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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7474F4001A X-Stat-Signature: n5uqfh9x7gj91tjdmxd1x9n571omzwmc X-Rspam-User: X-HE-Tag: 1706529912-160920 X-HE-Meta: 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 BygBEFGv nprnXUDf79bTlH+ZCc8xRae0sn6RoJrOERofgcwyQG6L/4iwOejfs9G8y/7M+Ntz8woWH2eWvwFLOoEe+s07M/rV0G20dTFUbVxyJe84wbJ39eQXm0JCkBJQYWrwyq+XhShh4TTadrXtUers4Fw5utoxPi78oFbLgfvtYHfQ8eAGhAuuE+hg9OZkwjv9kgJ0Mclrk0KpuM8YN7Qo= 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: As PTE-mapped large folios become more relevant (mTHP [1]) and there is the desire to shrink the metadata allocated for such large folios as well (memdesc [2]), how we track folio mappings gets more relevant. Over the years, we used folio mapping information to answer various questions: is this folio mapped by somebody else? do we have to COW on write fault? how do we adjust memory statistics? ... Let's talk about ongoing work in the mapcount area, get a common understanding of what the users of the different mapcounts are and what the implications of removing some would be: which questions could we answer differently, which questions would we not be able to answer precisely anymore, and what would be the implications of such changes? For example, can we tolerate some imprecise memory statistics? How expressive is the PSS when large folios are only partially mapped? Would we need a transition period and glue changes to a new CONFIG_ option? Do we really have to support THP and friends on 32bit? [1] https://patchwork.kernel.org/project/linux-mm/cover/20231207161211.2374093-1-ryan.roberts@arm.com/#25628022 [2] https://kernelnewbies.org/MatthewWilcox/Memdescs -- Cheers, David / dhildenb