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docs: sysctl: convert to ReST 

Rename the /proc/sys/ documentation files to ReST, using the
README file as a template for an index.rst, adding the other
files there via TOC markup.

Despite being written on different times with different
styles, try to make them somewhat coherent with a similar
look and feel, ensuring that they'll look nice as both
raw text file and as via the html output produced by the
Sphinx build system.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
alistair/sunxi64-5.4-dsi
Mauro Carvalho Chehab 2019-04-18 18:35:54 -03:00
parent 6baec31591
commit 53b9537509
17 changed files with 653 additions and 484 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/admin-guide/kernel-parameters.txt
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@ -3144,7 +3144,7 @@
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
'node', 'default' can be specified 'node', 'default' can be specified
This can be set from sysctl after boot. This can be set from sysctl after boot.
See Documentation/sysctl/vm.txt for details. See Documentation/sysctl/vm.rst for details.
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
See Documentation/debugging-via-ohci1394.txt for more See Documentation/debugging-via-ohci1394.txt for more

2
Documentation/admin-guide/mm/index.rst
View File

@ -11,7 +11,7 @@ processes address space and many other cool things.
Linux memory management is a complex system with many configurable Linux memory management is a complex system with many configurable
settings. Most of these settings are available via ``/proc`` settings. Most of these settings are available via ``/proc``
filesystem and can be quired and adjusted using ``sysctl``. These APIs filesystem and can be quired and adjusted using ``sysctl``. These APIs
are described in Documentation/sysctl/vm.txt and in `man 5 proc`_. are described in Documentation/sysctl/vm.rst and in `man 5 proc`_.
.. _man 5 proc: http://man7.org/linux/man-pages/man5/proc.5.html .. _man 5 proc: http://man7.org/linux/man-pages/man5/proc.5.html

2
Documentation/admin-guide/mm/ksm.rst
View File

@ -59,7 +59,7 @@ MADV_UNMERGEABLE is applied to a range which was never MADV_MERGEABLE.
If a region of memory must be split into at least one new MADV_MERGEABLE If a region of memory must be split into at least one new MADV_MERGEABLE
or MADV_UNMERGEABLE region, the madvise may return ENOMEM if the process or MADV_UNMERGEABLE region, the madvise may return ENOMEM if the process
will exceed ``vm.max_map_count`` (see Documentation/sysctl/vm.txt). will exceed ``vm.max_map_count`` (see Documentation/sysctl/vm.rst).
Like other madvise calls, they are intended for use on mapped areas of Like other madvise calls, they are intended for use on mapped areas of
the user address space: they will report ENOMEM if the specified range the user address space: they will report ENOMEM if the specified range

2
Documentation/core-api/printk-formats.rst
View File

@ -119,7 +119,7 @@ Kernel Pointers
For printing kernel pointers which should be hidden from unprivileged For printing kernel pointers which should be hidden from unprivileged
users. The behaviour of %pK depends on the kptr_restrict sysctl - see users. The behaviour of %pK depends on the kptr_restrict sysctl - see
Documentation/sysctl/kernel.txt for more details. Documentation/sysctl/kernel.rst for more details.
Unmodified Addresses Unmodified Addresses
-------------------- --------------------

2
Documentation/networking/ip-sysctl.txt
View File

@ -2287,7 +2287,7 @@ addr_scope_policy - INTEGER
/proc/sys/net/core/* /proc/sys/net/core/*
Please see: Documentation/sysctl/net.txt for descriptions of these entries. Please see: Documentation/sysctl/net.rst for descriptions of these entries.
/proc/sys/net/unix/* /proc/sys/net/unix/*

67
Documentation/sysctl/abi.rst 100644
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@ -0,0 +1,67 @@
================================
Documentation for /proc/sys/abi/
================================
kernel version 2.6.0.test2
Copyright (c) 2003, Fabian Frederick <ffrederick@users.sourceforge.net>
For general info: index.rst.
------------------------------------------------------------------------------
This path is binary emulation relevant aka personality types aka abi.
When a process is executed, it's linked to an exec_domain whose
personality is defined using values available from /proc/sys/abi.
You can find further details about abi in include/linux/personality.h.
Here are the files featuring in 2.6 kernel:
- defhandler_coff
- defhandler_elf
- defhandler_lcall7
- defhandler_libcso
- fake_utsname
- trace
defhandler_coff
---------------
defined value:
PER_SCOSVR3::
0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS | SHORT_INODE
defhandler_elf
--------------
defined value:
PER_LINUX::
0
defhandler_lcall7
-----------------
defined value :
PER_SVR4::
0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
defhandler_libsco
-----------------
defined value:
PER_SVR4::
0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
fake_utsname
------------
Unused
trace
-----
Unused

54
Documentation/sysctl/abi.txt
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@ -1,54 +0,0 @@
Documentation for /proc/sys/abi/* kernel version 2.6.0.test2
(c) 2003, Fabian Frederick <ffrederick@users.sourceforge.net>
For general info : README.
==============================================================
This path is binary emulation relevant aka personality types aka abi.
When a process is executed, it's linked to an exec_domain whose
personality is defined using values available from /proc/sys/abi.
You can find further details about abi in include/linux/personality.h.
Here are the files featuring in 2.6 kernel :
- defhandler_coff
- defhandler_elf
- defhandler_lcall7
- defhandler_libcso
- fake_utsname
- trace
===========================================================
defhandler_coff:
defined value :
PER_SCOSVR3
0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS | SHORT_INODE
===========================================================
defhandler_elf:
defined value :
PER_LINUX
0
===========================================================
defhandler_lcall7:
defined value :
PER_SVR4
0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
===========================================================
defhandler_libsco:
defined value:
PER_SVR4
0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
===========================================================
fake_utsname:
Unused
===========================================================
trace:
Unused
===========================================================

132
Documentation/sysctl/fs.txt → Documentation/sysctl/fs.rst
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@ -1,10 +1,16 @@
Documentation for /proc/sys/fs/* kernel version 2.2.10 ===============================
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org> Documentation for /proc/sys/fs/
(c) 2009, Shen Feng<shen@cn.fujitsu.com> ===============================
For general info and legal blurb, please look in README. kernel version 2.2.10
============================================================== 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 in This file contains documentation for the sysctl files in
/proc/sys/fs/ and is valid for Linux kernel version 2.2. /proc/sys/fs/ and is valid for Linux kernel version 2.2.
@ -16,9 +22,10 @@ system, it is advisable to read both documentation and source
before actually making adjustments. before actually making adjustments.
1. /proc/sys/fs 1. /proc/sys/fs
---------------------------------------------------------- ===============
Currently, these files are in /proc/sys/fs: Currently, these files are in /proc/sys/fs:
- aio-max-nr - aio-max-nr
- aio-nr - aio-nr
- dentry-state - dentry-state
@ -42,9 +49,9 @@ Currently, these files are in /proc/sys/fs:
- super-max - super-max
- super-nr - super-nr
==============================================================
aio-nr & aio-max-nr: aio-nr & aio-max-nr
-------------------
aio-nr is the running total of the number of events specified on the aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts. If aio-nr io_setup system call for all currently active aio contexts. If aio-nr
@ -52,12 +59,12 @@ reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures. of any kernel data structures.
==============================================================
dentry-state: dentry-state
------------
From linux/include/linux/dcache.h::
From linux/include/linux/dcache.h:
--------------------------------------------------------------
struct dentry_stat_t dentry_stat { struct dentry_stat_t dentry_stat {
int nr_dentry; int nr_dentry;
int nr_unused; int nr_unused;
@ -66,7 +73,6 @@ struct dentry_stat_t dentry_stat {
int nr_negative; /* # of unused negative dentries */ int nr_negative; /* # of unused negative dentries */
int dummy; /* Reserved for future use */ int dummy; /* Reserved for future use */
}; };
--------------------------------------------------------------
Dentries are dynamically allocated and deallocated. Dentries are dynamically allocated and deallocated.
@ -84,9 +90,9 @@ negative dentries which do not map to any files. Instead,
they help speeding up rejection of non-existing files provided they help speeding up rejection of non-existing files provided
by the users. by the users.
==============================================================
dquot-max & dquot-nr: dquot-max & dquot-nr
--------------------
The file dquot-max shows the maximum number of cached disk The file dquot-max shows the maximum number of cached disk
quota entries. quota entries.
@ -98,9 +104,9 @@ If the number of free cached disk quotas is very low and
you have some awesome number of simultaneous system users, you have some awesome number of simultaneous system users,
you might want to raise the limit. you might want to raise the limit.
==============================================================
file-max & file-nr: file-max & file-nr
------------------
The value in file-max denotes the maximum number of file- The value in file-max denotes the maximum number of file-
handles that the Linux kernel will allocate. When you get lots handles that the Linux kernel will allocate. When you get lots
@ -119,18 +125,19 @@ used file handles.
Attempts to allocate more file descriptors than file-max are Attempts to allocate more file descriptors than file-max are
reported with printk, look for "VFS: file-max limit <number> reported with printk, look for "VFS: file-max limit <number>
reached". reached".
==============================================================
nr_open:
nr_open
-------
This denotes the maximum number of file-handles a process can This denotes the maximum number of file-handles a process can
allocate. Default value is 1024*1024 (1048576) which should be allocate. Default value is 1024*1024 (1048576) which should be
enough for most machines. Actual limit depends on RLIMIT_NOFILE enough for most machines. Actual limit depends on RLIMIT_NOFILE
resource limit. resource limit.
==============================================================
inode-max, inode-nr & inode-state: inode-max, inode-nr & inode-state
---------------------------------
As with file handles, the kernel allocates the inode structures As with file handles, the kernel allocates the inode structures
dynamically, but can't free them yet. dynamically, but can't free them yet.
@ -157,9 +164,9 @@ preshrink is nonzero when the nr_inodes > inode-max and the
system needs to prune the inode list instead of allocating system needs to prune the inode list instead of allocating
more. more.
==============================================================
overflowgid & overflowuid: overflowgid & overflowuid
-------------------------
Some filesystems only support 16-bit UIDs and GIDs, although in Linux 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 UIDs and GIDs are 32 bits. When one of these filesystems is mounted
@ -169,18 +176,18 @@ to a fixed value before being written to disk.
These sysctls allow you to change the value of the fixed UID and GID. These sysctls allow you to change the value of the fixed UID and GID.
The default is 65534. The default is 65534.
==============================================================
pipe-user-pages-hard: pipe-user-pages-hard
--------------------
Maximum total number of pages a non-privileged user may allocate for pipes. 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 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 below the limit again. When set to 0, no limit is applied, which is the default
setting. setting.
==============================================================
pipe-user-pages-soft: pipe-user-pages-soft
--------------------
Maximum total number of pages a non-privileged user may allocate for pipes 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, before the pipe size gets limited to a single page. Once this limit is reached,
@ -190,9 +197,9 @@ 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 allocate up to 1024 pipes at their default size. When set to 0, no limit is
applied. applied.
==============================================================
protected_fifos: protected_fifos
---------------
The intent of this protection is to avoid unintentional writes to The intent of this protection is to avoid unintentional writes to
an attacker-controlled FIFO, where a program expected to create a regular an attacker-controlled FIFO, where a program expected to create a regular
@ -208,9 +215,9 @@ When set to "2" it also applies to group writable sticky directories.
This protection is based on the restrictions in Openwall. This protection is based on the restrictions in Openwall.
==============================================================
protected_hardlinks: protected_hardlinks
--------------------
A long-standing class of security issues is the hardlink-based A long-standing class of security issues is the hardlink-based
time-of-check-time-of-use race, most commonly seen in world-writable time-of-check-time-of-use race, most commonly seen in world-writable
@ -228,9 +235,9 @@ 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. This protection is based on the restrictions in Openwall and grsecurity.
==============================================================
protected_regular: protected_regular
-----------------
This protection is similar to protected_fifos, but it This protection is similar to protected_fifos, but it
avoids writes to an attacker-controlled regular file, where a program avoids writes to an attacker-controlled regular file, where a program
@ -244,9 +251,9 @@ owned by the owner of the directory.
When set to "2" it also applies to group writable sticky directories. When set to "2" it also applies to group writable sticky directories.
==============================================================
protected_symlinks: protected_symlinks
------------------
A long-standing class of security issues is the symlink-based A long-standing class of security issues is the symlink-based
time-of-check-time-of-use race, most commonly seen in world-writable time-of-check-time-of-use race, most commonly seen in world-writable
@ -264,34 +271,38 @@ follower match, or when the directory owner matches the symlink's owner.
This protection is based on the restrictions in Openwall and grsecurity. This protection is based on the restrictions in Openwall and grsecurity.
==============================================================
suid_dumpable: suid_dumpable:
--------------
This value can be used to query and set the core dump mode for setuid This value can be used to query and set the core dump mode for setuid
or otherwise protected/tainted binaries. The modes are or otherwise protected/tainted binaries. The modes are
0 - (default) - traditional behaviour. Any process which has changed = ========== ===============================================================
0 (default) traditional behaviour. Any process which has changed
privilege levels or is execute only will not be dumped. privilege levels or is execute only will not be dumped.
1 - (debug) - all processes dump core when possible. The core dump is 1 (debug) all processes dump core when possible. The core dump is
owned by the current user and no security is applied. This is owned by the current user and no security is applied. This is
intended for system debugging situations only. Ptrace is unchecked. intended for system debugging situations only.
This is insecure as it allows regular users to examine the memory Ptrace is unchecked.
contents of privileged processes. This is insecure as it allows regular users to examine the
2 - (suidsafe) - any binary which normally would not be dumped is dumped 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 is set to anyway, but only if the "core_pattern" kernel sysctl is set to
either a pipe handler or a fully qualified path. (For more details either a pipe handler or a fully qualified path. (For more
on this limitation, see CVE-2006-2451.) This mode is appropriate details on this limitation, see CVE-2006-2451.) This mode is
when administrators are attempting to debug problems in a normal appropriate when administrators are attempting to debug
environment, and either have a core dump pipe handler that knows problems in a normal environment, and either have a core dump
to treat privileged core dumps with care, or specific directory pipe handler that knows to treat privileged core dumps with
defined for catching core dumps. If a core dump happens without care, or specific directory defined for catching core dumps.
a pipe handler or fully qualifid path, a message will be emitted If a core dump happens without a pipe handler or fully
to syslog warning about the lack of a correct setting. qualified path, a message will be emitted to syslog warning
about the lack of a correct setting.
= ========== ===============================================================
==============================================================
super-max & super-nr: super-max & super-nr
--------------------
These numbers control the maximum number of superblocks, and These numbers control the maximum number of superblocks, and
thus the maximum number of mounted filesystems the kernel thus the maximum number of mounted filesystems the kernel
@ -299,33 +310,33 @@ can have. You only need to increase super-max if you need to
mount more filesystems than the current value in super-max mount more filesystems than the current value in super-max
allows you to. allows you to.
==============================================================
aio-nr & aio-max-nr: aio-nr & aio-max-nr
-------------------
aio-nr shows the current system-wide number of asynchronous io aio-nr shows the current system-wide number of asynchronous io
requests. aio-max-nr allows you to change the maximum value requests. aio-max-nr allows you to change the maximum value
aio-nr can grow to. aio-nr can grow to.
==============================================================
mount-max: mount-max
---------
This denotes the maximum number of mounts that may exist This denotes the maximum number of mounts that may exist
in a mount namespace. in a mount namespace.
==============================================================
2. /proc/sys/fs/binfmt_misc 2. /proc/sys/fs/binfmt_misc
---------------------------------------------------------- ===========================
Documentation for the files in /proc/sys/fs/binfmt_misc is Documentation for the files in /proc/sys/fs/binfmt_misc is
in Documentation/admin-guide/binfmt-misc.rst. in Documentation/admin-guide/binfmt-misc.rst.
3. /proc/sys/fs/mqueue - POSIX message queues filesystem 3. /proc/sys/fs/mqueue - POSIX message queues filesystem
---------------------------------------------------------- ========================================================
The "mqueue" filesystem provides the necessary kernel features to enable the The "mqueue" filesystem provides the necessary kernel features to enable the
creation of a user space library that implements the POSIX message queues creation of a user space library that implements the POSIX message queues
@ -356,7 +367,7 @@ the default message size value if attr parameter of mq_open(2) is NULL. If it
exceed msgsize_max, the default value is initialized msgsize_max. exceed msgsize_max, the default value is initialized msgsize_max.
4. /proc/sys/fs/epoll - Configuration options for the epoll interface 4. /proc/sys/fs/epoll - Configuration options for the epoll interface
-------------------------------------------------------- =====================================================================
This directory contains configuration options for the epoll(7) interface. This directory contains configuration options for the epoll(7) interface.
@ -371,4 +382,3 @@ Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
on a 64bit one. on a 64bit one.
The current default value for max_user_watches is the 1/32 of the available The current default value for max_user_watches is the 1/32 of the available
low memory, divided for the "watch" cost in bytes. low memory, divided for the "watch" cost in bytes.

36
Documentation/sysctl/README → Documentation/sysctl/index.rst
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@ -1,5 +1,12 @@
Documentation for /proc/sys/ kernel version 2.2.10 :orphan:
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
===========================
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 'Why', I hear you ask, 'would anyone even _want_ documentation
for them sysctl files? If anybody really needs it, it's all in for them sysctl files? If anybody really needs it, it's all in
@ -12,11 +19,12 @@ have the time or knowledge to read the source code.
Furthermore, the programmers who built sysctl have built it to Furthermore, the programmers who built sysctl have built it to
be actually used, not just for the fun of programming it :-) be actually used, not just for the fun of programming it :-)
============================================================== ------------------------------------------------------------------------------
Legal blurb: Legal blurb:
As usual, there are two main things to consider: As usual, there are two main things to consider:
1. you get what you pay for 1. you get what you pay for
2. it's free 2. it's free
@ -35,15 +43,17 @@ stories to: <riel@nl.linux.org>
Rik van Riel. Rik van Riel.
============================================================== --------------------------------------------------------------
Introduction: Introduction
============
Sysctl is a means of configuring certain aspects of the kernel Sysctl is a means of configuring certain aspects of the kernel
at run-time, and the /proc/sys/ directory is there so that you at run-time, and the /proc/sys/ directory is there so that you
don't even need special tools to do it! don't even need special tools to do it!
In fact, there are only four things needed to use these config In fact, there are only four things needed to use these config
facilities: facilities:
- a running Linux system - a running Linux system
- root access - root access
- common sense (this is especially hard to come by these days) - common sense (this is especially hard to come by these days)
@ -54,7 +64,9 @@ several (arch-dependent?) subdirs. Each subdir is mainly about
one part of the kernel, so you can do configuration on a piece one part of the kernel, so you can do configuration on a piece
by piece basis, or just some 'thematic frobbing'. by piece basis, or just some 'thematic frobbing'.
The subdirs are about: This documentation is about:
=============== ===============================================================
abi/ execution domains & personalities abi/ execution domains & personalities
debug/ <empty> debug/ <empty>
dev/ device specific information (eg dev/cdrom/info) dev/ device specific information (eg dev/cdrom/info)
@ -70,7 +82,19 @@ sunrpc/ SUN Remote Procedure Call (NFS)
vm/ memory management tuning vm/ memory management tuning
buffer and cache management buffer and cache management
user/ Per user per user namespace limits user/ Per user per user namespace limits
=============== ===============================================================
These are the subdirs I have on my system. There might be more 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 or other subdirs in another setup. If you see another dir, I'd
really like to hear about it :-) really like to hear about it :-)
.. toctree::
:maxdepth: 1
abi
fs
kernel
net
sunrpc
user
vm

328
Documentation/sysctl/kernel.txt → Documentation/sysctl/kernel.rst
View File

@ -1,10 +1,16 @@
Documentation for /proc/sys/kernel/* kernel version 2.2.10 ===================================
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org> Documentation for /proc/sys/kernel/
(c) 2009, Shen Feng<shen@cn.fujitsu.com> ===================================
For general info and legal blurb, please look in README. kernel version 2.2.10
============================================================== 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 index.rst.
------------------------------------------------------------------------------
This file contains documentation for the sysctl files in This file contains documentation for the sysctl files in
/proc/sys/kernel/ and is valid for Linux kernel version 2.2. /proc/sys/kernel/ and is valid for Linux kernel version 2.2.
@ -101,9 +107,9 @@ show up in /proc/sys/kernel:
- watchdog_thresh - watchdog_thresh
- version - version
==============================================================
acct: acct:
=====
highwater lowwater frequency highwater lowwater frequency
@ -118,18 +124,18 @@ That is, suspend accounting if there left <= 2% free; resume it
if we got >=4%; consider information about amount of free space if we got >=4%; consider information about amount of free space
valid for 30 seconds. valid for 30 seconds.
==============================================================
acpi_video_flags: acpi_video_flags:
=================
flags flags
See Doc*/kernel/power/video.txt, it allows mode of video boot to be See Doc*/kernel/power/video.txt, it allows mode of video boot to be
set during run time. set during run time.
==============================================================
auto_msgmni: auto_msgmni:
============
This variable has no effect and may be removed in future kernel This variable has no effect and may be removed in future kernel
releases. Reading it always returns 0. releases. Reading it always returns 0.
@ -139,9 +145,8 @@ Echoing "1" into this file enabled msgmni automatic recomputing.
Echoing "0" turned it off. auto_msgmni default value was 1. Echoing "0" turned it off. auto_msgmni default value was 1.
==============================================================
bootloader_type: bootloader_type:
================
x86 bootloader identification x86 bootloader identification
@ -156,9 +161,9 @@ the value 340 = 0x154.
See the type_of_loader and ext_loader_type fields in See the type_of_loader and ext_loader_type fields in
Documentation/x86/boot.rst for additional information. Documentation/x86/boot.rst for additional information.
==============================================================
bootloader_version: bootloader_version:
===================
x86 bootloader version x86 bootloader version
@ -168,27 +173,31 @@ file will contain the value 564 = 0x234.
See the type_of_loader and ext_loader_ver fields in See the type_of_loader and ext_loader_ver fields in
Documentation/x86/boot.rst for additional information. Documentation/x86/boot.rst for additional information.
==============================================================
cap_last_cap cap_last_cap:
=============
Highest valid capability of the running kernel. Exports Highest valid capability of the running kernel. Exports
CAP_LAST_CAP from the kernel. CAP_LAST_CAP from the kernel.
==============================================================
core_pattern: core_pattern:
=============
core_pattern is used to specify a core dumpfile pattern name. 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; * 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 certain string patterns (beginning with '%') are substituted with
their actual values. their actual values.
. backward compatibility with core_uses_pid: * backward compatibility with core_uses_pid:
If core_pattern does not include "%p" (default does not) If core_pattern does not include "%p" (default does not)
and core_uses_pid is set, then .PID will be appended to and core_uses_pid is set, then .PID will be appended to
the filename. the filename.
. corename format specifiers:
* corename format specifiers::
%<NUL> '%' is dropped %<NUL> '%' is dropped
%% output one '%' %% output one '%'
%p pid %p pid
@ -205,13 +214,14 @@ core_pattern is used to specify a core dumpfile pattern name.
%e executable filename (may be shortened) %e executable filename (may be shortened)
%E executable path %E executable path
%<OTHER> both are dropped %<OTHER> both are dropped
. If the first character of the pattern is a '|', the kernel will treat
* 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 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. written to the standard input of that program instead of to a file.
==============================================================
core_pipe_limit: core_pipe_limit:
================
This sysctl is only applicable when core_pattern is configured to pipe 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 files to a user space helper (when the first character of
@ -232,9 +242,9 @@ parallel, but that no waiting will take place (i.e. the collecting
process is not guaranteed access to /proc/<crashing pid>/). This process is not guaranteed access to /proc/<crashing pid>/). This
value defaults to 0. value defaults to 0.
==============================================================
core_uses_pid: core_uses_pid:
==============
The default coredump filename is "core". By setting The default coredump filename is "core". By setting
core_uses_pid to 1, the coredump filename becomes core.PID. core_uses_pid to 1, the coredump filename becomes core.PID.
@ -242,9 +252,9 @@ If core_pattern does not include "%p" (default does not)
and core_uses_pid is set, then .PID will be appended to and core_uses_pid is set, then .PID will be appended to
the filename. the filename.
==============================================================
ctrl-alt-del: ctrl-alt-del:
=============
When the value in this file is 0, ctrl-alt-del is trapped and 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. sent to the init(1) program to handle a graceful restart.
@ -252,14 +262,15 @@ When, however, the value is > 0, Linux's reaction to a Vulcan
Nerve Pinch (tm) will be an immediate reboot, without even Nerve Pinch (tm) will be an immediate reboot, without even
syncing its dirty buffers. syncing its dirty buffers.
Note: when a program (like dosemu) has the keyboard in 'raw' Note:
when a program (like dosemu) has the keyboard in 'raw'
mode, the ctrl-alt-del is intercepted by the program before it 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 ever reaches the kernel tty layer, and it's up to the program
to decide what to do with it. to decide what to do with it.
==============================================================
dmesg_restrict: dmesg_restrict:
===============
This toggle indicates whether unprivileged users are prevented This toggle indicates whether unprivileged users are prevented
from using dmesg(8) to view messages from the kernel's log buffer. from using dmesg(8) to view messages from the kernel's log buffer.
@ -270,16 +281,19 @@ dmesg(8).
The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the
default value of dmesg_restrict. default value of dmesg_restrict.
==============================================================
domainname & hostname: domainname & hostname:
======================
These files can be used to set the NIS/YP domainname and the 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 hostname of your box in exactly the same way as the commands
domainname and hostname, i.e.: domainname and hostname, i.e.::
# echo "darkstar" > /proc/sys/kernel/hostname # echo "darkstar" > /proc/sys/kernel/hostname
# echo "mydomain" > /proc/sys/kernel/domainname # echo "mydomain" > /proc/sys/kernel/domainname
has the same effect as
has the same effect as::
# hostname "darkstar" # hostname "darkstar"
# domainname "mydomain" # domainname "mydomain"
@ -290,8 +304,9 @@ Information Service) or YP (Yellow Pages) domainname. These two
domain names are in general different. For a detailed discussion domain names are in general different. For a detailed discussion
see the hostname(1) man page. see the hostname(1) man page.
==============================================================
hardlockup_all_cpu_backtrace: hardlockup_all_cpu_backtrace:
=============================
This value controls the hard lockup detector behavior when a hard This value controls the hard lockup detector behavior when a hard
lockup condition is detected as to whether or not to gather further lockup condition is detected as to whether or not to gather further
@ -301,9 +316,10 @@ will be initiated.
0: do nothing. This is the default behavior. 0: do nothing. This is the default behavior.
1: on detection capture more debug information. 1: on detection capture more debug information.
==============================================================
hardlockup_panic: hardlockup_panic:
=================
This parameter can be used to control whether the kernel panics This parameter can be used to control whether the kernel panics
when a hard lockup is detected. when a hard lockup is detected.
@ -314,16 +330,16 @@ when a hard lockup is detected.
See Documentation/lockup-watchdogs.txt for more information. This can See Documentation/lockup-watchdogs.txt for more information. This can
also be set using the nmi_watchdog kernel parameter. also be set using the nmi_watchdog kernel parameter.
==============================================================
hotplug: hotplug:
========
Path for the hotplug policy agent. Path for the hotplug policy agent.
Default value is "/sbin/hotplug". Default value is "/sbin/hotplug".
==============================================================
hung_task_panic: hung_task_panic:
================
Controls the kernel's behavior when a hung task is detected. Controls the kernel's behavior when a hung task is detected.
This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
@ -332,27 +348,28 @@ This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
1: panic immediately. 1: panic immediately.
==============================================================
hung_task_check_count: hung_task_check_count:
======================
The upper bound on the number of tasks that are checked. The upper bound on the number of tasks that are checked.
This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
==============================================================
hung_task_timeout_secs: hung_task_timeout_secs:
=======================
When a task in D state did not get scheduled When a task in D state did not get scheduled
for more than this value report a warning. for more than this value report a warning.
This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
0: means infinite timeout - no checking done. 0: means infinite timeout - no checking done.
Possible values to set are in range {0..LONG_MAX/HZ}. Possible values to set are in range {0..LONG_MAX/HZ}.
==============================================================
hung_task_check_interval_secs: hung_task_check_interval_secs:
==============================
Hung task check interval. If hung task checking is enabled Hung task check interval. If hung task checking is enabled
(see hung_task_timeout_secs), the check is done every (see hung_task_timeout_secs), the check is done every
@ -362,9 +379,9 @@ This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
0 (default): means use hung_task_timeout_secs as checking interval. 0 (default): means use hung_task_timeout_secs as checking interval.
Possible values to set are in range {0..LONG_MAX/HZ}. Possible values to set are in range {0..LONG_MAX/HZ}.
==============================================================
hung_task_warnings: hung_task_warnings:
===================
The maximum number of warnings to report. During a check interval The maximum number of warnings to report. During a check interval
if a hung task is detected, this value is decreased by 1. if a hung task is detected, this value is decreased by 1.
@ -373,9 +390,9 @@ This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
-1: report an infinite number of warnings. -1: report an infinite number of warnings.
==============================================================
hyperv_record_panic_msg: hyperv_record_panic_msg:
========================
Controls whether the panic kmsg data should be reported to Hyper-V. Controls whether the panic kmsg data should be reported to Hyper-V.
@ -383,9 +400,9 @@ Controls whether the panic kmsg data should be reported to Hyper-V.
1: report the panic kmsg data. This is the default behavior. 1: report the panic kmsg data. This is the default behavior.
==============================================================
kexec_load_disabled: kexec_load_disabled:
====================
A toggle indicating if the kexec_load syscall has been disabled. This A toggle indicating if the kexec_load syscall has been disabled. This
value defaults to 0 (false: kexec_load enabled), but can be set to 1 value defaults to 0 (false: kexec_load enabled), but can be set to 1
@ -395,9 +412,9 @@ loaded before disabling the syscall, allowing a system to set up (and
later use) an image without it being altered. Generally used together later use) an image without it being altered. Generally used together
with the "modules_disabled" sysctl. with the "modules_disabled" sysctl.
==============================================================
kptr_restrict: kptr_restrict:
==============
This toggle indicates whether restrictions are placed on This toggle indicates whether restrictions are placed on
exposing kernel addresses via /proc and other interfaces. exposing kernel addresses via /proc and other interfaces.
@ -420,16 +437,16 @@ values to unprivileged users is a concern.
When kptr_restrict is set to (2), kernel pointers printed using When kptr_restrict is set to (2), kernel pointers printed using
%pK will be replaced with 0's regardless of privileges. %pK will be replaced with 0's regardless of privileges.
==============================================================
l2cr: (PPC only) l2cr: (PPC only)
================
This flag controls the L2 cache of G3 processor boards. If This flag controls the L2 cache of G3 processor boards. If
0, the cache is disabled. Enabled if nonzero. 0, the cache is disabled. Enabled if nonzero.
==============================================================
modules_disabled: modules_disabled:
=================
A toggle value indicating if modules are allowed to be loaded A toggle value indicating if modules are allowed to be loaded
in an otherwise modular kernel. This toggle defaults to off in an otherwise modular kernel. This toggle defaults to off
@ -437,9 +454,9 @@ in an otherwise modular kernel. This toggle defaults to off
neither loaded nor unloaded, and the toggle cannot be set back neither loaded nor unloaded, and the toggle cannot be set back
to false. Generally used with the "kexec_load_disabled" toggle. to false. Generally used with the "kexec_load_disabled" toggle.
==============================================================
msg_next_id, sem_next_id, and shm_next_id: msg_next_id, sem_next_id, and shm_next_id:
==========================================
These three toggles allows to specify desired id for next allocated IPC These three toggles allows to specify desired id for next allocated IPC
object: message, semaphore or shared memory respectively. object: message, semaphore or shared memory respectively.
@ -454,14 +471,15 @@ it's up to userspace, how to handle an object with "wrong" id.
successful IPC object allocation. If an IPC object allocation syscall successful IPC object allocation. If an IPC object allocation syscall
fails, it is undefined if the value remains unmodified or is reset to -1. fails, it is undefined if the value remains unmodified or is reset to -1.
==============================================================
nmi_watchdog: nmi_watchdog:
=============
This parameter can be used to control the NMI watchdog This parameter can be used to control the NMI watchdog
(i.e. the hard lockup detector) on x86 systems. (i.e. the hard lockup detector) on x86 systems.
0 - disable the hard lockup detector 0 - disable the hard lockup detector
1 - enable the hard lockup detector 1 - enable the hard lockup detector
The hard lockup detector monitors each CPU for its ability to respond to The hard lockup detector monitors each CPU for its ability to respond to
@ -470,15 +488,15 @@ that are programmed to generate Non-Maskable Interrupts (NMIs) periodically
while a CPU is busy. Hence, the alternative name 'NMI watchdog'. 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 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 in a KVM virtual machine. This default can be overridden by adding::
nmi_watchdog=1 nmi_watchdog=1
to the guest kernel command line (see Documentation/admin-guide/kernel-parameters.rst). to the guest kernel command line (see Documentation/admin-guide/kernel-parameters.rst).
==============================================================
numa_balancing numa_balancing:
===============
Enables/disables automatic page fault based NUMA memory Enables/disables automatic page fault based NUMA memory
balancing. Memory is moved automatically to nodes balancing. Memory is moved automatically to nodes
@ -500,10 +518,9 @@ faults may be controlled by the numa_balancing_scan_period_min_ms,
numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms,
numa_balancing_scan_size_mb, and numa_balancing_settle_count sysctls. numa_balancing_scan_size_mb, and numa_balancing_settle_count sysctls.
============================================================== numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb
===============================================================================================================================
numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms,
numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb
Automatic NUMA balancing scans tasks address space and unmaps pages to Automatic NUMA balancing scans tasks address space and unmaps pages to
detect if pages are properly placed or if the data should be migrated to a detect if pages are properly placed or if the data should be migrated to a
@ -539,9 +556,11 @@ rate for each task.
numa_balancing_scan_size_mb is how many megabytes worth of pages are numa_balancing_scan_size_mb is how many megabytes worth of pages are
scanned for a given scan. scanned for a given scan.
==============================================================
osrelease, ostype & version: osrelease, ostype & version:
============================
::
# cat osrelease # cat osrelease
2.1.88 2.1.88
@ -556,9 +575,9 @@ this is the fifth kernel built from this source base and the
date behind it indicates the time the kernel was built. date behind it indicates the time the kernel was built.
The only way to tune these values is to rebuild the kernel :-) The only way to tune these values is to rebuild the kernel :-)
==============================================================
overflowgid & overflowuid: overflowgid & overflowuid:
==========================
if your architecture did not always support 32-bit UIDs (i.e. arm, 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 i386, m68k, sh, and sparc32), a fixed UID and GID will be returned to
@ -568,17 +587,17 @@ actual UID or GID would exceed 65535.
These sysctls allow you to change the value of the fixed UID and GID. These sysctls allow you to change the value of the fixed UID and GID.
The default is 65534. The default is 65534.
==============================================================
panic: panic:
======
The value in this file represents the number of seconds the kernel The value in this file represents the number of seconds the kernel
waits before rebooting on a panic. When you use the software watchdog, waits before rebooting on a panic. When you use the software watchdog,
the recommended setting is 60. the recommended setting is 60.
==============================================================
panic_on_io_nmi: panic_on_io_nmi:
================
Controls the kernel's behavior when a CPU receives an NMI caused by Controls the kernel's behavior when a CPU receives an NMI caused by
an IO error. an IO error.
@ -591,20 +610,20 @@ an IO error.
servers issue this sort of NMI when the dump button is pushed, servers issue this sort of NMI when the dump button is pushed,
and you can use this option to take a crash dump. and you can use this option to take a crash dump.
==============================================================
panic_on_oops: panic_on_oops:
==============
Controls the kernel's behaviour when an oops or BUG is encountered. Controls the kernel's behaviour when an oops or BUG is encountered.
0: try to continue operation 0: try to continue operation
1: panic immediately. If the `panic' sysctl is also non-zero then the 1: panic immediately. If the `panic` sysctl is also non-zero then the
machine will be rebooted. machine will be rebooted.
==============================================================
panic_on_stackoverflow: panic_on_stackoverflow:
=======================
Controls the kernel's behavior when detecting the overflows of Controls the kernel's behavior when detecting the overflows of
kernel, IRQ and exception stacks except a user stack. kernel, IRQ and exception stacks except a user stack.
@ -614,9 +633,9 @@ This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled.
1: panic immediately. 1: panic immediately.
==============================================================
panic_on_unrecovered_nmi: panic_on_unrecovered_nmi:
=========================
The default Linux behaviour on an NMI of either memory or unknown is The default Linux behaviour on an NMI of either memory or unknown is
to continue operation. For many environments such as scientific to continue operation. For many environments such as scientific
@ -627,9 +646,9 @@ A small number of systems do generate NMI's for bizarre random reasons
such as power management so the default is off. That sysctl works like such as power management so the default is off. That sysctl works like
the existing panic controls already in that directory. the existing panic controls already in that directory.
==============================================================
panic_on_warn: panic_on_warn:
==============
Calls panic() in the WARN() path when set to 1. This is useful to avoid 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(). a kernel rebuild when attempting to kdump at the location of a WARN().
@ -638,25 +657,28 @@ a kernel rebuild when attempting to kdump at the location of a WARN().
1: call panic() after printing out WARN() location. 1: call panic() after printing out WARN() location.
==============================================================
panic_print: panic_print:
============
Bitmask for printing system info when panic happens. User can chose Bitmask for printing system info when panic happens. User can chose
combination of the following bits: combination of the following bits:
bit 0: print all tasks info ===== ========================================
bit 1: print system memory info bit 0 print all tasks info
bit 2: print timer info bit 1 print system memory info
bit 3: print locks info if CONFIG_LOCKDEP is on bit 2 print timer info
bit 4: print ftrace buffer bit 3 print locks info if CONFIG_LOCKDEP is on
bit 4 print ftrace buffer
===== ========================================
So for example to print tasks and memory info on panic, user can::
So for example to print tasks and memory info on panic, user can:
echo 3 > /proc/sys/kernel/panic_print echo 3 > /proc/sys/kernel/panic_print
==============================================================
panic_on_rcu_stall: panic_on_rcu_stall:
===================
When set to 1, calls panic() after RCU stall detection messages. This 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. is useful to define the root cause of RCU stalls using a vmcore.
@ -665,9 +687,9 @@ is useful to define the root cause of RCU stalls using a vmcore.
1: panic() after printing RCU stall messages. 1: panic() after printing RCU stall messages.
==============================================================
perf_cpu_time_max_percent: perf_cpu_time_max_percent:
==========================
Hints to the kernel how much CPU time it should be allowed to Hints to the kernel how much CPU time it should be allowed to
use to handle perf sampling events. If the perf subsystem use to handle perf sampling events. If the perf subsystem
@ -680,10 +702,12 @@ unexpectedly take too long to execute, the NMIs can become
stacked up next to each other so much that nothing else is stacked up next to each other so much that nothing else is
allowed to execute. allowed to execute.
0: disable the mechanism. Do not monitor or correct perf's 0:
disable the mechanism. Do not monitor or correct perf's
sampling rate no matter how CPU time it takes. sampling rate no matter how CPU time it takes.
1-100: attempt to throttle perf's sample rate to this 1-100:
attempt to throttle perf's sample rate to this
percentage of CPU. Note: the kernel calculates an percentage of CPU. Note: the kernel calculates an
"expected" length of each sample event. 100 here means "expected" length of each sample event. 100 here means
100% of that expected length. Even if this is set to 100% of that expected length. Even if this is set to
@ -691,23 +715,30 @@ allowed to execute.
length is exceeded. Set to 0 if you truly do not care length is exceeded. Set to 0 if you truly do not care
how much CPU is consumed. how much CPU is consumed.
==============================================================
perf_event_paranoid: perf_event_paranoid:
====================
Controls use of the performance events system by unprivileged Controls use of the performance events system by unprivileged
users (without CAP_SYS_ADMIN). The default value is 2. users (without CAP_SYS_ADMIN). The default value is 2.
-1: Allow use of (almost) all events by all users === ==================================================================
Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK -1 Allow use of (almost) all events by all users
>=0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
Disallow raw tracepoint access by users without CAP_SYS_ADMIN Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
>=1: Disallow CPU event access by users without CAP_SYS_ADMIN
>=2: Disallow kernel profiling by users without CAP_SYS_ADMIN >=0 Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
Disallow raw tracepoint access by users without CAP_SYS_ADMIN
>=1 Disallow CPU event access by users without CAP_SYS_ADMIN
>=2 Disallow kernel profiling by users without CAP_SYS_ADMIN
=== ==================================================================
==============================================================
perf_event_max_stack: perf_event_max_stack:
=====================
Controls maximum number of stack frames to copy for (attr.sample_type & Controls maximum number of stack frames to copy for (attr.sample_type &
PERF_SAMPLE_CALLCHAIN) configured events, for instance, when using PERF_SAMPLE_CALLCHAIN) configured events, for instance, when using
@ -718,17 +749,17 @@ enabled, otherwise writing to this file will return -EBUSY.
The default value is 127. The default value is 127.
==============================================================
perf_event_mlock_kb: perf_event_mlock_kb:
====================
Control size of per-cpu ring buffer not counted agains mlock limit. Control size of per-cpu ring buffer not counted agains mlock limit.
The default value is 512 + 1 page The default value is 512 + 1 page
==============================================================
perf_event_max_contexts_per_stack: perf_event_max_contexts_per_stack:
==================================
Controls maximum number of stack frame context entries for Controls maximum number of stack frame context entries for
(attr.sample_type & PERF_SAMPLE_CALLCHAIN) configured events, for (attr.sample_type & PERF_SAMPLE_CALLCHAIN) configured events, for
@ -739,25 +770,25 @@ enabled, otherwise writing to this file will return -EBUSY.
The default value is 8. The default value is 8.
==============================================================
pid_max: pid_max:
========
PID allocation wrap value. When the kernel's next PID value PID allocation wrap value. When the kernel's next PID value
reaches this value, it wraps back to a minimum PID value. reaches this value, it wraps back to a minimum PID value.
PIDs of value pid_max or larger are not allocated. PIDs of value pid_max or larger are not allocated.
==============================================================
ns_last_pid: ns_last_pid:
============
The last pid allocated in the current (the one task using this sysctl 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 lives in) pid namespace. When selecting a pid for a next task on fork
kernel tries to allocate a number starting from this one. kernel tries to allocate a number starting from this one.
==============================================================
powersave-nap: (PPC only) powersave-nap: (PPC only)
=========================
If set, Linux-PPC will use the 'nap' mode of powersaving, If set, Linux-PPC will use the 'nap' mode of powersaving,
otherwise the 'doze' mode will be used. otherwise the 'doze' mode will be used.
@ -765,6 +796,7 @@ otherwise the 'doze' mode will be used.
============================================================== ==============================================================
printk: printk:
=======
The four values in printk denote: console_loglevel, The four values in printk denote: console_loglevel,
default_message_loglevel, minimum_console_loglevel and default_message_loglevel, minimum_console_loglevel and
@ -774,25 +806,29 @@ These values influence printk() behavior when printing or
logging error messages. See 'man 2 syslog' for more info on logging error messages. See 'man 2 syslog' for more info on
the different loglevels. the different loglevels.
- console_loglevel: messages with a higher priority than - console_loglevel:
messages with a higher priority than
this will be printed to the console this will be printed to the console
- default_message_loglevel: messages without an explicit priority - default_message_loglevel:
messages without an explicit priority
will be printed with this priority will be printed with this priority
- minimum_console_loglevel: minimum (highest) value to which - minimum_console_loglevel:
minimum (highest) value to which
console_loglevel can be set console_loglevel can be set
- default_console_loglevel: default value for console_loglevel - default_console_loglevel:
default value for console_loglevel
==============================================================
printk_delay: printk_delay:
=============
Delay each printk message in printk_delay milliseconds Delay each printk message in printk_delay milliseconds
Value from 0 - 10000 is allowed. Value from 0 - 10000 is allowed.
==============================================================
printk_ratelimit: printk_ratelimit:
=================
Some warning messages are rate limited. printk_ratelimit specifies Some warning messages are rate limited. printk_ratelimit specifies
the minimum length of time between these messages (in jiffies), by the minimum length of time between these messages (in jiffies), by
@ -800,48 +836,52 @@ default we allow one every 5 seconds.
A value of 0 will disable rate limiting. A value of 0 will disable rate limiting.
==============================================================
printk_ratelimit_burst: printk_ratelimit_burst:
=======================
While long term we enforce one message per printk_ratelimit While long term we enforce one message per printk_ratelimit
seconds, we do allow a burst of messages to pass through. seconds, we do allow a burst of messages to pass through.
printk_ratelimit_burst specifies the number of messages we can printk_ratelimit_burst specifies the number of messages we can
send before ratelimiting kicks in. send before ratelimiting kicks in.
==============================================================
printk_devkmsg: printk_devkmsg:
===============
Control the logging to /dev/kmsg from userspace: Control the logging to /dev/kmsg from userspace:
ratelimit: default, ratelimited ratelimit:
default, ratelimited
on: unlimited logging to /dev/kmsg from userspace on: unlimited logging to /dev/kmsg from userspace
off: logging to /dev/kmsg disabled off: logging to /dev/kmsg disabled
The kernel command line parameter printk.devkmsg= overrides this and is 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 a one-time setting until next reboot: once set, it cannot be changed by
this sysctl interface anymore. this sysctl interface anymore.
==============================================================
randomize_va_space: randomize_va_space:
===================
This option can be used to select the type of process address This option can be used to select the type of process address
space randomization that is used in the system, for architectures space randomization that is used in the system, for architectures
that support this feature. that support this feature.
0 - Turn the process address space randomization off. This is the == ===========================================================================
0 Turn the process address space randomization off. This is the
default for architectures that do not support this feature anyways, default for architectures that do not support this feature anyways,
and kernels that are booted with the "norandmaps" parameter. and kernels that are booted with the "norandmaps" parameter.
1 - Make the addresses of mmap base, stack and VDSO page randomized. 1 Make the addresses of mmap base, stack and VDSO page randomized.
This, among other things, implies that shared libraries will be This, among other things, implies that shared libraries will be
loaded to random addresses. Also for PIE-linked binaries, the loaded to random addresses. Also for PIE-linked binaries, the
location of code start is randomized. This is the default if the location of code start is randomized. This is the default if the
CONFIG_COMPAT_BRK option is enabled. CONFIG_COMPAT_BRK option is enabled.
2 - Additionally enable heap randomization. This is the default if 2 Additionally enable heap randomization. This is the default if
CONFIG_COMPAT_BRK is disabled. CONFIG_COMPAT_BRK is disabled.
There are a few legacy applications out there (such as some ancient There are a few legacy applications out there (such as some ancient
@ -854,18 +894,19 @@ that support this feature.
Systems with ancient and/or broken binaries should be configured Systems with ancient and/or broken binaries should be configured
with CONFIG_COMPAT_BRK enabled, which excludes the heap from process with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
address space randomization. address space randomization.
== ===========================================================================
==============================================================
reboot-cmd: (Sparc only) reboot-cmd: (Sparc only)
========================
??? This seems to be a way to give an argument to the Sparc ??? 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 ROM/Flash boot loader. Maybe to tell it what to do after
rebooting. ??? rebooting. ???
==============================================================
rtsig-max & rtsig-nr: rtsig-max & rtsig-nr:
=====================
The file rtsig-max can be used to tune the maximum number The file rtsig-max can be used to tune the maximum number
of POSIX realtime (queued) signals that can be outstanding of POSIX realtime (queued) signals that can be outstanding
@ -873,9 +914,9 @@ in the system.
rtsig-nr shows the number of RT signals currently queued. rtsig-nr shows the number of RT signals currently queued.
==============================================================
sched_energy_aware: sched_energy_aware:
===================
Enables/disables Energy Aware Scheduling (EAS). EAS starts Enables/disables Energy Aware Scheduling (EAS). EAS starts
automatically on platforms where it can run (that is, automatically on platforms where it can run (that is,
@ -884,17 +925,17 @@ Model available). If your platform happens to meet the
requirements for EAS but you do not want to use it, change requirements for EAS but you do not want to use it, change
this value to 0. this value to 0.
==============================================================
sched_schedstats: sched_schedstats:
=================
Enables/disables scheduler statistics. Enabling this feature Enables/disables scheduler statistics. Enabling this feature
incurs a small amount of overhead in the scheduler but is incurs a small amount of overhead in the scheduler but is
useful for debugging and performance tuning. useful for debugging and performance tuning.
==============================================================
sg-big-buff: sg-big-buff:
============
This file shows the size of the generic SCSI (sg) buffer. This file shows the size of the generic SCSI (sg) buffer.
You can't tune it just yet, but you could change it on You can't tune it just yet, but you could change it on
@ -905,9 +946,9 @@ There shouldn't be any reason to change this value. If
you can come up with one, you probably know what you you can come up with one, you probably know what you
are doing anyway :) are doing anyway :)
==============================================================
shmall: shmall:
=======
This parameter sets the total amount of shared memory pages that This parameter sets the total amount of shared memory pages that
can be used system wide. Hence, SHMALL should always be at least can be used system wide. Hence, SHMALL should always be at least
@ -918,18 +959,18 @@ system, you can run the following command:
# getconf PAGE_SIZE # getconf PAGE_SIZE
==============================================================
shmmax: shmmax:
=======
This value can be used to query and set the run time limit This value can be used to query and set the run time limit
on the maximum shared memory segment size that can be created. on the maximum shared memory segment size that can be created.
Shared memory segments up to 1Gb are now supported in the Shared memory segments up to 1Gb are now supported in the
kernel. This value defaults to SHMMAX. kernel. This value defaults to SHMMAX.
==============================================================
shm_rmid_forced: shm_rmid_forced:
================
Linux lets you set resource limits, including how much memory one Linux lets you set resource limits, including how much memory one
process can consume, via setrlimit(2). Unfortunately, shared memory process can consume, via setrlimit(2). Unfortunately, shared memory
@ -948,28 +989,30 @@ need this.
Note that if you change this from 0 to 1, already created segments Note that if you change this from 0 to 1, already created segments
without users and with a dead originative process will be destroyed. without users and with a dead originative process will be destroyed.
==============================================================
sysctl_writes_strict: sysctl_writes_strict:
=====================
Control how file position affects the behavior of updating sysctl values Control how file position affects the behavior of updating sysctl values
via the /proc/sys interface: via the /proc/sys interface:
-1 - Legacy per-write sysctl value handling, with no printk warnings. == ======================================================================
-1 Legacy per-write sysctl value handling, with no printk warnings.
Each write syscall must fully contain the sysctl value to be Each write syscall must fully contain the sysctl value to be
written, and multiple writes on the same sysctl file descriptor written, and multiple writes on the same sysctl file descriptor
will rewrite the sysctl value, regardless of file position. will rewrite the sysctl value, regardless of file position.
0 - Same behavior as above, but warn about processes that perform writes 0 Same behavior as above, but warn about processes that perform writes
to a sysctl file descriptor when the file position is not 0. to a sysctl file descriptor when the file position is not 0.
1 - (default) Respect file position when writing sysctl strings. Multiple 1 (default) Respect file position when writing sysctl strings. Multiple
writes will append to the sysctl value buffer. Anything past the max writes will append to the sysctl value buffer. Anything past the max
length of the sysctl value buffer will be ignored. Writes to numeric 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 sysctl entries must always be at file position 0 and the value must
be fully contained in the buffer sent in the write syscall. be fully contained in the buffer sent in the write syscall.
== ======================================================================
==============================================================
softlockup_all_cpu_backtrace: softlockup_all_cpu_backtrace:
=============================
This value controls the soft lockup detector thread's behavior This value controls the soft lockup detector thread's behavior
when a soft lockup condition is detected as to whether or not when a soft lockup condition is detected as to whether or not
@ -983,13 +1026,14 @@ NMI.
1: on detection capture more debug information. 1: on detection capture more debug information.
==============================================================
soft_watchdog soft_watchdog:
==============
This parameter can be used to control the soft lockup detector. This parameter can be used to control the soft lockup detector.
0 - disable the soft lockup detector 0 - disable the soft lockup detector
1 - enable the soft lockup detector 1 - enable the soft lockup detector
The soft lockup detector monitors CPUs for threads that are hogging the CPUs The soft lockup detector monitors CPUs for threads that are hogging the CPUs
@ -999,9 +1043,9 @@ interrupts which are needed for the 'watchdog/N' threads to be woken up by
the watchdog timer function, otherwise the NMI watchdog - if enabled - can the watchdog timer function, otherwise the NMI watchdog - if enabled - can
detect a hard lockup condition. detect a hard lockup condition.
==============================================================
stack_erasing stack_erasing:
==============
This parameter can be used to control kernel stack erasing at the end This parameter can be used to control kernel stack erasing at the end
of syscalls for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK. of syscalls for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK.
@ -1015,37 +1059,40 @@ compilation sees a 1% slowdown, other systems and workloads may vary.
1: kernel stack erasing is enabled (default), it is performed before 1: kernel stack erasing is enabled (default), it is performed before
returning to the userspace at the end of syscalls. returning to the userspace at the end of syscalls.
==============================================================
tainted tainted
=======
Non-zero if the kernel has been tainted. Numeric values, which can be 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. ORed together. The letters are seen in "Tainted" line of Oops reports.
1 (P): proprietary module was loaded ====== ===== ==============================================================
2 (F): module was force loaded 1 `(P)` proprietary module was loaded
4 (S): SMP kernel oops on an officially SMP incapable processor 2 `(F)` module was force loaded
8 (R): module was force unloaded 4 `(S)` SMP kernel oops on an officially SMP incapable processor
16 (M): processor reported a Machine Check Exception (MCE) 8 `(R)` module was force unloaded
32 (B): bad page referenced or some unexpected page flags 16 `(M)` processor reported a Machine Check Exception (MCE)
64 (U): taint requested by userspace application 32 `(B)` bad page referenced or some unexpected page flags
128 (D): kernel died recently, i.e. there was an OOPS or BUG 64 `(U)` taint requested by userspace application
256 (A): an ACPI table was overridden by user 128 `(D)` kernel died recently, i.e. there was an OOPS or BUG
512 (W): kernel issued warning 256 `(A)` an ACPI table was overridden by user
1024 (C): staging driver was loaded 512 `(W)` kernel issued warning
2048 (I): workaround for bug in platform firmware applied 1024 `(C)` staging driver was loaded
4096 (O): externally-built ("out-of-tree") module was loaded 2048 `(I)` workaround for bug in platform firmware applied
8192 (E): unsigned module was loaded 4096 `(O)` externally-built ("out-of-tree") module was loaded
16384 (L): soft lockup occurred 8192 `(E)` unsigned module was loaded
32768 (K): kernel has been live patched 16384 `(L)` soft lockup occurred
65536 (X): Auxiliary taint, defined and used by for distros 32768 `(K)` kernel has been live patched
131072 (T): The kernel was built with the struct randomization plugin 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. See Documentation/admin-guide/tainted-kernels.rst for more information.
==============================================================
threads-max threads-max:
============
This value controls the maximum number of threads that can be created This value controls the maximum number of threads that can be created
using fork(). using fork().
@ -1055,8 +1102,10 @@ maximum number of threads is created, the thread structures occupy only
a part (1/8th) of the available RAM pages. a part (1/8th) of the available RAM pages.
The minimum value that can be written to threads-max is 20. The minimum value that can be written to threads-max is 20.
The maximum value that can be written to threads-max is given by the The maximum value that can be written to threads-max is given by the
constant FUTEX_TID_MASK (0x3fffffff). constant FUTEX_TID_MASK (0x3fffffff).
If a value outside of this range is written to threads-max an error If a value outside of this range is written to threads-max an error
EINVAL occurs. EINVAL occurs.
@ -1064,9 +1113,9 @@ The value written is checked against the available RAM pages. If the
thread structures would occupy too much (more than 1/8th) of the thread structures would occupy too much (more than 1/8th) of the
available RAM pages threads-max is reduced accordingly. available RAM pages threads-max is reduced accordingly.
==============================================================
unknown_nmi_panic: unknown_nmi_panic:
==================
The value in this file affects behavior of handling NMI. When the 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 value is non-zero, unknown NMI is trapped and then panic occurs. At
@ -1075,28 +1124,29 @@ that time, kernel debugging information is displayed on console.
NMI switch that most IA32 servers have fires unknown NMI up, for NMI switch that most IA32 servers have fires unknown NMI up, for
example. If a system hangs up, try pressing the NMI switch. example. If a system hangs up, try pressing the NMI switch.
==============================================================
watchdog: watchdog:
=========
This parameter can be used to disable or enable the soft lockup detector 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. _and_ the NMI watchdog (i.e. the hard lockup detector) at the same time.
0 - disable both lockup detectors 0 - disable both lockup detectors
1 - enable both lockup detectors 1 - enable both lockup detectors
The soft lockup detector and the NMI watchdog can also be disabled or The soft lockup detector and the NMI watchdog can also be disabled or
enabled individually, using the soft_watchdog and nmi_watchdog parameters. enabled individually, using the soft_watchdog and nmi_watchdog parameters.
If the watchdog parameter is read, for example by executing If the watchdog parameter is read, for example by executing::
cat /proc/sys/kernel/watchdog cat /proc/sys/kernel/watchdog
the output of this command (0 or 1) shows the logical OR of soft_watchdog the output of this command (0 or 1) shows the logical OR of soft_watchdog
and nmi_watchdog. and nmi_watchdog.
==============================================================
watchdog_cpumask: watchdog_cpumask:
=================
This value can be used to control on which cpus the watchdog may run. 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 The default cpumask is all possible cores, but if NO_HZ_FULL is
@ -1111,13 +1161,13 @@ if a kernel lockup was suspected on those cores.
The argument value is the standard cpulist format for cpumasks, 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 so for example to enable the watchdog on cores 0, 2, 3, and 4 you
might say: might say::
echo 0,2-4 > /proc/sys/kernel/watchdog_cpumask echo 0,2-4 > /proc/sys/kernel/watchdog_cpumask
==============================================================
watchdog_thresh: watchdog_thresh:
================
This value can be used to control the frequency of hrtimer and NMI This value can be used to control the frequency of hrtimer and NMI
events and the soft and hard lockup thresholds. The default threshold events and the soft and hard lockup thresholds. The default threshold
@ -1125,5 +1175,3 @@ is 10 seconds.
The softlockup threshold is (2 * watchdog_thresh). Setting this The softlockup threshold is (2 * watchdog_thresh). Setting this
tunable to zero will disable lockup detection altogether. tunable to zero will disable lockup detection altogether.
==============================================================

101
Documentation/sysctl/net.txt → Documentation/sysctl/net.rst
View File

@ -1,12 +1,25 @@
Documentation for /proc/sys/net/* ================================
(c) 1999 Terrehon Bowden <terrehon@pacbell.net> Documentation for /proc/sys/net/
Bodo Bauer <bb@ricochet.net> ================================
(c) 2000 Jorge Nerin <comandante@zaralinux.com>
(c) 2009 Shen Feng <shen@cn.fujitsu.com>
For general info and legal blurb, please look in README. 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 This file contains the documentation for the sysctl files in
/proc/sys/net /proc/sys/net
@ -17,8 +30,10 @@ see only some of them, depending on your kernel's configuration.
Table : Subdirectories in /proc/sys/net Table : Subdirectories in /proc/sys/net
..............................................................................
========= =================== = ========== ==================
Directory Content Directory Content Directory Content Directory Content
========= =================== = ========== ==================
core General parameter appletalk Appletalk protocol core General parameter appletalk Appletalk protocol
unix Unix domain sockets netrom NET/ROM unix Unix domain sockets netrom NET/ROM
802 E802 protocol ax25 AX25 802 E802 protocol ax25 AX25
@ -27,10 +42,10 @@ Table : Subdirectories in /proc/sys/net
ipx IPX token-ring IBM token ring ipx IPX token-ring IBM token ring
bridge Bridging decnet DEC net bridge Bridging decnet DEC net
ipv6 IP version 6 tipc TIPC ipv6 IP version 6 tipc TIPC
.............................................................................. ========= =================== = ========== ==================
1. /proc/sys/net/core - Network core options 1. /proc/sys/net/core - Network core options
------------------------------------------------------- ============================================
bpf_jit_enable bpf_jit_enable
-------------- --------------
@ -44,6 +59,7 @@ 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 through bpf(2) and passing a verifier in the kernel, a JIT will then
translate these BPF proglets into native CPU instructions. There are translate these BPF proglets into native CPU instructions. There are
two flavors of JITs, the newer eBPF JIT currently supported on: two flavors of JITs, the newer eBPF JIT currently supported on:
- x86_64 - x86_64
- x86_32 - x86_32
- arm64 - arm64
@ -55,6 +71,7 @@ two flavors of JITs, the newer eBPF JIT currently supported on:
- riscv - riscv
And the older cBPF JIT supported on the following archs: And the older cBPF JIT supported on the following archs:
- mips - mips
- ppc - ppc
- sparc - sparc
@ -66,9 +83,10 @@ tcpdump filters, seccomp rules, etc, but not mentioned eBPF
programs loaded through bpf(2). programs loaded through bpf(2).
Values: Values:
0 - disable the JIT (default value)
1 - enable the JIT - 0 - disable the JIT (default value)
2 - enable the JIT and ask the compiler to emit traces on kernel log. - 1 - enable the JIT
- 2 - enable the JIT and ask the compiler to emit traces on kernel log.
bpf_jit_harden bpf_jit_harden
-------------- --------------
@ -76,10 +94,12 @@ bpf_jit_harden
This enables hardening for the BPF JIT compiler. Supported are eBPF This enables hardening for the BPF JIT compiler. Supported are eBPF
JIT backends. Enabling hardening trades off performance, but can JIT backends. Enabling hardening trades off performance, but can
mitigate JIT spraying. mitigate JIT spraying.
Values: Values:
0 - disable JIT hardening (default value)
1 - enable JIT hardening for unprivileged users only - 0 - disable JIT hardening (default value)
2 - enable JIT hardening for all users - 1 - enable JIT hardening for unprivileged users only
- 2 - enable JIT hardening for all users
bpf_jit_kallsyms bpf_jit_kallsyms
---------------- ----------------
@ -89,9 +109,11 @@ addresses to the kernel, meaning they neither show up in traces nor
in /proc/kallsyms. This enables export of these addresses, which can in /proc/kallsyms. This enables export of these addresses, which can
be used for debugging/tracing. If bpf_jit_harden is enabled, this be used for debugging/tracing. If bpf_jit_harden is enabled, this
feature is disabled. feature is disabled.
Values : Values :
0 - disable JIT kallsyms export (default value)
1 - enable JIT kallsyms export for privileged users only - 0 - disable JIT kallsyms export (default value)
- 1 - enable JIT kallsyms export for privileged users only
bpf_jit_limit bpf_jit_limit
------------- -------------
@ -102,7 +124,7 @@ been surpassed. bpf_jit_limit contains the value of the global limit
in bytes. in bytes.
dev_weight dev_weight
-------------- ----------
The maximum number of packets that kernel can handle on a NAPI interrupt, 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 it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
@ -111,7 +133,7 @@ aggregated packet is counted as one packet in this context.
Default: 64 Default: 64
dev_weight_rx_bias dev_weight_rx_bias
-------------- ------------------
RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function 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 of the driver for the per softirq cycle netdev_budget. This parameter influences
@ -120,19 +142,22 @@ 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. 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 (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). on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias).
Default: 1 Default: 1
dev_weight_tx_bias dev_weight_tx_bias
-------------- ------------------
Scales the maximum number of packets that can be processed during a TX softirq cycle. 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 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. 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). Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias).
Default: 1 Default: 1
default_qdisc default_qdisc
-------------- -------------
The default queuing discipline to use for network devices. This allows The default queuing discipline to use for network devices. This allows
overriding the default of pfifo_fast with an alternative. Since the default overriding the default of pfifo_fast with an alternative. Since the default
@ -144,17 +169,21 @@ 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 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 leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
default to noqueue. default to noqueue.
Default: pfifo_fast Default: pfifo_fast
busy_read busy_read
---------------- ---------
Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL) 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. 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. 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, 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 which is the preferred method of enabling. If you need to enable the feature
globally via sysctl, a value of 50 is recommended. globally via sysctl, a value of 50 is recommended.
Will increase power usage. Will increase power usage.
Default: 0 (off) Default: 0 (off)
busy_poll busy_poll
@ -167,7 +196,9 @@ For more than that you probably want to use epoll.
Note that only sockets with SO_BUSY_POLL set will be busy polled, 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 so you want to either selectively set SO_BUSY_POLL on those sockets or set
sysctl.net.busy_read globally. sysctl.net.busy_read globally.
Will increase power usage. Will increase power usage.
Default: 0 (off) Default: 0 (off)
rmem_default rmem_default
@ -185,6 +216,7 @@ tstamp_allow_data
Allow processes to receive tx timestamps looped together with the original Allow processes to receive tx timestamps looped together with the original
packet contents. If disabled, transmit timestamp requests from unprivileged packet contents. If disabled, transmit timestamp requests from unprivileged
processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set. processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
Default: 1 (on) Default: 1 (on)
@ -250,14 +282,19 @@ randomly generated.
Some user space might need to gather its content even if drivers do not Some user space might need to gather its content even if drivers do not
provide ethtool -x support yet. provide ethtool -x support yet.
::
myhost:~# cat /proc/sys/net/core/netdev_rss_key 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) 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. File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
Note: Note:
/proc/sys/net/core/netdev_rss_key contains 52 bytes of key, /proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
but most drivers only use 40 bytes of it. but most drivers only use 40 bytes of it.
::
myhost:~# ethtool -x eth0 myhost:~# ethtool -x eth0
RX flow hash indirection table for eth0 with 8 RX ring(s): RX flow hash indirection table for eth0 with 8 RX ring(s):
0: 0 1 2 3 4 5 6 7 0: 0 1 2 3 4 5 6 7
@ -293,7 +330,7 @@ user space is responsible for creating them if needed.
Default : 0 (for compatibility reasons) Default : 0 (for compatibility reasons)
devconf_inherit_init_net devconf_inherit_init_net
---------------------------- ------------------------
Controls if a new network namespace should inherit all current Controls if a new network namespace should inherit all current
settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By
@ -307,7 +344,7 @@ forced to reset to their default values.
Default : 0 (for compatibility reasons) Default : 0 (for compatibility reasons)
2. /proc/sys/net/unix - Parameters for Unix domain sockets 2. /proc/sys/net/unix - Parameters for Unix domain sockets
------------------------------------------------------- ----------------------------------------------------------
There is only one file in this directory. There is only one file in this directory.
unix_dgram_qlen limits the max number of datagrams queued in Unix domain unix_dgram_qlen limits the max number of datagrams queued in Unix domain
@ -315,13 +352,13 @@ socket's buffer. It will not take effect unless PF_UNIX flag is specified.
3. /proc/sys/net/ipv4 - IPV4 settings 3. /proc/sys/net/ipv4 - IPV4 settings
------------------------------------------------------- -------------------------------------
Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
descriptions of these entries. descriptions of these entries.
4. Appletalk 4. Appletalk
------------------------------------------------------- ------------
The /proc/sys/net/appletalk directory holds the Appletalk configuration data The /proc/sys/net/appletalk directory holds the Appletalk configuration data
when Appletalk is loaded. The configurable parameters are: when Appletalk is loaded. The configurable parameters are:
@ -366,7 +403,7 @@ route flags, and the device the route is using.
5. IPX 5. IPX
------------------------------------------------------- ------
The IPX protocol has no tunable values in proc/sys/net. The IPX protocol has no tunable values in proc/sys/net.
@ -391,14 +428,16 @@ gives the destination network, the router node (or Directly) and the network
address of the router (or Connected) for internal networks. address of the router (or Connected) for internal networks.
6. TIPC 6. TIPC
------------------------------------------------------- -------
tipc_rmem tipc_rmem
---------- ---------
The TIPC protocol now has a tunable for the receive memory, similar to the 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) tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
::
# cat /proc/sys/net/tipc/tipc_rmem # cat /proc/sys/net/tipc/tipc_rmem
4252725 34021800 68043600 4252725 34021800 68043600
# #
@ -409,7 +448,7 @@ 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. preserved in order to be consistent with things like tcp_rmem.
named_timeout named_timeout
-------------- -------------
TIPC name table updates are distributed asynchronously in a cluster, without TIPC name table updates are distributed asynchronously in a cluster, without
any form of transaction handling. This means that different race scenarios are any form of transaction handling. This means that different race scenarios are

13
Documentation/sysctl/sunrpc.txt → Documentation/sysctl/sunrpc.rst
View File

@ -1,9 +1,14 @@
Documentation for /proc/sys/sunrpc/* kernel version 2.2.10 ===================================
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org> Documentation for /proc/sys/sunrpc/
===================================
For general info and legal blurb, please look in README. 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 This file contains the documentation for the sysctl files in
/proc/sys/sunrpc and is valid for Linux kernel version 2.2. /proc/sys/sunrpc and is valid for Linux kernel version 2.2.

32
Documentation/sysctl/user.txt → Documentation/sysctl/user.rst
View File

@ -1,7 +1,12 @@
Documentation for /proc/sys/user/* kernel version 4.9.0 =================================
(c) 2016 Eric Biederman <ebiederm@xmission.com> 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 This file contains the documentation for the sysctl files in
/proc/sys/user. /proc/sys/user.
@ -30,37 +35,44 @@ user namespace does not allow a user to escape their current limits.
Currently, these files are in /proc/sys/user: Currently, these files are in /proc/sys/user:
- max_cgroup_namespaces max_cgroup_namespaces
=====================
The maximum number of cgroup namespaces that any user in the current The maximum number of cgroup namespaces that any user in the current
user namespace may create. user namespace may create.
- max_ipc_namespaces max_ipc_namespaces
==================
The maximum number of ipc namespaces that any user in the current The maximum number of ipc namespaces that any user in the current
user namespace may create. user namespace may create.
- max_mnt_namespaces max_mnt_namespaces
==================
The maximum number of mount namespaces that any user in the current The maximum number of mount namespaces that any user in the current
user namespace may create. user namespace may create.
- max_net_namespaces max_net_namespaces
==================
The maximum number of network namespaces that any user in the The maximum number of network namespaces that any user in the
current user namespace may create. current user namespace may create.
- max_pid_namespaces max_pid_namespaces
==================
The maximum number of pid namespaces that any user in the current The maximum number of pid namespaces that any user in the current
user namespace may create. user namespace may create.
- max_user_namespaces max_user_namespaces
===================
The maximum number of user namespaces that any user in the current The maximum number of user namespaces that any user in the current
user namespace may create. user namespace may create.
- max_uts_namespaces max_uts_namespaces
==================
The maximum number of user namespaces that any user in the current The maximum number of user namespaces that any user in the current
user namespace may create. user namespace may create.

206
Documentation/sysctl/vm.txt → Documentation/sysctl/vm.rst
View File

@ -1,10 +1,16 @@
Documentation for /proc/sys/vm/* kernel version 2.6.29 ===============================
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org> Documentation for /proc/sys/vm/
(c) 2008 Peter W. Morreale <pmorreale@novell.com> ===============================
For general info and legal blurb, please look in README. 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 This file contains the documentation for the sysctl files in
/proc/sys/vm and is valid for Linux kernel version 2.6.29. /proc/sys/vm and is valid for Linux kernel version 2.6.29.
@ -68,9 +74,9 @@ Currently, these files are in /proc/sys/vm:
- watermark_scale_factor - watermark_scale_factor
- zone_reclaim_mode - zone_reclaim_mode
==============================================================
admin_reserve_kbytes admin_reserve_kbytes
====================
The amount of free memory in the system that should be reserved for users The amount of free memory in the system that should be reserved for users
with the capability cap_sys_admin. with the capability cap_sys_admin.
@ -97,25 +103,25 @@ On x86_64 this is about 128MB.
Changing this takes effect whenever an application requests memory. Changing this takes effect whenever an application requests memory.
==============================================================
block_dump block_dump
==========
block_dump enables block I/O debugging when set to a nonzero value. More block_dump enables block I/O debugging when set to a nonzero value. More
information on block I/O debugging is in Documentation/laptops/laptop-mode.rst. information on block I/O debugging is in Documentation/laptops/laptop-mode.rst.
==============================================================
compact_memory compact_memory
==============
Available only when CONFIG_COMPACTION is set. When 1 is written to the file, 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 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 blocks where possible. This can be important for example in the allocation of
huge pages although processes will also directly compact memory as required. huge pages although processes will also directly compact memory as required.
==============================================================
compact_unevictable_allowed compact_unevictable_allowed
===========================
Available only when CONFIG_COMPACTION is set. When set to 1, compaction is 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. allowed to examine the unevictable lru (mlocked pages) for pages to compact.
@ -123,21 +129,22 @@ 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 acceptable trade for large contiguous free memory. Set to 0 to prevent
compaction from moving pages that are unevictable. Default value is 1. compaction from moving pages that are unevictable. Default value is 1.
==============================================================
dirty_background_bytes dirty_background_bytes
======================
Contains the amount of dirty memory at which the background kernel Contains the amount of dirty memory at which the background kernel
flusher threads will start writeback. flusher threads will start writeback.
Note: dirty_background_bytes is the counterpart of dirty_background_ratio. Only 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 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 immediately taken into account to evaluate the dirty memory limits and the
other appears as 0 when read. other appears as 0 when read.
==============================================================
dirty_background_ratio dirty_background_ratio
======================
Contains, as a percentage of total available memory that contains free pages Contains, as a percentage of total available memory that contains free pages
and reclaimable pages, the number of pages at which the background kernel and reclaimable pages, the number of pages at which the background kernel
@ -145,9 +152,9 @@ flusher threads will start writing out dirty data.
The total available memory is not equal to total system memory. The total available memory is not equal to total system memory.
==============================================================
dirty_bytes dirty_bytes
===========
Contains the amount of dirty memory at which a process generating disk writes Contains the amount of dirty memory at which a process generating disk writes
will itself start writeback. will itself start writeback.
@ -161,18 +168,18 @@ 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 value lower than this limit will be ignored and the old configuration will be
retained. retained.
==============================================================
dirty_expire_centisecs dirty_expire_centisecs
======================
This tunable is used to define when dirty data is old enough to be eligible 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 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 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. interval will be written out next time a flusher thread wakes up.
==============================================================
dirty_ratio dirty_ratio
===========
Contains, as a percentage of total available memory that contains free pages 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 and reclaimable pages, the number of pages at which a process which is
@ -180,9 +187,9 @@ generating disk writes will itself start writing out dirty data.
The total available memory is not equal to total system memory. The total available memory is not equal to total system memory.
==============================================================
dirtytime_expire_seconds dirtytime_expire_seconds
========================
When a lazytime inode is constantly having its pages dirtied, the inode with 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 an updated timestamp will never get chance to be written out. And, if the
@ -192,34 +199,39 @@ 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. 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. And, it is also used as the interval to wakeup dirtytime_writeback thread.
==============================================================
dirty_writeback_centisecs dirty_writeback_centisecs
=========================
The kernel flusher threads will periodically wake up and write `old' data The kernel flusher threads will periodically wake up and write `old` data
out to disk. This tunable expresses the interval between those wakeups, in out to disk. This tunable expresses the interval between those wakeups, in
100'ths of a second. 100'ths of a second.
Setting this to zero disables periodic writeback altogether. Setting this to zero disables periodic writeback altogether.
==============================================================
drop_caches drop_caches
===========
Writing to this will cause the kernel to drop clean caches, as well as Writing to this will cause the kernel to drop clean caches, as well as
reclaimable slab objects like dentries and inodes. Once dropped, their reclaimable slab objects like dentries and inodes. Once dropped, their
memory becomes free. memory becomes free.
To free pagecache: To free pagecache::
echo 1 > /proc/sys/vm/drop_caches echo 1 > /proc/sys/vm/drop_caches
To free reclaimable slab objects (includes dentries and inodes):
To free reclaimable slab objects (includes dentries and inodes)::
echo 2 > /proc/sys/vm/drop_caches echo 2 > /proc/sys/vm/drop_caches
To free slab objects and pagecache:
To free slab objects and pagecache::
echo 3 > /proc/sys/vm/drop_caches echo 3 > /proc/sys/vm/drop_caches
This is a non-destructive operation and will not free any dirty objects. 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 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 `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 number of dirty objects on the system and create more candidates to be
dropped. dropped.
@ -233,16 +245,16 @@ dropped objects, especially if they were under heavy use. Because of this,
use outside of a testing or debugging environment is not recommended. use outside of a testing or debugging environment is not recommended.
You may see informational messages in your kernel log when this file is You may see informational messages in your kernel log when this file is
used: used::
cat (1234): drop_caches: 3 cat (1234): drop_caches: 3
These are informational only. They do not mean that anything is wrong 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. with your system. To disable them, echo 4 (bit 2) into drop_caches.
==============================================================
extfrag_threshold extfrag_threshold
=================
This parameter affects whether the kernel will compact memory or direct This parameter affects whether the kernel will compact memory or direct
reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in
@ -254,9 +266,9 @@ implies that the allocation will succeed as long as watermarks are met.
The kernel will not compact memory in a zone if the The kernel will not compact memory in a zone if the
fragmentation index is <= extfrag_threshold. The default value is 500. fragmentation index is <= extfrag_threshold. The default value is 500.
==============================================================
highmem_is_dirtyable highmem_is_dirtyable
====================
Available only for systems with CONFIG_HIGHMEM enabled (32b systems). Available only for systems with CONFIG_HIGHMEM enabled (32b systems).
@ -274,30 +286,30 @@ 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 only use the low memory and they can fill it up with dirty data without
any throttling. any throttling.
==============================================================
hugetlb_shm_group hugetlb_shm_group
=================
hugetlb_shm_group contains group id that is allowed to create SysV hugetlb_shm_group contains group id that is allowed to create SysV
shared memory segment using hugetlb page. shared memory segment using hugetlb page.
==============================================================
laptop_mode laptop_mode
===========
laptop_mode is a knob that controls "laptop mode". All the things that are laptop_mode is a knob that controls "laptop mode". All the things that are
controlled by this knob are discussed in Documentation/laptops/laptop-mode.rst. controlled by this knob are discussed in Documentation/laptops/laptop-mode.rst.
==============================================================
legacy_va_layout legacy_va_layout
================
If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel
will use the legacy (2.4) layout for all processes. will use the legacy (2.4) layout for all processes.
==============================================================
lowmem_reserve_ratio lowmem_reserve_ratio
====================
For some specialised workloads on highmem machines it is dangerous for For some specialised workloads on highmem machines it is dangerous for
the kernel to allow process memory to be allocated from the "lowmem" the kernel to allow process memory to be allocated from the "lowmem"
@ -308,7 +320,7 @@ And on large highmem machines this lack of reclaimable lowmem memory
can be fatal. can be fatal.
So the Linux page allocator has a mechanism which prevents allocations So the Linux page allocator has a mechanism which prevents allocations
which _could_ use highmem from using too much lowmem. This means that which *could* use highmem from using too much lowmem. This means that
a certain amount of lowmem is defended from the possibility of being a certain amount of lowmem is defended from the possibility of being
captured into pinned user memory. captured into pinned user memory.
@ -316,25 +328,23 @@ captured into pinned user memory.
mechanism will also defend that region from allocations which could use mechanism will also defend that region from allocations which could use
highmem or lowmem). highmem or lowmem).
The `lowmem_reserve_ratio' tunable determines how aggressive the kernel is The `lowmem_reserve_ratio` tunable determines how aggressive the kernel is
in defending these lower zones. in defending these lower zones.
If you have a machine which uses highmem or ISA DMA and your 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 applications are using mlock(), or if you are running with no swap then
you probably should change the lowmem_reserve_ratio setting. you probably should change the lowmem_reserve_ratio setting.
The lowmem_reserve_ratio is an array. You can see them by reading this file. The lowmem_reserve_ratio is an array. You can see them by reading this file::
-
% cat /proc/sys/vm/lowmem_reserve_ratio % cat /proc/sys/vm/lowmem_reserve_ratio
256 256 32 256 256 32
-
But, these values are not used directly. The kernel calculates # of protection 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 pages for each zones from them. These are shown as array of protection pages
in /proc/zoneinfo like followings. (This is an example of x86-64 box). in /proc/zoneinfo like followings. (This is an example of x86-64 box).
Each zone has an array of protection pages like this. Each zone has an array of protection pages like this::
-
Node 0, zone DMA Node 0, zone DMA
pages free 1355 pages free 1355
min 3 min 3
@ -348,7 +358,7 @@ Node 0, zone DMA
pagesets pagesets
cpu: 0 pcp: 0 cpu: 0 pcp: 0
: :
-
These protections are added to score to judge whether this zone should be used These protections are added to score to judge whether this zone should be used
for page allocation or should be reclaimed. for page allocation or should be reclaimed.
@ -359,7 +369,7 @@ not be used because pages_free(1355) is smaller than watermark + protection[2]
normal page requirement. If requirement is DMA zone(index=0), protection[0] normal page requirement. If requirement is DMA zone(index=0), protection[0]
(=0) is used. (=0) is used.
zone[i]'s protection[j] is calculated by following expression. zone[i]'s protection[j] is calculated by following expression::
(i < j): (i < j):
zone[i]->protection[j] zone[i]->protection[j]
@ -371,8 +381,12 @@ zone[i]'s protection[j] is calculated by following expression.
(not necessary, but looks 0) (not necessary, but looks 0)
The default values of lowmem_reserve_ratio[i] are The default values of lowmem_reserve_ratio[i] are
=== ====================================
256 (if zone[i] means DMA or DMA32 zone) 256 (if zone[i] means DMA or DMA32 zone)
32 (others). 32 (others)
=== ====================================
As above expression, they are reciprocal number of ratio. As above expression, they are reciprocal number of ratio.
256 means 1/256. # of protection pages becomes about "0.39%" of total managed 256 means 1/256. # of protection pages becomes about "0.39%" of total managed
pages of higher zones on the node. pages of higher zones on the node.
@ -381,9 +395,9 @@ 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 The minimum value is 1 (1/1 -> 100%). The value less than 1 completely
disables protection of the pages. disables protection of the pages.
==============================================================
max_map_count: max_map_count:
==============
This file contains the maximum number of memory map areas a process 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 may have. Memory map areas are used as a side-effect of calling
@ -396,9 +410,9 @@ e.g., up to one or two maps per allocation.
The default value is 65536. The default value is 65536.
=============================================================
memory_failure_early_kill: memory_failure_early_kill:
==========================
Control how to kill processes when uncorrected memory error (typically Control how to kill processes when uncorrected memory error (typically
a 2bit error in a memory module) is detected in the background by hardware a 2bit error in a memory module) is detected in the background by hardware
@ -424,9 +438,9 @@ check handling and depends on the hardware capabilities.
Applications can override this setting individually with the PR_MCE_KILL prctl Applications can override this setting individually with the PR_MCE_KILL prctl
==============================================================
memory_failure_recovery memory_failure_recovery
=======================
Enable memory failure recovery (when supported by the platform) Enable memory failure recovery (when supported by the platform)
@ -434,9 +448,9 @@ Enable memory failure recovery (when supported by the platform)
0: Always panic on a memory failure. 0: Always panic on a memory failure.
==============================================================
min_free_kbytes: min_free_kbytes
===============
This is used to force the Linux VM to keep a minimum number This is used to force the Linux VM to keep a minimum number
of kilobytes free. The VM uses this number to compute a of kilobytes free. The VM uses this number to compute a
@ -450,9 +464,9 @@ become subtly broken, and prone to deadlock under high loads.
Setting this too high will OOM your machine instantly. Setting this too high will OOM your machine instantly.
=============================================================
min_slab_ratio: min_slab_ratio
==============
This is available only on NUMA kernels. This is available only on NUMA kernels.
@ -468,9 +482,9 @@ Note that slab reclaim is triggered in a per zone / node fashion.
The process of reclaiming slab memory is currently not node specific The process of reclaiming slab memory is currently not node specific
and may not be fast. and may not be fast.
=============================================================
min_unmapped_ratio: min_unmapped_ratio
==================
This is available only on NUMA kernels. This is available only on NUMA kernels.
@ -485,9 +499,9 @@ files and similar are considered.
The default is 1 percent. The default is 1 percent.
==============================================================
mmap_min_addr mmap_min_addr
=============
This file indicates the amount of address space which a user process will This file indicates the amount of address space which a user process will
be restricted from mmapping. Since kernel null dereference bugs could be restricted from mmapping. Since kernel null dereference bugs could
@ -498,9 +512,9 @@ security module. Setting this value to something like 64k will allow the
vast majority of applications to work correctly and provide defense in depth vast majority of applications to work correctly and provide defense in depth
against future potential kernel bugs. against future potential kernel bugs.
==============================================================
mmap_rnd_bits: mmap_rnd_bits
=============
This value can be used to select the number of bits to use to 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 determine the random offset to the base address of vma regions
@ -511,9 +525,9 @@ by the architecture's minimum and maximum supported values.
This value can be changed after boot using the This value can be changed after boot using the
/proc/sys/vm/mmap_rnd_bits tunable /proc/sys/vm/mmap_rnd_bits tunable
==============================================================
mmap_rnd_compat_bits: mmap_rnd_compat_bits
====================
This value can be used to select the number of bits to use to 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 determine the random offset to the base address of vma regions
@ -525,35 +539,35 @@ architecture's minimum and maximum supported values.
This value can be changed after boot using the This value can be changed after boot using the
/proc/sys/vm/mmap_rnd_compat_bits tunable /proc/sys/vm/mmap_rnd_compat_bits tunable
==============================================================
nr_hugepages nr_hugepages
============
Change the minimum size of the hugepage pool. Change the minimum size of the hugepage pool.
See Documentation/admin-guide/mm/hugetlbpage.rst See Documentation/admin-guide/mm/hugetlbpage.rst
==============================================================
nr_hugepages_mempolicy nr_hugepages_mempolicy
======================
Change the size of the hugepage pool at run-time on a specific Change the size of the hugepage pool at run-time on a specific
set of NUMA nodes. set of NUMA nodes.
See Documentation/admin-guide/mm/hugetlbpage.rst See Documentation/admin-guide/mm/hugetlbpage.rst
==============================================================
nr_overcommit_hugepages nr_overcommit_hugepages
=======================
Change the maximum size of the hugepage pool. The maximum is Change the maximum size of the hugepage pool. The maximum is
nr_hugepages + nr_overcommit_hugepages. nr_hugepages + nr_overcommit_hugepages.
See Documentation/admin-guide/mm/hugetlbpage.rst See Documentation/admin-guide/mm/hugetlbpage.rst
==============================================================
nr_trim_pages nr_trim_pages
=============
This is available only on NOMMU kernels. This is available only on NOMMU kernels.
@ -568,14 +582,15 @@ The default value is 1.
See Documentation/nommu-mmap.txt for more information. See Documentation/nommu-mmap.txt for more information.
==============================================================
numa_zonelist_order numa_zonelist_order
===================
This sysctl is only for NUMA and it is deprecated. Anything but This sysctl is only for NUMA and it is deprecated. Anything but
Node order will fail! Node order will fail!
'where the memory is allocated from' is controlled by zonelists. 'where the memory is allocated from' is controlled by zonelists.
(This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation. (This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation.
you may be able to read ZONE_DMA as ZONE_DMA32...) you may be able to read ZONE_DMA as ZONE_DMA32...)
@ -585,7 +600,7 @@ This means that a memory allocation request for GFP_KERNEL will
get memory from ZONE_DMA only when ZONE_NORMAL is not available. get memory from ZONE_DMA only when ZONE_NORMAL is not available.
In NUMA case, you can think of following 2 types of order. 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 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 (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. (B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
@ -616,9 +631,9 @@ order will be selected.
Default order is recommended unless this is causing problems for your Default order is recommended unless this is causing problems for your
system/application. system/application.
==============================================================
oom_dump_tasks oom_dump_tasks
==============
Enables a system-wide task dump (excluding kernel threads) to be produced Enables a system-wide task dump (excluding kernel threads) to be produced
when the kernel performs an OOM-killing and includes such information as when the kernel performs an OOM-killing and includes such information as
@ -638,9 +653,9 @@ OOM killer actually kills a memory-hogging task.
The default value is 1 (enabled). The default value is 1 (enabled).
==============================================================
oom_kill_allocating_task oom_kill_allocating_task
========================
This enables or disables killing the OOM-triggering task in This enables or disables killing the OOM-triggering task in
out-of-memory situations. out-of-memory situations.
@ -659,9 +674,9 @@ is used in oom_kill_allocating_task.
The default value is 0. The default value is 0.
==============================================================
overcommit_kbytes: overcommit_kbytes
=================
When overcommit_memory is set to 2, the committed address space is not 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. permitted to exceed swap plus this amount of physical RAM. See below.
@ -670,9 +685,9 @@ 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 of them may be specified at a time. Setting one disables the other (which
then appears as 0 when read). then appears as 0 when read).
==============================================================
overcommit_memory: overcommit_memory
=================
This value contains a flag that enables memory overcommitment. This value contains a flag that enables memory overcommitment.
@ -695,17 +710,17 @@ The default value is 0.
See Documentation/vm/overcommit-accounting.rst and See Documentation/vm/overcommit-accounting.rst and
mm/util.c::__vm_enough_memory() for more information. mm/util.c::__vm_enough_memory() for more information.
==============================================================
overcommit_ratio: overcommit_ratio
================
When overcommit_memory is set to 2, the committed address When overcommit_memory is set to 2, the committed address
space is not permitted to exceed swap plus this percentage space is not permitted to exceed swap plus this percentage
of physical RAM. See above. of physical RAM. See above.
==============================================================
page-cluster page-cluster
============
page-cluster controls the number of pages up to which consecutive pages 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 are read in from swap in a single attempt. This is the swap counterpart
@ -725,9 +740,9 @@ 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 extra faults and I/O delays for following faults if they would have been part of
that consecutive pages readahead would have brought in. that consecutive pages readahead would have brought in.
=============================================================
panic_on_oom panic_on_oom
============
This enables or disables panic on out-of-memory feature. This enables or disables panic on out-of-memory feature.
@ -747,14 +762,16 @@ above-mentioned. Even oom happens under memory cgroup, the whole
system panics. system panics.
The default value is 0. The default value is 0.
1 and 2 are for failover of clustering. Please select either 1 and 2 are for failover of clustering. Please select either
according to your policy of failover. according to your policy of failover.
panic_on_oom=2+kdump gives you very strong tool to investigate panic_on_oom=2+kdump gives you very strong tool to investigate
why oom happens. You can get snapshot. why oom happens. You can get snapshot.
=============================================================
percpu_pagelist_fraction percpu_pagelist_fraction
========================
This is the fraction of pages at most (high mark pcp->high) in each zone that This is the fraction of pages at most (high mark pcp->high) in each zone that
are allocated for each per cpu page list. The min value for this is 8. It are allocated for each per cpu page list. The min value for this is 8. It
@ -770,16 +787,16 @@ The initial value is zero. Kernel does not use this value at boot time to set
the high water marks for each per cpu page list. If the user writes '0' to this the high water marks for each per cpu page list. If the user writes '0' to this
sysctl, it will revert to this default behavior. sysctl, it will revert to this default behavior.
==============================================================
stat_interval stat_interval
=============
The time interval between which vm statistics are updated. The default The time interval between which vm statistics are updated. The default
is 1 second. is 1 second.
==============================================================
stat_refresh stat_refresh
============
Any read or write (by root only) flushes all the per-cpu vm statistics Any read or write (by root only) flushes all the per-cpu vm statistics
into their global totals, for more accurate reports when testing into their global totals, for more accurate reports when testing
@ -790,24 +807,26 @@ 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, (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.) with no ill effects: errors and warnings on these stats are suppressed.)
==============================================================
numa_stat numa_stat
=========
This interface allows runtime configuration of numa statistics. This interface allows runtime configuration of numa statistics.
When page allocation performance becomes a bottleneck and you can tolerate When page allocation performance becomes a bottleneck and you can tolerate
some possible tool breakage and decreased numa counter precision, you can some possible tool breakage and decreased numa counter precision, you can
do: do::
echo 0 > /proc/sys/vm/numa_stat echo 0 > /proc/sys/vm/numa_stat
When page allocation performance is not a bottleneck and you want all When page allocation performance is not a bottleneck and you want all
tooling to work, you can do: tooling to work, you can do::
echo 1 > /proc/sys/vm/numa_stat echo 1 > /proc/sys/vm/numa_stat
==============================================================
swappiness swappiness
==========
This control is used to define how aggressive the kernel will swap This control is used to define how aggressive the kernel will swap
memory pages. Higher values will increase aggressiveness, lower values memory pages. Higher values will increase aggressiveness, lower values
@ -817,9 +836,9 @@ than the high water mark in a zone.
The default value is 60. The default value is 60.
==============================================================
unprivileged_userfaultfd unprivileged_userfaultfd
========================
This flag controls whether unprivileged users can use the userfaultfd This flag controls whether unprivileged users can use the userfaultfd
system calls. Set this to 1 to allow unprivileged users to use the system calls. Set this to 1 to allow unprivileged users to use the
@ -828,9 +847,9 @@ privileged users (with SYS_CAP_PTRACE capability).
The default value is 1. The default value is 1.
==============================================================
- user_reserve_kbytes user_reserve_kbytes
===================
When overcommit_memory is set to 2, "never overcommit" mode, reserve When overcommit_memory is set to 2, "never overcommit" mode, reserve
min(3% of current process size, user_reserve_kbytes) of free memory. min(3% of current process size, user_reserve_kbytes) of free memory.
@ -846,10 +865,9 @@ Any subsequent attempts to execute a command will result in
Changing this takes effect whenever an application requests memory. Changing this takes effect whenever an application requests memory.
==============================================================
vfs_cache_pressure vfs_cache_pressure
------------------ ==================
This percentage value controls the tendency of the kernel to reclaim This percentage value controls the tendency of the kernel to reclaim
the memory which is used for caching of directory and inode objects. the memory which is used for caching of directory and inode objects.
@ -867,9 +885,9 @@ 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 directory and inode objects. With vfs_cache_pressure=1000, it will look for
ten times more freeable objects than there are. ten times more freeable objects than there are.
=============================================================
watermark_boost_factor: watermark_boost_factor
======================
This factor controls the level of reclaim when memory is being fragmented. 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 It defines the percentage of the high watermark of a zone that will be
@ -887,9 +905,9 @@ 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 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. (e.g. 2MB on 64-bit x86). A boost factor of 0 will disable the feature.
=============================================================
watermark_scale_factor: watermark_scale_factor
======================
This factor controls the aggressiveness of kswapd. It defines the This factor controls the aggressiveness of kswapd. It defines the
amount of memory left in a node/system before kswapd is woken up and amount of memory left in a node/system before kswapd is woken up and
@ -905,20 +923,22 @@ that the number of free pages kswapd maintains for latency reasons is
too small for the allocation bursts occurring in the system. This knob too small for the allocation bursts occurring in the system. This knob
can then be used to tune kswapd aggressiveness accordingly. can then be used to tune kswapd aggressiveness accordingly.
==============================================================
zone_reclaim_mode: zone_reclaim_mode
=================
Zone_reclaim_mode allows someone to set more or less aggressive approaches to 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 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 zone reclaim occurs. Allocations will be satisfied from other zones / nodes
in the system. in the system.
This is value ORed together of This is value OR'ed together of
1 = Zone reclaim on = ===================================
2 = Zone reclaim writes dirty pages out 1 Zone reclaim on
4 = Zone reclaim swaps pages 2 Zone reclaim writes dirty pages out
4 Zone reclaim swaps pages
= ===================================
zone_reclaim_mode is disabled by default. For file servers or workloads zone_reclaim_mode is disabled by default. For file servers or workloads
that benefit from having their data cached, zone_reclaim_mode should be that benefit from having their data cached, zone_reclaim_mode should be
@ -942,5 +962,3 @@ of other processes running on other nodes will not be affected.
Allowing regular swap effectively restricts allocations to the local Allowing regular swap effectively restricts allocations to the local
node unless explicitly overridden by memory policies or cpuset node unless explicitly overridden by memory policies or cpuset
configurations. configurations.
============ End of Document =================================

2
Documentation/vm/unevictable-lru.rst
View File

@ -439,7 +439,7 @@ Compacting MLOCKED Pages
The unevictable LRU can be scanned for compactable regions and the default The unevictable LRU can be scanned for compactable regions and the default
behavior is to do so. /proc/sys/vm/compact_unevictable_allowed controls behavior is to do so. /proc/sys/vm/compact_unevictable_allowed controls
this behavior (see Documentation/sysctl/vm.txt). Once scanning of the this behavior (see Documentation/sysctl/vm.rst). Once scanning of the
unevictable LRU is enabled, the work of compaction is mostly handled by unevictable LRU is enabled, the work of compaction is mostly handled by
the page migration code and the same work flow as described in MIGRATING the page migration code and the same work flow as described in MIGRATING
MLOCKED PAGES will apply. MLOCKED PAGES will apply.

2
kernel/panic.c
View File

@ -372,7 +372,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
/** /**
* print_tainted - return a string to represent the kernel taint state. * print_tainted - return a string to represent the kernel taint state.
* *
* For individual taint flag meanings, see Documentation/sysctl/kernel.txt * For individual taint flag meanings, see Documentation/sysctl/kernel.rst
* *
* The string is overwritten by the next call to print_tainted(), * The string is overwritten by the next call to print_tainted(),
* but is always NULL terminated. * but is always NULL terminated.

2
mm/swap.c
View File

@ -8,7 +8,7 @@
/* /*
* This file contains the default values for the operation of the * This file contains the default values for the operation of the
* Linux VM subsystem. Fine-tuning documentation can be found in * Linux VM subsystem. Fine-tuning documentation can be found in
* Documentation/sysctl/vm.txt. * Documentation/sysctl/vm.rst.
* Started 18.12.91 * Started 18.12.91
* Swap aging added 23.2.95, Stephen Tweedie. * Swap aging added 23.2.95, Stephen Tweedie.
* Buffermem limits added 12.3.98, Rik van Riel. * Buffermem limits added 12.3.98, Rik van Riel.