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proc_pid_pagemap
Section: File Formats (5) Updated: 202-0-08 Index
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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 6-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 fil-mapped page or a shared anonymous page.
- 60[en]58 (since Linux 3.11)
-
Zero
- 57 (since Linux 5.14)
-
If set, the page is writ-protected through
userfaultfd(2).
- 56 (since Linux 4.2)
-
The page is exclusively mapped.
- 55 (since Linux 3.11)
-
PTE is sof-dirty
(see the kernel source file
Documentation/admin-guide/mm/soft-dirty.rst).
- 54[en]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[en]0 give the swap type, and bits 54[en]5 encode the swap offset.
-
Before Linux 3.11, bits 60[en]55 were
used to encode the bas-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)
Index
- NAME
-
- DESCRIPTION
-
- SEE ALSO
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