Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

8 files changed, 3792 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/abi.rst b/Documentation/admin-guide/sysctl/abi.rst
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--- /dev/null
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@@ -0,0 +1,34 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+================================
+Documentation for /proc/sys/abi/
+================================
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="abi" \
+..         Documentation/admin-guide/sysctl/abi.rst \
+..         $(git grep -l register_sysctl_)
+
+Copyright (c) 2020, Stephen Kitt
+
+For general info, see Documentation/admin-guide/sysctl/index.rst.
+
+------------------------------------------------------------------------------
+
+The files in ``/proc/sys/abi`` can be used to see and modify
+ABI-related settings.
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/kernel``:
+
+.. contents:: :local:
+
+vsyscall32 (x86)
+================
+
+Determines whether the kernels maps a vDSO page into 32-bit processes;
+can be set to 1 to enable, or 0 to disable. Defaults to enabled if
+``CONFIG_COMPAT_VDSO`` is set, disabled otherwise.
+
+This controls the same setting as the ``vdso32`` kernel boot
+parameter.
diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst
new file mode 100644
index 0000000000..a321b84ecc
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+===============================
+Documentation for /proc/sys/fs/
+===============================
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+Copyright (c) 2009,        Shen Feng<shen@cn.fujitsu.com>
+
+For general info and legal blurb, please look in intro.rst.
+
+------------------------------------------------------------------------------
+
+This file contains documentation for the sysctl files and directories
+in ``/proc/sys/fs/``.
+
+The files in this directory can be used to tune and monitor
+miscellaneous and general things in the operation of the Linux
+kernel. Since some of the files *can* be used to screw up your
+system, it is advisable to read both documentation and source
+before actually making adjustments.
+
+1. /proc/sys/fs
+===============
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/fs``:
+
+.. contents:: :local:
+
+
+aio-nr & aio-max-nr
+-------------------
+
+``aio-nr`` shows the current system-wide number of asynchronous io
+requests.  ``aio-max-nr`` allows you to change the maximum value
+``aio-nr`` can grow to.  If ``aio-nr`` reaches ``aio-nr-max`` then
+``io_setup`` will fail with ``EAGAIN``.  Note that raising
+``aio-max-nr`` does not result in the
+pre-allocation or re-sizing of any kernel data structures.
+
+
+dentry-state
+------------
+
+This file shows the values in ``struct dentry_stat``, as defined in
+``linux/include/linux/dcache.h``::
+
+  struct dentry_stat_t dentry_stat {
+        int nr_dentry;
+        int nr_unused;
+        int age_limit;         /* age in seconds */
+        int want_pages;        /* pages requested by system */
+        int nr_negative;       /* # of unused negative dentries */
+        int dummy;             /* Reserved for future use */
+  };
+
+Dentries are dynamically allocated and deallocated.
+
+``nr_dentry`` shows the total number of dentries allocated (active
++ unused). ``nr_unused shows`` the number of dentries that are not
+actively used, but are saved in the LRU list for future reuse.
+
+``age_limit`` is the age in seconds after which dcache entries
+can be reclaimed when memory is short and ``want_pages`` is
+nonzero when ``shrink_dcache_pages()`` has been called and the
+dcache isn't pruned yet.
+
+``nr_negative`` shows the number of unused dentries that are also
+negative dentries which do not map to any files. Instead,
+they help speeding up rejection of non-existing files provided
+by the users.
+
+
+file-max & file-nr
+------------------
+
+The value in ``file-max`` denotes the maximum number of file-
+handles that the Linux kernel will allocate. When you get lots
+of error messages about running out of file handles, you might
+want to increase this limit.
+
+Historically,the kernel was able to allocate file handles
+dynamically, but not to free them again. The three values in
+``file-nr`` denote the number of allocated file handles, the number
+of allocated but unused file handles, and the maximum number of
+file handles. Linux 2.6 and later always reports 0 as the number of free
+file handles -- this is not an error, it just means that the
+number of allocated file handles exactly matches the number of
+used file handles.
+
+Attempts to allocate more file descriptors than ``file-max`` are
+reported with ``printk``, look for::
+
+  VFS: file-max limit <number> reached
+
+in the kernel logs.
+
+
+inode-nr & inode-state
+----------------------
+
+As with file handles, the kernel allocates the inode structures
+dynamically, but can't free them yet.
+
+The file ``inode-nr`` contains the first two items from
+``inode-state``, so we'll skip to that file...
+
+``inode-state`` contains three actual numbers and four dummies.
+The actual numbers are, in order of appearance, ``nr_inodes``,
+``nr_free_inodes`` and ``preshrink``.
+
+``nr_inodes`` stands for the number of inodes the system has
+allocated.
+
+``nr_free_inodes`` represents the number of free inodes (?) and
+preshrink is nonzero when the
+system needs to prune the inode list instead of allocating
+more.
+
+
+mount-max
+---------
+
+This denotes the maximum number of mounts that may exist
+in a mount namespace.
+
+
+nr_open
+-------
+
+This denotes the maximum number of file-handles a process can
+allocate. Default value is 1024*1024 (1048576) which should be
+enough for most machines. Actual limit depends on ``RLIMIT_NOFILE``
+resource limit.
+
+
+overflowgid & overflowuid
+-------------------------
+
+Some filesystems only support 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 a fixed value before being written to disk.
+
+These sysctls allow you to change the value of the fixed UID and GID.
+The default is 65534.
+
+
+pipe-user-pages-hard
+--------------------
+
+Maximum total number of pages a non-privileged user may allocate for pipes.
+Once this limit is reached, no new pipes may be allocated until usage goes
+below the limit again. When set to 0, no limit is applied, which is the default
+setting.
+
+
+pipe-user-pages-soft
+--------------------
+
+Maximum total number of pages a non-privileged user may allocate for pipes
+before the pipe size gets limited to a single page. Once this limit is reached,
+new pipes will be limited to a single page in size for this user in order to
+limit total memory usage, and trying to increase them using ``fcntl()`` will be
+denied until usage goes below the limit again. The default value allows to
+allocate up to 1024 pipes at their default size. When set to 0, no limit is
+applied.
+
+
+protected_fifos
+---------------
+
+The intent of this protection is to avoid unintentional writes to
+an attacker-controlled FIFO, where a program expected to create a regular
+file.
+
+When set to "0", writing to FIFOs is unrestricted.
+
+When set to "1" don't allow ``O_CREAT`` open on FIFOs that we don't own
+in world writable sticky directories, unless they are owned by the
+owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+This protection is based on the restrictions in Openwall.
+
+
+protected_hardlinks
+--------------------
+
+A long-standing class of security issues is the hardlink-based
+time-of-check-time-of-use race, most commonly seen in world-writable
+directories like ``/tmp``. The common method of exploitation of this flaw
+is to cross privilege boundaries when following a given hardlink (i.e. a
+root process follows a hardlink created by another user). Additionally,
+on systems without separated partitions, this stops unauthorized users
+from "pinning" vulnerable setuid/setgid files against being upgraded by
+the administrator, or linking to special files.
+
+When set to "0", hardlink creation behavior is unrestricted.
+
+When set to "1" hardlinks cannot be created by users if they do not
+already own the source file, or do not have read/write access to it.
+
+This protection is based on the restrictions in Openwall and grsecurity.
+
+
+protected_regular
+-----------------
+
+This protection is similar to `protected_fifos`_, but it
+avoids writes to an attacker-controlled regular file, where a program
+expected to create one.
+
+When set to "0", writing to regular files is unrestricted.
+
+When set to "1" don't allow ``O_CREAT`` open on regular files that we
+don't own in world writable sticky directories, unless they are
+owned by the owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+
+protected_symlinks
+------------------
+
+A long-standing class of security issues is the symlink-based
+time-of-check-time-of-use race, most commonly seen in world-writable
+directories like ``/tmp``. The common method of exploitation of this flaw
+is to cross privilege boundaries when following a given symlink (i.e. a
+root process follows a symlink belonging to another user). For a likely
+incomplete list of hundreds of examples across the years, please see:
+https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp
+
+When set to "0", symlink following behavior is unrestricted.
+
+When set to "1" symlinks are permitted to be followed only when outside
+a sticky world-writable directory, or when the uid of the symlink and
+follower match, or when the directory owner matches the symlink's owner.
+
+This protection is based on the restrictions in Openwall and grsecurity.
+
+
+suid_dumpable
+-------------
+
+This value can be used to query and set the core dump mode for setuid
+or otherwise protected/tainted binaries. The modes are
+
+=   ==========  ===============================================================
+0   (default)	Traditional behaviour. Any process which has changed
+		privilege levels or is execute only will not be dumped.
+1   (debug)	All processes dump core when possible. The core dump is
+		owned by the current user and no security is applied. This is
+		intended for system debugging situations only.
+		Ptrace is unchecked.
+		This is insecure as it allows regular users to examine the
+		memory contents of privileged processes.
+2   (suidsafe)	Any binary which normally would not be dumped is dumped
+		anyway, but only if the ``core_pattern`` kernel sysctl (see
+		:ref:`Documentation/admin-guide/sysctl/kernel.rst <core_pattern>`)
+		is set to
+		either a pipe handler or a fully qualified path. (For more
+		details on this limitation, see CVE-2006-2451.) This mode is
+		appropriate when administrators are attempting to debug
+		problems in a normal environment, and either have a core dump
+		pipe handler that knows to treat privileged core dumps with
+		care, or specific directory defined for catching core dumps.
+		If a core dump happens without a pipe handler or fully
+		qualified path, a message will be emitted to syslog warning
+		about the lack of a correct setting.
+=   ==========  ===============================================================
+
+
+
+2. /proc/sys/fs/binfmt_misc
+===========================
+
+Documentation for the files in ``/proc/sys/fs/binfmt_misc`` is
+in Documentation/admin-guide/binfmt-misc.rst.
+
+
+3. /proc/sys/fs/mqueue - POSIX message queues filesystem
+========================================================
+
+
+The "mqueue"  filesystem provides  the necessary kernel features to enable the
+creation of a  user space  library that  implements  the  POSIX message queues
+API (as noted by the  MSG tag in the  POSIX 1003.1-2001 version  of the System
+Interfaces specification.)
+
+The "mqueue" filesystem contains values for determining/setting the
+amount of resources used by the file system.
+
+``/proc/sys/fs/mqueue/queues_max`` is a read/write file for
+setting/getting the maximum number of message queues allowed on the
+system.
+
+``/proc/sys/fs/mqueue/msg_max`` is a read/write file for
+setting/getting the maximum number of messages in a queue value.  In
+fact it is the limiting value for another (user) limit which is set in
+``mq_open`` invocation.  This attribute of a queue must be less than
+or equal to ``msg_max``.
+
+``/proc/sys/fs/mqueue/msgsize_max`` is a read/write file for
+setting/getting the maximum message size value (it is an attribute of
+every message queue, set during its creation).
+
+``/proc/sys/fs/mqueue/msg_default`` is a read/write file for
+setting/getting the default number of messages in a queue value if the
+``attr`` parameter of ``mq_open(2)`` is ``NULL``. If it exceeds
+``msg_max``, the default value is initialized to ``msg_max``.
+
+``/proc/sys/fs/mqueue/msgsize_default`` is a read/write file for
+setting/getting the default message size value if the ``attr``
+parameter of ``mq_open(2)`` is ``NULL``. If it exceeds
+``msgsize_max``, the default value is initialized to ``msgsize_max``.
+
+4. /proc/sys/fs/epoll - Configuration options for the epoll interface
+=====================================================================
+
+This directory contains configuration options for the epoll(7) interface.
+
+max_user_watches
+----------------
+
+Every epoll file descriptor can store a number of files to be monitored
+for event readiness. Each one of these monitored files constitutes a "watch".
+This configuration option sets the maximum number of "watches" that are
+allowed for each user.
+Each "watch" costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes
+on a 64-bit one.
+The current default value for ``max_user_watches`` is 4% of the
+available low memory, divided by the "watch" cost in bytes.
diff --git a/Documentation/admin-guide/sysctl/index.rst b/Documentation/admin-guide/sysctl/index.rst
new file mode 100644
index 0000000000..03346f98c7
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+++ b/Documentation/admin-guide/sysctl/index.rst
@@ -0,0 +1,98 @@
+===========================
+Documentation for /proc/sys
+===========================
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+------------------------------------------------------------------------------
+
+'Why', I hear you ask, 'would anyone even _want_ documentation
+for them sysctl files? If anybody really needs it, it's all in
+the source...'
+
+Well, this documentation is written because some people either
+don't know they need to tweak something, or because they don't
+have the time or knowledge to read the source code.
+
+Furthermore, the programmers who built sysctl have built it to
+be actually used, not just for the fun of programming it :-)
+
+------------------------------------------------------------------------------
+
+Legal blurb:
+
+As usual, there are two main things to consider:
+
+1. you get what you pay for
+2. it's free
+
+The consequences are that I won't guarantee the correctness of
+this document, and if you come to me complaining about how you
+screwed up your system because of wrong documentation, I won't
+feel sorry for you. I might even laugh at you...
+
+But of course, if you _do_ manage to screw up your system using
+only the sysctl options used in this file, I'd like to hear of
+it. Not only to have a great laugh, but also to make sure that
+you're the last RTFMing person to screw up.
+
+In short, e-mail your suggestions, corrections and / or horror
+stories to: <riel@nl.linux.org>
+
+Rik van Riel.
+
+--------------------------------------------------------------
+
+Introduction
+============
+
+Sysctl is a means of configuring certain aspects of the kernel
+at run-time, and the /proc/sys/ directory is there so that you
+don't even need special tools to do it!
+In fact, there are only four things needed to use these config
+facilities:
+
+- a running Linux system
+- root access
+- common sense (this is especially hard to come by these days)
+- knowledge of what all those values mean
+
+As a quick 'ls /proc/sys' will show, the directory consists of
+several (arch-dependent?) subdirs. Each subdir is mainly about
+one part of the kernel, so you can do configuration on a piece
+by piece basis, or just some 'thematic frobbing'.
+
+This documentation is about:
+
+=============== ===============================================================
+abi/		execution domains & personalities
+debug/		<empty>
+dev/		device specific information (eg dev/cdrom/info)
+fs/		specific filesystems
+		filehandle, inode, dentry and quota tuning
+		binfmt_misc <Documentation/admin-guide/binfmt-misc.rst>
+kernel/		global kernel info / tuning
+		miscellaneous stuff
+net/		networking stuff, for documentation look in:
+		<Documentation/networking/>
+proc/		<empty>
+sunrpc/		SUN Remote Procedure Call (NFS)
+vm/		memory management tuning
+		buffer and cache management
+user/		Per user per user namespace limits
+=============== ===============================================================
+
+These are the subdirs I have on my system. There might be more
+or other subdirs in another setup. If you see another dir, I'd
+really like to hear about it :-)
+
+.. toctree::
+   :maxdepth: 1
+
+   abi
+   fs
+   kernel
+   net
+   sunrpc
+   user
+   vm
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
new file mode 100644
index 0000000000..cf33de56da
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -0,0 +1,1666 @@
+===================================
+Documentation for /proc/sys/kernel/
+===================================
+
+.. See scripts/check-sysctl-docs to keep this up to date
+
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+Copyright (c) 2009,        Shen Feng<shen@cn.fujitsu.com>
+
+For general info and legal blurb, please look in
+Documentation/admin-guide/sysctl/index.rst.
+
+------------------------------------------------------------------------------
+
+This file contains documentation for the sysctl files in
+``/proc/sys/kernel/``.
+
+The files in this directory can be used to tune and monitor
+miscellaneous and general things in the operation of the Linux
+kernel. Since some of the files *can* be used to screw up your
+system, it is advisable to read both documentation and source
+before actually making adjustments.
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/kernel``:
+
+.. contents:: :local:
+
+
+acct
+====
+
+::
+
+    highwater lowwater frequency
+
+If BSD-style process accounting is enabled these values control
+its behaviour. If free space on filesystem where the log lives
+goes below ``lowwater``\ % accounting suspends. If free space gets
+above ``highwater``\ % accounting resumes. ``frequency`` determines
+how often do we check the amount of free space (value is in
+seconds). Default:
+
+::
+
+    4 2 30
+
+That is, suspend accounting if free space drops below 2%; resume it
+if it increases to at least 4%; consider information about amount of
+free space valid for 30 seconds.
+
+
+acpi_video_flags
+================
+
+See Documentation/power/video.rst. This allows the video resume mode to be set,
+in a similar fashion to the ``acpi_sleep`` kernel parameter, by
+combining the following values:
+
+= =======
+1 s3_bios
+2 s3_mode
+4 s3_beep
+= =======
+
+arch
+====
+
+The machine hardware name, the same output as ``uname -m``
+(e.g. ``x86_64`` or ``aarch64``).
+
+auto_msgmni
+===========
+
+This variable has no effect and may be removed in future kernel
+releases. Reading it always returns 0.
+Up to Linux 3.17, it enabled/disabled automatic recomputing of
+`msgmni`_
+upon memory add/remove or upon IPC namespace creation/removal.
+Echoing "1" into this file enabled msgmni automatic recomputing.
+Echoing "0" turned it off. The default value was 1.
+
+
+bootloader_type (x86 only)
+==========================
+
+This gives the bootloader type number as indicated by the bootloader,
+shifted left by 4, and OR'd with the low four bits of the bootloader
+version.  The reason for this encoding is that this used to match the
+``type_of_loader`` field in the kernel header; the encoding is kept for
+backwards compatibility.  That is, if the full bootloader type number
+is 0x15 and the full version number is 0x234, this file will contain
+the value 340 = 0x154.
+
+See the ``type_of_loader`` and ``ext_loader_type`` fields in
+Documentation/arch/x86/boot.rst for additional information.
+
+
+bootloader_version (x86 only)
+=============================
+
+The complete bootloader version number.  In the example above, this
+file will contain the value 564 = 0x234.
+
+See the ``type_of_loader`` and ``ext_loader_ver`` fields in
+Documentation/arch/x86/boot.rst for additional information.
+
+
+bpf_stats_enabled
+=================
+
+Controls whether the kernel should collect statistics on BPF programs
+(total time spent running, number of times run...). Enabling
+statistics causes a slight reduction in performance on each program
+run. The statistics can be seen using ``bpftool``.
+
+= ===================================
+0 Don't collect statistics (default).
+1 Collect statistics.
+= ===================================
+
+
+cad_pid
+=======
+
+This is the pid which will be signalled on reboot (notably, by
+Ctrl-Alt-Delete). Writing a value to this file which doesn't
+correspond to a running process will result in ``-ESRCH``.
+
+See also `ctrl-alt-del`_.
+
+
+cap_last_cap
+============
+
+Highest valid capability of the running kernel.  Exports
+``CAP_LAST_CAP`` from the kernel.
+
+
+.. _core_pattern:
+
+core_pattern
+============
+
+``core_pattern`` is used to specify a core dumpfile pattern name.
+
+* max length 127 characters; default value is "core"
+* ``core_pattern`` is used as a pattern template for the output
+  filename; certain string patterns (beginning with '%') are
+  substituted with their actual values.
+* backward compatibility with ``core_uses_pid``:
+
+	If ``core_pattern`` does not include "%p" (default does not)
+	and ``core_uses_pid`` is set, then .PID will be appended to
+	the filename.
+
+* corename format specifiers
+
+	========	==========================================
+	%<NUL>		'%' is dropped
+	%%		output one '%'
+	%p		pid
+	%P		global pid (init PID namespace)
+	%i		tid
+	%I		global tid (init PID namespace)
+	%u		uid (in initial user namespace)
+	%g		gid (in initial user namespace)
+	%d		dump mode, matches ``PR_SET_DUMPABLE`` and
+			``/proc/sys/fs/suid_dumpable``
+	%s		signal number
+	%t		UNIX time of dump
+	%h		hostname
+	%e		executable filename (may be shortened, could be changed by prctl etc)
+	%f      	executable filename
+	%E		executable path
+	%c		maximum size of core file by resource limit RLIMIT_CORE
+	%C		CPU the task ran on
+	%<OTHER>	both are dropped
+	========	==========================================
+
+* If the first character of the pattern is a '|', the kernel will treat
+  the rest of the pattern as a command to run.  The core dump will be
+  written to the standard input of that program instead of to a file.
+
+
+core_pipe_limit
+===============
+
+This sysctl is only applicable when `core_pattern`_ is configured to
+pipe core files to a user space helper (when the first character of
+``core_pattern`` is a '|', see above).
+When collecting cores via a pipe to an application, it is occasionally
+useful for the collecting application to gather data about the
+crashing process from its ``/proc/pid`` directory.
+In order to do this safely, the kernel must wait for the collecting
+process to exit, so as not to remove the crashing processes proc files
+prematurely.
+This in turn creates the possibility that a misbehaving userspace
+collecting process can block the reaping of a crashed process simply
+by never exiting.
+This sysctl defends against that.
+It defines how many concurrent crashing processes may be piped to user
+space applications in parallel.
+If this value is exceeded, then those crashing processes above that
+value are noted via the kernel log and their cores are skipped.
+0 is a special value, indicating that unlimited processes may be
+captured in parallel, but that no waiting will take place (i.e. the
+collecting process is not guaranteed access to ``/proc/<crashing
+pid>/``).
+This value defaults to 0.
+
+
+core_uses_pid
+=============
+
+The default coredump filename is "core".  By setting
+``core_uses_pid`` to 1, the coredump filename becomes core.PID.
+If `core_pattern`_ does not include "%p" (default does not)
+and ``core_uses_pid`` is set, then .PID will be appended to
+the filename.
+
+
+ctrl-alt-del
+============
+
+When the value in this file is 0, ctrl-alt-del is trapped and
+sent to the ``init(1)`` program to handle a graceful restart.
+When, however, the value is > 0, 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.
+
+
+dmesg_restrict
+==============
+
+This toggle indicates whether unprivileged users are prevented
+from using ``dmesg(8)`` to view messages from the kernel's log
+buffer.
+When ``dmesg_restrict`` is set to 0 there are no restrictions.
+When ``dmesg_restrict`` is set to 1, users must have
+``CAP_SYSLOG`` to use ``dmesg(8)``.
+
+The kernel config option ``CONFIG_SECURITY_DMESG_RESTRICT`` sets the
+default value of ``dmesg_restrict``.
+
+
+domainname & hostname
+=====================
+
+These files can be used to set the NIS/YP domainname and the
+hostname of your box in exactly the same way as the commands
+domainname and hostname, i.e.::
+
+	# echo "darkstar" > /proc/sys/kernel/hostname
+	# echo "mydomain" > /proc/sys/kernel/domainname
+
+has the same effect as::
+
+	# hostname "darkstar"
+	# domainname "mydomain"
+
+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 ``hostname(1)`` man page.
+
+
+firmware_config
+===============
+
+See Documentation/driver-api/firmware/fallback-mechanisms.rst.
+
+The entries in this directory allow the firmware loader helper
+fallback to be controlled:
+
+* ``force_sysfs_fallback``, when set to 1, forces the use of the
+  fallback;
+* ``ignore_sysfs_fallback``, when set to 1, ignores any fallback.
+
+
+ftrace_dump_on_oops
+===================
+
+Determines whether ``ftrace_dump()`` should be called on an oops (or
+kernel panic). This will output the contents of the ftrace buffers to
+the console.  This is very useful for capturing traces that lead to
+crashes and outputting them to a serial console.
+
+= ===================================================
+0 Disabled (default).
+1 Dump buffers of all CPUs.
+2 Dump the buffer of the CPU that triggered the oops.
+= ===================================================
+
+
+ftrace_enabled, stack_tracer_enabled
+====================================
+
+See Documentation/trace/ftrace.rst.
+
+
+hardlockup_all_cpu_backtrace
+============================
+
+This value controls the hard lockup detector behavior when a hard
+lockup condition is detected as to whether or not to gather further
+debug information. If enabled, arch-specific all-CPU stack dumping
+will be initiated.
+
+= ============================================
+0 Do nothing. This is the default behavior.
+1 On detection capture more debug information.
+= ============================================
+
+
+hardlockup_panic
+================
+
+This parameter can be used to control whether the kernel panics
+when a hard lockup is detected.
+
+= ===========================
+0 Don't panic on hard lockup.
+1 Panic on hard lockup.
+= ===========================
+
+See Documentation/admin-guide/lockup-watchdogs.rst for more information.
+This can also be set using the nmi_watchdog kernel parameter.
+
+
+hotplug
+=======
+
+Path for the hotplug policy agent.
+Default value is ``CONFIG_UEVENT_HELPER_PATH``, which in turn defaults
+to the empty string.
+
+This file only exists when ``CONFIG_UEVENT_HELPER`` is enabled. Most
+modern systems rely exclusively on the netlink-based uevent source and
+don't need this.
+
+
+hung_task_all_cpu_backtrace
+===========================
+
+If this option is set, the kernel will send an NMI to all CPUs to dump
+their backtraces when a hung task is detected. This file shows up if
+CONFIG_DETECT_HUNG_TASK and CONFIG_SMP are enabled.
+
+0: Won't show all CPUs backtraces when a hung task is detected.
+This is the default behavior.
+
+1: Will non-maskably interrupt all CPUs and dump their backtraces when
+a hung task is detected.
+
+
+hung_task_panic
+===============
+
+Controls the kernel's behavior when a hung task is detected.
+This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+
+= =================================================
+0 Continue operation. This is the default behavior.
+1 Panic immediately.
+= =================================================
+
+
+hung_task_check_count
+=====================
+
+The upper bound on the number of tasks that are checked.
+This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+
+
+hung_task_timeout_secs
+======================
+
+When a task in D state did not get scheduled
+for more than this value report a warning.
+This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+
+0 means infinite timeout, no checking is done.
+
+Possible values to set are in range {0:``LONG_MAX``/``HZ``}.
+
+
+hung_task_check_interval_secs
+=============================
+
+Hung task check interval. If hung task checking is enabled
+(see `hung_task_timeout_secs`_), the check is done every
+``hung_task_check_interval_secs`` seconds.
+This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+
+0 (default) means use ``hung_task_timeout_secs`` as checking
+interval.
+
+Possible values to set are in range {0:``LONG_MAX``/``HZ``}.
+
+
+hung_task_warnings
+==================
+
+The maximum number of warnings to report. During a check interval
+if a hung task is detected, this value is decreased by 1.
+When this value reaches 0, no more warnings will be reported.
+This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+
+-1: report an infinite number of warnings.
+
+
+hyperv_record_panic_msg
+=======================
+
+Controls whether the panic kmsg data should be reported to Hyper-V.
+
+= =========================================================
+0 Do not report panic kmsg data.
+1 Report the panic kmsg data. This is the default behavior.
+= =========================================================
+
+
+ignore-unaligned-usertrap
+=========================
+
+On architectures where unaligned accesses cause traps, and where this
+feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN``;
+currently, ``arc``, ``ia64`` and ``loongarch``), controls whether all
+unaligned traps are logged.
+
+= =============================================================
+0 Log all unaligned accesses.
+1 Only warn the first time a process traps. This is the default
+  setting.
+= =============================================================
+
+See also `unaligned-trap`_ and `unaligned-dump-stack`_. On ``ia64``,
+this allows system administrators to override the
+``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded.
+
+
+io_uring_disabled
+=================
+
+Prevents all processes from creating new io_uring instances. Enabling this
+shrinks the kernel's attack surface.
+
+= ======================================================================
+0 All processes can create io_uring instances as normal. This is the
+  default setting.
+1 io_uring creation is disabled (io_uring_setup() will fail with
+  -EPERM) for unprivileged processes not in the io_uring_group group.
+  Existing io_uring instances can still be used.  See the
+  documentation for io_uring_group for more information.
+2 io_uring creation is disabled for all processes. io_uring_setup()
+  always fails with -EPERM. Existing io_uring instances can still be
+  used.
+= ======================================================================
+
+
+io_uring_group
+==============
+
+When io_uring_disabled is set to 1, a process must either be
+privileged (CAP_SYS_ADMIN) or be in the io_uring_group group in order
+to create an io_uring instance.  If io_uring_group is set to -1 (the
+default), only processes with the CAP_SYS_ADMIN capability may create
+io_uring instances.
+
+
+kexec_load_disabled
+===================
+
+A toggle indicating if the syscalls ``kexec_load`` and
+``kexec_file_load`` have been disabled.
+This value defaults to 0 (false: ``kexec_*load`` enabled), but can be
+set to 1 (true: ``kexec_*load`` disabled).
+Once true, kexec can no longer be used, and the toggle cannot be set
+back to false.
+This allows a kexec image to be loaded before disabling the syscall,
+allowing a system to set up (and later use) an image without it being
+altered.
+Generally used together with the `modules_disabled`_ sysctl.
+
+kexec_load_limit_panic
+======================
+
+This parameter specifies a limit to the number of times the syscalls
+``kexec_load`` and ``kexec_file_load`` can be called with a crash
+image. It can only be set with a more restrictive value than the
+current one.
+
+== ======================================================
+-1 Unlimited calls to kexec. This is the default setting.
+N  Number of calls left.
+== ======================================================
+
+kexec_load_limit_reboot
+=======================
+
+Similar functionality as ``kexec_load_limit_panic``, but for a normal
+image.
+
+kptr_restrict
+=============
+
+This toggle indicates whether restrictions are placed on
+exposing kernel addresses via ``/proc`` and other interfaces.
+
+When ``kptr_restrict`` is set to 0 (the default) the address is hashed
+before printing.
+(This is the equivalent to %p.)
+
+When ``kptr_restrict`` is set to 1, kernel pointers printed using the
+%pK format specifier will be replaced with 0s unless the user has
+``CAP_SYSLOG`` and effective user and group ids are equal to the real
+ids.
+This is because %pK checks are done at read() time rather than open()
+time, so if permissions are elevated between the open() and the read()
+(e.g via a setuid binary) then %pK will not leak kernel pointers to
+unprivileged users.
+Note, this is a temporary solution only.
+The correct long-term solution is to do the permission checks at
+open() time.
+Consider removing world read permissions from files that use %pK, and
+using `dmesg_restrict`_ to protect against uses of %pK in ``dmesg(8)``
+if leaking kernel pointer values to unprivileged users is a concern.
+
+When ``kptr_restrict`` is set to 2, kernel pointers printed using
+%pK will be replaced with 0s regardless of privileges.
+
+
+modprobe
+========
+
+The full path to the usermode helper for autoloading kernel modules,
+by default ``CONFIG_MODPROBE_PATH``, which in turn defaults to
+"/sbin/modprobe".  This binary is executed when the kernel requests a
+module.  For example, if userspace passes an unknown filesystem type
+to mount(), then the kernel will automatically request the
+corresponding filesystem module by executing this usermode helper.
+This usermode helper should insert the needed module into the kernel.
+
+This sysctl only affects module autoloading.  It has no effect on the
+ability to explicitly insert modules.
+
+This sysctl can be used to debug module loading requests::
+
+    echo '#! /bin/sh' > /tmp/modprobe
+    echo 'echo "$@" >> /tmp/modprobe.log' >> /tmp/modprobe
+    echo 'exec /sbin/modprobe "$@"' >> /tmp/modprobe
+    chmod a+x /tmp/modprobe
+    echo /tmp/modprobe > /proc/sys/kernel/modprobe
+
+Alternatively, if this sysctl is set to the empty string, then module
+autoloading is completely disabled.  The kernel will not try to
+execute a usermode helper at all, nor will it call the
+kernel_module_request LSM hook.
+
+If CONFIG_STATIC_USERMODEHELPER=y is set in the kernel configuration,
+then the configured static usermode helper overrides this sysctl,
+except that the empty string is still accepted to completely disable
+module autoloading as described above.
+
+modules_disabled
+================
+
+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.  Generally used with the `kexec_load_disabled`_ toggle.
+
+
+.. _msgmni:
+
+msgmax, msgmnb, and msgmni
+==========================
+
+``msgmax`` is the maximum size of an IPC message, in bytes. 8192 by
+default (``MSGMAX``).
+
+``msgmnb`` is the maximum size of an IPC queue, in bytes. 16384 by
+default (``MSGMNB``).
+
+``msgmni`` is the maximum number of IPC queues. 32000 by default
+(``MSGMNI``).
+
+
+msg_next_id, sem_next_id, and shm_next_id (System V IPC)
+========================================================
+
+These three toggles allows to specify desired id for next allocated IPC
+object: message, semaphore or shared memory respectively.
+
+By default they are equal to -1, which means generic allocation logic.
+Possible values to set are in range {0:``INT_MAX``}.
+
+Notes:
+  1) kernel doesn't guarantee, that new object will have desired id. So,
+     it's up to userspace, how to handle an object with "wrong" id.
+  2) Toggle with non-default value will be set back to -1 by kernel after
+     successful IPC object allocation. If an IPC object allocation syscall
+     fails, it is undefined if the value remains unmodified or is reset to -1.
+
+
+ngroups_max
+===========
+
+Maximum number of supplementary groups, _i.e._ the maximum size which
+``setgroups`` will accept. Exports ``NGROUPS_MAX`` from the kernel.
+
+
+
+nmi_watchdog
+============
+
+This parameter can be used to control the NMI watchdog
+(i.e. the hard lockup detector) on x86 systems.
+
+= =================================
+0 Disable the hard lockup detector.
+1 Enable the hard lockup detector.
+= =================================
+
+The hard lockup detector monitors each CPU for its ability to respond to
+timer interrupts. The mechanism utilizes CPU performance counter registers
+that are programmed to generate Non-Maskable Interrupts (NMIs) periodically
+while a CPU is busy. Hence, the alternative name 'NMI watchdog'.
+
+The NMI watchdog is disabled by default if the kernel is running as a guest
+in a KVM virtual machine. This default can be overridden by adding::
+
+   nmi_watchdog=1
+
+to the guest kernel command line (see
+Documentation/admin-guide/kernel-parameters.rst).
+
+
+nmi_wd_lpm_factor (PPC only)
+============================
+
+Factor to apply to the NMI watchdog timeout (only when ``nmi_watchdog`` is
+set to 1). This factor represents the percentage added to
+``watchdog_thresh`` when calculating the NMI watchdog timeout during an
+LPM. The soft lockup timeout is not impacted.
+
+A value of 0 means no change. The default value is 200 meaning the NMI
+watchdog is set to 30s (based on ``watchdog_thresh`` equal to 10).
+
+
+numa_balancing
+==============
+
+Enables/disables and configures automatic page fault based NUMA memory
+balancing.  Memory is moved automatically to nodes that access it often.
+The value to set can be the result of ORing the following:
+
+= =================================
+0 NUMA_BALANCING_DISABLED
+1 NUMA_BALANCING_NORMAL
+2 NUMA_BALANCING_MEMORY_TIERING
+= =================================
+
+Or NUMA_BALANCING_NORMAL to optimize page placement among different
+NUMA nodes to reduce remote accessing.  On NUMA machines, there is a
+performance penalty if remote memory is accessed by a CPU. When this
+feature is enabled the kernel samples what task thread is accessing
+memory by periodically unmapping pages and later trapping a page
+fault. At the time of the page fault, it is determined if the data
+being accessed should be migrated to a local memory node.
+
+The unmapping of pages and trapping faults incur additional overhead that
+ideally is offset by improved memory locality but there is no universal
+guarantee. If the target workload is already bound to NUMA nodes then this
+feature should be disabled.
+
+Or NUMA_BALANCING_MEMORY_TIERING to optimize page placement among
+different types of memory (represented as different NUMA nodes) to
+place the hot pages in the fast memory.  This is implemented based on
+unmapping and page fault too.
+
+numa_balancing_promote_rate_limit_MBps
+======================================
+
+Too high promotion/demotion throughput between different memory types
+may hurt application latency.  This can be used to rate limit the
+promotion throughput.  The per-node max promotion throughput in MB/s
+will be limited to be no more than the set value.
+
+A rule of thumb is to set this to less than 1/10 of the PMEM node
+write bandwidth.
+
+oops_all_cpu_backtrace
+======================
+
+If this option is set, the kernel will send an NMI to all CPUs to dump
+their backtraces when an oops event occurs. It should be used as a last
+resort in case a panic cannot be triggered (to protect VMs running, for
+example) or kdump can't be collected. This file shows up if CONFIG_SMP
+is enabled.
+
+0: Won't show all CPUs backtraces when an oops is detected.
+This is the default behavior.
+
+1: Will non-maskably interrupt all CPUs and dump their backtraces when
+an oops event is detected.
+
+
+oops_limit
+==========
+
+Number of kernel oopses after which the kernel should panic when
+``panic_on_oops`` is not set. Setting this to 0 disables checking
+the count. Setting this to  1 has the same effect as setting
+``panic_on_oops=1``. The default value is 10000.
+
+
+osrelease, ostype & version
+===========================
+
+::
+
+  # cat osrelease
+  2.1.88
+  # cat ostype
+  Linux
+  # cat version
+  #5 Wed Feb 25 21:49:24 MET 1998
+
+The files ``osrelease`` and ``ostype`` should be clear enough.
+``version``
+needs a little more clarification however. The '#5' means that
+this is the fifth kernel built from this source base and the
+date behind it indicates the time the kernel was built.
+The only way to tune these values is to rebuild the kernel :-)
+
+
+overflowgid & overflowuid
+=========================
+
+if your architecture did not always support 32-bit UIDs (i.e. arm,
+i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
+applications that use the old 16-bit UID/GID system calls, if the
+actual UID or GID would exceed 65535.
+
+These sysctls allow you to change the value of the fixed UID and GID.
+The default is 65534.
+
+
+panic
+=====
+
+The value in this file determines the behaviour of the kernel on a
+panic:
+
+* if zero, the kernel will loop forever;
+* if negative, the kernel will reboot immediately;
+* if positive, the kernel will reboot after the corresponding number
+  of seconds.
+
+When you use the software watchdog, the recommended setting is 60.
+
+
+panic_on_io_nmi
+===============
+
+Controls the kernel's behavior when a CPU receives an NMI caused by
+an IO error.
+
+= ==================================================================
+0 Try to continue operation (default).
+1 Panic immediately. The IO error triggered an NMI. This indicates a
+  serious system condition which could result in IO data corruption.
+  Rather than continuing, panicking might be a better choice. Some
+  servers issue this sort of NMI when the dump button is pushed,
+  and you can use this option to take a crash dump.
+= ==================================================================
+
+
+panic_on_oops
+=============
+
+Controls the kernel's behaviour when an oops or BUG is encountered.
+
+= ===================================================================
+0 Try to continue operation.
+1 Panic immediately.  If the `panic` sysctl is also non-zero then the
+  machine will be rebooted.
+= ===================================================================
+
+
+panic_on_stackoverflow
+======================
+
+Controls the kernel's behavior when detecting the overflows of
+kernel, IRQ and exception stacks except a user stack.
+This file shows up if ``CONFIG_DEBUG_STACKOVERFLOW`` is enabled.
+
+= ==========================
+0 Try to continue operation.
+1 Panic immediately.
+= ==========================
+
+
+panic_on_unrecovered_nmi
+========================
+
+The default Linux behaviour on an NMI of either memory or unknown is
+to continue operation. For many environments such as scientific
+computing it is preferable that the box is taken out and the error
+dealt with than an uncorrected parity/ECC error get propagated.
+
+A small number of systems do generate NMIs for bizarre random reasons
+such as power management so the default is off. That sysctl works like
+the existing panic controls already in that directory.
+
+
+panic_on_warn
+=============
+
+Calls panic() in the WARN() path when set to 1.  This is useful to avoid
+a kernel rebuild when attempting to kdump at the location of a WARN().
+
+= ================================================
+0 Only WARN(), default behaviour.
+1 Call panic() after printing out WARN() location.
+= ================================================
+
+
+panic_print
+===========
+
+Bitmask for printing system info when panic happens. User can chose
+combination of the following bits:
+
+=====  ============================================
+bit 0  print all tasks info
+bit 1  print system memory info
+bit 2  print timer info
+bit 3  print locks info if ``CONFIG_LOCKDEP`` is on
+bit 4  print ftrace buffer
+bit 5  print all printk messages in buffer
+bit 6  print all CPUs backtrace (if available in the arch)
+=====  ============================================
+
+So for example to print tasks and memory info on panic, user can::
+
+  echo 3 > /proc/sys/kernel/panic_print
+
+
+panic_on_rcu_stall
+==================
+
+When set to 1, calls panic() after RCU stall detection messages. This
+is useful to define the root cause of RCU stalls using a vmcore.
+
+= ============================================================
+0 Do not panic() when RCU stall takes place, default behavior.
+1 panic() after printing RCU stall messages.
+= ============================================================
+
+max_rcu_stall_to_panic
+======================
+
+When ``panic_on_rcu_stall`` is set to 1, this value determines the
+number of times that RCU can stall before panic() is called.
+
+When ``panic_on_rcu_stall`` is set to 0, this value is has no effect.
+
+perf_cpu_time_max_percent
+=========================
+
+Hints to the kernel how much CPU time it should be allowed to
+use to handle perf sampling events.  If the perf subsystem
+is informed that its samples are exceeding this limit, it
+will drop its sampling frequency to attempt to reduce its CPU
+usage.
+
+Some perf sampling happens in NMIs.  If these samples
+unexpectedly take too long to execute, the NMIs can become
+stacked up next to each other so much that nothing else is
+allowed to execute.
+
+===== ========================================================
+0     Disable the mechanism.  Do not monitor or correct perf's
+      sampling rate no matter how CPU time it takes.
+
+1-100 Attempt to throttle perf's sample rate to this
+      percentage of CPU.  Note: the kernel calculates an
+      "expected" length of each sample event.  100 here means
+      100% of that expected length.  Even if this is set to
+      100, you may still see sample throttling if this
+      length is exceeded.  Set to 0 if you truly do not care
+      how much CPU is consumed.
+===== ========================================================
+
+
+perf_event_paranoid
+===================
+
+Controls use of the performance events system by unprivileged
+users (without CAP_PERFMON).  The default value is 2.
+
+For backward compatibility reasons access to system performance
+monitoring and observability remains open for CAP_SYS_ADMIN
+privileged processes but CAP_SYS_ADMIN usage for secure system
+performance monitoring and observability operations is discouraged
+with respect to CAP_PERFMON use cases.
+
+===  ==================================================================
+ -1  Allow use of (almost) all events by all users.
+
+     Ignore mlock limit after perf_event_mlock_kb without
+     ``CAP_IPC_LOCK``.
+
+>=0  Disallow ftrace function tracepoint by users without
+     ``CAP_PERFMON``.
+
+     Disallow raw tracepoint access by users without ``CAP_PERFMON``.
+
+>=1  Disallow CPU event access by users without ``CAP_PERFMON``.
+
+>=2  Disallow kernel profiling by users without ``CAP_PERFMON``.
+===  ==================================================================
+
+
+perf_event_max_stack
+====================
+
+Controls maximum number of stack frames to copy for (``attr.sample_type &
+PERF_SAMPLE_CALLCHAIN``) configured events, for instance, when using
+'``perf record -g``' or '``perf trace --call-graph fp``'.
+
+This can only be done when no events are in use that have callchains
+enabled, otherwise writing to this file will return ``-EBUSY``.
+
+The default value is 127.
+
+
+perf_event_mlock_kb
+===================
+
+Control size of per-cpu ring buffer not counted against mlock limit.
+
+The default value is 512 + 1 page
+
+
+perf_event_max_contexts_per_stack
+=================================
+
+Controls maximum number of stack frame context entries for
+(``attr.sample_type & PERF_SAMPLE_CALLCHAIN``) configured events, for
+instance, when using '``perf record -g``' or '``perf trace --call-graph fp``'.
+
+This can only be done when no events are in use that have callchains
+enabled, otherwise writing to this file will return ``-EBUSY``.
+
+The default value is 8.
+
+
+perf_user_access (arm64 and riscv only)
+=======================================
+
+Controls user space access for reading perf event counters.
+
+arm64
+=====
+
+The default value is 0 (access disabled).
+
+When set to 1, user space can read performance monitor counter registers
+directly.
+
+See Documentation/arch/arm64/perf.rst for more information.
+
+riscv
+=====
+
+When set to 0, user space access is disabled.
+
+The default value is 1, user space can read performance monitor counter
+registers through perf, any direct access without perf intervention will trigger
+an illegal instruction.
+
+When set to 2, which enables legacy mode (user space has direct access to cycle
+and insret CSRs only). Note that this legacy value is deprecated and will be
+removed once all user space applications are fixed.
+
+Note that the time CSR is always directly accessible to all modes.
+
+pid_max
+=======
+
+PID allocation wrap value.  When the kernel's next PID value
+reaches this value, it wraps back to a minimum PID value.
+PIDs of value ``pid_max`` or larger are not allocated.
+
+
+ns_last_pid
+===========
+
+The last pid allocated in the current (the one task using this sysctl
+lives in) pid namespace. When selecting a pid for a next task on fork
+kernel tries to allocate a number starting from this one.
+
+
+powersave-nap (PPC only)
+========================
+
+If set, Linux-PPC will use the 'nap' mode of powersaving,
+otherwise the 'doze' mode will be used.
+
+
+==============================================================
+
+printk
+======
+
+The four values in printk denote: ``console_loglevel``,
+``default_message_loglevel``, ``minimum_console_loglevel`` and
+``default_console_loglevel`` respectively.
+
+These values influence printk() behavior when printing or
+logging error messages. See '``man 2 syslog``' for more info on
+the different loglevels.
+
+======================== =====================================
+console_loglevel         messages with a higher priority than
+                         this will be printed to the console
+default_message_loglevel messages without an explicit priority
+                         will be printed with this priority
+minimum_console_loglevel minimum (highest) value to which
+                         console_loglevel can be set
+default_console_loglevel default value for console_loglevel
+======================== =====================================
+
+
+printk_delay
+============
+
+Delay each printk message in ``printk_delay`` milliseconds
+
+Value from 0 - 10000 is allowed.
+
+
+printk_ratelimit
+================
+
+Some warning messages are rate limited. ``printk_ratelimit`` specifies
+the minimum length of time between these messages (in seconds).
+The default value is 5 seconds.
+
+A value of 0 will disable rate limiting.
+
+
+printk_ratelimit_burst
+======================
+
+While long term we enforce one message per `printk_ratelimit`_
+seconds, we do allow a burst of messages to pass through.
+``printk_ratelimit_burst`` specifies the number of messages we can
+send before ratelimiting kicks in.
+
+The default value is 10 messages.
+
+
+printk_devkmsg
+==============
+
+Control the logging to ``/dev/kmsg`` from userspace:
+
+========= =============================================
+ratelimit default, ratelimited
+on        unlimited logging to /dev/kmsg from userspace
+off       logging to /dev/kmsg disabled
+========= =============================================
+
+The kernel command line parameter ``printk.devkmsg=`` overrides this and is
+a one-time setting until next reboot: once set, it cannot be changed by
+this sysctl interface anymore.
+
+==============================================================
+
+
+pty
+===
+
+See Documentation/filesystems/devpts.rst.
+
+
+random
+======
+
+This is a directory, with the following entries:
+
+* ``boot_id``: a UUID generated the first time this is retrieved, and
+  unvarying after that;
+
+* ``uuid``: a UUID generated every time this is retrieved (this can
+  thus be used to generate UUIDs at will);
+
+* ``entropy_avail``: the pool's entropy count, in bits;
+
+* ``poolsize``: the entropy pool size, in bits;
+
+* ``urandom_min_reseed_secs``: obsolete (used to determine the minimum
+  number of seconds between urandom pool reseeding). This file is
+  writable for compatibility purposes, but writing to it has no effect
+  on any RNG behavior;
+
+* ``write_wakeup_threshold``: when the entropy count drops below this
+  (as a number of bits), processes waiting to write to ``/dev/random``
+  are woken up. This file is writable for compatibility purposes, but
+  writing to it has no effect on any RNG behavior.
+
+
+randomize_va_space
+==================
+
+This option can be used to select the type of process address
+space randomization that is used in the system, for architectures
+that support this feature.
+
+==  ===========================================================================
+0   Turn the process address space randomization off.  This is the
+    default for architectures that do not support this feature anyways,
+    and kernels that are booted with the "norandmaps" parameter.
+
+1   Make the addresses of mmap base, stack and VDSO page randomized.
+    This, among other things, implies that shared libraries will be
+    loaded to random addresses.  Also for PIE-linked binaries, the
+    location of code start is randomized.  This is the default if the
+    ``CONFIG_COMPAT_BRK`` option is enabled.
+
+2   Additionally enable heap randomization.  This is the default if
+    ``CONFIG_COMPAT_BRK`` is disabled.
+
+    There are a few legacy applications out there (such as some ancient
+    versions of libc.so.5 from 1996) that assume that brk area starts
+    just after the end of the code+bss.  These applications break when
+    start of the brk area is randomized.  There are however no known
+    non-legacy applications that would be broken this way, so for most
+    systems it is safe to choose full randomization.
+
+    Systems with ancient and/or broken binaries should be configured
+    with ``CONFIG_COMPAT_BRK`` enabled, which excludes the heap from process
+    address space randomization.
+==  ===========================================================================
+
+
+real-root-dev
+=============
+
+See Documentation/admin-guide/initrd.rst.
+
+
+reboot-cmd (SPARC only)
+=======================
+
+??? This 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. ???
+
+
+sched_energy_aware
+==================
+
+Enables/disables Energy Aware Scheduling (EAS). EAS starts
+automatically on platforms where it can run (that is,
+platforms with asymmetric CPU topologies and having an Energy
+Model available). If your platform happens to meet the
+requirements for EAS but you do not want to use it, change
+this value to 0.
+
+task_delayacct
+===============
+
+Enables/disables task delay accounting (see
+Documentation/accounting/delay-accounting.rst. Enabling this feature incurs
+a small amount of overhead in the scheduler but is useful for debugging
+and performance tuning. It is required by some tools such as iotop.
+
+sched_schedstats
+================
+
+Enables/disables scheduler statistics. Enabling this feature
+incurs a small amount of overhead in the scheduler but is
+useful for debugging and performance tuning.
+
+sched_util_clamp_min
+====================
+
+Max allowed *minimum* utilization.
+
+Default value is 1024, which is the maximum possible value.
+
+It means that any requested uclamp.min value cannot be greater than
+sched_util_clamp_min, i.e., it is restricted to the range
+[0:sched_util_clamp_min].
+
+sched_util_clamp_max
+====================
+
+Max allowed *maximum* utilization.
+
+Default value is 1024, which is the maximum possible value.
+
+It means that any requested uclamp.max value cannot be greater than
+sched_util_clamp_max, i.e., it is restricted to the range
+[0:sched_util_clamp_max].
+
+sched_util_clamp_min_rt_default
+===============================
+
+By default Linux is tuned for performance. Which means that RT tasks always run
+at the highest frequency and most capable (highest capacity) CPU (in
+heterogeneous systems).
+
+Uclamp achieves this by setting the requested uclamp.min of all RT tasks to
+1024 by default, which effectively boosts the tasks to run at the highest
+frequency and biases them to run on the biggest CPU.
+
+This knob allows admins to change the default behavior when uclamp is being
+used. In battery powered devices particularly, running at the maximum
+capacity and frequency will increase energy consumption and shorten the battery
+life.
+
+This knob is only effective for RT tasks which the user hasn't modified their
+requested uclamp.min value via sched_setattr() syscall.
+
+This knob will not escape the range constraint imposed by sched_util_clamp_min
+defined above.
+
+For example if
+
+	sched_util_clamp_min_rt_default = 800
+	sched_util_clamp_min = 600
+
+Then the boost will be clamped to 600 because 800 is outside of the permissible
+range of [0:600]. This could happen for instance if a powersave mode will
+restrict all boosts temporarily by modifying sched_util_clamp_min. As soon as
+this restriction is lifted, the requested sched_util_clamp_min_rt_default
+will take effect.
+
+seccomp
+=======
+
+See Documentation/userspace-api/seccomp_filter.rst.
+
+
+sg-big-buff
+===========
+
+This file shows the size of the generic SCSI (sg) buffer.
+You can't tune it just yet, but you could change it on
+compile time by editing ``include/scsi/sg.h`` and changing
+the value of ``SG_BIG_BUFF``.
+
+There shouldn't be any reason to change this value. If
+you can come up with one, you probably know what you
+are doing anyway :)
+
+
+shmall
+======
+
+This parameter sets the total amount of shared memory pages that
+can be used system wide. Hence, ``shmall`` should always be at least
+``ceil(shmmax/PAGE_SIZE)``.
+
+If you are not sure what the default ``PAGE_SIZE`` is on your Linux
+system, you can run the following command::
+
+	# getconf PAGE_SIZE
+
+
+shmmax
+======
+
+This value can be used to query and set the run time limit
+on the maximum shared memory segment size that can be created.
+Shared memory segments up to 1Gb are now supported in the
+kernel.  This value defaults to ``SHMMAX``.
+
+
+shmmni
+======
+
+This value determines the maximum number of shared memory segments.
+4096 by default (``SHMMNI``).
+
+
+shm_rmid_forced
+===============
+
+Linux lets you set resource limits, including how much memory one
+process can consume, via ``setrlimit(2)``.  Unfortunately, shared memory
+segments are allowed to exist without association with any process, and
+thus might not be counted against any resource limits.  If enabled,
+shared memory segments are automatically destroyed when their attach
+count becomes zero after a detach or a process termination.  It will
+also destroy segments that were created, but never attached to, on exit
+from the process.  The only use left for ``IPC_RMID`` is to immediately
+destroy an unattached segment.  Of course, this breaks the way things are
+defined, so some applications might stop working.  Note that this
+feature will do you no good unless you also configure your resource
+limits (in particular, ``RLIMIT_AS`` and ``RLIMIT_NPROC``).  Most systems don't
+need this.
+
+Note that if you change this from 0 to 1, already created segments
+without users and with a dead originative process will be destroyed.
+
+
+sysctl_writes_strict
+====================
+
+Control how file position affects the behavior of updating sysctl values
+via the ``/proc/sys`` interface:
+
+  ==   ======================================================================
+  -1   Legacy per-write sysctl value handling, with no printk warnings.
+       Each write syscall must fully contain the sysctl value to be
+       written, and multiple writes on the same sysctl file descriptor
+       will rewrite the sysctl value, regardless of file position.
+   0   Same behavior as above, but warn about processes that perform writes
+       to a sysctl file descriptor when the file position is not 0.
+   1   (default) Respect file position when writing sysctl strings. Multiple
+       writes will append to the sysctl value buffer. Anything past the max
+       length of the sysctl value buffer will be ignored. Writes to numeric
+       sysctl entries must always be at file position 0 and the value must
+       be fully contained in the buffer sent in the write syscall.
+  ==   ======================================================================
+
+
+softlockup_all_cpu_backtrace
+============================
+
+This value controls the soft lockup detector thread's behavior
+when a soft lockup condition is detected as to whether or not
+to gather further debug information. If enabled, each cpu will
+be issued an NMI and instructed to capture stack trace.
+
+This feature is only applicable for architectures which support
+NMI.
+
+= ============================================
+0 Do nothing. This is the default behavior.
+1 On detection capture more debug information.
+= ============================================
+
+
+softlockup_panic
+=================
+
+This parameter can be used to control whether the kernel panics
+when a soft lockup is detected.
+
+= ============================================
+0 Don't panic on soft lockup.
+1 Panic on soft lockup.
+= ============================================
+
+This can also be set using the softlockup_panic kernel parameter.
+
+
+soft_watchdog
+=============
+
+This parameter can be used to control the soft lockup detector.
+
+= =================================
+0 Disable the soft lockup detector.
+1 Enable the soft lockup detector.
+= =================================
+
+The soft lockup detector monitors CPUs for threads that are hogging the CPUs
+without rescheduling voluntarily, and thus prevent the 'migration/N' threads
+from running, causing the watchdog work fail to execute. The mechanism depends
+on the CPUs ability to respond to timer interrupts which are needed for the
+watchdog work to be queued by the watchdog timer function, otherwise the NMI
+watchdog — if enabled — can detect a hard lockup condition.
+
+
+split_lock_mitigate (x86 only)
+==============================
+
+On x86, each "split lock" imposes a system-wide performance penalty. On larger
+systems, large numbers of split locks from unprivileged users can result in
+denials of service to well-behaved and potentially more important users.
+
+The kernel mitigates these bad users by detecting split locks and imposing
+penalties: forcing them to wait and only allowing one core to execute split
+locks at a time.
+
+These mitigations can make those bad applications unbearably slow. Setting
+split_lock_mitigate=0 may restore some application performance, but will also
+increase system exposure to denial of service attacks from split lock users.
+
+= ===================================================================
+0 Disable the mitigation mode - just warns the split lock on kernel log
+  and exposes the system to denials of service from the split lockers.
+1 Enable the mitigation mode (this is the default) - penalizes the split
+  lockers with intentional performance degradation.
+= ===================================================================
+
+
+stack_erasing
+=============
+
+This parameter can be used to control kernel stack erasing at the end
+of syscalls for kernels built with ``CONFIG_GCC_PLUGIN_STACKLEAK``.
+
+That erasing reduces the information which kernel stack leak bugs
+can reveal and blocks some uninitialized stack variable attacks.
+The tradeoff is the performance impact: on a single CPU system kernel
+compilation sees a 1% slowdown, other systems and workloads may vary.
+
+= ====================================================================
+0 Kernel stack erasing is disabled, STACKLEAK_METRICS are not updated.
+1 Kernel stack erasing is enabled (default), it is performed before
+  returning to the userspace at the end of syscalls.
+= ====================================================================
+
+
+stop-a (SPARC only)
+===================
+
+Controls Stop-A:
+
+= ====================================
+0 Stop-A has no effect.
+1 Stop-A breaks to the PROM (default).
+= ====================================
+
+Stop-A is always enabled on a panic, so that the user can return to
+the boot PROM.
+
+
+sysrq
+=====
+
+See Documentation/admin-guide/sysrq.rst.
+
+
+tainted
+=======
+
+Non-zero if the kernel has been tainted. Numeric values, which can be
+ORed together. The letters are seen in "Tainted" line of Oops reports.
+
+======  =====  ==============================================================
+     1  `(P)`  proprietary module was loaded
+     2  `(F)`  module was force loaded
+     4  `(S)`  kernel running on an out of specification system
+     8  `(R)`  module was force unloaded
+    16  `(M)`  processor reported a Machine Check Exception (MCE)
+    32  `(B)`  bad page referenced or some unexpected page flags
+    64  `(U)`  taint requested by userspace application
+   128  `(D)`  kernel died recently, i.e. there was an OOPS or BUG
+   256  `(A)`  an ACPI table was overridden by user
+   512  `(W)`  kernel issued warning
+  1024  `(C)`  staging driver was loaded
+  2048  `(I)`  workaround for bug in platform firmware applied
+  4096  `(O)`  externally-built ("out-of-tree") module was loaded
+  8192  `(E)`  unsigned module was loaded
+ 16384  `(L)`  soft lockup occurred
+ 32768  `(K)`  kernel has been live patched
+ 65536  `(X)`  Auxiliary taint, defined and used by for distros
+131072  `(T)`  The kernel was built with the struct randomization plugin
+======  =====  ==============================================================
+
+See Documentation/admin-guide/tainted-kernels.rst for more information.
+
+Note:
+  writes to this sysctl interface will fail with ``EINVAL`` if the kernel is
+  booted with the command line option ``panic_on_taint=<bitmask>,nousertaint``
+  and any of the ORed together values being written to ``tainted`` match with
+  the bitmask declared on panic_on_taint.
+  See Documentation/admin-guide/kernel-parameters.rst for more details on
+  that particular kernel command line option and its optional
+  ``nousertaint`` switch.
+
+threads-max
+===========
+
+This value controls the maximum number of threads that can be created
+using ``fork()``.
+
+During initialization the kernel sets this value such that even if the
+maximum number of threads is created, the thread structures occupy only
+a part (1/8th) of the available RAM pages.
+
+The minimum value that can be written to ``threads-max`` is 1.
+
+The maximum value that can be written to ``threads-max`` is given by the
+constant ``FUTEX_TID_MASK`` (0x3fffffff).
+
+If a value outside of this range is written to ``threads-max`` an
+``EINVAL`` error occurs.
+
+
+traceoff_on_warning
+===================
+
+When set, disables tracing (see Documentation/trace/ftrace.rst) when a
+``WARN()`` is hit.
+
+
+tracepoint_printk
+=================
+
+When tracepoints are sent to printk() (enabled by the ``tp_printk``
+boot parameter), this entry provides runtime control::
+
+    echo 0 > /proc/sys/kernel/tracepoint_printk
+
+will stop tracepoints from being sent to printk(), and::
+
+    echo 1 > /proc/sys/kernel/tracepoint_printk
+
+will send them to printk() again.
+
+This only works if the kernel was booted with ``tp_printk`` enabled.
+
+See Documentation/admin-guide/kernel-parameters.rst and
+Documentation/trace/boottime-trace.rst.
+
+
+.. _unaligned-dump-stack:
+
+unaligned-dump-stack (ia64)
+===========================
+
+When logging unaligned accesses, controls whether the stack is
+dumped.
+
+= ===================================================
+0 Do not dump the stack. This is the default setting.
+1 Dump the stack.
+= ===================================================
+
+See also `ignore-unaligned-usertrap`_.
+
+
+unaligned-trap
+==============
+
+On architectures where unaligned accesses cause traps, and where this
+feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW``; currently,
+``arc``, ``parisc`` and ``loongarch``), controls whether unaligned traps
+are caught and emulated (instead of failing).
+
+= ========================================================
+0 Do not emulate unaligned accesses.
+1 Emulate unaligned accesses. This is the default setting.
+= ========================================================
+
+See also `ignore-unaligned-usertrap`_.
+
+
+unknown_nmi_panic
+=================
+
+The value in this file affects behavior of handling NMI. When the
+value is non-zero, unknown NMI is trapped and then panic occurs. At
+that time, kernel debugging information is displayed on console.
+
+NMI switch that most IA32 servers have fires unknown NMI up, for
+example.  If a system hangs up, try pressing the NMI switch.
+
+
+unprivileged_bpf_disabled
+=========================
+
+Writing 1 to this entry will disable unprivileged calls to ``bpf()``;
+once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` or ``CAP_BPF``
+will return ``-EPERM``. Once set to 1, this can't be cleared from the
+running kernel anymore.
+
+Writing 2 to this entry will also disable unprivileged calls to ``bpf()``,
+however, an admin can still change this setting later on, if needed, by
+writing 0 or 1 to this entry.
+
+If ``BPF_UNPRIV_DEFAULT_OFF`` is enabled in the kernel config, then this
+entry will default to 2 instead of 0.
+
+= =============================================================
+0 Unprivileged calls to ``bpf()`` are enabled
+1 Unprivileged calls to ``bpf()`` are disabled without recovery
+2 Unprivileged calls to ``bpf()`` are disabled
+= =============================================================
+
+
+warn_limit
+==========
+
+Number of kernel warnings after which the kernel should panic when
+``panic_on_warn`` is not set. Setting this to 0 disables checking
+the warning count. Setting this to 1 has the same effect as setting
+``panic_on_warn=1``. The default value is 0.
+
+
+watchdog
+========
+
+This parameter can be used to disable or enable the soft lockup detector
+*and* the NMI watchdog (i.e. the hard lockup detector) at the same time.
+
+= ==============================
+0 Disable both lockup detectors.
+1 Enable both lockup detectors.
+= ==============================
+
+The soft lockup detector and the NMI watchdog can also be disabled or
+enabled individually, using the ``soft_watchdog`` and ``nmi_watchdog``
+parameters.
+If the ``watchdog`` parameter is read, for example by executing::
+
+   cat /proc/sys/kernel/watchdog
+
+the output of this command (0 or 1) shows the logical OR of
+``soft_watchdog`` and ``nmi_watchdog``.
+
+
+watchdog_cpumask
+================
+
+This value can be used to control on which cpus the watchdog may run.
+The default cpumask is all possible cores, but if ``NO_HZ_FULL`` is
+enabled in the kernel config, and cores are specified with the
+``nohz_full=`` boot argument, those cores are excluded by default.
+Offline cores can be included in this mask, and if the core is later
+brought online, the watchdog will be started based on the mask value.
+
+Typically this value would only be touched in the ``nohz_full`` case
+to re-enable cores that by default were not running the watchdog,
+if a kernel lockup was suspected on those cores.
+
+The argument value is the standard cpulist format for cpumasks,
+so for example to enable the watchdog on cores 0, 2, 3, and 4 you
+might say::
+
+  echo 0,2-4 > /proc/sys/kernel/watchdog_cpumask
+
+
+watchdog_thresh
+===============
+
+This value can be used to control the frequency of hrtimer and NMI
+events and the soft and hard lockup thresholds. The default threshold
+is 10 seconds.
+
+The softlockup threshold is (``2 * watchdog_thresh``). Setting this
+tunable to zero will disable lockup detection altogether.
diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
new file mode 100644
index 0000000000..4877563241
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -0,0 +1,505 @@
+================================
+Documentation for /proc/sys/net/
+================================
+
+Copyright
+
+Copyright (c) 1999
+
+	- Terrehon Bowden <terrehon@pacbell.net>
+	- Bodo Bauer <bb@ricochet.net>
+
+Copyright (c) 2000
+
+	- Jorge Nerin <comandante@zaralinux.com>
+
+Copyright (c) 2009
+
+	- Shen Feng <shen@cn.fujitsu.com>
+
+For general info and legal blurb, please look in index.rst.
+
+------------------------------------------------------------------------------
+
+This file contains the documentation for the sysctl files in
+/proc/sys/net
+
+The interface  to  the  networking  parts  of  the  kernel  is  located  in
+/proc/sys/net. The following table shows all possible subdirectories.  You may
+see only some of them, depending on your kernel's configuration.
+
+
+Table : Subdirectories in /proc/sys/net
+
+ ========= =================== = ========== ===================
+ Directory Content               Directory  Content
+ ========= =================== = ========== ===================
+ 802       E802 protocol         mptcp      Multipath TCP
+ appletalk Appletalk protocol    netfilter  Network Filter
+ ax25      AX25                  netrom     NET/ROM
+ bridge    Bridging              rose       X.25 PLP layer
+ core      General parameter     tipc       TIPC
+ ethernet  Ethernet protocol     unix       Unix domain sockets
+ ipv4      IP version 4          x25        X.25 protocol
+ ipv6      IP version 6
+ ========= =================== = ========== ===================
+
+1. /proc/sys/net/core - Network core options
+============================================
+
+bpf_jit_enable
+--------------
+
+This enables the BPF Just in Time (JIT) compiler. BPF is a flexible
+and efficient infrastructure allowing to execute bytecode at various
+hook points. It is used in a number of Linux kernel subsystems such
+as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints)
+and security (e.g. seccomp). LLVM has a BPF back end that can compile
+restricted C into a sequence of BPF instructions. After program load
+through bpf(2) and passing a verifier in the kernel, a JIT will then
+translate these BPF proglets into native CPU instructions. There are
+two flavors of JITs, the newer eBPF JIT currently supported on:
+
+  - x86_64
+  - x86_32
+  - arm64
+  - arm32
+  - ppc64
+  - ppc32
+  - sparc64
+  - mips64
+  - s390x
+  - riscv64
+  - riscv32
+
+And the older cBPF JIT supported on the following archs:
+
+  - mips
+  - sparc
+
+eBPF JITs are a superset of cBPF JITs, meaning the kernel will
+migrate cBPF instructions into eBPF instructions and then JIT
+compile them transparently. Older cBPF JITs can only translate
+tcpdump filters, seccomp rules, etc, but not mentioned eBPF
+programs loaded through bpf(2).
+
+Values:
+
+	- 0 - disable the JIT (default value)
+	- 1 - enable the JIT
+	- 2 - enable the JIT and ask the compiler to emit traces on kernel log.
+
+bpf_jit_harden
+--------------
+
+This enables hardening for the BPF JIT compiler. Supported are eBPF
+JIT backends. Enabling hardening trades off performance, but can
+mitigate JIT spraying.
+
+Values:
+
+	- 0 - disable JIT hardening (default value)
+	- 1 - enable JIT hardening for unprivileged users only
+	- 2 - enable JIT hardening for all users
+
+where "privileged user" in this context means a process having
+CAP_BPF or CAP_SYS_ADMIN in the root user name space.
+
+bpf_jit_kallsyms
+----------------
+
+When BPF JIT compiler is enabled, then compiled images are unknown
+addresses to the kernel, meaning they neither show up in traces nor
+in /proc/kallsyms. This enables export of these addresses, which can
+be used for debugging/tracing. If bpf_jit_harden is enabled, this
+feature is disabled.
+
+Values :
+
+	- 0 - disable JIT kallsyms export (default value)
+	- 1 - enable JIT kallsyms export for privileged users only
+
+bpf_jit_limit
+-------------
+
+This enforces a global limit for memory allocations to the BPF JIT
+compiler in order to reject unprivileged JIT requests once it has
+been surpassed. bpf_jit_limit contains the value of the global limit
+in bytes.
+
+dev_weight
+----------
+
+The maximum number of packets that kernel can handle on a NAPI interrupt,
+it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
+aggregated packet is counted as one packet in this context.
+
+Default: 64
+
+dev_weight_rx_bias
+------------------
+
+RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function
+of the driver for the per softirq cycle netdev_budget. This parameter influences
+the proportion of the configured netdev_budget that is spent on RPS based packet
+processing during RX softirq cycles. It is further meant for making current
+dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack.
+(see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based
+on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias).
+
+Default: 1
+
+dev_weight_tx_bias
+------------------
+
+Scales the maximum number of packets that can be processed during a TX softirq cycle.
+Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric
+net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog.
+
+Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias).
+
+Default: 1
+
+default_qdisc
+-------------
+
+The default queuing discipline to use for network devices. This allows
+overriding the default of pfifo_fast with an alternative. Since the default
+queuing discipline is created without additional parameters so is best suited
+to queuing disciplines that work well without configuration like stochastic
+fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
+queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
+which require setting up classes and bandwidths. Note that physical multiqueue
+interfaces still use mq as root qdisc, which in turn uses this default for its
+leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
+default to noqueue.
+
+Default: pfifo_fast
+
+busy_read
+---------
+
+Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
+Approximate time in us to busy loop waiting for packets on the device queue.
+This sets the default value of the SO_BUSY_POLL socket option.
+Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
+which is the preferred method of enabling. If you need to enable the feature
+globally via sysctl, a value of 50 is recommended.
+
+Will increase power usage.
+
+Default: 0 (off)
+
+busy_poll
+----------------
+Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
+Approximate time in us to busy loop waiting for events.
+Recommended value depends on the number of sockets you poll on.
+For several sockets 50, for several hundreds 100.
+For more than that you probably want to use epoll.
+Note that only sockets with SO_BUSY_POLL set will be busy polled,
+so you want to either selectively set SO_BUSY_POLL on those sockets or set
+sysctl.net.busy_read globally.
+
+Will increase power usage.
+
+Default: 0 (off)
+
+rmem_default
+------------
+
+The default setting of the socket receive buffer in bytes.
+
+rmem_max
+--------
+
+The maximum receive socket buffer size in bytes.
+
+rps_default_mask
+----------------
+
+The default RPS CPU mask used on newly created network devices. An empty
+mask means RPS disabled by default.
+
+tstamp_allow_data
+-----------------
+Allow processes to receive tx timestamps looped together with the original
+packet contents. If disabled, transmit timestamp requests from unprivileged
+processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
+
+Default: 1 (on)
+
+
+wmem_default
+------------
+
+The default setting (in bytes) of the socket send buffer.
+
+wmem_max
+--------
+
+The maximum send socket buffer size in bytes.
+
+message_burst and message_cost
+------------------------------
+
+These parameters  are used to limit the warning messages written to the kernel
+log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
+denial-of-service attack  impossible. A higher message_cost factor, results in
+fewer messages that will be written. Message_burst controls when messages will
+be dropped.  The  default  settings  limit  warning messages to one every five
+seconds.
+
+warnings
+--------
+
+This sysctl is now unused.
+
+This was used to control console messages from the networking stack that
+occur because of problems on the network like duplicate address or bad
+checksums.
+
+These messages are now emitted at KERN_DEBUG and can generally be enabled
+and controlled by the dynamic_debug facility.
+
+netdev_budget
+-------------
+
+Maximum number of packets taken from all interfaces in one polling cycle (NAPI
+poll). In one polling cycle interfaces which are registered to polling are
+probed in a round-robin manner. Also, a polling cycle may not exceed
+netdev_budget_usecs microseconds, even if netdev_budget has not been
+exhausted.
+
+netdev_budget_usecs
+---------------------
+
+Maximum number of microseconds in one NAPI polling cycle. Polling
+will exit when either netdev_budget_usecs have elapsed during the
+poll cycle or the number of packets processed reaches netdev_budget.
+
+netdev_max_backlog
+------------------
+
+Maximum number of packets, queued on the INPUT side, when the interface
+receives packets faster than kernel can process them.
+
+netdev_rss_key
+--------------
+
+RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
+randomly generated.
+Some user space might need to gather its content even if drivers do not
+provide ethtool -x support yet.
+
+::
+
+  myhost:~# cat /proc/sys/net/core/netdev_rss_key
+  84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total)
+
+File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
+
+Note:
+  /proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
+  but most drivers only use 40 bytes of it.
+
+::
+
+  myhost:~# ethtool -x eth0
+  RX flow hash indirection table for eth0 with 8 RX ring(s):
+      0:    0     1     2     3     4     5     6     7
+  RSS hash key:
+  84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
+
+netdev_tstamp_prequeue
+----------------------
+
+If set to 0, RX packet timestamps can be sampled after RPS processing, when
+the target CPU processes packets. It might give some delay on timestamps, but
+permit to distribute the load on several cpus.
+
+If set to 1 (default), timestamps are sampled as soon as possible, before
+queueing.
+
+netdev_unregister_timeout_secs
+------------------------------
+
+Unregister network device timeout in seconds.
+This option controls the timeout (in seconds) used to issue a warning while
+waiting for a network device refcount to drop to 0 during device
+unregistration. A lower value may be useful during bisection to detect
+a leaked reference faster. A larger value may be useful to prevent false
+warnings on slow/loaded systems.
+Default value is 10, minimum 1, maximum 3600.
+
+skb_defer_max
+-------------
+
+Max size (in skbs) of the per-cpu list of skbs being freed
+by the cpu which allocated them. Used by TCP stack so far.
+
+Default: 64
+
+optmem_max
+----------
+
+Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
+of struct cmsghdr structures with appended data.
+
+fb_tunnels_only_for_init_net
+----------------------------
+
+Controls if fallback tunnels (like tunl0, gre0, gretap0, erspan0,
+sit0, ip6tnl0, ip6gre0) are automatically created. There are 3 possibilities
+(a) value = 0; respective fallback tunnels are created when module is
+loaded in every net namespaces (backward compatible behavior).
+(b) value = 1; [kcmd value: initns] respective fallback tunnels are
+created only in init net namespace and every other net namespace will
+not have them.
+(c) value = 2; [kcmd value: none] fallback tunnels are not created
+when a module is loaded in any of the net namespace. Setting value to
+"2" is pointless after boot if these modules are built-in, so there is
+a kernel command-line option that can change this default. Please refer to
+Documentation/admin-guide/kernel-parameters.txt for additional details.
+
+Not creating fallback tunnels gives control to userspace to create
+whatever is needed only and avoid creating devices which are redundant.
+
+Default : 0  (for compatibility reasons)
+
+devconf_inherit_init_net
+------------------------
+
+Controls if a new network namespace should inherit all current
+settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By
+default, we keep the current behavior: for IPv4 we inherit all current
+settings from init_net and for IPv6 we reset all settings to default.
+
+If set to 1, both IPv4 and IPv6 settings are forced to inherit from
+current ones in init_net. If set to 2, both IPv4 and IPv6 settings are
+forced to reset to their default values. If set to 3, both IPv4 and IPv6
+settings are forced to inherit from current ones in the netns where this
+new netns has been created.
+
+Default : 0  (for compatibility reasons)
+
+txrehash
+--------
+
+Controls default hash rethink behaviour on socket when SO_TXREHASH option is set
+to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt).
+
+If set to 1 (default), hash rethink is performed on listening socket.
+If set to 0, hash rethink is not performed.
+
+gro_normal_batch
+----------------
+
+Maximum number of the segments to batch up on output of GRO. When a packet
+exits GRO, either as a coalesced superframe or as an original packet which
+GRO has decided not to coalesce, it is placed on a per-NAPI list. This
+list is then passed to the stack when the number of segments reaches the
+gro_normal_batch limit.
+
+high_order_alloc_disable
+------------------------
+
+By default the allocator for page frags tries to use high order pages (order-3
+on x86). While the default behavior gives good results in most cases, some users
+might have hit a contention in page allocations/freeing. This was especially
+true on older kernels (< 5.14) when high-order pages were not stored on per-cpu
+lists. This allows to opt-in for order-0 allocation instead but is now mostly of
+historical importance.
+
+Default: 0
+
+2. /proc/sys/net/unix - Parameters for Unix domain sockets
+----------------------------------------------------------
+
+There is only one file in this directory.
+unix_dgram_qlen limits the max number of datagrams queued in Unix domain
+socket's buffer. It will not take effect unless PF_UNIX flag is specified.
+
+
+3. /proc/sys/net/ipv4 - IPV4 settings
+-------------------------------------
+Please see: Documentation/networking/ip-sysctl.rst and
+Documentation/admin-guide/sysctl/net.rst for descriptions of these entries.
+
+
+4. Appletalk
+------------
+
+The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
+when Appletalk is loaded. The configurable parameters are:
+
+aarp-expiry-time
+----------------
+
+The amount  of  time  we keep an ARP entry before expiring it. Used to age out
+old hosts.
+
+aarp-resolve-time
+-----------------
+
+The amount of time we will spend trying to resolve an Appletalk address.
+
+aarp-retransmit-limit
+---------------------
+
+The number of times we will retransmit a query before giving up.
+
+aarp-tick-time
+--------------
+
+Controls the rate at which expires are checked.
+
+The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
+on a machine.
+
+The fields  indicate  the DDP type, the local address (in network:node format)
+the remote  address,  the  size of the transmit pending queue, the size of the
+received queue  (bytes waiting for applications to read) the state and the uid
+owning the socket.
+
+/proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
+shows the  name  of the interface, its Appletalk address, the network range on
+that address  (or  network number for phase 1 networks), and the status of the
+interface.
+
+/proc/net/atalk_route lists  each  known  network  route.  It lists the target
+(network) that the route leads to, the router (may be directly connected), the
+route flags, and the device the route is using.
+
+5. TIPC
+-------
+
+tipc_rmem
+---------
+
+The TIPC protocol now has a tunable for the receive memory, similar to the
+tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
+
+::
+
+    # cat /proc/sys/net/tipc/tipc_rmem
+    4252725 34021800        68043600
+    #
+
+The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
+are scaled (shifted) versions of that same value.  Note that the min value
+is not at this point in time used in any meaningful way, but the triplet is
+preserved in order to be consistent with things like tcp_rmem.
+
+named_timeout
+-------------
+
+TIPC name table updates are distributed asynchronously in a cluster, without
+any form of transaction handling. This means that different race scenarios are
+possible. One such is that a name withdrawal sent out by one node and received
+by another node may arrive after a second, overlapping name publication already
+has been accepted from a third node, although the conflicting updates
+originally may have been issued in the correct sequential order.
+If named_timeout is nonzero, failed topology updates will be placed on a defer
+queue until another event arrives that clears the error, or until the timeout
+expires. Value is in milliseconds.
diff --git a/Documentation/admin-guide/sysctl/sunrpc.rst b/Documentation/admin-guide/sysctl/sunrpc.rst
new file mode 100644
index 0000000000..09780a682a
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/sunrpc.rst
@@ -0,0 +1,25 @@
+===================================
+Documentation for /proc/sys/sunrpc/
+===================================
+
+kernel version 2.2.10
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+For general info and legal blurb, please look in index.rst.
+
+------------------------------------------------------------------------------
+
+This file contains the documentation for the sysctl files in
+/proc/sys/sunrpc and is valid for Linux kernel version 2.2.
+
+The files in this directory can be used to (re)set the debug
+flags of the SUN Remote Procedure Call (RPC) subsystem in
+the Linux kernel. This stuff is used for NFS, KNFSD and
+maybe a few other things as well.
+
+The files in there are used to control the debugging flags:
+rpc_debug, nfs_debug, nfsd_debug and nlm_debug.
+
+These flags are for kernel hackers only. You should read the
+source code in net/sunrpc/ for more information.
diff --git a/Documentation/admin-guide/sysctl/user.rst b/Documentation/admin-guide/sysctl/user.rst
new file mode 100644
index 0000000000..c458245893
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/user.rst
@@ -0,0 +1,84 @@
+=================================
+Documentation for /proc/sys/user/
+=================================
+
+kernel version 4.9.0
+
+Copyright (c) 2016		Eric Biederman <ebiederm@xmission.com>
+
+------------------------------------------------------------------------------
+
+This file contains the documentation for the sysctl files in
+/proc/sys/user.
+
+The files in this directory can be used to override the default
+limits on the number of namespaces and other objects that have
+per user per user namespace limits.
+
+The primary purpose of these limits is to stop programs that
+malfunction and attempt to create a ridiculous number of objects,
+before the malfunction becomes a system wide problem.  It is the
+intention that the defaults of these limits are set high enough that
+no program in normal operation should run into these limits.
+
+The creation of per user per user namespace objects are charged to
+the user in the user namespace who created the object and
+verified to be below the per user limit in that user namespace.
+
+The creation of objects is also charged to all of the users
+who created user namespaces the creation of the object happens
+in (user namespaces can be nested) and verified to be below the per user
+limits in the user namespaces of those users.
+
+This recursive counting of created objects ensures that creating a
+user namespace does not allow a user to escape their current limits.
+
+Currently, these files are in /proc/sys/user:
+
+max_cgroup_namespaces
+=====================
+
+  The maximum number of cgroup namespaces that any user in the current
+  user namespace may create.
+
+max_ipc_namespaces
+==================
+
+  The maximum number of ipc namespaces that any user in the current
+  user namespace may create.
+
+max_mnt_namespaces
+==================
+
+  The maximum number of mount namespaces that any user in the current
+  user namespace may create.
+
+max_net_namespaces
+==================
+
+  The maximum number of network namespaces that any user in the
+  current user namespace may create.
+
+max_pid_namespaces
+==================
+
+  The maximum number of pid namespaces that any user in the current
+  user namespace may create.
+
+max_time_namespaces
+===================
+
+  The maximum number of time namespaces that any user in the current
+  user namespace may create.
+
+max_user_namespaces
+===================
+
+  The maximum number of user namespaces that any user in the current
+  user namespace may create.
+
+max_uts_namespaces
+==================
+
+  The maximum number of user namespaces that any user in the current
+  user namespace may create.
diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
new file mode 100644
index 0000000000..45ba1f4dc0
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -0,0 +1,1046 @@
+===============================
+Documentation for /proc/sys/vm/
+===============================
+
+kernel version 2.6.29
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+Copyright (c) 2008         Peter W. Morreale <pmorreale@novell.com>
+
+For general info and legal blurb, please look in index.rst.
+
+------------------------------------------------------------------------------
+
+This file contains the documentation for the sysctl files in
+/proc/sys/vm and is valid for Linux kernel version 2.6.29.
+
+The files in this directory can be used to tune the operation
+of the virtual memory (VM) subsystem of the Linux kernel and
+the writeout of dirty data to disk.
+
+Default values and initialization routines for most of these
+files can be found in mm/swap.c.
+
+Currently, these files are in /proc/sys/vm:
+
+- admin_reserve_kbytes
+- compact_memory
+- compaction_proactiveness
+- compact_unevictable_allowed
+- dirty_background_bytes
+- dirty_background_ratio
+- dirty_bytes
+- dirty_expire_centisecs
+- dirty_ratio
+- dirtytime_expire_seconds
+- dirty_writeback_centisecs
+- drop_caches
+- extfrag_threshold
+- highmem_is_dirtyable
+- hugetlb_shm_group
+- laptop_mode
+- legacy_va_layout
+- lowmem_reserve_ratio
+- max_map_count
+- memory_failure_early_kill
+- memory_failure_recovery
+- min_free_kbytes
+- min_slab_ratio
+- min_unmapped_ratio
+- mmap_min_addr
+- mmap_rnd_bits
+- mmap_rnd_compat_bits
+- nr_hugepages
+- nr_hugepages_mempolicy
+- nr_overcommit_hugepages
+- nr_trim_pages         (only if CONFIG_MMU=n)
+- numa_zonelist_order
+- oom_dump_tasks
+- oom_kill_allocating_task
+- overcommit_kbytes
+- overcommit_memory
+- overcommit_ratio
+- page-cluster
+- page_lock_unfairness
+- panic_on_oom
+- percpu_pagelist_high_fraction
+- stat_interval
+- stat_refresh
+- numa_stat
+- swappiness
+- unprivileged_userfaultfd
+- user_reserve_kbytes
+- vfs_cache_pressure
+- watermark_boost_factor
+- watermark_scale_factor
+- zone_reclaim_mode
+
+
+admin_reserve_kbytes
+====================
+
+The amount of free memory in the system that should be reserved for users
+with the capability cap_sys_admin.
+
+admin_reserve_kbytes defaults to min(3% of free pages, 8MB)
+
+That should provide enough for the admin to log in and kill a process,
+if necessary, under the default overcommit 'guess' mode.
+
+Systems running under overcommit 'never' should increase this to account
+for the full Virtual Memory Size of programs used to recover. Otherwise,
+root may not be able to log in to recover the system.
+
+How do you calculate a minimum useful reserve?
+
+sshd or login + bash (or some other shell) + top (or ps, kill, etc.)
+
+For overcommit 'guess', we can sum resident set sizes (RSS).
+On x86_64 this is about 8MB.
+
+For overcommit 'never', we can take the max of their virtual sizes (VSZ)
+and add the sum of their RSS.
+On x86_64 this is about 128MB.
+
+Changing this takes effect whenever an application requests memory.
+
+
+compact_memory
+==============
+
+Available only when CONFIG_COMPACTION is set. When 1 is written to the file,
+all zones are compacted such that free memory is available in contiguous
+blocks where possible. This can be important for example in the allocation of
+huge pages although processes will also directly compact memory as required.
+
+compaction_proactiveness
+========================
+
+This tunable takes a value in the range [0, 100] with a default value of
+20. This tunable determines how aggressively compaction is done in the
+background. Write of a non zero value to this tunable will immediately
+trigger the proactive compaction. Setting it to 0 disables proactive compaction.
+
+Note that compaction has a non-trivial system-wide impact as pages
+belonging to different processes are moved around, which could also lead
+to latency spikes in unsuspecting applications. The kernel employs
+various heuristics to avoid wasting CPU cycles if it detects that
+proactive compaction is not being effective.
+
+Be careful when setting it to extreme values like 100, as that may
+cause excessive background compaction activity.
+
+compact_unevictable_allowed
+===========================
+
+Available only when CONFIG_COMPACTION is set. When set to 1, compaction is
+allowed to examine the unevictable lru (mlocked pages) for pages to compact.
+This should be used on systems where stalls for minor page faults are an
+acceptable trade for large contiguous free memory.  Set to 0 to prevent
+compaction from moving pages that are unevictable.  Default value is 1.
+On CONFIG_PREEMPT_RT the default value is 0 in order to avoid a page fault, due
+to compaction, which would block the task from becoming active until the fault
+is resolved.
+
+
+dirty_background_bytes
+======================
+
+Contains the amount of dirty memory at which the background kernel
+flusher threads will start writeback.
+
+Note:
+  dirty_background_bytes is the counterpart of dirty_background_ratio. Only
+  one of them may be specified at a time. When one sysctl is written it is
+  immediately taken into account to evaluate the dirty memory limits and the
+  other appears as 0 when read.
+
+
+dirty_background_ratio
+======================
+
+Contains, as a percentage of total available memory that contains free pages
+and reclaimable pages, the number of pages at which the background kernel
+flusher threads will start writing out dirty data.
+
+The total available memory is not equal to total system memory.
+
+
+dirty_bytes
+===========
+
+Contains the amount of dirty memory at which a process generating disk writes
+will itself start writeback.
+
+Note: dirty_bytes is the counterpart of dirty_ratio. Only one of them may be
+specified at a time. When one sysctl is written it is immediately taken into
+account to evaluate the dirty memory limits and the other appears as 0 when
+read.
+
+Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any
+value lower than this limit will be ignored and the old configuration will be
+retained.
+
+
+dirty_expire_centisecs
+======================
+
+This tunable is used to define when dirty data is old enough to be eligible
+for writeout by the kernel flusher threads.  It is expressed in 100'ths
+of a second.  Data which has been dirty in-memory for longer than this
+interval will be written out next time a flusher thread wakes up.
+
+
+dirty_ratio
+===========
+
+Contains, as a percentage of total available memory that contains free pages
+and reclaimable pages, the number of pages at which a process which is
+generating disk writes will itself start writing out dirty data.
+
+The total available memory is not equal to total system memory.
+
+
+dirtytime_expire_seconds
+========================
+
+When a lazytime inode is constantly having its pages dirtied, the inode with
+an updated timestamp will never get chance to be written out.  And, if the
+only thing that has happened on the file system is a dirtytime inode caused
+by an atime update, a worker will be scheduled to make sure that inode
+eventually gets pushed out to disk.  This tunable is used to define when dirty
+inode is old enough to be eligible for writeback by the kernel flusher threads.
+And, it is also used as the interval to wakeup dirtytime_writeback thread.
+
+
+dirty_writeback_centisecs
+=========================
+
+The kernel flusher threads will periodically wake up and write `old` data
+out to disk.  This tunable expresses the interval between those wakeups, in
+100'ths of a second.
+
+Setting this to zero disables periodic writeback altogether.
+
+
+drop_caches
+===========
+
+Writing to this will cause the kernel to drop clean caches, as well as
+reclaimable slab objects like dentries and inodes.  Once dropped, their
+memory becomes free.
+
+To free pagecache::
+
+	echo 1 > /proc/sys/vm/drop_caches
+
+To free reclaimable slab objects (includes dentries and inodes)::
+
+	echo 2 > /proc/sys/vm/drop_caches
+
+To free slab objects and pagecache::
+
+	echo 3 > /proc/sys/vm/drop_caches
+
+This is a non-destructive operation and will not free any dirty objects.
+To increase the number of objects freed by this operation, the user may run
+`sync` prior to writing to /proc/sys/vm/drop_caches.  This will minimize the
+number of dirty objects on the system and create more candidates to be
+dropped.
+
+This file is not a means to control the growth of the various kernel caches
+(inodes, dentries, pagecache, etc...)  These objects are automatically
+reclaimed by the kernel when memory is needed elsewhere on the system.
+
+Use of this file can cause performance problems.  Since it discards cached
+objects, it may cost a significant amount of I/O and CPU to recreate the
+dropped objects, especially if they were under heavy use.  Because of this,
+use outside of a testing or debugging environment is not recommended.
+
+You may see informational messages in your kernel log when this file is
+used::
+
+	cat (1234): drop_caches: 3
+
+These are informational only.  They do not mean that anything is wrong
+with your system.  To disable them, echo 4 (bit 2) into drop_caches.
+
+
+extfrag_threshold
+=================
+
+This parameter affects whether the kernel will compact memory or direct
+reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in
+debugfs shows what the fragmentation index for each order is in each zone in
+the system. Values tending towards 0 imply allocations would fail due to lack
+of memory, values towards 1000 imply failures are due to fragmentation and -1
+implies that the allocation will succeed as long as watermarks are met.
+
+The kernel will not compact memory in a zone if the
+fragmentation index is <= extfrag_threshold. The default value is 500.
+
+
+highmem_is_dirtyable
+====================
+
+Available only for systems with CONFIG_HIGHMEM enabled (32b systems).
+
+This parameter controls whether the high memory is considered for dirty
+writers throttling.  This is not the case by default which means that
+only the amount of memory directly visible/usable by the kernel can
+be dirtied. As a result, on systems with a large amount of memory and
+lowmem basically depleted writers might be throttled too early and
+streaming writes can get very slow.
+
+Changing the value to non zero would allow more memory to be dirtied
+and thus allow writers to write more data which can be flushed to the
+storage more effectively. Note this also comes with a risk of pre-mature
+OOM killer because some writers (e.g. direct block device writes) can
+only use the low memory and they can fill it up with dirty data without
+any throttling.
+
+
+hugetlb_shm_group
+=================
+
+hugetlb_shm_group contains group id that is allowed to create SysV
+shared memory segment using hugetlb page.
+
+
+laptop_mode
+===========
+
+laptop_mode is a knob that controls "laptop mode". All the things that are
+controlled by this knob are discussed in Documentation/admin-guide/laptops/laptop-mode.rst.
+
+
+legacy_va_layout
+================
+
+If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel
+will use the legacy (2.4) layout for all processes.
+
+
+lowmem_reserve_ratio
+====================
+
+For some specialised workloads on highmem machines it is dangerous for
+the kernel to allow process memory to be allocated from the "lowmem"
+zone.  This is because that memory could then be pinned via the mlock()
+system call, or by unavailability of swapspace.
+
+And on large highmem machines this lack of reclaimable lowmem memory
+can be fatal.
+
+So the Linux page allocator has a mechanism which prevents allocations
+which *could* use highmem from using too much lowmem.  This means that
+a certain amount of lowmem is defended from the possibility of being
+captured into pinned user memory.
+
+(The same argument applies to the old 16 megabyte ISA DMA region.  This
+mechanism will also defend that region from allocations which could use
+highmem or lowmem).
+
+The `lowmem_reserve_ratio` tunable determines how aggressive the kernel is
+in defending these lower zones.
+
+If you have a machine which uses highmem or ISA DMA and your
+applications are using mlock(), or if you are running with no swap then
+you probably should change the lowmem_reserve_ratio setting.
+
+The lowmem_reserve_ratio is an array. You can see them by reading this file::
+
+	% cat /proc/sys/vm/lowmem_reserve_ratio
+	256     256     32
+
+But, these values are not used directly. The kernel calculates # of protection
+pages for each zones from them. These are shown as array of protection pages
+in /proc/zoneinfo like the following. (This is an example of x86-64 box).
+Each zone has an array of protection pages like this::
+
+  Node 0, zone      DMA
+    pages free     1355
+          min      3
+          low      3
+          high     4
+	:
+	:
+      numa_other   0
+          protection: (0, 2004, 2004, 2004)
+	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    pagesets
+      cpu: 0 pcp: 0
+          :
+
+These protections are added to score to judge whether this zone should be used
+for page allocation or should be reclaimed.
+
+In this example, if normal pages (index=2) are required to this DMA zone and
+watermark[WMARK_HIGH] is used for watermark, the kernel judges this zone should
+not be used because pages_free(1355) is smaller than watermark + protection[2]
+(4 + 2004 = 2008). If this protection value is 0, this zone would be used for
+normal page requirement. If requirement is DMA zone(index=0), protection[0]
+(=0) is used.
+
+zone[i]'s protection[j] is calculated by following expression::
+
+  (i < j):
+    zone[i]->protection[j]
+    = (total sums of managed_pages from zone[i+1] to zone[j] on the node)
+      / lowmem_reserve_ratio[i];
+  (i = j):
+     (should not be protected. = 0;
+  (i > j):
+     (not necessary, but looks 0)
+
+The default values of lowmem_reserve_ratio[i] are
+
+    === ====================================
+    256 (if zone[i] means DMA or DMA32 zone)
+    32  (others)
+    === ====================================
+
+As above expression, they are reciprocal number of ratio.
+256 means 1/256. # of protection pages becomes about "0.39%" of total managed
+pages of higher zones on the node.
+
+If you would like to protect more pages, smaller values are effective.
+The minimum value is 1 (1/1 -> 100%). The value less than 1 completely
+disables protection of the pages.
+
+
+max_map_count:
+==============
+
+This file contains the maximum number of memory map areas a process
+may have. Memory map areas are used as a side-effect of calling
+malloc, directly by mmap, mprotect, and madvise, and also when loading
+shared libraries.
+
+While most applications need less than a thousand maps, certain
+programs, particularly malloc debuggers, may consume lots of them,
+e.g., up to one or two maps per allocation.
+
+The default value is 65530.
+
+
+memory_failure_early_kill:
+==========================
+
+Control how to kill processes when uncorrected memory error (typically
+a 2bit error in a memory module) is detected in the background by hardware
+that cannot be handled by the kernel. 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 to prevent any data
+corruptions from propagating.
+
+1: Kill all processes that have the corrupted and not reloadable page mapped
+as soon as the corruption is detected.  Note this is not supported
+for a few types of pages, like kernel internally allocated data or
+the swap cache, but works for the majority of user pages.
+
+0: Only unmap the corrupted page from all processes and only kill a process
+who tries to access it.
+
+The kill is done using a catchable SIGBUS with BUS_MCEERR_AO, so processes can
+handle this if they want to.
+
+This is only active on architectures/platforms with advanced machine
+check handling and depends on the hardware capabilities.
+
+Applications can override this setting individually with the PR_MCE_KILL prctl
+
+
+memory_failure_recovery
+=======================
+
+Enable memory failure recovery (when supported by the platform)
+
+1: Attempt recovery.
+
+0: Always panic on a memory failure.
+
+
+min_free_kbytes
+===============
+
+This is used to force the Linux VM to keep a minimum number
+of kilobytes free.  The VM uses this number to compute a
+watermark[WMARK_MIN] value for each lowmem zone in the system.
+Each lowmem zone gets a number of reserved free pages based
+proportionally on its size.
+
+Some minimal amount of memory is needed to satisfy PF_MEMALLOC
+allocations; if you set this to lower than 1024KB, your system will
+become subtly broken, and prone to deadlock under high loads.
+
+Setting this too high will OOM your machine instantly.
+
+
+min_slab_ratio
+==============
+
+This is available only on NUMA kernels.
+
+A percentage of the total pages in each zone.  On Zone reclaim
+(fallback from the local zone occurs) slabs will be reclaimed if more
+than this percentage of pages in a zone are reclaimable slab pages.
+This insures that the slab growth stays under control even in NUMA
+systems that rarely perform global reclaim.
+
+The default is 5 percent.
+
+Note that slab reclaim is triggered in a per zone / node fashion.
+The process of reclaiming slab memory is currently not node specific
+and may not be fast.
+
+
+min_unmapped_ratio
+==================
+
+This is available only on NUMA kernels.
+
+This is a percentage of the total pages in each zone. Zone reclaim will
+only occur if more than this percentage of pages are in a state that
+zone_reclaim_mode allows to be reclaimed.
+
+If zone_reclaim_mode has the value 4 OR'd, then the percentage is compared
+against all file-backed unmapped pages including swapcache pages and tmpfs
+files. Otherwise, only unmapped pages backed by normal files but not tmpfs
+files and similar are considered.
+
+The default is 1 percent.
+
+
+mmap_min_addr
+=============
+
+This file indicates the amount of address space  which a user process will
+be restricted from mmapping.  Since kernel null dereference bugs could
+accidentally operate based on the information in the first couple of pages
+of memory userspace processes should not be allowed to write to them.  By
+default this value is set to 0 and no protections will be enforced by the
+security module.  Setting this value to something like 64k will allow the
+vast majority of applications to work correctly and provide defense in depth
+against future potential kernel bugs.
+
+
+mmap_rnd_bits
+=============
+
+This value can be used to select the number of bits to use to
+determine the random offset to the base address of vma regions
+resulting from mmap allocations on architectures which support
+tuning address space randomization.  This value will be bounded
+by the architecture's minimum and maximum supported values.
+
+This value can be changed after boot using the
+/proc/sys/vm/mmap_rnd_bits tunable
+
+
+mmap_rnd_compat_bits
+====================
+
+This value can be used to select the number of bits to use to
+determine the random offset to the base address of vma regions
+resulting from mmap allocations for applications run in
+compatibility mode on architectures which support tuning address
+space randomization.  This value will be bounded by the
+architecture's minimum and maximum supported values.
+
+This value can be changed after boot using the
+/proc/sys/vm/mmap_rnd_compat_bits tunable
+
+
+nr_hugepages
+============
+
+Change the minimum size of the hugepage pool.
+
+See Documentation/admin-guide/mm/hugetlbpage.rst
+
+
+hugetlb_optimize_vmemmap
+========================
+
+This knob is not available when the size of 'struct page' (a structure defined
+in include/linux/mm_types.h) is not power of two (an unusual system config could
+result in this).
+
+Enable (set to 1) or disable (set to 0) HugeTLB Vmemmap Optimization (HVO).
+
+Once enabled, the vmemmap pages of subsequent allocation of HugeTLB pages from
+buddy allocator will be optimized (7 pages per 2MB HugeTLB page and 4095 pages
+per 1GB HugeTLB page), whereas already allocated HugeTLB pages will not be
+optimized.  When those optimized HugeTLB pages are freed from the HugeTLB pool
+to the buddy allocator, the vmemmap pages representing that range needs to be
+remapped again and the vmemmap pages discarded earlier need to be rellocated
+again.  If your use case is that HugeTLB pages are allocated 'on the fly' (e.g.
+never explicitly allocating HugeTLB pages with 'nr_hugepages' but only set
+'nr_overcommit_hugepages', those overcommitted HugeTLB pages are allocated 'on
+the fly') instead of being pulled from the HugeTLB pool, you should weigh the
+benefits of memory savings against the more overhead (~2x slower than before)
+of allocation or freeing HugeTLB pages between the HugeTLB pool and the buddy
+allocator.  Another behavior to note is that if the system is under heavy memory
+pressure, it could prevent the user from freeing HugeTLB pages from the HugeTLB
+pool to the buddy allocator since the allocation of vmemmap pages could be
+failed, you have to retry later if your system encounter this situation.
+
+Once disabled, the vmemmap pages of subsequent allocation of HugeTLB pages from
+buddy allocator will not be optimized meaning the extra overhead at allocation
+time from buddy allocator disappears, whereas already optimized HugeTLB pages
+will not be affected.  If you want to make sure there are no optimized HugeTLB
+pages, you can set "nr_hugepages" to 0 first and then disable this.  Note that
+writing 0 to nr_hugepages will make any "in use" HugeTLB pages become surplus
+pages.  So, those surplus pages are still optimized until they are no longer
+in use.  You would need to wait for those surplus pages to be released before
+there are no optimized pages in the system.
+
+
+nr_hugepages_mempolicy
+======================
+
+Change the size of the hugepage pool at run-time on a specific
+set of NUMA nodes.
+
+See Documentation/admin-guide/mm/hugetlbpage.rst
+
+
+nr_overcommit_hugepages
+=======================
+
+Change the maximum size of the hugepage pool. The maximum is
+nr_hugepages + nr_overcommit_hugepages.
+
+See Documentation/admin-guide/mm/hugetlbpage.rst
+
+
+nr_trim_pages
+=============
+
+This is available only on NOMMU kernels.
+
+This value adjusts the excess page trimming behaviour of power-of-2 aligned
+NOMMU mmap allocations.
+
+A value of 0 disables trimming of allocations entirely, while a value of 1
+trims excess pages aggressively. Any value >= 1 acts as the watermark where
+trimming of allocations is initiated.
+
+The default value is 1.
+
+See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
+
+
+numa_zonelist_order
+===================
+
+This sysctl is only for NUMA and it is deprecated. Anything but
+Node order will fail!
+
+'where the memory is allocated from' is controlled by zonelists.
+
+(This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation.
+you may be able to read ZONE_DMA as ZONE_DMA32...)
+
+In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following.
+ZONE_NORMAL -> ZONE_DMA
+This means that a memory allocation request for GFP_KERNEL will
+get memory from ZONE_DMA only when ZONE_NORMAL is not available.
+
+In NUMA case, you can think of following 2 types of order.
+Assume 2 node NUMA and below is zonelist of Node(0)'s GFP_KERNEL::
+
+  (A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL
+  (B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
+
+Type(A) offers the best locality for processes on Node(0), but ZONE_DMA
+will be used before ZONE_NORMAL exhaustion. This increases possibility of
+out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small.
+
+Type(B) cannot offer the best locality but is more robust against OOM of
+the DMA zone.
+
+Type(A) is called as "Node" order. Type (B) is "Zone" order.
+
+"Node order" orders the zonelists by node, then by zone within each node.
+Specify "[Nn]ode" for node order
+
+"Zone Order" orders the zonelists by zone type, then by node within each
+zone.  Specify "[Zz]one" for zone order.
+
+Specify "[Dd]efault" to request automatic configuration.
+
+On 32-bit, the Normal zone needs to be preserved for allocations accessible
+by the kernel, so "zone" order will be selected.
+
+On 64-bit, devices that require DMA32/DMA are relatively rare, so "node"
+order will be selected.
+
+Default order is recommended unless this is causing problems for your
+system/application.
+
+
+oom_dump_tasks
+==============
+
+Enables a system-wide task dump (excluding kernel threads) to be produced
+when the kernel performs an OOM-killing and includes such information as
+pid, uid, tgid, vm size, rss, pgtables_bytes, swapents, oom_score_adj
+score, and name.  This is helpful to determine why the OOM killer was
+invoked, to identify the rogue task that caused it, and to determine why
+the OOM killer chose the task it did to kill.
+
+If this is set to 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 conditions when the
+information may not be desired.
+
+If this is set to non-zero, this information is shown whenever the
+OOM killer actually kills a memory-hogging task.
+
+The default value is 1 (enabled).
+
+
+oom_kill_allocating_task
+========================
+
+This enables or disables killing the OOM-triggering task in
+out-of-memory situations.
+
+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.
+
+If this is set to non-zero, the OOM killer simply kills the task that
+triggered the out-of-memory condition.  This avoids the expensive
+tasklist scan.
+
+If panic_on_oom is selected, it takes precedence over whatever value
+is used in oom_kill_allocating_task.
+
+The default value is 0.
+
+
+overcommit_kbytes
+=================
+
+When overcommit_memory is set to 2, the committed address space is not
+permitted to exceed swap plus this amount of physical RAM. See below.
+
+Note: overcommit_kbytes is the counterpart of overcommit_ratio. Only one
+of them may be specified at a time. Setting one disables the other (which
+then appears as 0 when read).
+
+
+overcommit_memory
+=================
+
+This value contains a flag that enables memory overcommitment.
+
+When this flag is 0, the kernel attempts to estimate the amount
+of free memory left when userspace requests more memory.
+
+When this flag is 1, the kernel pretends there is always enough
+memory until it actually runs out.
+
+When this flag is 2, the kernel uses a "never overcommit"
+policy that attempts to prevent any overcommit of memory.
+Note that user_reserve_kbytes affects this policy.
+
+This feature can be very useful because there are a lot of
+programs that malloc() huge amounts of memory "just-in-case"
+and don't use much of it.
+
+The default value is 0.
+
+See Documentation/mm/overcommit-accounting.rst and
+mm/util.c::__vm_enough_memory() for more information.
+
+
+overcommit_ratio
+================
+
+When overcommit_memory is set to 2, the committed address
+space is not permitted to exceed swap plus this percentage
+of physical RAM.  See above.
+
+
+page-cluster
+============
+
+page-cluster controls the number of pages up to which consecutive pages
+are read in from swap in a single attempt. This is the swap counterpart
+to page cache readahead.
+The mentioned consecutivity is not in terms of virtual/physical addresses,
+but consecutive on swap space - that means they were swapped out together.
+
+It is a logarithmic value - setting it to zero means "1 page", setting
+it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
+Zero disables swap readahead completely.
+
+The default value is three (eight pages at a time).  There may be some
+small benefits in tuning this to a different value if your workload is
+swap-intensive.
+
+Lower values mean lower latencies for initial faults, but at the same time
+extra faults and I/O delays for following faults if they would have been part of
+that consecutive pages readahead would have brought in.
+
+
+page_lock_unfairness
+====================
+
+This value determines the number of times that the page lock can be
+stolen from under a waiter. After the lock is stolen the number of times
+specified in this file (default is 5), the "fair lock handoff" semantics
+will apply, and the waiter will only be awakened if the lock can be taken.
+
+panic_on_oom
+============
+
+This enables or disables panic on out-of-memory feature.
+
+If this is set to 0, the kernel will kill some rogue process,
+called oom_killer.  Usually, oom_killer can kill rogue processes and
+system will survive.
+
+If this is set to 1, the kernel panics when out-of-memory happens.
+However, if a process limits using nodes by mempolicy/cpusets,
+and those nodes become memory exhaustion status, one process
+may be killed by oom-killer. No panic occurs in this case.
+Because other nodes' memory may be free. This means system total status
+may be not fatal yet.
+
+If this is set to 2, the kernel panics compulsorily even on the
+above-mentioned. Even oom happens under memory cgroup, the whole
+system panics.
+
+The default value is 0.
+
+1 and 2 are for failover of clustering. Please select either
+according to your policy of failover.
+
+panic_on_oom=2+kdump gives you very strong tool to investigate
+why oom happens. You can get snapshot.
+
+
+percpu_pagelist_high_fraction
+=============================
+
+This is the fraction of pages in each zone that are can be stored to
+per-cpu page lists. It is an upper boundary that is divided depending
+on the number of online CPUs. The min value for this is 8 which means
+that we do not allow more than 1/8th of pages in each zone to be stored
+on per-cpu page lists. This entry only changes the value of hot per-cpu
+page lists. A user can specify a number like 100 to allocate 1/100th of
+each zone between per-cpu lists.
+
+The batch value of each per-cpu page list remains the same regardless of
+the value of the high fraction so allocation latencies are unaffected.
+
+The initial value is zero. Kernel uses this value to set the high pcp->high
+mark based on the low watermark for the zone and the number of local
+online CPUs.  If the user writes '0' to this sysctl, it will revert to
+this default behavior.
+
+
+stat_interval
+=============
+
+The time interval between which vm statistics are updated.  The default
+is 1 second.
+
+
+stat_refresh
+============
+
+Any read or write (by root only) flushes all the per-cpu vm statistics
+into their global totals, for more accurate reports when testing
+e.g. cat /proc/sys/vm/stat_refresh /proc/meminfo
+
+As a side-effect, it also checks for negative totals (elsewhere reported
+as 0) and "fails" with EINVAL if any are found, with a warning in dmesg.
+(At time of writing, a few stats are known sometimes to be found negative,
+with no ill effects: errors and warnings on these stats are suppressed.)
+
+
+numa_stat
+=========
+
+This interface allows runtime configuration of numa statistics.
+
+When page allocation performance becomes a bottleneck and you can tolerate
+some possible tool breakage and decreased numa counter precision, you can
+do::
+
+	echo 0 > /proc/sys/vm/numa_stat
+
+When page allocation performance is not a bottleneck and you want all
+tooling to work, you can do::
+
+	echo 1 > /proc/sys/vm/numa_stat
+
+
+swappiness
+==========
+
+This control is used to define the rough relative IO cost of swapping
+and filesystem paging, as a value between 0 and 200. At 100, the VM
+assumes equal IO cost and will thus apply memory pressure to the page
+cache and swap-backed pages equally; lower values signify more
+expensive swap IO, higher values indicates cheaper.
+
+Keep in mind that filesystem IO patterns under memory pressure tend to
+be more efficient than swap's random IO. An optimal value will require
+experimentation and will also be workload-dependent.
+
+The default value is 60.
+
+For in-memory swap, like zram or zswap, as well as hybrid setups that
+have swap on faster devices than the filesystem, values beyond 100 can
+be considered. For example, if the random IO against the swap device
+is on average 2x faster than IO from the filesystem, swappiness should
+be 133 (x + 2x = 200, 2x = 133.33).
+
+At 0, the kernel will not initiate swap until the amount of free and
+file-backed pages is less than the high watermark in a zone.
+
+
+unprivileged_userfaultfd
+========================
+
+This flag controls the mode in which unprivileged users can use the
+userfaultfd system calls. Set this to 0 to restrict unprivileged users
+to handle page faults in user mode only. In this case, users without
+SYS_CAP_PTRACE must pass UFFD_USER_MODE_ONLY in order for userfaultfd to
+succeed. Prohibiting use of userfaultfd for handling faults from kernel
+mode may make certain vulnerabilities more difficult to exploit.
+
+Set this to 1 to allow unprivileged users to use the userfaultfd system
+calls without any restrictions.
+
+The default value is 0.
+
+Another way to control permissions for userfaultfd is to use
+/dev/userfaultfd instead of userfaultfd(2). See
+Documentation/admin-guide/mm/userfaultfd.rst.
+
+user_reserve_kbytes
+===================
+
+When overcommit_memory is set to 2, "never overcommit" mode, reserve
+min(3% of current process size, user_reserve_kbytes) of free memory.
+This is intended to prevent a user from starting a single memory hogging
+process, such that they cannot recover (kill the hog).
+
+user_reserve_kbytes defaults to min(3% of the current process size, 128MB).
+
+If this is reduced to zero, then the user will be allowed to allocate
+all free memory with a single process, minus admin_reserve_kbytes.
+Any subsequent attempts to execute a command will result in
+"fork: Cannot allocate memory".
+
+Changing this takes effect whenever an application requests memory.
+
+
+vfs_cache_pressure
+==================
+
+This percentage value controls the tendency of the kernel to reclaim
+the memory which is used for caching of directory and inode objects.
+
+At the default value of vfs_cache_pressure=100 the kernel will attempt to
+reclaim dentries and inodes at a "fair" rate with respect to pagecache and
+swapcache reclaim.  Decreasing vfs_cache_pressure causes the kernel to prefer
+to retain dentry and inode caches. When vfs_cache_pressure=0, the kernel will
+never reclaim dentries and inodes due to memory pressure and this can easily
+lead to out-of-memory conditions. Increasing vfs_cache_pressure beyond 100
+causes the kernel to prefer to reclaim dentries and inodes.
+
+Increasing vfs_cache_pressure significantly beyond 100 may have negative
+performance impact. Reclaim code needs to take various locks to find freeable
+directory and inode objects. With vfs_cache_pressure=1000, it will look for
+ten times more freeable objects than there are.
+
+
+watermark_boost_factor
+======================
+
+This factor controls the level of reclaim when memory is being fragmented.
+It defines the percentage of the high watermark of a zone that will be
+reclaimed if pages of different mobility are being mixed within pageblocks.
+The intent is that compaction has less work to do in the future and to
+increase the success rate of future high-order allocations such as SLUB
+allocations, THP and hugetlbfs pages.
+
+To make it sensible with respect to the watermark_scale_factor
+parameter, the unit is in fractions of 10,000. The default value of
+15,000 means that up to 150% of the high watermark will be reclaimed in the
+event of a pageblock being mixed due to fragmentation. The level of reclaim
+is determined by the number of fragmentation events that occurred in the
+recent past. If this value is smaller than a pageblock then a pageblocks
+worth of pages will be reclaimed (e.g.  2MB on 64-bit x86). A boost factor
+of 0 will disable the feature.
+
+
+watermark_scale_factor
+======================
+
+This factor controls the aggressiveness of kswapd. It defines the
+amount of memory left in a node/system before kswapd is woken up and
+how much memory needs to be free before kswapd goes back to sleep.
+
+The unit is in fractions of 10,000. The default value of 10 means the
+distances between watermarks are 0.1% of the available memory in the
+node/system. The maximum value is 3000, or 30% of memory.
+
+A high rate of threads entering direct reclaim (allocstall) or kswapd
+going to sleep prematurely (kswapd_low_wmark_hit_quickly) can indicate
+that the number of free pages kswapd maintains for latency reasons is
+too small for the allocation bursts occurring in the system. This knob
+can then be used to tune kswapd aggressiveness accordingly.
+
+
+zone_reclaim_mode
+=================
+
+Zone_reclaim_mode allows someone to set more or less aggressive approaches to
+reclaim memory when a zone runs out of memory. If it is set to zero then no
+zone reclaim occurs. Allocations will be satisfied from other zones / nodes
+in the system.
+
+This is value OR'ed together of
+
+=	===================================
+1	Zone reclaim on
+2	Zone reclaim writes dirty pages out
+4	Zone reclaim swaps pages
+=	===================================
+
+zone_reclaim_mode is disabled by default.  For file servers or workloads
+that benefit from having their data cached, zone_reclaim_mode should be
+left disabled as the caching effect is likely to be more important than
+data locality.
+
+Consider enabling one or more zone_reclaim mode bits if it's known that the
+workload is partitioned such that each partition fits within a NUMA node
+and that accessing remote memory would cause a measurable performance
+reduction.  The page allocator will take additional actions before
+allocating off node pages.
+
+Allowing zone reclaim to write out pages stops processes that are
+writing large amounts of data from dirtying pages on other nodes. Zone
+reclaim will write out dirty pages if a zone fills up and so effectively
+throttle the process. This may decrease the performance of a single process
+since it cannot use all of system memory to buffer the outgoing writes
+anymore but it preserve the memory on other nodes so that the performance
+of other processes running on other nodes will not be affected.
+
+Allowing regular swap effectively restricts allocations to the local
+node unless explicitly overridden by memory policies or cpuset
+configurations.