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The folio itself is not split, so nr_ptes surely will be equal to >>> something >1 here right? >> >> Thanks for elaborating. >> >> So, >> >> Case 1: folio splitting => nr_ptes = 1 => the question of a/d bit smearing >> disappears. >> >> Case 2: page table splitting => consec PTEs point to the same large folio >> => nr_ptes > 1 => get_and_clear_full_ptes() will smear a/d bits on the >> new ptes, which is correct because we are still pointing to the same large >> folio. >> > OK awesome, I thought as much, just wanted to make sure :) we are good then. > > The accessed/dirty bits really matter at a folio granularity (and especially > with respect to reclaim/writeback which both operate at folio level) so the > smearing as you say is fine. > > This patch therefore looks fine, only the trivial comment fixup. > > I ran the series on my x86-64 setup (fwiw) with no build/mm selftest errors. Thanks! > > Sorry to be a pain but could you respin with the commit message for this patch > updated to explicitly mention that the logic applies for the non-contPTE split > PTE case (and therefore also helps performance there)? That and the trivial > thing of dropping that comment. What do you mean by the non-contpte case? In that case the PTEs do not point to the same folio or are misaligned, and there will be no optimization. This patch is optimizing two things: 1) ptep_get() READ_ONCE accesses 2) reduction in number of TLBIs for contig blocks, both of which happen in the contpte case. In general, the patch should have a minor improvement on other arches because we are detecting a batch and processing it together, thus saving on a few function calls, but the main benefit is for arm64. > > Then we should be good for a tag unless somebody else spots something > egregious :) > > Thanks for this! Good improvement. > > [snip] > > Cheers, Lorenzo