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NAME | DESCRIPTION | SEE ALSO | COLOPHON |
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proc_pid_clear_refs(5) File Formats Manual proc_pid_clear_refs(5)
/proc/pid/clear_refs - reset the PG_Referenced and ACCESSED/YOUNG
bits
/proc/pid/clear_refs (since Linux 2.6.22)
This is a write-only file, writable only by owner of the
process.
The following values may be written to the file:
1 (since Linux 2.6.22)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all the pages associated with the process. (Before
Linux 2.6.32, writing any nonzero value to this
file had this effect.)
2 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all anonymous pages associated with the process.
3 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all file-mapped pages associated with the process.
Clearing the PG_Referenced and ACCESSED/YOUNG bits
provides a method to measure approximately how much memory
a process is using. One first inspects the values in the
"Referenced" fields for the VMAs shown in /proc/pid/smaps
to get an idea of the memory footprint of the process.
One then clears the PG_Referenced and ACCESSED/YOUNG bits
and, after some measured time interval, once again
inspects the values in the "Referenced" fields to get an
idea of the change in memory footprint of the process
during the measured interval. If one is interested only
in inspecting the selected mapping types, then the value 2
or 3 can be used instead of 1.
Further values can be written to affect different
properties:
4 (since Linux 3.11)
Clear the soft-dirty bit for all the pages
associated with the process. This is used (in
conjunction with /proc/pid/pagemap) by the check-
point restore system to discover which pages of a
process have been dirtied since the file
/proc/pid/clear_refs was written to.
5 (since Linux 4.0)
Reset the peak resident set size ("high water
mark") to the process's current resident set size
value.
Writing any value to /proc/pid/clear_refs other than those
listed above has no effect.
The /proc/pid/clear_refs file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
proc(5)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 proc_pid_clear_refs(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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