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Shutemov" Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 79F831C0002 X-Stat-Signature: umueujpapa11wfowj94h3o6yq8xhg6d9 X-HE-Tag: 1677111410-120000 X-HE-Meta: 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 NSGm7KES p7npxV9S0vbyDhL199ojd2TEOqss2w4LuvGifwY9zKwSANZ50fANjhEDUEXV8mzkIpn7pB7ZueUqcaMgZIIbghTJsogdMXSsTozBikCWUY0Nr9/nLOjTQs+j4FspdjrLQfmdKgWBrecGYnH/II2Qz7YyCEOICJS6Z+ci6EbTeq0B8rpZja/Gm7gWGFCqfPhylPxkJLp46KpOMrH06t9fIAybp3aPQ6awOrr78qi1rWSexYnfFJOPVw2ZgdwZEs9zB7xJsmRosMFJYYs7bASPGMEsBVHH1UHEKAvsMBpm3N2c0lbyMqfD/bzFzCJEq9mOkGcJsq+TOJ5wISk/l75evoarMbZqDUIiVr6pYLOvHcPvq5F9Q4NRlB2aVAnyRgdOohjAB 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: On Wed, Feb 22, 2023 at 3:56 PM Yu Zhao wrote: > > Currently anonymous folios only support two orders: 0 and the PMD > order. Flexible orders for anonymous folios can resist both internal > or external fragmentations when the PMD order is too underutilized or > costly to allocate. Flexible orders can also leverage the TLB > coalescing feature, .e.g., order 3 for AMD and order 4 for ARM CPUs. > > Discussion points: > 1. The page fault path: determining the best order and the fallback policy. > 2. The reclaim path: detecting the utilization and the splitting policy. > 3. The refcount and the mapcount models, e.g., reuse the PMD-mapped > THP model or not. > 4. The splitting, and the collapsing if needed. > 5. Other paths: COW, GUP, madvise(), mprotect(), page migration, etc. > > A bit of history: > I discussed this topic at Matthew's THP Cabal meeting a couple of > years ago, as one of the major use cases of folios. Around the same > time, I tried to get Hugh to work with me on it, since he tried > something similar back in 2001 [1]. William's page clustering from > 2003 [2] is also based on that, btw. Then I put the idea on the back > burner. > > Now it seems to be a good time to revisit. Yang Shi and I have been > looking at some details, trying to scope out the work that would be > required. We don't have anything definitive yet, but we should have > enough to share by the time of the LSF/MM/BPF. This might be useful for Android. I would like to participate in this discussion. > > [1] https://lore.kernel.org/linux-mm/Pine.LNX.4.21.0107051737340.1577-100000@localhost.localdomain/ > [2] https://lwn.net/Articles/23785/ >