'\" t
.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com>
.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com>
.\" and scsi additions from Michael Neuffer (neuffer@mail.uni-mainz.de)
.\" and sysctl additions from Andries Brouwer (aeb@cwi.nl)
.\" and System V IPC (as well as various other) additions from
.\" Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified 1995-05-17 by faith@cs.unc.edu
.\" Minor changes by aeb and Marty Leisner (leisner@sdsp.mc.xerox.com).
.\" Modified 1996-04-13, 1996-07-22 by aeb@cwi.nl
.\" Modified 2001-12-16 by rwhron@earthlink.net
.\" Modified 2002-07-13 by jbelton@shaw.ca
.\" Modified 2002-07-22, 2003-05-27, 2004-04-06, 2004-05-25
.\"    by Michael Kerrisk <mtk.manpages@gmail.com>
.\" 2004-11-17, mtk -- updated notes on /proc/loadavg
.\" 2004-12-01, mtk, rtsig-max and rtsig-nr went away in Linux 2.6.8
.\" 2004-12-14, mtk, updated 'statm', and fixed error in order of list
.\" 2005-05-12, mtk, updated 'stat'
.\" 2005-07-13, mtk, added /proc/sys/fs/mqueue/*
.\" 2005-09-16, mtk, Added /proc/sys/fs/suid_dumpable
.\" 2005-09-19, mtk, added /proc/zoneinfo
.\" 2005-03-01, mtk, moved /proc/sys/fs/mqueue/* material to mq_overview.7.
.\" 2008-06-05, mtk, Added /proc/[pid]/oom_score, /proc/[pid]/oom_adj,
.\"     /proc/[pid]/limits, /proc/[pid]/mountinfo, /proc/[pid]/mountstats,
.\"     and /proc/[pid]/fdinfo/*.
.\" 2008-06-19, mtk, Documented /proc/[pid]/status.
.\" 2008-07-15, mtk, added /proc/config.gz
.\"
.TH proc 5 (date) "Linux man-pages (unreleased)"
.SH NAME
proc \- process information, system information, and sysctl pseudo-filesystem
.SH DESCRIPTION
The
.B proc
filesystem is a pseudo-filesystem which provides an interface to
kernel data structures.
It is commonly mounted at
.IR /proc .
Typically, it is mounted automatically by the system,
but it can also be mounted manually using a command such as:
.PP
.in +4n
.EX
mount \-t proc proc /proc
.EE
.in
.PP
Most of the files in the
.B proc
filesystem are read-only,
but some files are writable, allowing kernel variables to be changed.
.\"
.SS Mount options
The
.B proc
filesystem supports the following mount options:
.TP
.BR hidepid "=\fIn\fP (since Linux 3.3)"
.\" commit 0499680a42141d86417a8fbaa8c8db806bea1201
This option controls who can access the information in
.IR /proc/ pid
directories.
The argument,
.IR n ,
is one of the following values:
.RS
.TP 4
0
Everybody may access all
.IR /proc/ pid
directories.
This is the traditional behavior,
and the default if this mount option is not specified.
.TP
1
Users may not access files and subdirectories inside any
.IR /proc/ pid
directories but their own (the
.IR /proc/ pid
directories themselves remain visible).
Sensitive files such as
.IR /proc/ pid /cmdline
and
.IR /proc/ pid /status
are now protected against other users.
This makes it impossible to learn whether any user is running a
specific program
(so long as the program doesn't otherwise reveal itself by its behavior).
.\" As an additional bonus, since
.\" .IR /proc/[pid]/cmdline
.\" is inaccessible for other users,
.\" poorly written programs passing sensitive information via
.\" program arguments are now protected against local eavesdroppers.
.TP
2
As for mode 1, but in addition the
.IR /proc/ pid
directories belonging to other users become invisible.
This means that
.IR /proc/ pid
entries can no longer be used to discover the PIDs on the system.
This doesn't hide the fact that a process with a specific PID value exists
(it can be learned by other means, for example, by "kill \-0 $PID"),
but it hides a process's UID and GID,
which could otherwise be learned by employing
.BR stat (2)
on a
.IR /proc/ pid
directory.
This greatly complicates an attacker's task of gathering
information about running processes (e.g., discovering whether
some daemon is running with elevated privileges,
whether another user is running some sensitive program,
whether other users are running any program at all, and so on).
.RE
.TP
.BR gid "=\fIgid\fP (since Linux 3.3)"
.\" commit 0499680a42141d86417a8fbaa8c8db806bea1201
Specifies the ID of a group whose members are authorized to
learn process information otherwise prohibited by
.B hidepid
(i.e., users in this group behave as though
.I /proc
was mounted with
.IR hidepid=0 ).
This group should be used instead of approaches such as putting
nonroot users into the
.BR sudoers (5)
file.
.\"
.SS Overview
Underneath
.IR /proc ,
there are the following general groups of files and subdirectories:
.TP
.IR /proc/ "pid subdirectories"
Each one of these subdirectories contains files and subdirectories
exposing information about the process with the corresponding process ID.
.IP
Underneath each of the
.IR /proc/ pid
directories, a
.I task
subdirectory contains subdirectories of the form
.IR task/ tid,
which contain corresponding information about each of the threads
in the process, where
.I tid
is the kernel thread ID of the thread.
.IP
The
.IR /proc/ pid
subdirectories are visible when iterating through
.I /proc
with
.BR getdents (2)
(and thus are visible when one uses
.BR ls (1)
to view the contents of
.IR /proc ).
.TP
.IR /proc/ "tid subdirectories"
Each one of these subdirectories contains files and subdirectories
exposing information about the thread with the corresponding thread ID.
The contents of these directories are the same as the corresponding
.IR /proc/ pid /task/ tid
directories.
.IP
The
.IR /proc/ tid
subdirectories are
.I not
visible when iterating through
.I /proc
with
.BR getdents (2)
(and thus are
.I not
visible when one uses
.BR ls (1)
to view the contents of
.IR /proc ).
.TP
.I /proc/self
When a process accesses this magic symbolic link,
it resolves to the process's own
.IR /proc/ pid
directory.
.TP
.I /proc/thread\-self
When a thread accesses this magic symbolic link,
it resolves to the process's own
.IR /proc/self/task/ tid
directory.
.TP
.I /proc/[a\-z]*
Various other files and subdirectories under
.I /proc
expose system-wide information.
.PP
All of the above are described in more detail below.
.\"
.SS Files and directories
The following list provides details of many of the files and directories
under the
.I /proc
hierarchy.
.\" FIXME Describe /proc/[pid]/sessionid
.\"	  commit 1e0bd7550ea9cf474b1ad4c6ff5729a507f75fdc
.\"       CONFIG_AUDITSYSCALL
.\"       Added in Linux 2.6.25; read-only; only readable by real UID
.\"
.\" FIXME Describe /proc/[pid]/sched
.\"       Added in Linux 2.6.23
.\"       CONFIG_SCHED_DEBUG, and additional fields if CONFIG_SCHEDSTATS
.\"       Displays various scheduling parameters
.\"       This file can be written, to reset stats
.\"       The set of fields exposed by this file have changed
.\"	  significantly over time.
.\"       commit 43ae34cb4cd650d1eb4460a8253a8e747ba052ac
.\"
.\" FIXME Describe /proc/[pid]/schedstats and
.\"       /proc/[pid]/task/[tid]/schedstats
.\"       Added in Linux 2.6.9
.\"       CONFIG_SCHEDSTATS
.TP
.I /proc/kcore
This file represents the physical memory of the system and is stored
in the ELF core file format.
With this pseudo-file, and an unstripped
kernel
.RI ( /usr/src/linux/vmlinux )
binary, GDB can be used to
examine the current state of any kernel data structures.
.IP
The total length of the file is the size of physical memory (RAM) plus
4\ KiB.
.TP
.IR /proc/keys " (since Linux 2.6.10)"
See
.BR keyrings (7).
.TP
.IR /proc/key\-users " (since Linux 2.6.10)"
See
.BR keyrings (7).
.TP
.I /proc/kmsg
This file can be used instead of the
.BR syslog (2)
system call to read kernel messages.
A process must have superuser
privileges to read this file, and only one process should read this
file.
This file should not be read if a syslog process is running
which uses the
.BR syslog (2)
system call facility to log kernel messages.
.IP
Information in this file is retrieved with the
.BR dmesg (1)
program.
.TP
.IR /proc/kpagecgroup " (since Linux 4.3)"
.\" commit 80ae2fdceba8313b0433f899bdd9c6c463291a17
This file contains a 64-bit inode number of
the memory cgroup each page is charged to,
indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
.IP
The
.I /proc/kpagecgroup
file is present only if the
.B CONFIG_MEMCG
kernel configuration option is enabled.
.TP
.IR /proc/kpagecount " (since Linux 2.6.25)"
This file contains a 64-bit count of the number of
times each physical page frame is mapped,
indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
.IP
The
.I /proc/kpagecount
file is present only if the
.B CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
.TP
.IR /proc/kpageflags " (since Linux 2.6.25)"
This file contains 64-bit masks corresponding to each physical page frame;
it is indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
The bits are as follows:
.RS
.IP
.TS
r l l l.
0	-	KPF_LOCKED
1	-	KPF_ERROR
2	-	KPF_REFERENCED
3	-	KPF_UPTODATE
4	-	KPF_DIRTY
5	-	KPF_LRU
6	-	KPF_ACTIVE
7	-	KPF_SLAB
8	-	KPF_WRITEBACK
9	-	KPF_RECLAIM
10	-	KPF_BUDDY
11	-	KPF_MMAP	(since Linux 2.6.31)
12	-	KPF_ANON	(since Linux 2.6.31)
13	-	KPF_SWAPCACHE	(since Linux 2.6.31)
14	-	KPF_SWAPBACKED	(since Linux 2.6.31)
15	-	KPF_COMPOUND_HEAD	(since Linux 2.6.31)
16	-	KPF_COMPOUND_TAIL	(since Linux 2.6.31)
17	-	KPF_HUGE	(since Linux 2.6.31)
18	-	KPF_UNEVICTABLE	(since Linux 2.6.31)
19	-	KPF_HWPOISON	(since Linux 2.6.31)
20	-	KPF_NOPAGE	(since Linux 2.6.31)
21	-	KPF_KSM	(since Linux 2.6.32)
22	-	KPF_THP	(since Linux 3.4)
23	-	KPF_BALLOON	(since Linux 3.18)
.\" KPF_BALLOON: commit 09316c09dde33aae14f34489d9e3d243ec0d5938
24	-	KPF_ZERO_PAGE	(since Linux 4.0)
.\" KPF_ZERO_PAGE: commit 56873f43abdcd574b25105867a990f067747b2f4
25	-	KPF_IDLE	(since Linux 4.3)
.\" KPF_IDLE: commit f074a8f49eb87cde95ac9d040ad5e7ea4f029738
26	-	KPF_PGTABLE	(since Linux 4.18)
.\" KPF_PGTABLE: commit 1d40a5ea01d53251c23c7be541d3f4a656cfc537
.TE
.RE
.IP
For further details on the meanings of these bits,
see the kernel source file
.IR Documentation/admin\-guide/mm/pagemap.rst .
Before Linux 2.6.29,
.\" commit ad3bdefe877afb47480418fdb05ecd42842de65e
.\" commit e07a4b9217d1e97d2f3a62b6b070efdc61212110
.BR KPF_WRITEBACK ,
.BR KPF_RECLAIM ,
.BR KPF_BUDDY ,
and
.B KPF_LOCKED
did not report correctly.
.IP
The
.I /proc/kpageflags
file is present only if the
.B CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
.TP
.I /proc/loadavg
The first three fields in this file are load average figures
giving the number of jobs in the run queue (state R)
or waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes.
They are the same as the load average numbers given by
.BR uptime (1)
and other programs.
The fourth field consists of two numbers separated by a slash (/).
The first of these is the number of currently runnable kernel
scheduling entities (processes, threads).
The value after the slash is the number of kernel scheduling entities
that currently exist on the system.
The fifth field is the PID of the process that was most
recently created on the system.
.TP
.I /proc/locks
This file shows current file locks
.RB ( flock "(2) and " fcntl (2))
and leases
.RB ( fcntl (2)).
.IP
An example of the content shown in this file is the following:
.IP
.in +4n
.EX
1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128
2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF
3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF
4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF
5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0
6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1
7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335
8: OFDLCK ADVISORY  WRITE \-1 08:01:8713209 128 191
.EE
.in
.IP
The fields shown in each line are as follows:
.RS
.IP [1] 5
The ordinal position of the lock in the list.
.IP [2]
The lock type.
Values that may appear here include:
.RS
.TP
.B FLOCK
This is a BSD file lock created using
.BR flock (2).
.TP
.B OFDLCK
This is an open file description (OFD) lock created using
.BR fcntl (2).
.TP
.B POSIX
This is a POSIX byte-range lock created using
.BR fcntl (2).
.RE
.IP [3]
Among the strings that can appear here are the following:
.RS
.TP
.B ADVISORY
This is an advisory lock.
.TP
.B MANDATORY
This is a mandatory lock.
.RE
.IP [4]
The type of lock.
Values that can appear here are:
.RS
.TP
.B READ
This is a POSIX or OFD read lock, or a BSD shared lock.
.TP
.B WRITE
This is a POSIX or OFD write lock, or a BSD exclusive lock.
.RE
.IP [5]
The PID of the process that owns the lock.
.IP
Because OFD locks are not owned by a single process
(since multiple processes may have file descriptors that
refer to the same open file description),
the value \-1 is displayed in this field for OFD locks.
(Before Linux 4.14,
.\" commit 9d5b86ac13c573795525ecac6ed2db39ab23e2a8
a bug meant that the PID of the process that
initially acquired the lock was displayed instead of the value \-1.)
.IP [6]
Three colon-separated subfields that identify the major and minor device
ID of the device containing the filesystem where the locked file resides,
followed by the inode number of the locked file.
.IP [7]
The byte offset of the first byte of the lock.
For BSD locks, this value is always 0.
.IP [8]
The byte offset of the last byte of the lock.
.B EOF
in this field means that the lock extends to the end of the file.
For BSD locks, the value shown is always
.IR EOF .
.RE
.IP
Since Linux 4.9,
.\" commit d67fd44f697dff293d7cdc29af929241b669affe
the list of locks shown in
.I /proc/locks
is filtered to show just the locks for the processes in the PID
namespace (see
.BR pid_namespaces (7))
for which the
.I /proc
filesystem was mounted.
(In the initial PID namespace,
there is no filtering of the records shown in this file.)
.IP
The
.BR lslocks (8)
command provides a bit more information about each lock.
.TP
.IR /proc/malloc " (only up to and including Linux 2.2)"
.\" It looks like this only ever did something back in 1.0 days
This file is present only if
.B CONFIG_DEBUG_MALLOC
was defined during compilation.
.TP
.I /proc/meminfo
This file reports statistics about memory usage on the system.
It is used by
.BR free (1)
to report the amount of free and used memory (both physical and swap)
on the system as well as the shared memory and buffers used by the
kernel.
Each line of the file consists of a parameter name, followed by a colon,
the value of the parameter, and an option unit of measurement (e.g., "kB").
The list below describes the parameter names and
the format specifier required to read the field value.
Except as noted below,
all of the fields have been present since at least Linux 2.6.0.
Some fields are displayed only if the kernel was configured
with various options; those dependencies are noted in the list.
.RS
.TP
.IR MemTotal " %lu"
Total usable RAM (i.e., physical RAM minus a few reserved
bits and the kernel binary code).
.TP
.IR MemFree " %lu"
The sum of
.IR LowFree + HighFree .
.TP
.IR MemAvailable " %lu (since Linux 3.14)"
An estimate of how much memory is available for starting new
applications, without swapping.
.TP
.IR Buffers " %lu"
Relatively temporary storage for raw disk blocks that
shouldn't get tremendously large (20 MB or so).
.TP
.IR Cached " %lu"
In-memory cache for files read from the disk (the page cache).
Doesn't include
.IR SwapCached .
.TP
.IR SwapCached " %lu"
Memory that once was swapped out, is swapped back in but
still also is in the swap file.
(If memory pressure is high, these pages
don't need to be swapped out again because they are already
in the swap file.
This saves I/O.)
.TP
.IR Active " %lu"
Memory that has been used more recently and usually not
reclaimed unless absolutely necessary.
.TP
.IR Inactive " %lu"
Memory which has been less recently used.
It is more eligible to be reclaimed for other purposes.
.TP
.IR Active(anon) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Inactive(anon) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Active(file) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Inactive(file) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Unevictable " %lu (since Linux 2.6.28)"
(From Linux 2.6.28 to Linux 2.6.30,
\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
[To be documented.]
.TP
.IR Mlocked " %lu (since Linux 2.6.28)"
(From Linux 2.6.28 to Linux 2.6.30,
\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
[To be documented.]
.TP
.IR HighTotal " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Total amount of highmem.
Highmem is all memory above \[ti]860 MB of physical memory.
Highmem areas are for use by user-space programs,
or for the page cache.
The kernel must use tricks to access
this memory, making it slower to access than lowmem.
.TP
.IR HighFree " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Amount of free highmem.
.TP
.IR LowTotal " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Total amount of lowmem.
Lowmem is memory which can be used for everything that
highmem can be used for, but it is also available for the
kernel's use for its own data structures.
Among many other things,
it is where everything from
.I Slab
is allocated.
Bad things happen when you're out of lowmem.
.TP
.IR LowFree " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Amount of free lowmem.
.TP
.IR MmapCopy " %lu (since Linux 2.6.29)"
.RB ( CONFIG_MMU
is required.)
[To be documented.]
.TP
.IR SwapTotal " %lu"
Total amount of swap space available.
.TP
.IR SwapFree " %lu"
Amount of swap space that is currently unused.
.TP
.IR Dirty " %lu"
Memory which is waiting to get written back to the disk.
.TP
.IR Writeback " %lu"
Memory which is actively being written back to the disk.
.TP
.IR AnonPages " %lu (since Linux 2.6.18)"
Non-file backed pages mapped into user-space page tables.
.TP
.IR Mapped " %lu"
Files which have been mapped into memory (with
.BR mmap (2)),
such as libraries.
.TP
.IR Shmem " %lu (since Linux 2.6.32)"
Amount of memory consumed in
.BR tmpfs (5)
filesystems.
.TP
.IR KReclaimable " %lu (since Linux 4.20)"
Kernel allocations that the kernel will attempt to reclaim
under memory pressure.
Includes
.I SReclaimable
(below), and other direct allocations with a shrinker.
.TP
.IR Slab " %lu"
In-kernel data structures cache.
(See
.BR slabinfo (5).)
.TP
.IR SReclaimable " %lu (since Linux 2.6.19)"
Part of
.IR Slab ,
that might be reclaimed, such as caches.
.TP
.IR SUnreclaim " %lu (since Linux 2.6.19)"
Part of
.IR Slab ,
that cannot be reclaimed on memory pressure.
.TP
.IR KernelStack " %lu (since Linux 2.6.32)"
Amount of memory allocated to kernel stacks.
.TP
.IR PageTables " %lu (since Linux 2.6.18)"
Amount of memory dedicated to the lowest level of page tables.
.TP
.IR Quicklists " %lu (since Linux 2.6.27)"
(\fBCONFIG_QUICKLIST\fP is required.)
[To be documented.]
.TP
.IR NFS_Unstable " %lu (since Linux 2.6.18)"
NFS pages sent to the server, but not yet committed to stable storage.
.TP
.IR Bounce " %lu (since Linux 2.6.18)"
Memory used for block device "bounce buffers".
.TP
.IR WritebackTmp " %lu (since Linux 2.6.26)"
Memory used by FUSE for temporary writeback buffers.
.TP
.IR CommitLimit " %lu (since Linux 2.6.10)"
This is the total amount of memory currently available to
be allocated on the system, expressed in kilobytes.
This limit is adhered to
only if strict overcommit accounting is enabled (mode 2 in
.IR /proc/sys/vm/overcommit_memory ).
The limit is calculated according to the formula described under
.IR /proc/sys/vm/overcommit_memory .
For further details, see the kernel source file
.IR Documentation/vm/overcommit\-accounting.rst .
.TP
.IR Committed_AS " %lu"
The amount of memory presently allocated on the system.
The committed memory is a sum of all of the memory which
has been allocated by processes, even if it has not been
"used" by them as of yet.
A process which allocates 1 GB of memory (using
.BR malloc (3)
or similar), but touches only 300 MB of that memory will show up
as using only 300 MB of memory even if it has the address space
allocated for the entire 1 GB.
.IP
This 1 GB is memory which has been "committed" to by the VM
and can be used at any time by the allocating application.
With strict overcommit enabled on the system (mode 2 in
.IR /proc/sys/vm/overcommit_memory ),
allocations which would exceed the
.I CommitLimit
will not be permitted.
This is useful if one needs to guarantee that processes will not
fail due to lack of memory once that memory has been successfully allocated.
.TP
.IR VmallocTotal " %lu"
Total size of vmalloc memory area.
.TP
.IR VmallocUsed " %lu"
Amount of vmalloc area which is used.
Since Linux 4.4,
.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0
this field is no longer calculated, and is hard coded as 0.
See
.IR /proc/vmallocinfo .
.TP
.IR VmallocChunk " %lu"
Largest contiguous block of vmalloc area which is free.
Since Linux 4.4,
.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0
this field is no longer calculated and is hard coded as 0.
See
.IR /proc/vmallocinfo .
.TP
.IR HardwareCorrupted " %lu (since Linux 2.6.32)"
(\fBCONFIG_MEMORY_FAILURE\fP is required.)
[To be documented.]
.TP
.IR LazyFree " %lu (since Linux 4.12)"
Shows the amount of memory marked by
.BR madvise (2)
.BR MADV_FREE .
.TP
.IR AnonHugePages " %lu (since Linux 2.6.38)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Non-file backed huge pages mapped into user-space page tables.
.TP
.IR ShmemHugePages " %lu (since Linux 4.8)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Memory used by shared memory (shmem) and
.BR tmpfs (5)
allocated with huge pages.
.TP
.IR ShmemPmdMapped " %lu (since Linux 4.8)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Shared memory mapped into user space with huge pages.
.TP
.IR CmaTotal " %lu (since Linux 3.1)"
Total CMA (Contiguous Memory Allocator) pages.
(\fBCONFIG_CMA\fP is required.)
.TP
.IR CmaFree " %lu (since Linux 3.1)"
Free CMA (Contiguous Memory Allocator) pages.
(\fBCONFIG_CMA\fP is required.)
.TP
.IR HugePages_Total " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The size of the pool of huge pages.
.TP
.IR HugePages_Free " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The number of huge pages in the pool that are not yet allocated.
.TP
.IR HugePages_Rsvd " %lu (since Linux 2.6.17)"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
This is the number of huge pages for
which a commitment to allocate from the pool has been made,
but no allocation has yet been made.
These reserved huge pages
guarantee that an application will be able to allocate a
huge page from the pool of huge pages at fault time.
.TP
.IR HugePages_Surp " %lu (since Linux 2.6.24)"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
This is the number of huge pages in
the pool above the value in
.IR /proc/sys/vm/nr_hugepages .
The maximum number of surplus huge pages is controlled by
.IR /proc/sys/vm/nr_overcommit_hugepages .
.TP
.IR Hugepagesize " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The size of huge pages.
.TP
.IR DirectMap4k " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 4 kB pages.
(x86.)
.TP
.IR DirectMap4M " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 4 MB pages.
(x86 with
.B CONFIG_X86_64
or
.B CONFIG_X86_PAE
enabled.)
.TP
.IR DirectMap2M " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 2 MB pages.
(x86 with neither
.B CONFIG_X86_64
nor
.B CONFIG_X86_PAE
enabled.)
.TP
.IR DirectMap1G " %lu (since Linux 2.6.27)"
(x86 with
.B CONFIG_X86_64
and
.B CONFIG_X86_DIRECT_GBPAGES
enabled.)
.RE
.TP
.I /proc/modules
A text list of the modules that have been loaded by the system.
See also
.BR lsmod (8).
.TP
.I /proc/mtrr
Memory Type Range Registers.
See the Linux kernel source file
.I Documentation/x86/mtrr.rst
(or
.I Documentation/x86/mtrr.txt
.\" commit 7225e75144b9718cbbe1820d9c011c809d5773fd
before Linux 5.2, or
.I Documentation/mtrr.txt
before Linux 2.6.28)
for details.
.TP
.I /proc/partitions
Contains the major and minor numbers of each partition as well as the number
of 1024-byte blocks and the partition name.
.TP
.I /proc/pci
This is a listing of all PCI devices found during kernel initialization
and their configuration.
.IP
This file has been deprecated in favor of a new
.I /proc
interface for PCI
.RI ( /proc/bus/pci ).
It became optional in Linux 2.2 (available with
.B CONFIG_PCI_OLD_PROC
set at kernel compilation).
It became once more nonoptionally enabled in Linux 2.4.
Next, it was deprecated in Linux 2.6 (still available with
.B CONFIG_PCI_LEGACY_PROC
set), and finally removed altogether since Linux 2.6.17.
.\" FIXME Document /proc/sched_debug (since Linux 2.6.23)
.\" See also /proc/[pid]/sched
.TP
.IR /proc/profile " (since Linux 2.4)"
This file is present only if the kernel was booted with the
.I profile=1
command-line option.
It exposes kernel profiling information in a binary format for use by
.BR readprofile (1).
Writing (e.g., an empty string) to this file resets the profiling counters;
on some architectures,
writing a binary integer "profiling multiplier" of size
.I sizeof(int)
sets the profiling interrupt frequency.
.TP
.I /proc/scsi
A directory with the
.I scsi
mid-level pseudo-file and various SCSI low-level
driver directories,
which contain a file for each SCSI host in this system, all of
which give the status of some part of the SCSI IO subsystem.
These files contain ASCII structures and are, therefore, readable with
.BR cat (1).
.IP
You can also write to some of the files to reconfigure the subsystem or
switch certain features on or off.
.TP
.I /proc/scsi/scsi
This is a listing of all SCSI devices known to the kernel.
The listing is similar to the one seen during bootup.
scsi currently supports only the \fIadd\-single\-device\fP command which
allows root to add a hotplugged device to the list of known devices.
.IP
The command
.IP
.in +4n
.EX
echo \[aq]scsi add\-single\-device 1 0 5 0\[aq] > /proc/scsi/scsi
.EE
.in
.IP
will cause
host scsi1 to scan on SCSI channel 0 for a device on ID 5 LUN 0.
If there
is already a device known on this address or the address is invalid, an
error will be returned.
.TP
.IR /proc/scsi/ drivername
\fIdrivername\fP can currently be NCR53c7xx, aha152x, aha1542, aha1740,
aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000, pas16, qlogic,
scsi_debug, seagate, t128, u15\-24f, ultrastore, or wd7000.
These directories show up for all drivers that registered at least one
SCSI HBA.
Every directory contains one file per registered host.
Every host-file is named after the number the host was assigned during
initialization.
.IP
Reading these files will usually show driver and host configuration,
statistics, and so on.
.IP
Writing to these files allows different things on different hosts.
For example, with the \fIlatency\fP and \fInolatency\fP commands,
root can switch on and off command latency measurement code in the
eata_dma driver.
With the \fIlockup\fP and \fIunlock\fP commands,
root can control bus lockups simulated by the scsi_debug driver.
.TP
.I /proc/slabinfo
Information about kernel caches.
See
.BR slabinfo (5)
for details.
.TP
.I /proc/stat
kernel/system statistics.
Varies with architecture.
Common
entries include:
.RS
.TP
.I cpu  10132153 290696 3084719 46828483 16683 0 25195 0 175628 0
.TQ
.I cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
The amount of time, measured in units of
USER_HZ (1/100ths of a second on most architectures, use
.I sysconf(_SC_CLK_TCK)
to obtain the right value),
.\" 1024 on Alpha and ia64
that the system ("cpu" line) or the specific CPU ("cpu\fIN\fR" line)
spent in various states:
.RS
.TP
.I user
(1) Time spent in user mode.
.TP
.I nice
(2) Time spent in user mode with low priority (nice).
.TP
.I system
(3) Time spent in system mode.
.TP
.I idle
(4) Time spent in the idle task.
.\" FIXME . Actually, the following info about the /proc/stat 'cpu' field
.\"       does not seem to be quite right (at least in Linux 2.6.12 or Linux 3.6):
.\"       the idle time in /proc/uptime does not quite match this value
This value should be USER_HZ times the
second entry in the
.I /proc/uptime
pseudo-file.
.TP
.IR iowait " (since Linux 2.5.41)"
(5) Time waiting for I/O to complete.
This value is not reliable, for the following reasons:
.\" See kernel commit 9c240d757658a3ae9968dd309e674c61f07c7f48
.RS
.IP \[bu] 3
The CPU will not wait for I/O to complete;
iowait is the time that a task is waiting for I/O to complete.
When a CPU goes into idle state for outstanding task I/O,
another task will be scheduled on this CPU.
.IP \[bu]
On a multi-core CPU,
the task waiting for I/O to complete is not running on any CPU,
so the iowait of each CPU is difficult to calculate.
.IP \[bu]
The value in this field may
.I decrease
in certain conditions.
.RE
.TP
.IR irq " (since Linux 2.6.0)"
.\" Precisely: Linux 2.6.0-test4
(6) Time servicing interrupts.
.TP
.IR softirq " (since Linux 2.6.0)"
.\" Precisely: Linux 2.6.0-test4
(7) Time servicing softirqs.
.TP
.IR steal " (since Linux 2.6.11)"
(8) Stolen time, which is the time spent in other operating systems when
running in a virtualized environment
.TP
.IR guest " (since Linux 2.6.24)"
(9) Time spent running a virtual CPU for guest
operating systems under the control of the Linux kernel.
.\" See Changelog entry for 5e84cfde51cf303d368fcb48f22059f37b3872de
.TP
.IR guest_nice " (since Linux 2.6.33)"
.\" commit ce0e7b28fb75cb003cfc8d0238613aaf1c55e797
(10) Time spent running a niced guest (virtual CPU for guest
operating systems under the control of the Linux kernel).
.RE
.TP
\fIpage 5741 1808\fP
The number of pages the system paged in and the number that were paged
out (from disk).
.TP
\fIswap 1 0\fP
The number of swap pages that have been brought in and out.
.TP
.\" FIXME . The following is not the full picture for the 'intr' of
.\"       /proc/stat on 2.6:
\fIintr 1462898\fP
This line shows counts of interrupts serviced since boot time,
for each of the possible system interrupts.
The first column is the total of all interrupts serviced
including unnumbered architecture specific interrupts;
each subsequent column is the total for that particular numbered interrupt.
Unnumbered interrupts are not shown, only summed into the total.
.TP
\fIdisk_io: (2,0):(31,30,5764,1,2) (3,0):\fP...
(major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
.br
(Linux 2.4 only)
.TP
\fIctxt 115315\fP
The number of context switches that the system underwent.
.TP
\fIbtime 769041601\fP
boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
.TP
\fIprocesses 86031\fP
Number of forks since boot.
.TP
\fIprocs_running 6\fP
Number of processes in runnable state.
(Linux 2.5.45 onward.)
.TP
\fIprocs_blocked 2\fP
Number of processes blocked waiting for I/O to complete.
(Linux 2.5.45 onward.)
.TP
.I softirq 229245889 94 60001584 13619 5175704 2471304 28 51212741 59130143 0 51240672
.\" commit d3d64df21d3d0de675a0d3ffa7c10514f3644b30
This line shows the number of softirq for all CPUs.
The first column is the total of all softirqs and
each subsequent column is the total for particular softirq.
(Linux 2.6.31 onward.)
.RE
.TP
.I /proc/swaps
Swap areas in use.
See also
.BR swapon (8).
.TP
.I /proc/sys
This directory (present since Linux 1.3.57) contains a number of files
and subdirectories corresponding to kernel variables.
These variables can be read and in some cases modified using
the \fI/proc\fP filesystem, and the (deprecated)
.BR sysctl (2)
system call.
.IP
String values may be terminated by either \[aq]\e0\[aq] or \[aq]\en\[aq].
.IP
Integer and long values may be written either in decimal or in
hexadecimal notation (e.g., 0x3FFF).
When writing multiple integer or long values, these may be separated
by any of the following whitespace characters:
\[aq]\ \[aq], \[aq]\et\[aq], or \[aq]\en\[aq].
Using other separators leads to the error
.BR EINVAL .
.TP
.IR /proc/sys/abi " (since Linux 2.4.10)"
This directory may contain files with application binary information.
.\" On some systems, it is not present.
See the Linux kernel source file
.I Documentation/sysctl/abi.rst
(or
.I Documentation/sysctl/abi.txt
before Linux 5.3)
for more information.
.TP
.I /proc/sys/debug
This directory may be empty.
.TP
.I /proc/sys/dev
This directory contains device-specific information (e.g.,
.IR dev/cdrom/info ).
On
some systems, it may be empty.
.TP
.I /proc/sys/fs
This directory contains the files and subdirectories for kernel variables
related to filesystems.
.TP
.IR /proc/sys/fs/aio\-max\-nr " and " /proc/sys/fs/aio\-nr " (since Linux 2.6.4)"
.I aio\-nr
is the running total of the number of events specified by
.BR io_setup (2)
calls for all currently active AIO contexts.
If
.I aio\-nr
reaches
.IR aio\-max\-nr ,
then
.BR io_setup (2)
will fail with the error
.BR EAGAIN .
Raising
.I aio\-max\-nr
does not result in the preallocation or resizing
of any kernel data structures.
.TP
.I /proc/sys/fs/binfmt_misc
Documentation for files in this directory can be found
in the Linux kernel source in the file
.I Documentation/admin\-guide/binfmt\-misc.rst
(or in
.I Documentation/binfmt_misc.txt
on older kernels).
.TP
.IR /proc/sys/fs/dentry\-state " (since Linux 2.2)"
This file contains information about the status of the
directory cache (dcache).
The file contains six numbers,
.IR nr_dentry ,
.IR nr_unused ,
.I age_limit
(age in seconds),
.I want_pages
(pages requested by system) and two dummy values.
.RS
.IP \[bu] 3
.I nr_dentry
is the number of allocated dentries (dcache entries).
This field is unused in Linux 2.2.
.IP \[bu]
.I nr_unused
is the number of unused dentries.
.IP \[bu]
.I age_limit
.\" looks like this is unused in Linux 2.2 to Linux 2.6
is the age in seconds after which dcache entries
can be reclaimed when memory is short.
.IP \[bu]
.I want_pages
.\" looks like this is unused in Linux 2.2 to Linux 2.6
is nonzero when the kernel has called shrink_dcache_pages() and the
dcache isn't pruned yet.
.RE
.TP
.I /proc/sys/fs/dir\-notify\-enable
This file can be used to disable or enable the
.I dnotify
interface described in
.BR fcntl (2)
on a system-wide basis.
A value of 0 in this file disables the interface,
and a value of 1 enables it.
.TP
.I /proc/sys/fs/dquot\-max
This file shows the maximum number of cached disk quota entries.
On some (2.4) systems, it is not present.
If the number of free cached disk quota entries is very low and
you have some awesome number of simultaneous system users,
you might want to raise the limit.
.TP
.I /proc/sys/fs/dquot\-nr
This file shows the number of allocated disk quota
entries and the number of free disk quota entries.
.TP
.IR /proc/sys/fs/epoll " (since Linux 2.6.28)"
This directory contains the file
.IR max_user_watches ,
which can be used to limit the amount of kernel memory consumed by the
.I epoll
interface.
For further details, see
.BR epoll (7).
.TP
.I /proc/sys/fs/file\-max
This file defines
a system-wide limit on the number of open files for all processes.
System calls that fail when encountering this limit fail with the error
.BR ENFILE .
(See also
.BR setrlimit (2),
which can be used by a process to set the per-process limit,
.BR RLIMIT_NOFILE ,
on the number of files it may open.)
If you get lots
of error messages in the kernel log about running out of file handles
(open file descriptions)
(look for "VFS: file\-max limit <number> reached"),
try increasing this value:
.IP
.in +4n
.EX
echo 100000 > /proc/sys/fs/file\-max
.EE
.in
.IP
Privileged processes
.RB ( CAP_SYS_ADMIN )
can override the
.I file\-max
limit.
.TP
.I /proc/sys/fs/file\-nr
This (read-only) file contains three numbers:
the number of allocated file handles
(i.e., the number of open file descriptions; see
.BR open (2));
the number of free file handles;
and the maximum number of file handles (i.e., the same value as
.IR /proc/sys/fs/file\-max ).
If the number of allocated file handles is close to the
maximum, you should consider increasing the maximum.
Before Linux 2.6,
the kernel allocated file handles dynamically,
but it didn't free them again.
Instead the free file handles were kept in a list for reallocation;
the "free file handles" value indicates the size of that list.
A large number of free file handles indicates that there was
a past peak in the usage of open file handles.
Since Linux 2.6, the kernel does deallocate freed file handles,
and the "free file handles" value is always zero.
.TP
.IR /proc/sys/fs/inode\-max " (only present until Linux 2.2)"
This file contains the maximum number of in-memory inodes.
This value should be 3\[en]4 times larger
than the value in
.IR file\-max ,
since \fIstdin\fP, \fIstdout\fP
and network sockets also need an inode to handle them.
When you regularly run out of inodes, you need to increase this value.
.IP
Starting with Linux 2.4,
there is no longer a static limit on the number of inodes,
and this file is removed.
.TP
.I /proc/sys/fs/inode\-nr
This file contains the first two values from
.IR inode\-state .
.TP
.I /proc/sys/fs/inode\-state
This file
contains seven numbers:
.IR nr_inodes ,
.IR nr_free_inodes ,
.IR preshrink ,
and four dummy values (always zero).
.IP
.I nr_inodes
is the number of inodes the system has allocated.
.\" This can be slightly more than
.\" .I inode\-max
.\" because Linux allocates them one page full at a time.
.I nr_free_inodes
represents the number of free inodes.
.IP
.I preshrink
is nonzero when the
.I nr_inodes
>
.I inode\-max
and the system needs to prune the inode list instead of allocating more;
since Linux 2.4, this field is a dummy value (always zero).
.TP
.IR /proc/sys/fs/inotify " (since Linux 2.6.13)"
This directory contains files
.IR max_queued_events ", " max_user_instances ", and " max_user_watches ,
that can be used to limit the amount of kernel memory consumed by the
.I inotify
interface.
For further details, see
.BR inotify (7).
.TP
.I /proc/sys/fs/lease\-break\-time
This file specifies the grace period that the kernel grants to a process
holding a file lease
.RB ( fcntl (2))
after it has sent a signal to that process notifying it
that another process is waiting to open the file.
If the lease holder does not remove or downgrade the lease within
this grace period, the kernel forcibly breaks the lease.
.TP
.I /proc/sys/fs/leases\-enable
This file can be used to enable or disable file leases
.RB ( fcntl (2))
on a system-wide basis.
If this file contains the value 0, leases are disabled.
A nonzero value enables leases.
.TP
.IR /proc/sys/fs/mount\-max " (since Linux 4.9)"
.\" commit d29216842a85c7970c536108e093963f02714498
The value in this file specifies the maximum number of mounts that may exist
in a mount namespace.
The default value in this file is 100,000.
.TP
.IR /proc/sys/fs/mqueue " (since Linux 2.6.6)"
This directory contains files
.IR msg_max ", " msgsize_max ", and " queues_max ,
controlling the resources used by POSIX message queues.
See
.BR mq_overview (7)
for details.
.TP
.IR /proc/sys/fs/nr_open " (since Linux 2.6.25)"
.\" commit 9cfe015aa424b3c003baba3841a60dd9b5ad319b
This file imposes a ceiling on the value to which the
.B RLIMIT_NOFILE
resource limit can be raised (see
.BR getrlimit (2)).
This ceiling is enforced for both unprivileged and privileged process.
The default value in this file is 1048576.
(Before Linux 2.6.25, the ceiling for
.B RLIMIT_NOFILE
was hard-coded to the same value.)
.TP
.IR /proc/sys/fs/overflowgid " and " /proc/sys/fs/overflowuid
These files
allow you to change the value of the fixed UID and GID.
The default is 65534.
Some filesystems support only 16-bit UIDs and GIDs, although in Linux
UIDs and GIDs are 32 bits.
When one of these filesystems is mounted
with writes enabled, any UID or GID that would exceed 65535 is translated
to the overflow value before being written to disk.
.TP
.IR /proc/sys/fs/pipe\-max\-size " (since Linux 2.6.35)"
See
.BR pipe (7).
.TP
.IR /proc/sys/fs/pipe\-user\-pages\-hard " (since Linux 4.5)"
See
.BR pipe (7).
.TP
.IR /proc/sys/fs/pipe\-user\-pages\-soft " (since Linux 4.5)"
See
.BR pipe (7).
.TP
.IR /proc/sys/fs/protected_fifos " (since Linux 4.19)"
The value in this file is/can be set to one of the following:
.RS
.TP 4
0
Writing to FIFOs is unrestricted.
.TP
1
Don't allow
.B O_CREAT
.BR open (2)
on FIFOs that the caller doesn't own in world-writable sticky directories,
unless the FIFO is owned by the owner of the directory.
.TP
2
As for the value 1,
but the restriction also applies to group-writable sticky directories.
.RE
.IP
The intent of the above protections is to avoid unintentional writes to an
attacker-controlled FIFO when a program expected to create a regular file.
.TP
.IR /proc/sys/fs/protected_hardlinks " (since Linux 3.6)"
.\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7
When the value in this file is 0,
no restrictions are placed on the creation of hard links
(i.e., this is the historical behavior before Linux 3.6).
When the value in this file is 1,
a hard link can be created to a target file
only if one of the following conditions is true:
.RS
.IP \[bu] 3
The calling process has the
.B CAP_FOWNER
capability in its user namespace
and the file UID has a mapping in the namespace.
.IP \[bu]
The filesystem UID of the process creating the link matches
the owner (UID) of the target file
(as described in
.BR credentials (7),
a process's filesystem UID is normally the same as its effective UID).
.IP \[bu]
All of the following conditions are true:
.RS 4
.IP \[bu] 3
the target is a regular file;
.IP \[bu]
the target file does not have its set-user-ID mode bit enabled;
.IP \[bu]
the target file does not have both its set-group-ID and
group-executable mode bits enabled; and
.IP \[bu]
the caller has permission to read and write the target file
(either via the file's permissions mask or because it has
suitable capabilities).
.RE
.RE
.IP
The default value in this file is 0.
Setting the value to 1
prevents a longstanding class of security issues caused by
hard-link-based time-of-check, time-of-use races,
most commonly seen in world-writable directories such as
.IR /tmp .
The common method of exploiting this flaw
is to cross privilege boundaries when following a given hard link
(i.e., a root process follows a hard link created by another user).
Additionally, on systems without separated partitions,
this stops unauthorized users from "pinning" vulnerable set-user-ID and
set-group-ID files against being upgraded by
the administrator, or linking to special files.
.TP
.IR /proc/sys/fs/protected_regular " (since Linux 4.19)"
The value in this file is/can be set to one of the following:
.RS
.TP 4
0
Writing to regular files is unrestricted.
.TP
1
Don't allow
.B O_CREAT
.BR open (2)
on regular files that the caller doesn't own in
world-writable sticky directories,
unless the regular file is owned by the owner of the directory.
.TP
2
As for the value 1,
but the restriction also applies to group-writable sticky directories.
.RE
.IP
The intent of the above protections is similar to
.IR protected_fifos ,
but allows an application to
avoid writes to an attacker-controlled regular file,
where the application expected to create one.
.TP
.IR /proc/sys/fs/protected_symlinks " (since Linux 3.6)"
.\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7
When the value in this file is 0,
no restrictions are placed on following symbolic links
(i.e., this is the historical behavior before Linux 3.6).
When the value in this file is 1, symbolic links are followed only
in the following circumstances:
.RS
.IP \[bu] 3
the filesystem UID of the process following the link matches
the owner (UID) of the symbolic link
(as described in
.BR credentials (7),
a process's filesystem UID is normally the same as its effective UID);
.IP \[bu]
the link is not in a sticky world-writable directory; or
.IP \[bu]
the symbolic link and its parent directory have the same owner (UID)
.RE
.IP
A system call that fails to follow a symbolic link
because of the above restrictions returns the error
.B EACCES
in
.IR errno .
.IP
The default value in this file is 0.
Setting the value to 1 avoids a longstanding class of security issues
based on time-of-check, time-of-use races when accessing symbolic links.
.TP
.IR /proc/sys/fs/suid_dumpable " (since Linux 2.6.13)"
.\" The following is based on text from Documentation/sysctl/kernel.txt
The value in this file is assigned to a process's "dumpable" flag
in the circumstances described in
.BR prctl (2).
In effect,
the value in this file determines whether core dump files are
produced for set-user-ID or otherwise protected/tainted binaries.
The "dumpable" setting also affects the ownership of files in a process's
.IR /proc/ pid
directory, as described above.
.IP
Three different integer values can be specified:
.RS
.TP
\fI0\ (default)\fP
.\" In kernel source: SUID_DUMP_DISABLE
This provides the traditional (pre-Linux 2.6.13) behavior.
A core dump will not be produced for a process which has
changed credentials (by calling
.BR seteuid (2),
.BR setgid (2),
or similar, or by executing a set-user-ID or set-group-ID program)
or whose binary does not have read permission enabled.
.TP
\fI1\ ("debug")\fP
.\" In kernel source: SUID_DUMP_USER
All processes dump core when possible.
(Reasons why a process might nevertheless not dump core are described in
.BR core (5).)
The core dump is owned by the filesystem user ID of the dumping process
and no security is applied.
This is intended for system debugging situations only:
this mode is insecure because it allows unprivileged users to
examine the memory contents of privileged processes.
.TP
\fI2\ ("suidsafe")\fP
.\" In kernel source: SUID_DUMP_ROOT
Any binary which normally would not be dumped (see "0" above)
is dumped readable by root only.
This allows the user to remove the core dump file but not to read it.
For security reasons core dumps in this mode will not overwrite one
another or other files.
This mode is appropriate when administrators are
attempting to debug problems in a normal environment.
.IP
Additionally, since Linux 3.6,
.\" 9520628e8ceb69fa9a4aee6b57f22675d9e1b709
.I /proc/sys/kernel/core_pattern
must either be an absolute pathname
or a pipe command, as detailed in
.BR core (5).
Warnings will be written to the kernel log if
.I core_pattern
does not follow these rules, and no core dump will be produced.
.\" 54b501992dd2a839e94e76aa392c392b55080ce8
.RE
.IP
For details of the effect of a process's "dumpable" setting
on ptrace access mode checking, see
.BR ptrace (2).
.TP
.I /proc/sys/fs/super\-max
This file
controls the maximum number of superblocks, and
thus the maximum number of mounted filesystems the kernel
can have.
You need increase only
.I super\-max
if you need to mount more filesystems than the current value in
.I super\-max
allows you to.
.TP
.I /proc/sys/fs/super\-nr
This file
contains the number of filesystems currently mounted.
.TP
.I /proc/sys/kernel
This directory contains files controlling a range of kernel parameters,
as described below.
.TP
.I /proc/sys/kernel/acct
This file
contains three numbers:
.IR highwater ,
.IR lowwater ,
and
.IR frequency .
If BSD-style process accounting is enabled, these values control
its behavior.
If free space on filesystem where the log lives goes below
.I lowwater
percent, accounting suspends.
If free space gets above
.I highwater
percent, accounting resumes.
.I frequency
determines
how often the kernel checks the amount of free space (value is in
seconds).
Default values are 4, 2, and 30.
That is, suspend accounting if 2% or less space is free; resume it
if 4% or more space is free; consider information about amount of free space
valid for 30 seconds.
.TP
.IR /proc/sys/kernel/auto_msgmni " (Linux 2.6.27 to Linux 3.18)"
.\" commit 9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e (introduces feature)
.\" commit 0050ee059f7fc86b1df2527aaa14ed5dc72f9973 (rendered redundant)
From Linux 2.6.27 to Linux 3.18,
this file was used to control recomputing of the value in
.I /proc/sys/kernel/msgmni
upon the addition or removal of memory or upon IPC namespace creation/removal.
Echoing "1" into this file enabled
.I msgmni
automatic recomputing (and triggered a recomputation of
.I msgmni
based on the current amount of available memory and number of IPC namespaces).
Echoing "0" disabled automatic recomputing.
(Automatic recomputing was also disabled if a value was explicitly assigned to
.IR /proc/sys/kernel/msgmni .)
The default value in
.I auto_msgmni
was 1.
.IP
Since Linux 3.19, the content of this file has no effect (because
.I msgmni
.\" FIXME Must document the 3.19 'msgmni' changes.
defaults to near the maximum value possible),
and reads from this file always return the value "0".
.TP
.IR /proc/sys/kernel/cap_last_cap " (since Linux 3.2)"
See
.BR capabilities (7).
.TP
.IR /proc/sys/kernel/cap\-bound " (from Linux 2.2 to Linux 2.6.24)"
This file holds the value of the kernel
.I "capability bounding set"
(expressed as a signed decimal number).
This set is ANDed against the capabilities permitted to a process
during
.BR execve (2).
Starting with Linux 2.6.25,
the system-wide capability bounding set disappeared,
and was replaced by a per-thread bounding set; see
.BR capabilities (7).
.TP
.I /proc/sys/kernel/core_pattern
See
.BR core (5).
.TP
.I /proc/sys/kernel/core_pipe_limit
See
.BR core (5).
.TP
.I /proc/sys/kernel/core_uses_pid
See
.BR core (5).
.TP
.I /proc/sys/kernel/ctrl\-alt\-del
This file
controls the handling of Ctrl-Alt-Del from the keyboard.
When the value in this file is 0, Ctrl-Alt-Del is trapped and
sent to the
.BR init (1)
program to handle a graceful restart.
When the value is greater than zero, Linux's reaction to a Vulcan
Nerve Pinch (tm) will be an immediate reboot, without even
syncing its dirty buffers.
Note: when a program (like dosemu) has the keyboard in "raw"
mode, the Ctrl-Alt-Del is intercepted by the program before it
ever reaches the kernel tty layer, and it's up to the program
to decide what to do with it.
.TP
.IR /proc/sys/kernel/dmesg_restrict " (since Linux 2.6.37)"
The value in this file determines who can see kernel syslog contents.
A value of 0 in this file imposes no restrictions.
If the value is 1, only privileged users can read the kernel syslog.
(See
.BR syslog (2)
for more details.)
Since Linux 3.4,
.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8
only users with the
.B CAP_SYS_ADMIN
capability may change the value in this file.
.TP
.IR /proc/sys/kernel/domainname " and " /proc/sys/kernel/hostname
can be used to set the NIS/YP domainname and the
hostname of your box in exactly the same way as the commands
.BR domainname (1)
and
.BR hostname (1),
that is:
.IP
.in +4n
.EX
.RB "#" " echo \[aq]darkstar\[aq] > /proc/sys/kernel/hostname"
.RB "#" " echo \[aq]mydomain\[aq] > /proc/sys/kernel/domainname"
.EE
.in
.IP
has the same effect as
.IP
.in +4n
.EX
.RB "#" " hostname \[aq]darkstar\[aq]"
.RB "#" " domainname \[aq]mydomain\[aq]"
.EE
.in
.IP
Note, however, that the classic darkstar.frop.org has the
hostname "darkstar" and DNS (Internet Domain Name Server)
domainname "frop.org", not to be confused with the NIS (Network
Information Service) or YP (Yellow Pages) domainname.
These two
domain names are in general different.
For a detailed discussion
see the
.BR hostname (1)
man page.
.TP
.I /proc/sys/kernel/hotplug
This file
contains the pathname for the hotplug policy agent.
The default value in this file is
.IR /sbin/hotplug .
.TP
.\" Removed in commit 87f504e5c78b910b0c1d6ffb89bc95e492322c84 (tglx/history.git)
.IR /proc/sys/kernel/htab\-reclaim " (before Linux 2.4.9.2)"
(PowerPC only) If this file is set to a nonzero value,
the PowerPC htab
.\" removed in commit 1b483a6a7b2998e9c98ad985d7494b9b725bd228, before Linux 2.6.28
(see kernel file
.IR Documentation/powerpc/ppc_htab.txt )
is pruned
each time the system hits the idle loop.
.TP
.I /proc/sys/kernel/keys/*
This directory contains various files that define parameters and limits
for the key-management facility.
These files are described in
.BR keyrings (7).
.TP
.IR /proc/sys/kernel/kptr_restrict " (since Linux 2.6.38)"
.\" 455cd5ab305c90ffc422dd2e0fb634730942b257
The value in this file determines whether kernel addresses are exposed via
.I /proc
files and other interfaces.
A value of 0 in this file imposes no restrictions.
If the value is 1, kernel pointers printed using the
.I %pK
format specifier will be replaced with zeros unless the user has the
.B CAP_SYSLOG
capability.
If the value is 2, kernel pointers printed using the
.I %pK
format specifier will be replaced with zeros regardless
of the user's capabilities.
The initial default value for this file was 1,
but the default was changed
.\" commit 411f05f123cbd7f8aa1edcae86970755a6e2a9d9
to 0 in Linux 2.6.39.
Since Linux 3.4,
.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8
only users with the
.B CAP_SYS_ADMIN
capability can change the value in this file.
.TP
.I /proc/sys/kernel/l2cr
(PowerPC only) This file
contains a flag that controls the L2 cache of G3 processor
boards.
If 0, the cache is disabled.
Enabled if nonzero.
.TP
.I /proc/sys/kernel/modprobe
This file contains the pathname for the kernel module loader.
The default value is
.IR /sbin/modprobe .
The file is present only if the kernel is built with the
.B CONFIG_MODULES
.RB ( CONFIG_KMOD
in Linux 2.6.26 and earlier)
option enabled.
It is described by the Linux kernel source file
.I Documentation/kmod.txt
(present only in Linux 2.4 and earlier).
.TP
.IR /proc/sys/kernel/modules_disabled " (since Linux 2.6.31)"
.\" 3d43321b7015387cfebbe26436d0e9d299162ea1
.\" From Documentation/sysctl/kernel.txt
A toggle value indicating if modules are allowed to be loaded
in an otherwise modular kernel.
This toggle defaults to off (0), but can be set true (1).
Once true, modules can be neither loaded nor unloaded,
and the toggle cannot be set back to false.
The file is present only if the kernel is built with the
.B CONFIG_MODULES
option enabled.
.TP
.IR /proc/sys/kernel/msgmax " (since Linux 2.2)"
This file defines
a system-wide limit specifying the maximum number of bytes in
a single message written on a System V message queue.
.TP
.IR /proc/sys/kernel/msgmni " (since Linux 2.4)"
This file defines the system-wide limit on the number of
message queue identifiers.
See also
.IR /proc/sys/kernel/auto_msgmni .
.TP
.IR /proc/sys/kernel/msgmnb " (since Linux 2.2)"
This file defines a system-wide parameter used to initialize the
.I msg_qbytes
setting for subsequently created message queues.
The
.I msg_qbytes
setting specifies the maximum number of bytes that may be written to the
message queue.
.TP
.IR /proc/sys/kernel/ngroups_max " (since Linux 2.6.4)"
This is a read-only file that displays the upper limit on the
number of a process's group memberships.
.TP
.IR /proc/sys/kernel/ns_last_pid " (since Linux 3.3)"
See
.BR pid_namespaces (7).
.TP
.IR /proc/sys/kernel/ostype " and " /proc/sys/kernel/osrelease
These files
give substrings of
.IR /proc/version .
.TP
.IR /proc/sys/kernel/overflowgid " and " /proc/sys/kernel/overflowuid
These files duplicate the files
.I /proc/sys/fs/overflowgid
and
.IR /proc/sys/fs/overflowuid .
.TP
.I /proc/sys/kernel/panic
This file gives read/write access to the kernel variable
.IR panic_timeout .
If this is zero, the kernel will loop on a panic; if nonzero,
it indicates that the kernel should autoreboot after this number
of seconds.
When you use the
software watchdog device driver, the recommended setting is 60.
.TP
.IR /proc/sys/kernel/panic_on_oops " (since Linux 2.5.68)"
This file controls the kernel's behavior when an oops
or BUG is encountered.
If this file contains 0, then the system
tries to continue operation.
If it contains 1, then the system
delays a few seconds (to give klogd time to record the oops output)
and then panics.
If the
.I /proc/sys/kernel/panic
file is also nonzero, then the machine will be rebooted.
.TP
.IR /proc/sys/kernel/pid_max " (since Linux 2.5.34)"
This file specifies the value at which PIDs wrap around
(i.e., the value in this file is one greater than the maximum PID).
PIDs greater than this value are not allocated;
thus, the value in this file also acts as a system-wide limit
on the total number of processes and threads.
The default value for this file, 32768,
results in the same range of PIDs as on earlier kernels.
On 32-bit platforms, 32768 is the maximum value for
.IR pid_max .
On 64-bit systems,
.I pid_max
can be set to any value up to 2\[ha]22
.RB ( PID_MAX_LIMIT ,
approximately 4 million).
.\" Prior to Linux 2.6.10, pid_max could also be raised above 32768 on 32-bit
.\" platforms, but this broke /proc/[pid]
.\" See http://marc.theaimsgroup.com/?l=linux-kernel&m=109513010926152&w=2
.TP
.IR /proc/sys/kernel/powersave\-nap " (PowerPC only)"
This file contains a flag.
If set, Linux-PPC will use the "nap" mode of
powersaving,
otherwise the "doze" mode will be used.
.TP
.I /proc/sys/kernel/printk
See
.BR syslog (2).
.TP
.IR /proc/sys/kernel/pty " (since Linux 2.6.4)"
This directory contains two files relating to the number of UNIX 98
pseudoterminals (see
.BR pts (4))
on the system.
.TP
.I /proc/sys/kernel/pty/max
This file defines the maximum number of pseudoterminals.
.\" FIXME Document /proc/sys/kernel/pty/reserve
.\"     New in Linux 3.3
.\"     commit e9aba5158a80098447ff207a452a3418ae7ee386
.TP
.I /proc/sys/kernel/pty/nr
This read-only file
indicates how many pseudoterminals are currently in use.
.TP
.I /proc/sys/kernel/random
This directory
contains various parameters controlling the operation of the file
.IR /dev/random .
See
.BR random (4)
for further information.
.TP
.IR /proc/sys/kernel/random/uuid " (since Linux 2.4)"
Each read from this read-only file returns a randomly generated 128-bit UUID,
as a string in the standard UUID format.
.TP
.IR /proc/sys/kernel/randomize_va_space " (since Linux 2.6.12)"
.\" Some further details can be found in Documentation/sysctl/kernel.txt
Select the address space layout randomization (ASLR) policy for the system
(on architectures that support ASLR).
Three values are supported for this file:
.RS
.TP
.B 0
Turn ASLR off.
This is the default for architectures that don't support ASLR,
and when the kernel is booted with the
.I norandmaps
parameter.
.TP
.B 1
Make the addresses of
.BR mmap (2)
allocations, the stack, and the VDSO page randomized.
Among other things, this means that shared libraries will be
loaded at randomized addresses.
The text segment of PIE-linked binaries will also be loaded
at a randomized address.
This value is the default if the kernel was configured with
.BR CONFIG_COMPAT_BRK .
.TP
.B 2
(Since Linux 2.6.25)
.\" commit c1d171a002942ea2d93b4fbd0c9583c56fce0772
Also support heap randomization.
This value is the default if the kernel was not configured with
.BR CONFIG_COMPAT_BRK .
.RE
.TP
.I /proc/sys/kernel/real\-root\-dev
This file is documented in the Linux kernel source file
.I Documentation/admin\-guide/initrd.rst
.\" commit 9d85025b0418163fae079c9ba8f8445212de8568
(or
.I Documentation/initrd.txt
before Linux 4.10).
.TP
.IR /proc/sys/kernel/reboot\-cmd " (Sparc only)"
This file seems to be a way to give an argument to the SPARC
ROM/Flash boot loader.
Maybe to tell it what to do after
rebooting?
.TP
.I /proc/sys/kernel/rtsig\-max
(Up to and including Linux 2.6.7; see
.BR setrlimit (2))
This file can be used to tune the maximum number
of POSIX real-time (queued) signals that can be outstanding
in the system.
.TP
.I /proc/sys/kernel/rtsig\-nr
(Up to and including Linux 2.6.7.)
This file shows the number of POSIX real-time signals currently queued.
.TP
.IR /proc/ pid /sched_autogroup_enabled " (since Linux 2.6.38)"
.\" commit 5091faa449ee0b7d73bc296a93bca9540fc51d0a
See
.BR sched (7).
.TP
.IR /proc/sys/kernel/sched_child_runs_first " (since Linux 2.6.23)"
If this file contains the value zero, then, after a
.BR fork (2),
the parent is first scheduled on the CPU.
If the file contains a nonzero value,
then the child is scheduled first on the CPU.
(Of course, on a multiprocessor system,
the parent and the child might both immediately be scheduled on a CPU.)
.TP
.IR /proc/sys/kernel/sched_rr_timeslice_ms " (since Linux 3.9)"
See
.BR sched_rr_get_interval (2).
.TP
.IR /proc/sys/kernel/sched_rt_period_us " (since Linux 2.6.25)"
See
.BR sched (7).
.TP
.IR /proc/sys/kernel/sched_rt_runtime_us " (since Linux 2.6.25)"
See
.BR sched (7).
.TP
.IR /proc/sys/kernel/seccomp " (since Linux 4.14)"
.\" commit 8e5f1ad116df6b0de65eac458d5e7c318d1c05af
This directory provides additional seccomp information and
configuration.
See
.BR seccomp (2)
for further details.
.TP
.IR /proc/sys/kernel/sem " (since Linux 2.4)"
This file contains 4 numbers defining limits for System V IPC semaphores.
These fields are, in order:
.RS
.TP
SEMMSL
The maximum semaphores per semaphore set.
.TP
SEMMNS
A system-wide limit on the number of semaphores in all semaphore sets.
.TP
SEMOPM
The maximum number of operations that may be specified in a
.BR semop (2)
call.
.TP
SEMMNI
A system-wide limit on the maximum number of semaphore identifiers.
.RE
.TP
.I /proc/sys/kernel/sg\-big\-buff
This file
shows the size of the generic SCSI device (sg) buffer.
You can't tune it just yet, but you could change it at
compile time by editing
.I include/scsi/sg.h
and changing
the value of
.BR SG_BIG_BUFF .
However, there shouldn't be any reason to change this value.
.TP
.IR /proc/sys/kernel/shm_rmid_forced " (since Linux 3.1)"
.\" commit b34a6b1da371ed8af1221459a18c67970f7e3d53
.\" See also Documentation/sysctl/kernel.txt
If this file is set to 1, all System V shared memory segments will
be marked for destruction as soon as the number of attached processes
falls to zero;
in other words, it is no longer possible to create shared memory segments
that exist independently of any attached process.
.IP
The effect is as though a
.BR shmctl (2)
.B IPC_RMID
is performed on all existing segments as well as all segments
created in the future (until this file is reset to 0).
Note that existing segments that are attached to no process will be
immediately destroyed when this file is set to 1.
Setting this option will also destroy segments that were created,
but never attached,
upon termination of the process that created the segment with
.BR shmget (2).
.IP
Setting this file to 1 provides a way of ensuring that
all System V shared memory segments are counted against the
resource usage and resource limits (see the description of
.B RLIMIT_AS
in
.BR getrlimit (2))
of at least one process.
.IP
Because setting this file to 1 produces behavior that is nonstandard
and could also break existing applications,
the default value in this file is 0.
Set this file to 1 only if you have a good understanding
of the semantics of the applications using
System V shared memory on your system.
.TP
.IR /proc/sys/kernel/shmall " (since Linux 2.2)"
This file
contains the system-wide limit on the total number of pages of
System V shared memory.
.TP
.IR /proc/sys/kernel/shmmax " (since Linux 2.2)"
This file
can be used to query and set the run-time limit
on the maximum (System V IPC) shared memory segment size that can be
created.
Shared memory segments up to 1 GB are now supported in the
kernel.
This value defaults to
.BR SHMMAX .
.TP
.IR /proc/sys/kernel/shmmni " (since Linux 2.4)"
This file
specifies the system-wide maximum number of System V shared memory
segments that can be created.
.TP
.IR /proc/sys/kernel/sysctl_writes_strict " (since Linux 3.16)"
.\" commit f88083005ab319abba5d0b2e4e997558245493c8
.\" commit 2ca9bb456ada8bcbdc8f77f8fc78207653bbaa92
.\" commit f4aacea2f5d1a5f7e3154e967d70cf3f711bcd61
.\" commit 24fe831c17ab8149413874f2fd4e5c8a41fcd294
The value in this file determines how the file offset affects
the behavior of updating entries in files under
.IR /proc/sys .
The file has three possible values:
.RS
.TP 4
\-1
This provides legacy handling, with no printk warnings.
Each
.BR write (2)
must fully contain the value to be written,
and multiple writes on the same file descriptor
will overwrite the entire value, regardless of the file position.
.TP
0
(default) This provides the same behavior as for \-1,
but printk warnings are written for processes that
perform writes when the file offset is not 0.
.TP
1
Respect the file offset when writing strings into
.I /proc/sys
files.
Multiple writes will
.I append
to the value buffer.
Anything written beyond the maximum length
of the value buffer will be ignored.
Writes to numeric
.I /proc/sys
entries must always be at file offset 0 and the value must be
fully contained in the buffer provided to
.BR write (2).
.\" FIXME .
.\"     With /proc/sys/kernel/sysctl_writes_strict==1, writes at an
.\"     offset other than 0 do not generate an error. Instead, the
.\"     write() succeeds, but the file is left unmodified.
.\"     This is surprising. The behavior may change in the future.
.\"     See thread.gmane.org/gmane.linux.man/9197
.\"		From: Michael Kerrisk (man-pages <mtk.manpages@...>
.\"		Subject: sysctl_writes_strict documentation + an oddity?
.\"		Newsgroups: gmane.linux.man, gmane.linux.kernel
.\"		Date: 2015-05-09 08:54:11 GMT
.RE
.TP
.I /proc/sys/kernel/sysrq
This file controls the functions allowed to be invoked by the SysRq key.
By default,
the file contains 1 meaning that every possible SysRq request is allowed
(in older kernel versions, SysRq was disabled by default,
and you were required to specifically enable it at run-time,
but this is not the case any more).
Possible values in this file are:
.RS
.TP 5
0
Disable sysrq completely
.TP
1
Enable all functions of sysrq
.TP
> 1
Bit mask of allowed sysrq functions, as follows:
.PD 0
.RS
.TP 5
\ \ 2
Enable control of console logging level
.TP
\ \ 4
Enable control of keyboard (SAK, unraw)
.TP
\ \ 8
Enable debugging dumps of processes etc.
.TP
\ 16
Enable sync command
.TP
\ 32
Enable remount read-only
.TP
\ 64
Enable signaling of processes (term, kill, oom-kill)
.TP
128
Allow reboot/poweroff
.TP
256
Allow nicing of all real-time tasks
.RE
.PD
.RE
.IP
This file is present only if the
.B CONFIG_MAGIC_SYSRQ
kernel configuration option is enabled.
For further details see the Linux kernel source file
.I Documentation/admin\-guide/sysrq.rst
.\" commit 9d85025b0418163fae079c9ba8f8445212de8568
(or
.I Documentation/sysrq.txt
before Linux 4.10).
.TP
.I /proc/sys/kernel/version
This file contains a string such as:
.IP
.in +4n
.EX
#5 Wed Feb 25 21:49:24 MET 1998
.EE
.in
.IP
The "#5" means that
this is the fifth kernel built from this source base and the
date following it indicates the time the kernel was built.
.TP
.IR /proc/sys/kernel/threads\-max " (since Linux 2.3.11)"
.\" The following is based on Documentation/sysctl/kernel.txt
This file specifies the system-wide limit on the number of
threads (tasks) that can be created on the system.
.IP
Since Linux 4.1,
.\" commit 230633d109e35b0a24277498e773edeb79b4a331
the value that can be written to
.I threads\-max
is bounded.
The minimum value that can be written is 20.
The maximum value that can be written is given by the
constant
.B FUTEX_TID_MASK
(0x3fffffff).
If a value outside of this range is written to
.IR threads\-max ,
the error
.B EINVAL
occurs.
.IP
The value written is checked against the available RAM pages.
If the thread structures would occupy too much (more than 1/8th)
of the available RAM pages,
.I threads\-max
is reduced accordingly.
.TP
.IR /proc/sys/kernel/yama/ptrace_scope " (since Linux 3.5)"
See
.BR ptrace (2).
.TP
.IR /proc/sys/kernel/zero\-paged " (PowerPC only)"
This file
contains a flag.
When enabled (nonzero), Linux-PPC will pre-zero pages in
the idle loop, possibly speeding up get_free_pages.
.TP
.I /proc/sys/net
This directory contains networking stuff.
Explanations for some of the files under this directory can be found in
.BR tcp (7)
and
.BR ip (7).
.TP
.I /proc/sys/net/core/bpf_jit_enable
See
.BR bpf (2).
.TP
.I /proc/sys/net/core/somaxconn
This file defines a ceiling value for the
.I backlog
argument of
.BR listen (2);
see the
.BR listen (2)
manual page for details.
.TP
.I /proc/sys/proc
This directory may be empty.
.TP
.I /proc/sys/sunrpc
This directory supports Sun remote procedure call for network filesystem
(NFS).
On some systems, it is not present.
.TP
.IR /proc/sys/user " (since Linux 4.9)"
See
.BR namespaces (7).
.TP
.I /proc/sys/vm
This directory contains files for memory management tuning, buffer, and
cache management.
.TP
.IR /proc/sys/vm/admin_reserve_kbytes " (since Linux 3.10)"
.\" commit 4eeab4f5580d11bffedc697684b91b0bca0d5009
This file defines the amount of free memory (in KiB) on the system that
should be reserved for users with the capability
.BR CAP_SYS_ADMIN .
.IP
The default value in this file is the minimum of [3% of free pages, 8MiB]
expressed as KiB.
The default is intended to provide enough for the superuser
to log in and kill a process, if necessary,
under the default overcommit 'guess' mode (i.e., 0 in
.IR /proc/sys/vm/overcommit_memory ).
.IP
Systems running in "overcommit never" mode (i.e., 2 in
.IR /proc/sys/vm/overcommit_memory )
should increase the value in this file to account
for the full virtual memory size of the programs used to recover (e.g.,
.BR login (1)
.BR ssh (1),
and
.BR top (1))
Otherwise, the superuser may not be able to log in to recover the system.
For example, on x86-64 a suitable value is 131072 (128MiB reserved).
.IP
Changing the value in this file takes effect whenever
an application requests memory.
.TP
.IR /proc/sys/vm/compact_memory " (since Linux 2.6.35)"
When 1 is written to this file, all zones are compacted such that free
memory is available in contiguous blocks where possible.
The effect of this action can be seen by examining
.IR /proc/buddyinfo .
.IP
Present only if the kernel was configured with
.BR CONFIG_COMPACTION .
.TP
.IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)"
Writing to this file causes the kernel to drop clean caches, dentries, and
inodes from memory, causing that memory to become free.
This can be useful for memory management testing and
performing reproducible filesystem benchmarks.
Because writing to this file causes the benefits of caching to be lost,
it can degrade overall system performance.
.IP
To free pagecache, use:
.IP
.in +4n
.EX
echo 1 > /proc/sys/vm/drop_caches
.EE
.in
.IP
To free dentries and inodes, use:
.IP
.in +4n
.EX
echo 2 > /proc/sys/vm/drop_caches
.EE
.in
.IP
To free pagecache, dentries, and inodes, use:
.IP
.in +4n
.EX
echo 3 > /proc/sys/vm/drop_caches
.EE
.in
.IP
Because writing to this file is a nondestructive operation and dirty objects
are not freeable, the
user should run
.BR sync (1)
first.
.TP
.IR  /proc/sys/vm/sysctl_hugetlb_shm_group " (since Linux 2.6.7)"
This writable file contains a group ID that is allowed
to allocate memory using huge pages.
If a process has a filesystem group ID or any supplementary group ID that
matches this group ID,
then it can make huge-page allocations without holding the
.B CAP_IPC_LOCK
capability; see
.BR memfd_create (2),
.BR mmap (2),
and
.BR shmget (2).
.TP
.IR /proc/sys/vm/legacy_va_layout " (since Linux 2.6.9)"
.\" The following is from Documentation/filesystems/proc.txt
If nonzero, this disables the new 32-bit memory-mapping layout;
the kernel will use the legacy (2.4) layout for all processes.
.TP
.IR /proc/sys/vm/memory_failure_early_kill " (since Linux 2.6.32)"
.\" The following is based on the text in Documentation/sysctl/vm.txt
Control how to kill processes when an uncorrected memory error
(typically a 2-bit error in a memory module)
that cannot be handled by the kernel
is detected in the background by hardware.
In some cases (like the page still having a valid copy on disk),
the kernel will handle the failure
transparently without affecting any applications.
But if there is no other up-to-date copy of the data,
it will kill processes to prevent any data corruptions from propagating.
.IP
The file has one of the following values:
.RS
.TP
.B 1
Kill all processes that have the corrupted-and-not-reloadable page mapped
as soon as the corruption is detected.
Note that this is not supported for a few types of pages,
such as kernel internally
allocated data or the swap cache, but works for the majority of user pages.
.TP
.B 0
Unmap the corrupted page from all processes and kill a process
only if it tries to access the page.
.RE
.IP
The kill is performed using a
.B SIGBUS
signal with
.I si_code
set to
.BR BUS_MCEERR_AO .
Processes can handle this if they want to; see
.BR sigaction (2)
for more details.
.IP
This feature is active only on architectures/platforms with advanced machine
check handling and depends on the hardware capabilities.
.IP
Applications can override the
.I memory_failure_early_kill
setting individually with the
.BR prctl (2)
.B PR_MCE_KILL
operation.
.IP
Present only if the kernel was configured with
.BR CONFIG_MEMORY_FAILURE .
.TP
.IR /proc/sys/vm/memory_failure_recovery " (since Linux 2.6.32)"
.\" The following is based on the text in Documentation/sysctl/vm.txt
Enable memory failure recovery (when supported by the platform).
.RS
.TP
.B 1
Attempt recovery.
.TP
.B 0
Always panic on a memory failure.
.RE
.IP
Present only if the kernel was configured with
.BR CONFIG_MEMORY_FAILURE .
.TP
.IR /proc/sys/vm/oom_dump_tasks " (since Linux 2.6.25)"
.\" The following is from Documentation/sysctl/vm.txt
Enables a system-wide task dump (excluding kernel threads) to be
produced when the kernel performs an OOM-killing.
The dump includes the following information
for each task (thread, process):
thread ID, real user ID, thread group ID (process ID),
virtual memory size, resident set size,
the CPU that the task is scheduled on,
oom_adj score (see the description of
.IR /proc/ pid /oom_adj ),
and command name.
This is helpful to determine why the OOM-killer was invoked
and to identify the rogue task that caused it.
.IP
If this contains the value zero, this information is suppressed.
On very large systems with thousands of tasks,
it may not be feasible to dump the memory state information for each one.
Such systems should not be forced to incur a performance penalty in
OOM situations when the information may not be desired.
.IP
If this is set to nonzero, this information is shown whenever the
OOM-killer actually kills a memory-hogging task.
.IP
The default value is 0.
.TP
.IR /proc/sys/vm/oom_kill_allocating_task " (since Linux 2.6.24)"
.\" The following is from Documentation/sysctl/vm.txt
This enables or disables killing the OOM-triggering task in
out-of-memory situations.
.IP
If this is set to zero, the OOM-killer will scan through the entire
tasklist and select a task based on heuristics to kill.
This normally selects a rogue memory-hogging task that
frees up a large amount of memory when killed.
.IP
If this is set to nonzero, the OOM-killer simply kills the task that
triggered the out-of-memory condition.
This avoids a possibly expensive tasklist scan.
.IP
If
.I /proc/sys/vm/panic_on_oom
is nonzero, it takes precedence over whatever value is used in
.IR /proc/sys/vm/oom_kill_allocating_task .
.IP
The default value is 0.
.TP
.IR /proc/sys/vm/overcommit_kbytes " (since Linux 3.14)"
.\" commit 49f0ce5f92321cdcf741e35f385669a421013cb7
This writable file provides an alternative to
.I /proc/sys/vm/overcommit_ratio
for controlling the
.I CommitLimit
when
.I /proc/sys/vm/overcommit_memory
has the value 2.
It allows the amount of memory overcommitting to be specified as
an absolute value (in kB),
rather than as a percentage, as is done with
.IR overcommit_ratio .
This allows for finer-grained control of
.I CommitLimit
on systems with extremely large memory sizes.
.IP
Only one of
.I overcommit_kbytes
or
.I overcommit_ratio
can have an effect:
if
.I overcommit_kbytes
has a nonzero value, then it is used to calculate
.IR CommitLimit ,
otherwise
.I overcommit_ratio
is used.
Writing a value to either of these files causes the
value in the other file to be set to zero.
.TP
.I /proc/sys/vm/overcommit_memory
This file contains the kernel virtual memory accounting mode.
Values are:
.RS
.IP
0: heuristic overcommit (this is the default)
.br
1: always overcommit, never check
.br
2: always check, never overcommit
.RE
.IP
In mode 0, calls of
.BR mmap (2)
with
.B MAP_NORESERVE
are not checked, and the default check is very weak,
leading to the risk of getting a process "OOM-killed".
.IP
In mode 1, the kernel pretends there is always enough memory,
until memory actually runs out.
One use case for this mode is scientific computing applications
that employ large sparse arrays.
Before Linux 2.6.0, any nonzero value implies mode 1.
.IP
In mode 2 (available since Linux 2.6), the total virtual address space
that can be allocated
.RI ( CommitLimit
in
.IR /proc/meminfo )
is calculated as
.IP
.in +4n
.EX
CommitLimit = (total_RAM \- total_huge_TLB) *
	      overcommit_ratio / 100 + total_swap
.EE
.in
.IP
where:
.RS
.IP \[bu] 3
.I total_RAM
is the total amount of RAM on the system;
.IP \[bu]
.I total_huge_TLB
is the amount of memory set aside for huge pages;
.IP \[bu]
.I overcommit_ratio
is the value in
.IR /proc/sys/vm/overcommit_ratio ;
and
.IP \[bu]
.I total_swap
is the amount of swap space.
.RE
.IP
For example, on a system with 16 GB of physical RAM, 16 GB
of swap, no space dedicated to huge pages, and an
.I overcommit_ratio
of 50, this formula yields a
.I CommitLimit
of 24 GB.
.IP
Since Linux 3.14, if the value in
.I /proc/sys/vm/overcommit_kbytes
is nonzero, then
.I CommitLimit
is instead calculated as:
.IP
.in +4n
.EX
CommitLimit = overcommit_kbytes + total_swap
.EE
.in
.IP
See also the description of
.I /proc/sys/vm/admin_reserve_kbytes
and
.IR /proc/sys/vm/user_reserve_kbytes .
.TP
.IR /proc/sys/vm/overcommit_ratio " (since Linux 2.6.0)"
This writable file defines a percentage by which memory
can be overcommitted.
The default value in the file is 50.
See the description of
.IR /proc/sys/vm/overcommit_memory .
.TP
.IR /proc/sys/vm/panic_on_oom " (since Linux 2.6.18)"
.\" The following is adapted from Documentation/sysctl/vm.txt
This enables or disables a kernel panic in
an out-of-memory situation.
.IP
If this file is set to the value 0,
the kernel's OOM-killer will kill some rogue process.
Usually, the OOM-killer is able to kill a rogue process and the
system will survive.
.IP
If this file is set to the value 1,
then the kernel normally panics when out-of-memory happens.
However, if a process limits allocations to certain nodes
using memory policies
.RB ( mbind (2)
.BR MPOL_BIND )
or cpusets
.RB ( cpuset (7))
and those nodes reach memory exhaustion status,
one process may be killed by the OOM-killer.
No panic occurs in this case:
because other nodes' memory may be free,
this means the system as a whole may not have reached
an out-of-memory situation yet.
.IP
If this file is set to the value 2,
the kernel always panics when an out-of-memory condition occurs.
.IP
The default value is 0.
1 and 2 are for failover of clustering.
Select either according to your policy of failover.
.TP
.I /proc/sys/vm/swappiness
.\" The following is from Documentation/sysctl/vm.txt
The value in this file controls how aggressively the kernel will swap
memory pages.
Higher values increase aggressiveness, lower values
decrease aggressiveness.
The default value is 60.
.TP
.IR /proc/sys/vm/user_reserve_kbytes " (since Linux 3.10)"
.\" commit c9b1d0981fcce3d9976d7b7a56e4e0503bc610dd
Specifies an amount of memory (in KiB) to reserve for user processes.
This is intended to prevent a user from starting a single memory hogging
process, such that they cannot recover (kill the hog).
The value in this file has an effect only when
.I /proc/sys/vm/overcommit_memory
is set to 2 ("overcommit never" mode).
In this case, the system reserves an amount of memory that is the minimum
of [3% of current process size,
.IR user_reserve_kbytes ].
.IP
The default value in this file is the minimum of [3% of free pages, 128MiB]
expressed as KiB.
.IP
If the value in this file is set to zero,
then a user will be allowed to allocate all free memory with a single process
(minus the amount reserved by
.IR /proc/sys/vm/admin_reserve_kbytes ).
Any subsequent attempts to execute a command will result in
"fork: Cannot allocate memory".
.IP
Changing the value in this file takes effect whenever
an application requests memory.
.TP
.IR /proc/sys/vm/unprivileged_userfaultfd " (since Linux 5.2)"
.\" cefdca0a86be517bc390fc4541e3674b8e7803b0
This (writable) file exposes a flag that controls whether
unprivileged processes are allowed to employ
.BR userfaultfd (2).
If this file has the value 1, then unprivileged processes may use
.BR userfaultfd (2).
If this file has the value 0, then only processes that have the
.B CAP_SYS_PTRACE
capability may employ
.BR userfaultfd (2).
The default value in this file is 1.
.TP
.IR /proc/sysrq\-trigger " (since Linux 2.4.21)"
Writing a character to this file triggers the same SysRq function as
typing ALT-SysRq-<character> (see the description of
.IR /proc/sys/kernel/sysrq ).
This file is normally writable only by
.IR root .
For further details see the Linux kernel source file
.I Documentation/admin\-guide/sysrq.rst
.\" commit 9d85025b0418163fae079c9ba8f8445212de8568
(or
.I Documentation/sysrq.txt
before Linux 4.10).
.TP
.I /proc/sysvipc
Subdirectory containing the pseudo-files
.IR msg ", " sem " and " shm "."
These files list the System V Interprocess Communication (IPC) objects
(respectively: message queues, semaphores, and shared memory)
that currently exist on the system,
providing similar information to that available via
.BR ipcs (1).
These files have headers and are formatted (one IPC object per line)
for easy understanding.
.BR sysvipc (7)
provides further background on the information shown by these files.
.TP
.IR /proc/timer_list " (since Linux 2.6.21)"
.\" commit 289f480af87e45f7a6de6ba9b4c061c2e259fe98
This read-only file exposes a list of all currently pending
(high-resolution) timers,
all clock-event sources, and their parameters in a human-readable form.
.TP
.IR /proc/timer_stats " (from  Linux 2.6.21 until Linux 4.10)"
.\" commit 82f67cd9fca8c8762c15ba7ed0d5747588c1e221
.\"	Date:   Fri Feb 16 01:28:13 2007 -0800
.\" Text largely derived from Documentation/timers/timer_stats.txt
.\" removed in commit dfb4357da6ddbdf57d583ba64361c9d792b0e0b1
.\"     Date:   Wed Feb 8 11:26:59 2017 -0800
This is a debugging facility to make timer (ab)use in a Linux
system visible to kernel and user-space developers.
It can be used by kernel and user-space developers to verify that
their code does not make undue use of timers.
The goal is to avoid unnecessary wakeups,
thereby optimizing power consumption.
.IP
If enabled in the kernel
.RB ( CONFIG_TIMER_STATS ),
but not used,
it has almost zero run-time overhead and a relatively small
data-structure overhead.
Even if collection is enabled at run time, overhead is low:
all the locking is per-CPU and lookup is hashed.
.IP
The
.I /proc/timer_stats
file is used both to control sampling facility and to read out the
sampled information.
.IP
The
.I timer_stats
functionality is inactive on bootup.
A sampling period can be started using the following command:
.IP
.in +4n
.EX
# echo 1 > /proc/timer_stats
.EE
.in
.IP
The following command stops a sampling period:
.IP
.in +4n
.EX
# echo 0 > /proc/timer_stats
.EE
.in
.IP
The statistics can be retrieved by:
.IP
.in +4n
.EX
$ cat /proc/timer_stats
.EE
.in
.IP
While sampling is enabled, each readout from
.I /proc/timer_stats
will see
newly updated statistics.
Once sampling is disabled, the sampled information
is kept until a new sample period is started.
This allows multiple readouts.
.IP
Sample output from
.IR /proc/timer_stats :
.IP
.in +4n
.EX
.RB $ " cat /proc/timer_stats"
Timer Stats Version: v0.3
Sample period: 1.764 s
Collection: active
  255,     0 swapper/3        hrtimer_start_range_ns (tick_sched_timer)
   71,     0 swapper/1        hrtimer_start_range_ns (tick_sched_timer)
   58,     0 swapper/0        hrtimer_start_range_ns (tick_sched_timer)
    4,  1694 gnome\-shell      mod_delayed_work_on (delayed_work_timer_fn)
   17,     7 rcu_sched        rcu_gp_kthread (process_timeout)
\&...
    1,  4911 kworker/u16:0    mod_delayed_work_on (delayed_work_timer_fn)
   1D,  2522 kworker/0:0      queue_delayed_work_on (delayed_work_timer_fn)
1029 total events, 583.333 events/sec
.EE
.in
.IP
The output columns are:
.RS
.IP [1] 5
a count of the number of events,
optionally (since Linux 2.6.23) followed by the letter \[aq]D\[aq]
.\" commit c5c061b8f9726bc2c25e19dec227933a13d1e6b7 deferrable timers
if this is a deferrable timer;
.IP [2]
the PID of the process that initialized the timer;
.IP [3]
the name of the process that initialized the timer;
.IP [4]
the function where the timer was initialized; and
(in parentheses)
the callback function that is associated with the timer.
.RE
.IP
During the Linux 4.11 development cycle,
this file  was removed because of security concerns,
as it exposes information across namespaces.
Furthermore, it is possible to obtain
the same information via in-kernel tracing facilities such as ftrace.
.TP
.I /proc/tty
Subdirectory containing the pseudo-files and subdirectories for
tty drivers and line disciplines.
.TP
.I /proc/uptime
This file contains two numbers (values in seconds): the uptime of the
system (including time spent in suspend) and the amount of time spent
in the idle process.
.TP
.I /proc/version
This string identifies the kernel version that is currently running.
It includes the contents of
.IR /proc/sys/kernel/ostype ,
.IR /proc/sys/kernel/osrelease ,
and
.IR /proc/sys/kernel/version .
For example:
.IP
.in +4n
.EX
Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994
.EE
.in
.\" FIXME 2.6.13 seems to have /proc/vmcore implemented; document this
.\" 	See Documentation/kdump/kdump.txt
.\"	commit 666bfddbe8b8fd4fd44617d6c55193d5ac7edb29
.\" 	Needs CONFIG_VMCORE
.\"
.TP
.IR /proc/vmstat " (since Linux 2.6.0)"
This file displays various virtual memory statistics.
Each line of this file contains a single name-value pair,
delimited by white space.
Some lines are present only if the kernel was configured with
suitable options.
(In some cases, the options required for particular files have changed
across kernel versions, so they are not listed here.
Details can be found by consulting the kernel source code.)
The following fields may be present:
.\" FIXME We need explanations for each of the following fields...
.RS
.TP
.IR nr_free_pages " (since Linux 2.6.31)"
.\" commit d23ad42324cc4378132e51f2fc5c9ba6cbe75182
.TP
.IR nr_alloc_batch " (since Linux 3.12)"
.\" commit 81c0a2bb515fd4daae8cab64352877480792b515
.TP
.IR nr_inactive_anon " (since Linux 2.6.28)"
.\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db
.TP
.IR nr_active_anon " (since Linux 2.6.28)"
.\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db
.TP
.IR nr_inactive_file " (since Linux 2.6.28)"
.\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db
.TP
.IR nr_active_file " (since Linux 2.6.28)"
.\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db
.TP
.IR nr_unevictable " (since Linux 2.6.28)"
.\" commit 7b854121eb3e5ba0241882ff939e2c485228c9c5
.TP
.IR nr_mlock " (since Linux 2.6.28)"
.\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820
.TP
.IR nr_anon_pages " (since Linux 2.6.18)"
.\" commit f3dbd34460ff54962d3e3244b6bcb7f5295356e6
.TP
.IR nr_mapped " (since Linux 2.6.0)"
.TP
.IR nr_file_pages " (since Linux 2.6.18)"
.\" commit 347ce434d57da80fd5809c0c836f206a50999c26
.TP
.IR nr_dirty " (since Linux 2.6.0)"
.TP
.IR nr_writeback " (since Linux 2.6.0)"
.TP
.IR nr_slab_reclaimable " (since Linux 2.6.19)"
.\" commit 972d1a7b140569084439a81265a0f15b74e924e0
.\" Linux 2.6.0 had nr_slab
.TP
.IR nr_slab_unreclaimable " (since Linux 2.6.19)"
.\" commit 972d1a7b140569084439a81265a0f15b74e924e0
.TP
.IR nr_page_table_pages " (since Linux 2.6.0)"
.TP
.IR nr_kernel_stack " (since Linux 2.6.32)"
.\" commit c6a7f5728a1db45d30df55a01adc130b4ab0327c
Amount of memory allocated to kernel stacks.
.TP
.IR nr_unstable " (since Linux 2.6.0)"
.TP
.IR nr_bounce " (since Linux 2.6.12)"
.\" commit edfbe2b0038723e5699ab22695ccd62b5542a5c1
.TP
.IR nr_vmscan_write " (since Linux 2.6.19)"
.\" commit e129b5c23c2b471d47f1c5d2b8b193fc2034af43
.TP
.IR nr_vmscan_immediate_reclaim " (since Linux 3.2)"
.\" commit 49ea7eb65e7c5060807fb9312b1ad4c3eab82e2c
.TP
.IR nr_writeback_temp " (since Linux 2.6.26)"
.\" commit fc3ba692a4d19019387c5acaea63131f9eab05dd
.TP
.IR nr_isolated_anon " (since Linux 2.6.32)"
.\" commit a731286de62294b63d8ceb3c5914ac52cc17e690
.TP
.IR nr_isolated_file " (since Linux 2.6.32)"
.\" commit a731286de62294b63d8ceb3c5914ac52cc17e690
.TP
.IR nr_shmem " (since Linux 2.6.32)"
.\" commit 4b02108ac1b3354a22b0d83c684797692efdc395
Pages used by shmem and
.BR tmpfs (5).
.TP
.IR nr_dirtied " (since Linux 2.6.37)"
.\" commit ea941f0e2a8c02ae876cd73deb4e1557248f258c
.TP
.IR nr_written " (since Linux 2.6.37)"
.\" commit ea941f0e2a8c02ae876cd73deb4e1557248f258c
.TP
.IR nr_pages_scanned " (since Linux 3.17)"
.\" commit 0d5d823ab4e608ec7b52ac4410de4cb74bbe0edd
.TP
.IR numa_hit " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR numa_miss " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR numa_foreign " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR numa_interleave " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR numa_local " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR numa_other " (since Linux 2.6.18)"
.\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5
.\" Present only if the kernel was configured with
.\" .BR CONFIG_NUMA .
.TP
.IR workingset_refault " (since Linux 3.15)"
.\" commit a528910e12ec7ee203095eb1711468a66b9b60b0
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR workingset_activate " (since Linux 3.15)"
.\" commit a528910e12ec7ee203095eb1711468a66b9b60b0
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR workingset_nodereclaim " (since Linux 3.15)"
.\" commit 449dd6984d0e47643c04c807f609dd56d48d5bcc
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR nr_anon_transparent_hugepages " (since Linux 2.6.38)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR nr_free_cma " (since Linux 3.7)"
.\" commit d1ce749a0db12202b711d1aba1d29e823034648d
Number of free CMA (Contiguous Memory Allocator) pages.
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR nr_dirty_threshold " (since Linux 2.6.37)"
.\" commit 79da826aee6a10902ef411bc65864bd02102fa83
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR nr_dirty_background_threshold " (since Linux 2.6.37)"
.\" commit 79da826aee6a10902ef411bc65864bd02102fa83
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgpgin " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgpgout " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pswpin " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pswpout " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgalloc_dma " (since Linux 2.6.5)"
.\" Linux 2.6.0 had pgalloc
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgalloc_dma32 " (since Linux 2.6.16)"
.\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgalloc_normal " (since Linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgalloc_high " (since Linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgalloc_movable " (since Linux 2.6.23)"
.\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgfree " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgactivate " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgdeactivate " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgfault " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgmajfault " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgrefill_dma " (since Linux 2.6.5)"
.\" Linux 2.6.0 had pgrefill
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgrefill_dma32 " (since Linux 2.6.16)"
.\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgrefill_normal " (since Linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgrefill_high " (since Linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgrefill_movable " (since Linux 2.6.23)"
.\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.\" Formerly there were
.\"     pgsteal_high
.\"     pgsteal_normal
.\"     pgsteal_dma32
.\"     pgsteal_dma
.\" These were split out into pgsteal_kswapd* and pgsteal_direct*
.\" in commit 904249aa68010c8e223263c922fcbb840a3f42e4
.TP
.IR pgsteal_kswapd_dma " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Linux 2.6.0 had pgsteal
.\" Present only if the kernel was configured with
.\" .\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_kswapd_dma32 " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_kswapd_normal " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_kswapd_high " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgsteal_kswapd_movable " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgsteal_direct_dma
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_direct_dma32 " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_direct_normal " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgsteal_direct_high " (since Linux 3.4)"
.\" commit 904249aa68010c8e223263c922fcbb840a3f42e4
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgsteal_direct_movable " (since Linux 2.6.23)"
.\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgscan_kswapd_dma
.\" Linux 2.6.0 had pgscan
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgscan_kswapd_dma32 " (since Linux 2.6.16)"
.\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgscan_kswapd_normal " (since Linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgscan_kswapd_high
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgscan_kswapd_movable " (since Linux 2.6.23)"
.\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgscan_direct_dma
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgscan_direct_dma32 " (since Linux 2.6.16)"
.\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgscan_direct_normal
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.I pgscan_direct_high
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HIGHMEM .
.TP
.IR pgscan_direct_movable " (since Linux 2.6.23)"
.\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgscan_direct_throttle " (since Linux 3.6)"
.\" commit 68243e76ee343d63c6cf76978588a885951e2818
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR zone_reclaim_failed " (since linux 2.6.31)"
.\" commit 24cf72518c79cdcda486ed26074ff8151291cf65
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA .
.TP
.IR pginodesteal " (since linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR slabs_scanned " (since linux 2.6.5)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR kswapd_inodesteal " (since linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR kswapd_low_wmark_hit_quickly " (since Linux 2.6.33)"
.\" commit bb3ab596832b920c703d1aea1ce76d69c0f71fb7
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR kswapd_high_wmark_hit_quickly " (since Linux 2.6.33)"
.\" commit bb3ab596832b920c703d1aea1ce76d69c0f71fb7
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pageoutrun " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR allocstall " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR pgrotated " (since Linux 2.6.0)"
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR drop_pagecache " (since Linux 3.15)"
.\" commit 5509a5d27b971a90b940e148ca9ca53312e4fa7a
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR drop_slab " (since Linux 3.15)"
.\" commit 5509a5d27b971a90b940e148ca9ca53312e4fa7a
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR numa_pte_updates " (since Linux 3.8)"
.\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA_BALANCING .
.TP
.IR numa_huge_pte_updates " (since Linux 3.13)"
.\" commit 72403b4a0fbdf433c1fe0127e49864658f6f6468
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA_BALANCING .
.TP
.IR numa_hint_faults " (since Linux 3.8)"
.\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA_BALANCING .
.TP
.IR numa_hint_faults_local " (since Linux 3.8)"
.\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA_BALANCING .
.TP
.IR numa_pages_migrated " (since Linux 3.8)"
.\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_NUMA_BALANCING
.\" and
.\" .BR CONFIG_NUMA_BALANCING .
.TP
.IR pgmigrate_success " (since Linux 3.8)"
.\" commit 5647bc293ab15f66a7b1cda850c5e9d162a6c7c2
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_MIGRATION .
.TP
.IR pgmigrate_fail " (since Linux 3.8)"
.\" commit 5647bc293ab15f66a7b1cda850c5e9d162a6c7c2
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_MIGRATION .
.TP
.IR compact_migrate_scanned " (since Linux 3.8)"
.\" commit 397487db696cae0b026a474a5cd66f4e372995e6
.\" Linux 3.8 dropped compact_blocks_moved, compact_pages_moved, and
.\"           compact_pagemigrate_failed
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR compact_free_scanned " (since Linux 3.8)"
.\" commit 397487db696cae0b026a474a5cd66f4e372995e6
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR compact_isolated " (since Linux 3.8)"
.\" commit 397487db696cae0b026a474a5cd66f4e372995e6
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR compact_stall " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR compact_fail " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR compact_success " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_COMPACTION .
.TP
.IR htlb_buddy_alloc_success " (since Linux 2.6.26)"
.\" commit 3b1163006332302117b1b2acf226d4014ff46525
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HUGETLB_PAGE .
.TP
.IR htlb_buddy_alloc_fail " (since Linux 2.6.26)"
.\" commit 3b1163006332302117b1b2acf226d4014ff46525
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_HUGETLB_PAGE .
.TP
.IR unevictable_pgs_culled " (since Linux 2.6.28)"
.\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_scanned " (since Linux 2.6.28)"
.\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_rescued " (since Linux 2.6.28)"
.\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_mlocked " (since Linux 2.6.28)"
.\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_munlocked " (since Linux 2.6.28)"
.\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_cleared " (since Linux 2.6.28)"
.\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.TP
.IR unevictable_pgs_stranded " (since Linux 2.6.28)"
.\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS .
.\" Linux 3.7 removed unevictable_pgs_mlockfreed
.TP
.IR thp_fault_alloc " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_fault_fallback " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_collapse_alloc " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_collapse_alloc_failed " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_split " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_zero_page_alloc " (since Linux 3.8)"
.\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR thp_zero_page_alloc_failed " (since Linux 3.8)"
.\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76
See the kernel source file
.IR Documentation/admin\-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_TRANSPARENT_HUGEPAGE .
.TP
.IR balloon_inflate " (since Linux 3.18)"
.\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_MEMORY_BALLOON .
.TP
.IR balloon_deflate " (since Linux 3.18)"
.\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.\" .BR CONFIG_MEMORY_BALLOON .
.TP
.IR balloon_migrate " (since Linux 3.18)"
.\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS ,
.\" .BR CONFIG_MEMORY_BALLOON ,
.\" and
.\" .BR CONFIG_BALLOON_COMPACTION .
.TP
.IR nr_tlb_remote_flush " (since Linux 3.12)"
.\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_TLBFLUSH
.\" and
.\" .BR CONFIG_SMP .
.TP
.IR nr_tlb_remote_flush_received " (since Linux 3.12)"
.\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_TLBFLUSH
.\" and
.\" .BR CONFIG_SMP .
.TP
.IR nr_tlb_local_flush_all " (since Linux 3.12)"
.\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_TLBFLUSH .
.TP
.IR nr_tlb_local_flush_one " (since Linux 3.12)"
.\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_TLBFLUSH .
.TP
.IR vmacache_find_calls " (since Linux 3.16)"
.\" commit 4f115147ff802267d0aa41e361c5aa5bd933d896
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_VM_VMACACHE .
.TP
.IR vmacache_find_hits " (since Linux 3.16)"
.\" commit 4f115147ff802267d0aa41e361c5aa5bd933d896
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_VM_VMACACHE .
.TP
.IR vmacache_full_flushes " (since Linux 3.19)"
.\" commit f5f302e21257ebb0c074bbafc37606c26d28cc3d
.\" Present only if the kernel was configured with
.\" .BR CONFIG_DEBUG_VM_VMACACHE .
.RE
.TP
.IR /proc/zoneinfo " (since Linux 2.6.13)"
This file displays information about memory zones.
This is useful for analyzing virtual memory behavior.
.\" FIXME more should be said about /proc/zoneinfo
.SH NOTES
Many files contain strings (e.g., the environment and command line)
that are in the internal format,
with subfields terminated by null bytes (\[aq]\e0\[aq]).
When inspecting such files, you may find that the results are more readable
if you use a command of the following form to display them:
.PP
.in +4n
.EX
.RB "$" " cat \fIfile\fP | tr \[aq]\e000\[aq] \[aq]\en\[aq]"
.EE
.in
.PP
This manual page is incomplete, possibly inaccurate, and is the kind
of thing that needs to be updated very often.
.\" .SH ACKNOWLEDGEMENTS
.\" The material on /proc/sys/fs and /proc/sys/kernel is closely based on
.\" kernel source documentation files written by Rik van Riel.
.SH SEE ALSO
.BR cat (1),
.BR dmesg (1),
.BR find (1),
.BR free (1),
.BR htop (1),
.BR init (1),
.BR ps (1),
.BR pstree (1),
.BR tr (1),
.BR uptime (1),
.BR chroot (2),
.BR mmap (2),
.BR readlink (2),
.BR syslog (2),
.BR slabinfo (5),
.BR sysfs (5),
.BR hier (7),
.BR namespaces (7),
.BR time (7),
.BR arp (8),
.BR hdparm (8),
.BR ifconfig (8),
.BR lsmod (8),
.BR lspci (8),
.BR mount (8),
.BR netstat (8),
.BR procinfo (8),
.BR route (8),
.BR sysctl (8)
.PP
The Linux kernel source files:
.IR Documentation/filesystems/proc.rst ,
.IR Documentation/admin\-guide/sysctl/fs.rst ,
.IR Documentation/admin\-guide/sysctl/kernel.rst ,
.IR Documentation/admin\-guide/sysctl/net.rst ,
and
.IR Documentation/admin\-guide/sysctl/vm.rst .