admin-guide/mm/pagemap.rst

36    swap. Unmapped pages return a null PFN. This allows determining
37    precisely which pages are mapped (or in swap) and comparing mapped
38    pages between processes.
100     An order N block has 2^N physically contiguous pages, with the BUDDY flag
103     A compound page with order N consists of 2^N physically contiguous pages.
106     pages are hugeTLB pages (Documentation/admin-guide/mm/hugetlbpage.rst),
108     However in this interface, only huge/giga pages are made visible
119     Identical memory pages dynamically shared between one or more processes.
121     Contiguous pages which construct transparent hugepages.
158    not a candidate for LRU page reclaims, e.g. ramfs pages,
186  3. Open ``/proc/pid/pagemap`` and seek to the pages you would like to examine.
194 in kpagecount, and tally up the number of pages that are only referenced
200 Page table entries for shared pages are cleared when the pages are zapped or
201 swapped out. This makes swapped out pages indistinguishable from never-allocated
211 lseek() can differentiate between accessed pages (present or swapped out) and
213 the pages are backed. For anonymous shared pages, the file can be found in
216 mincore() can differentiate between pages in memory (present, including swap
240 - Write-protect the pages. The ``PM_SCAN_WP_MATCHING`` is used to write-protect
241   the pages of interest. The ``PM_SCAN_CHECK_WPASYNC`` aborts the operation if
242   non-Async Write Protected pages are found. The ``PM_SCAN_WP_MATCHING`` can be
245   get and write protect the pages as well.
247 Following flags about pages are currently supported:
272  6. The optional maximum requested pages are specified in the ``max_pages``.
276 Find pages which have been written and WP them as well::
286 Find pages which have been written, are file backed, not swapped and either
302 the user can find the true soft-dirty pages in case of normal pages. (There may
303 still be extra dirty pages reported for THP or Hugetlb pages.)
317  5. Now the ``PAGEMAP_SCAN`` IOCTL can be used to either just find pages which
319     the pages as well.