Hey All, There are currently a number of paths where we can collapse file memory into THPs: 1a) khugepaged - target of vma being processed 1b) khugepaged - other vma found mapping file, able to lock mmap_lock in retract_page_tables() 1b) khugepaged - other vma found mapping file, deferred pte-mapped THP collapse, processed in collapse_pte_mapped_thp() 2) page fault finds hugepage in page cache + filemap_map_pages() In terms of system-enforced THP constraints: * vma flags + thps sysfs settings Checked in 1a. (1b now at least respects "never" THP mode after Yang Shi's cleanup series, but still doesn't respect "madvise" THP mode) * MMF_DISABLE_THP Checked in 1a and 1b I'm wondering if we should align these, and if so, in what direction? I would argue that a process marked MMF_DISABLE_THP, or a vma marked VM_NOHUGEPAGE, probably shouldn't be mapping at the pmd level, and that the appropriate checks should be added in those paths. Thanks, Zach
