less sparc code, but every UltraSPARC I-IV machine would pay 13-18% on reclaim for it, so I'd still lean towards C. If you feel strongly about B, though, I'm happy to send that instead. Best, Imre