man > proc_pid_pagemap(5)

proc_pid_pagemap(5)                      File Formats Manual                     proc_pid_pagemap(5)

NAME
       /proc/pid/pagemap - mapping of virtual pages

DESCRIPTION
       /proc/pid/pagemap (since Linux 2.6.25)
              This  file shows the mapping of each of the process's virtual pages into physical page
              frames or swap area.  It contains one 64-bit value for each  virtual  page,  with  the
              bits set as follows:

              63     If set, the page is present in RAM.

              62     If set, the page is in swap space

              61 (since Linux 3.5)
                     The page is a file-mapped page or a shared anonymous page.

              60–58 (since Linux 3.11)
                     Zero

              57 (since Linux 5.14)
                     If set, the page is write-protected through userfaultfd(2).

              56 (since Linux 4.2)
                     The page is exclusively mapped.

              55 (since Linux 3.11)
                     PTE   is   soft-dirty   (see   the   kernel   source   file   Documentation/ad‐
                     min-guide/mm/soft-dirty.rst).

              54–0   If the page is present in RAM (bit 63), then these bits provide the page  frame
                     number,  which  can be used to index /proc/kpageflags and /proc/kpagecount.  If
                     the page is present in swap (bit 62), then bits 4–0 give  the  swap  type,  and
                     bits 54–5 encode the swap offset.

              Before Linux 3.11, bits 60–55 were used to encode the base-2 log of the page size.

              To  employ  /proc/pid/pagemap efficiently, use /proc/pid/maps to determine which areas
              of memory are actually mapped and seek to skip over unmapped regions.

              The /proc/pid/pagemap file is present only if the CONFIG_PROC_PAGE_MONITOR kernel con‐
              figuration option is enabled.

              Permission  to  access   this   file   is   governed   by   a   ptrace   access   mode
              PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

SEE ALSO
       proc(5)

Linux man-pages 6.7                          2023-08-15                          proc_pid_pagemap(5)