On Mon, Nov 22, 2021 at 04:01:02PM -0800, Mina Almasry wrote: > Add PM_THP_MAPPED MAPPING to allow userspace to detect whether a given virt > address is currently mapped by a transparent huge page or not. Example > use case is a process requesting THPs from the kernel (via a huge tmpfs > mount for example), for a performance critical region of memory. The > userspace may want to query whether the kernel is actually backing this > memory by hugepages or not. So you want this bit to be clear if the memory is backed by a hugetlb page? > if (page && page_mapcount(page) == 1) > flags |= PM_MMAP_EXCLUSIVE; > + if (page && is_transparent_hugepage(page)) > + flags |= PM_THP_MAPPED; because honestly i'd expect it to be more useful to mean "This memory is mapped by a PMD entry" and then the code would look like: if (page) flags |= PM_PMD_MAPPED; (and put a corresponding change in pagemap_hugetlb_range)
