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authorRandy Dunlap <rdunlap@infradead.org>2024-10-29 11:03:20 -0700
committerJonathan Corbet <corbet@lwn.net>2024-11-04 11:03:24 -0700
commit32643e10dfdda489b322348465cd7b1b93ff10f3 (patch)
tree92d6c31e96deb7eb7db4e573a19dab673545af14 /Documentation
parent062d98be0e3f6dcf08e40a1101e967b2eb4fb92f (diff)
Documentation: admin: reorganize kernel-parameters intro
Reorganize the introduction to the kernel-parameters file to place related paragraphs together: - move module info together and near the beginning - add a Special Handling section for dashes, underscores, double quotes, cpu lists, and metric (KMG) suffixes. Expand the KMG suffixes to include TPE as well. - add a Kernel Build Options section Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Link: https://lore.kernel.org/r/20241029180320.412629-1-rdunlap@infradead.org
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.rst36
1 files changed, 23 insertions, 13 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index fdea7c26ef80..6247bbc9547c 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -27,6 +27,16 @@ kernel command line (/proc/cmdline) and collects module parameters
when it loads a module, so the kernel command line can be used for
loadable modules too.
+This document may not be entirely up to date and comprehensive. The command
+"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
+module. Loadable modules, after being loaded into the running kernel, also
+reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
+parameters may be changed at runtime by the command
+``echo -n ${value} > /sys/module/${modulename}/parameters/${parm}``.
+
+Special handling
+----------------
+
Hyphens (dashes) and underscores are equivalent in parameter names, so::
log_buf_len=1M print-fatal-signals=1
@@ -39,8 +49,8 @@ Double-quotes can be used to protect spaces in values, e.g.::
param="spaces in here"
-cpu lists:
-----------
+cpu lists
+~~~~~~~~~
Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
@@ -82,12 +92,17 @@ so that "nohz_full=all" is the equivalent of "nohz_full=0-N".
The semantics of "N" and "all" is supported on a level of bitmaps and holds for
all users of bitmap_parselist().
-This document may not be entirely up to date and comprehensive. The command
-"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
-module. Loadable modules, after being loaded into the running kernel, also
-reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
-parameters may be changed at runtime by the command
-``echo -n ${value} > /sys/module/${modulename}/parameters/${parm}``.
+Metric suffixes
+~~~~~~~~~~~~~~~
+
+The [KMG] suffix is commonly described after a number of kernel
+parameter values. 'K', 'M', 'G', 'T', 'P', and 'E' suffixes are allowed.
+These letters represent the _binary_ multipliers 'Kilo', 'Mega', 'Giga',
+'Tera', 'Peta', and 'Exa', equaling 2^10, 2^20, 2^30, 2^40, 2^50, and
+2^60 bytes respectively. Such letter suffixes can also be entirely omitted.
+
+Kernel Build Options
+--------------------
The parameters listed below are only valid if certain kernel build options
were enabled and if respective hardware is present. This list should be kept
@@ -211,10 +226,5 @@ a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/uapi/asm-generic/setup.h as COMMAND_LINE_SIZE.
-Finally, the [KMG] suffix is commonly described after a number of kernel
-parameter values. These 'K', 'M', and 'G' letters represent the _binary_
-multipliers 'Kilo', 'Mega', and 'Giga', equaling 2^10, 2^20, and 2^30
-bytes respectively. Such letter suffixes can also be entirely omitted:
-
.. include:: kernel-parameters.txt
:literal: