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This causes a >> performance regression for drivers that allocate pages with alloc_page() >> and insert them into VMAs via vm_insert_page(). These pages legitimately >> have a NULL folio->mapping, but they cannot be secretmem pages. > > How significant is the slowdown? About 2x! Sourab has a bunch of peer to peer IO cases that use 4K pages, that he ran. thanks, -- John Hubbard