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Diffstat (limited to 'man5/proc_pid_clear_refs.5')
| -rw-r--r-- | man5/proc_pid_clear_refs.5 | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/man5/proc_pid_clear_refs.5 b/man5/proc_pid_clear_refs.5 new file mode 100644 index 0000000..134a3b9 --- /dev/null +++ b/man5/proc_pid_clear_refs.5 @@ -0,0 +1,87 @@ +.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> +.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> +.\" +.\" SPDX-License-Identifier: GPL-3.0-or-later +.\" +.TH proc_pid_clear_refs 5 2023-09-07 "Linux man-pages 6.7" +.SH NAME +/proc/pid/clear_refs \- reset the PG_Referenced and ACCESSED/YOUNG bits +.SH DESCRIPTION +.TP +.IR /proc/ pid /clear_refs " (since Linux 2.6.22)" +.\" commit b813e931b4c8235bb42e301096ea97dbdee3e8fe (2.6.22) +.\" commit 398499d5f3613c47f2143b8c54a04efb5d7a6da9 (2.6.32) +.\" commit 040fa02077de01c7e08fa75be6125e4ca5636011 (3.11) +.\" +.\" "Clears page referenced bits shown in smaps output" +.\" write-only, writable only by the owner of the process +.IP +This is a write-only file, writable only by owner of the process. +.IP +The following values may be written to the file: +.RS +.TP +1 (since Linux 2.6.22) +.\" Internally: CLEAR_REFS_ALL +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.) +.TP +2 (since Linux 2.6.32) +.\" Internally: CLEAR_REFS_ANON +Reset the PG_Referenced and ACCESSED/YOUNG +bits for all anonymous pages associated with the process. +.TP +3 (since Linux 2.6.32) +.\" Internally: CLEAR_REFS_MAPPED +Reset the PG_Referenced and ACCESSED/YOUNG +bits for all file-mapped pages associated with the process. +.RE +.IP +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 +.IR /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. +.IP +Further values can be written to affect different properties: +.RS +.TP +4 (since Linux 3.11) +Clear the soft-dirty bit for all the pages associated with the process. +.\" Internally: CLEAR_REFS_SOFT_DIRTY +This is used (in conjunction with +.IR /proc/ pid /pagemap ) +by the check-point restore system to discover which pages of a process +have been dirtied since the file +.IR /proc/ pid /clear_refs +was written to. +.TP +5 (since Linux 4.0) +.\" Internally: CLEAR_REFS_MM_HIWATER_RSS +Reset the peak resident set size ("high water mark") to the process's +current resident set size value. +.RE +.IP +Writing any value to +.IR /proc/ pid /clear_refs +other than those listed above has no effect. +.IP +The +.IR /proc/ pid /clear_refs +file is present only if the +.B CONFIG_PROC_PAGE_MONITOR +kernel configuration option is enabled. +.SH SEE ALSO +.BR proc (5) |