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/admin-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 configuration 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 6.9.1             2024-05-02               proc_pid_pagemap(5)