tools/perf/Documentation/perf-config.txt - kernel/common - Git at Google

 perf-config(1)
 ==============

 NAME
 ----
 perf-config - Get and set variables in a configuration file.

 SYNOPSIS
 --------
 [verse]
 'perf config' [<file-option>] [section.name[=value] ...]
 or
 'perf config' [<file-option>] -l | --list

 DESCRIPTION
 -----------
 You can manage variables in a configuration file with this command.

 OPTIONS
 -------

 -l::
 --list::
 	Show current config variables, name and value, for all sections.

 --user::
 	For writing and reading options: write to user
 	'$HOME/.perfconfig' file or read it.

 --system::
 	For writing and reading options: write to system-wide
 	'$(sysconfdir)/perfconfig' or read it.

 CONFIGURATION FILE
 ------------------

 The perf configuration file contains many variables to change various
 aspects of each of its tools, including output, disk usage, etc.
 The '$HOME/.perfconfig' file is used to store a per-user configuration.
 The file '$(sysconfdir)/perfconfig' can be used to
 store a system-wide default configuration.

 When reading or writing, the values are read from the system and user
 configuration files by default, and options '--system' and '--user'
 can be used to tell the command to read from or write to only that location.

 Syntax
 ~~~~~~

 The file consist of sections. A section starts with its name
 surrounded by square brackets and continues till the next section
 begins. Each variable must be in a section, and have the form
 'name = value', for example:

 	[section]
 		name1 = value1
 		name2 = value2

 Section names are case sensitive and can contain any characters except
 newline (double quote `"` and backslash have to be escaped as `\"` and `\\`,
 respectively). Section headers can't span multiple lines.

 Example
 ~~~~~~~

 Given a $HOME/.perfconfig like this:

 #
 # This is the config file, and
 # a '#' and ';' character indicates a comment
 #

 	[colors]
 		# Color variables
 		top = red, default
 		medium = green, default
 		normal = lightgray, default
 		selected = white, lightgray
 		jump_arrows = blue, default
 		addr = magenta, default
 		root = white, blue

 	[tui]
 		# Defaults if linked with libslang
 		report = on
 		annotate = on
 		top = on

 	[buildid]
 		# Default, disable using /dev/null
 		dir = ~/.debug

 	[annotate]
 		# Defaults
 		hide_src_code = false
 		use_offset = true
 		jump_arrows = true
 		show_nr_jumps = false

 	[help]
 		# Format can be man, info, web or html
 		format = man
 		autocorrect = 0

 	[ui]
 		show-headers = true

 	[call-graph]
 		# fp (framepointer), dwarf
 		record-mode = fp
 		print-type = graph
 		order = caller
 		sort-key = function

 	[report]
 		# Defaults
 		sort-order = comm,dso,symbol
 		percent-limit = 0
 		queue-size = 0
 		children = true
 		group = true

 You can hide source code of annotate feature setting the config to false with

 	% perf config annotate.hide_src_code=true

 If you want to add or modify several config items, you can do like

 	% perf config ui.show-headers=false kmem.default=slab

 To modify the sort order of report functionality in user config file(i.e. `~/.perfconfig`), do

 	% perf config --user report sort-order=srcline

 To change colors of selected line to other foreground and background colors
 in system config file (i.e. `$(sysconf)/perfconfig`), do

 	% perf config --system colors.selected=yellow,green

 To query the record mode of call graph, do

 	% perf config call-graph.record-mode

 If you want to know multiple config key/value pairs, you can do like

 	% perf config report.queue-size call-graph.order report.children

 To query the config value of sort order of call graph in user config file (i.e. `~/.perfconfig`), do

 	% perf config --user call-graph.sort-order

 To query the config value of buildid directory in system config file (i.e. `$(sysconf)/perfconfig`), do

 	% perf config --system buildid.dir

 Variables
 ~~~~~~~~~

 colors.*::
 	The variables for customizing the colors used in the output for the
 	'report', 'top' and 'annotate' in the TUI. They should specify the
 	foreground and background colors, separated by a comma, for example:

 		medium = green, lightgray

 	If you want to use the color configured for you terminal, just leave it
 	as 'default', for example:

 		medium = default, lightgray

 	Available colors:
 	red, yellow, green, cyan, gray, black, blue,
 	white, default, magenta, lightgray

 	colors.top::
 		'top' means a overhead percentage which is more than 5%.
 		And values of this variable specify percentage colors.
 		Basic key values are foreground-color 'red' and
 		background-color 'default'.
 	colors.medium::
 		'medium' means a overhead percentage which has more than 0.5%.
 		Default values are 'green' and 'default'.
 	colors.normal::
 		'normal' means the rest of overhead percentages
 		except 'top', 'medium', 'selected'.
 		Default values are 'lightgray' and 'default'.
 	colors.selected::
 		This selects the colors for the current entry in a list of entries
 		from sub-commands (top, report, annotate).
 		Default values are 'black' and 'lightgray'.
 	colors.jump_arrows::
 		Colors for jump arrows on assembly code listings
 		such as 'jns', 'jmp', 'jane', etc.
 		Default values are 'blue', 'default'.
 	colors.addr::
 		This selects colors for addresses from 'annotate'.
 		Default values are 'magenta', 'default'.
 	colors.root::
 		Colors for headers in the output of a sub-commands (top, report).
 		Default values are 'white', 'blue'.

 tui.*, gtk.*::
 	Subcommands that can be configured here are 'top', 'report' and 'annotate'.
 	These values are booleans, for example:

 	[tui]
 		top = true

 	will make the TUI be the default for the 'top' subcommand. Those will be
 	available if the required libs were detected at tool build time.

 buildid.*::
 	buildid.dir::
 		Each executable and shared library in modern distributions comes with a
 		content based identifier that, if available, will be inserted in a
 		'perf.data' file header to, at analysis time find what is needed to do
 		symbol resolution, code annotation, etc.

 		The recording tools also stores a hard link or copy in a per-user
 		directory, $HOME/.debug/, of binaries, shared libraries, /proc/kallsyms
 		and /proc/kcore files to be used at analysis time.

 		The buildid.dir variable can be used to either change this directory
 		cache location, or to disable it altogether. If you want to disable it,
 		set buildid.dir to /dev/null. The default is $HOME/.debug

 annotate.*::
 	These options work only for TUI.
 	These are in control of addresses, jump function, source code
 	in lines of assembly code from a specific program.

 	annotate.hide_src_code::
 		If a program which is analyzed has source code,
 		this option lets 'annotate' print a list of assembly code with the source code.
 		For example, let's see a part of a program. There're four lines.
 		If this option is 'true', they can be printed
 		without source code from a program as below.

 		│        push   %rbp
 		│        mov    %rsp,%rbp
 		│        sub    $0x10,%rsp
 		│        mov    (%rdi),%rdx

 		But if this option is 'false', source code of the part
 		can be also printed as below. Default is 'false'.

 		│      struct rb_node *rb_next(const struct rb_node *node)
 		│      {
 		│        push   %rbp
 		│        mov    %rsp,%rbp
 		│        sub    $0x10,%rsp
 		│              struct rb_node *parent;
 		│
 		│              if (RB_EMPTY_NODE(node))
 		│        mov    (%rdi),%rdx
 		│              return n;

         annotate.use_offset::
 		Basing on a first address of a loaded function, offset can be used.
 		Instead of using original addresses of assembly code,
 		addresses subtracted from a base address can be printed.
 		Let's illustrate an example.
 		If a base address is 0XFFFFFFFF81624d50 as below,

 		ffffffff81624d50 <load0>

 		an address on assembly code has a specific absolute address as below

 		ffffffff816250b8:│  mov    0x8(%r14),%rdi

 		but if use_offset is 'true', an address subtracted from a base address is printed.
 		Default is true. This option is only applied to TUI.

 		             368:│  mov    0x8(%r14),%rdi

 	annotate.jump_arrows::
 		There can be jump instruction among assembly code.
 		Depending on a boolean value of jump_arrows,
 		arrows can be printed or not which represent
 		where do the instruction jump into as below.

 		│     ┌──jmp    1333
 		│     │  xchg   %ax,%ax
 		│1330:│  mov    %r15,%r10
 		│1333:└─→cmp    %r15,%r14

 		If jump_arrow is 'false', the arrows isn't printed as below.
 		Default is 'false'.

 		│      ↓ jmp    1333
 		│        xchg   %ax,%ax
 		│1330:   mov    %r15,%r10
 		│1333:   cmp    %r15,%r14

         annotate.show_linenr::
 		When showing source code if this option is 'true',
 		line numbers are printed as below.

 		│1628         if (type & PERF_SAMPLE_IDENTIFIER) {
 		│     ↓ jne    508
 		│1628                 data->id = *array;
 		│1629                 array++;
 		│1630         }

 		However if this option is 'false', they aren't printed as below.
 		Default is 'false'.

 		│             if (type & PERF_SAMPLE_IDENTIFIER) {
 		│     ↓ jne    508
 		│                     data->id = *array;
 		│                     array++;
 		│             }

         annotate.show_nr_jumps::
 		Let's see a part of assembly code.

 		│1382:   movb   $0x1,-0x270(%rbp)

 		If use this, the number of branches jumping to that address can be printed as below.
 		Default is 'false'.

 		│1 1382:   movb   $0x1,-0x270(%rbp)

         annotate.show_total_period::
 		To compare two records on an instruction base, with this option
 		provided, display total number of samples that belong to a line
 		in assembly code. If this option is 'true', total periods are printed
 		instead of percent values as below.

 		  302 │      mov    %eax,%eax

 		But if this option is 'false', percent values for overhead are printed i.e.
 		Default is 'false'.

 		99.93 │      mov    %eax,%eax

 hist.*::
 	hist.percentage::
 		This option control the way to calculate overhead of filtered entries -
 		that means the value of this option is effective only if there's a
 		filter (by comm, dso or symbol name). Suppose a following example:

 		       Overhead  Symbols
 		       ........  .......
 		        33.33%     foo
 		        33.33%     bar
 		        33.33%     baz

 	       This is an original overhead and we'll filter out the first 'foo'
 	       entry. The value of 'relative' would increase the overhead of 'bar'
 	       and 'baz' to 50.00% for each, while 'absolute' would show their
 	       current overhead (33.33%).

 ui.*::
 	ui.show-headers::
 		This option controls display of column headers (like 'Overhead' and 'Symbol')
 		in 'report' and 'top'. If this option is false, they are hidden.
 		This option is only applied to TUI.

 call-graph.*::
 	When sub-commands 'top' and 'report' work with -g/—-children
 	there're options in control of call-graph.

 	call-graph.record-mode::
 		The record-mode can be 'fp' (frame pointer), 'dwarf' and 'lbr'.
 		The value of 'dwarf' is effective only if perf detect needed library
 		(libunwind or a recent version of libdw).
 		'lbr' only work for cpus that support it.

 	call-graph.dump-size::
 		The size of stack to dump in order to do post-unwinding. Default is 8192 (byte).
 		When using dwarf into record-mode, the default size will be used if omitted.

 	call-graph.print-type::
 		The print-types can be graph (graph absolute), fractal (graph relative),
 		flat and folded. This option controls a way to show overhead for each callchain
 		entry. Suppose a following example.

                 Overhead  Symbols
                 ........  .......
                   40.00%  foo
                           |
                           ---foo
                              |
                              |--50.00%--bar
                              |          main
                              |
                               --50.00%--baz
                                         main

 		This output is a 'fractal' format. The 'foo' came from 'bar' and 'baz' exactly
 		half and half so 'fractal' shows 50.00% for each
 		(meaning that it assumes 100% total overhead of 'foo').

 		The 'graph' uses absolute overhead value of 'foo' as total so each of
 		'bar' and 'baz' callchain will have 20.00% of overhead.
 		If 'flat' is used, single column and linear exposure of call chains.
 		'folded' mean call chains are displayed in a line, separated by semicolons.

 	call-graph.order::
 		This option controls print order of callchains. The default is
 		'callee' which means callee is printed at top and then followed by its
 		caller and so on. The 'caller' prints it in reverse order.

 		If this option is not set and report.children or top.children is
 		set to true (or the equivalent command line option is given),
 		the default value of this option is changed to 'caller' for the
 		execution of 'perf report' or 'perf top'. Other commands will
 		still default to 'callee'.

 	call-graph.sort-key::
 		The callchains are merged if they contain same information.
 		The sort-key option determines a way to compare the callchains.
 		A value of 'sort-key' can be 'function' or 'address'.
 		The default is 'function'.

 	call-graph.threshold::
 		When there're many callchains it'd print tons of lines. So perf omits
 		small callchains under a certain overhead (threshold) and this option
 		control the threshold. Default is 0.5 (%). The overhead is calculated
 		by value depends on call-graph.print-type.

 	call-graph.print-limit::
 		This is a maximum number of lines of callchain printed for a single
 		histogram entry. Default is 0 which means no limitation.

 report.*::
 	report.sort_order::
 		Allows changing the default sort order from "comm,dso,symbol" to
 		some other default, for instance "sym,dso" may be more fitting for
 		kernel developers.
 	report.percent-limit::
 		This one is mostly the same as call-graph.threshold but works for
 		histogram entries. Entries having an overhead lower than this
 		percentage will not be printed. Default is '0'. If percent-limit
 		is '10', only entries which have more than 10% of overhead will be
 		printed.

 	report.queue-size::
 		This option sets up the maximum allocation size of the internal
 		event queue for ordering events. Default is 0, meaning no limit.

 	report.children::
 		'Children' means functions called from another function.
 		If this option is true, 'perf report' cumulates callchains of children
 		and show (accumulated) total overhead as well as 'Self' overhead.
 		Please refer to the 'perf report' manual. The default is 'true'.

 	report.group::
 		This option is to show event group information together.
 		Example output with this turned on, notice that there is one column
 		per event in the group, ref-cycles and cycles:

 		# group: {ref-cycles,cycles}
 		# ========
 		#
 		# Samples: 7K of event 'anon group { ref-cycles, cycles }'
 		# Event count (approx.): 6876107743
 		#
 		#         Overhead  Command      Shared Object               Symbol
 		# ................  .......  .................  ...................
 		#
 		    99.84%  99.76%  noploop  noploop            [.] main
 		     0.07%   0.00%  noploop  ld-2.15.so         [.] strcmp
 		     0.03%   0.00%  noploop  [kernel.kallsyms]  [k] timerqueue_del

 top.*::
 	top.children::
 		Same as 'report.children'. So if it is enabled, the output of 'top'
 		command will have 'Children' overhead column as well as 'Self' overhead
 		column by default.
 		The default is 'true'.

 man.*::
 	man.viewer::
 		This option can assign a tool to view manual pages when 'help'
 		subcommand was invoked. Supported tools are 'man', 'woman'
 		(with emacs client) and 'konqueror'. Default is 'man'.

 		New man viewer tool can be also added using 'man.<tool>.cmd'
 		or use different path using 'man.<tool>.path' config option.

 pager.*::
 	pager.<subcommand>::
 		When the subcommand is run on stdio, determine whether it uses
 		pager or not based on this value. Default is 'unspecified'.

 kmem.*::
 	kmem.default::
 		This option decides which allocator is to be analyzed if neither
 		'--slab' nor '--page' option is used. Default is 'slab'.

 record.*::
 	record.build-id::
 		This option can be 'cache', 'no-cache' or 'skip'.
 		'cache' is to post-process data and save/update the binaries into
 		the build-id cache (in ~/.debug). This is the default.
 		But if this option is 'no-cache', it will not update the build-id cache.
 		'skip' skips post-processing and does not update the cache.

 diff.*::
 	diff.order::
 		This option sets the number of columns to sort the result.
 		The default is 0, which means sorting by baseline.
 		Setting it to 1 will sort the result by delta (or other
 		compute method selected).

 	diff.compute::
 		This options sets the method for computing the diff result.
 		Possible values are 'delta', 'delta-abs', 'ratio' and
 		'wdiff'.  Default is 'delta'.

 SEE ALSO
 --------
 linkperf:perf[1]
	perf-config(1)
	==============

	NAME
	----
	perf-config - Get and set variables in a configuration file.

	SYNOPSIS
	--------
	[verse]
	'perf config' [<file-option>] [section.name[=value] ...]
	or
	'perf config' [<file-option>] -l \| --list

	DESCRIPTION
	-----------
	You can manage variables in a configuration file with this command.

	OPTIONS
	-------

	-l::
	--list::
	Show current config variables, name and value, for all sections.

	--user::
	For writing and reading options: write to user
	'$HOME/.perfconfig' file or read it.

	--system::
	For writing and reading options: write to system-wide
	'$(sysconfdir)/perfconfig' or read it.

	CONFIGURATION FILE
	------------------

	The perf configuration file contains many variables to change various
	aspects of each of its tools, including output, disk usage, etc.
	The '$HOME/.perfconfig' file is used to store a per-user configuration.
	The file '$(sysconfdir)/perfconfig' can be used to
	store a system-wide default configuration.

	When reading or writing, the values are read from the system and user
	configuration files by default, and options '--system' and '--user'
	can be used to tell the command to read from or write to only that location.

	Syntax
	~~~~~~

	The file consist of sections. A section starts with its name
	surrounded by square brackets and continues till the next section
	begins. Each variable must be in a section, and have the form
	'name = value', for example:

	[section]
	name1 = value1
	name2 = value2

	Section names are case sensitive and can contain any characters except
	newline (double quote `"` and backslash have to be escaped as `\"` and `\\`,
	respectively). Section headers can't span multiple lines.

	Example
	~~~~~~~

	Given a $HOME/.perfconfig like this:

	#
	# This is the config file, and
	# a '#' and ';' character indicates a comment
	#

	[colors]
	# Color variables
	top = red, default
	medium = green, default
	normal = lightgray, default
	selected = white, lightgray
	jump_arrows = blue, default
	addr = magenta, default
	root = white, blue

	[tui]
	# Defaults if linked with libslang
	report = on
	annotate = on
	top = on

	[buildid]
	# Default, disable using /dev/null
	dir = ~/.debug

	[annotate]
	# Defaults
	hide_src_code = false
	use_offset = true
	jump_arrows = true
	show_nr_jumps = false

	[help]
	# Format can be man, info, web or html
	format = man
	autocorrect = 0

	[ui]
	show-headers = true

	[call-graph]
	# fp (framepointer), dwarf
	record-mode = fp
	print-type = graph
	order = caller
	sort-key = function

	[report]
	# Defaults
	sort-order = comm,dso,symbol
	percent-limit = 0
	queue-size = 0
	children = true
	group = true

	You can hide source code of annotate feature setting the config to false with

	% perf config annotate.hide_src_code=true

	If you want to add or modify several config items, you can do like

	% perf config ui.show-headers=false kmem.default=slab

	To modify the sort order of report functionality in user config file(i.e. `~/.perfconfig`), do

	% perf config --user report sort-order=srcline

	To change colors of selected line to other foreground and background colors
	in system config file (i.e. `$(sysconf)/perfconfig`), do

	% perf config --system colors.selected=yellow,green

	To query the record mode of call graph, do

	% perf config call-graph.record-mode

	If you want to know multiple config key/value pairs, you can do like

	% perf config report.queue-size call-graph.order report.children

	To query the config value of sort order of call graph in user config file (i.e. `~/.perfconfig`), do

	% perf config --user call-graph.sort-order

	To query the config value of buildid directory in system config file (i.e. `$(sysconf)/perfconfig`), do

	% perf config --system buildid.dir

	Variables
	~~~~~~~~~

	colors.*::
	The variables for customizing the colors used in the output for the
	'report', 'top' and 'annotate' in the TUI. They should specify the
	foreground and background colors, separated by a comma, for example:

	medium = green, lightgray

	If you want to use the color configured for you terminal, just leave it
	as 'default', for example:

	medium = default, lightgray

	Available colors:
	red, yellow, green, cyan, gray, black, blue,
	white, default, magenta, lightgray

	colors.top::
	'top' means a overhead percentage which is more than 5%.
	And values of this variable specify percentage colors.
	Basic key values are foreground-color 'red' and
	background-color 'default'.
	colors.medium::
	'medium' means a overhead percentage which has more than 0.5%.
	Default values are 'green' and 'default'.
	colors.normal::
	'normal' means the rest of overhead percentages
	except 'top', 'medium', 'selected'.
	Default values are 'lightgray' and 'default'.
	colors.selected::
	This selects the colors for the current entry in a list of entries
	from sub-commands (top, report, annotate).
	Default values are 'black' and 'lightgray'.
	colors.jump_arrows::
	Colors for jump arrows on assembly code listings
	such as 'jns', 'jmp', 'jane', etc.
	Default values are 'blue', 'default'.
	colors.addr::
	This selects colors for addresses from 'annotate'.
	Default values are 'magenta', 'default'.
	colors.root::
	Colors for headers in the output of a sub-commands (top, report).
	Default values are 'white', 'blue'.

	tui., gtk.::
	Subcommands that can be configured here are 'top', 'report' and 'annotate'.
	These values are booleans, for example:

	[tui]
	top = true

	will make the TUI be the default for the 'top' subcommand. Those will be
	available if the required libs were detected at tool build time.

	buildid.*::
	buildid.dir::
	Each executable and shared library in modern distributions comes with a
	content based identifier that, if available, will be inserted in a
	'perf.data' file header to, at analysis time find what is needed to do
	symbol resolution, code annotation, etc.

	The recording tools also stores a hard link or copy in a per-user
	directory, $HOME/.debug/, of binaries, shared libraries, /proc/kallsyms
	and /proc/kcore files to be used at analysis time.

	The buildid.dir variable can be used to either change this directory
	cache location, or to disable it altogether. If you want to disable it,
	set buildid.dir to /dev/null. The default is $HOME/.debug

	annotate.*::
	These options work only for TUI.
	These are in control of addresses, jump function, source code
	in lines of assembly code from a specific program.

	annotate.hide_src_code::
	If a program which is analyzed has source code,
	this option lets 'annotate' print a list of assembly code with the source code.
	For example, let's see a part of a program. There're four lines.
	If this option is 'true', they can be printed
	without source code from a program as below.

	│ push %rbp
	│ mov %rsp,%rbp
	│ sub $0x10,%rsp
	│ mov (%rdi),%rdx

	But if this option is 'false', source code of the part
	can be also printed as below. Default is 'false'.

	│ struct rb_node rb_next(const struct rb_node node)
	│ {
	│ push %rbp
	│ mov %rsp,%rbp
	│ sub $0x10,%rsp
	│ struct rb_node *parent;
	│
	│ if (RB_EMPTY_NODE(node))
	│ mov (%rdi),%rdx
	│ return n;

	annotate.use_offset::
	Basing on a first address of a loaded function, offset can be used.
	Instead of using original addresses of assembly code,
	addresses subtracted from a base address can be printed.
	Let's illustrate an example.
	If a base address is 0XFFFFFFFF81624d50 as below,

	ffffffff81624d50 <load0>

	an address on assembly code has a specific absolute address as below

	ffffffff816250b8:│ mov 0x8(%r14),%rdi

	but if use_offset is 'true', an address subtracted from a base address is printed.
	Default is true. This option is only applied to TUI.

	368:│ mov 0x8(%r14),%rdi

	annotate.jump_arrows::
	There can be jump instruction among assembly code.
	Depending on a boolean value of jump_arrows,
	arrows can be printed or not which represent
	where do the instruction jump into as below.

	│ ┌──jmp 1333
	│ │ xchg %ax,%ax
	│1330:│ mov %r15,%r10
	│1333:└─→cmp %r15,%r14

	If jump_arrow is 'false', the arrows isn't printed as below.
	Default is 'false'.

	│ ↓ jmp 1333
	│ xchg %ax,%ax
	│1330: mov %r15,%r10
	│1333: cmp %r15,%r14

	annotate.show_linenr::
	When showing source code if this option is 'true',
	line numbers are printed as below.

	│1628 if (type & PERF_SAMPLE_IDENTIFIER) {
	│ ↓ jne 508
	│1628 data->id = *array;
	│1629 array++;
	│1630 }

	However if this option is 'false', they aren't printed as below.
	Default is 'false'.

	│ if (type & PERF_SAMPLE_IDENTIFIER) {
	│ ↓ jne 508
	│ data->id = *array;
	│ array++;
	│ }

	annotate.show_nr_jumps::
	Let's see a part of assembly code.

	│1382: movb $0x1,-0x270(%rbp)

	If use this, the number of branches jumping to that address can be printed as below.
	Default is 'false'.

	│1 1382: movb $0x1,-0x270(%rbp)

	annotate.show_total_period::
	To compare two records on an instruction base, with this option
	provided, display total number of samples that belong to a line
	in assembly code. If this option is 'true', total periods are printed
	instead of percent values as below.

	302 │ mov %eax,%eax

	But if this option is 'false', percent values for overhead are printed i.e.
	Default is 'false'.

	99.93 │ mov %eax,%eax

	hist.*::
	hist.percentage::
	This option control the way to calculate overhead of filtered entries -
	that means the value of this option is effective only if there's a
	filter (by comm, dso or symbol name). Suppose a following example:

	Overhead Symbols
	........ .......
	33.33% foo
	33.33% bar
	33.33% baz

	This is an original overhead and we'll filter out the first 'foo'
	entry. The value of 'relative' would increase the overhead of 'bar'
	and 'baz' to 50.00% for each, while 'absolute' would show their
	current overhead (33.33%).

	ui.*::
	ui.show-headers::
	This option controls display of column headers (like 'Overhead' and 'Symbol')
	in 'report' and 'top'. If this option is false, they are hidden.
	This option is only applied to TUI.

	call-graph.*::
	When sub-commands 'top' and 'report' work with -g/—-children
	there're options in control of call-graph.

	call-graph.record-mode::
	The record-mode can be 'fp' (frame pointer), 'dwarf' and 'lbr'.
	The value of 'dwarf' is effective only if perf detect needed library
	(libunwind or a recent version of libdw).
	'lbr' only work for cpus that support it.

	call-graph.dump-size::
	The size of stack to dump in order to do post-unwinding. Default is 8192 (byte).
	When using dwarf into record-mode, the default size will be used if omitted.

	call-graph.print-type::
	The print-types can be graph (graph absolute), fractal (graph relative),
	flat and folded. This option controls a way to show overhead for each callchain
	entry. Suppose a following example.

	Overhead Symbols
	........ .......
	40.00% foo
	\|
	---foo
	\|
	\|--50.00%--bar
	\| main
	\|
	--50.00%--baz
	main

	This output is a 'fractal' format. The 'foo' came from 'bar' and 'baz' exactly
	half and half so 'fractal' shows 50.00% for each
	(meaning that it assumes 100% total overhead of 'foo').

	The 'graph' uses absolute overhead value of 'foo' as total so each of
	'bar' and 'baz' callchain will have 20.00% of overhead.
	If 'flat' is used, single column and linear exposure of call chains.
	'folded' mean call chains are displayed in a line, separated by semicolons.

	call-graph.order::
	This option controls print order of callchains. The default is
	'callee' which means callee is printed at top and then followed by its
	caller and so on. The 'caller' prints it in reverse order.

	If this option is not set and report.children or top.children is
	set to true (or the equivalent command line option is given),
	the default value of this option is changed to 'caller' for the
	execution of 'perf report' or 'perf top'. Other commands will
	still default to 'callee'.

	call-graph.sort-key::
	The callchains are merged if they contain same information.
	The sort-key option determines a way to compare the callchains.
	A value of 'sort-key' can be 'function' or 'address'.
	The default is 'function'.

	call-graph.threshold::
	When there're many callchains it'd print tons of lines. So perf omits
	small callchains under a certain overhead (threshold) and this option
	control the threshold. Default is 0.5 (%). The overhead is calculated
	by value depends on call-graph.print-type.

	call-graph.print-limit::
	This is a maximum number of lines of callchain printed for a single
	histogram entry. Default is 0 which means no limitation.

	report.*::
	report.sort_order::
	Allows changing the default sort order from "comm,dso,symbol" to
	some other default, for instance "sym,dso" may be more fitting for
	kernel developers.
	report.percent-limit::
	This one is mostly the same as call-graph.threshold but works for
	histogram entries. Entries having an overhead lower than this
	percentage will not be printed. Default is '0'. If percent-limit
	is '10', only entries which have more than 10% of overhead will be
	printed.

	report.queue-size::
	This option sets up the maximum allocation size of the internal
	event queue for ordering events. Default is 0, meaning no limit.

	report.children::
	'Children' means functions called from another function.
	If this option is true, 'perf report' cumulates callchains of children
	and show (accumulated) total overhead as well as 'Self' overhead.
	Please refer to the 'perf report' manual. The default is 'true'.

	report.group::
	This option is to show event group information together.
	Example output with this turned on, notice that there is one column
	per event in the group, ref-cycles and cycles:

	# group: {ref-cycles,cycles}
	# ========
	#
	# Samples: 7K of event 'anon group { ref-cycles, cycles }'
	# Event count (approx.): 6876107743
	#
	# Overhead Command Shared Object Symbol
	# ................ ....... ................. ...................
	#
	99.84% 99.76% noploop noploop [.] main
	0.07% 0.00% noploop ld-2.15.so [.] strcmp
	0.03% 0.00% noploop [kernel.kallsyms] [k] timerqueue_del

	top.*::
	top.children::
	Same as 'report.children'. So if it is enabled, the output of 'top'
	command will have 'Children' overhead column as well as 'Self' overhead
	column by default.
	The default is 'true'.

	man.*::
	man.viewer::
	This option can assign a tool to view manual pages when 'help'
	subcommand was invoked. Supported tools are 'man', 'woman'
	(with emacs client) and 'konqueror'. Default is 'man'.

	New man viewer tool can be also added using 'man.<tool>.cmd'
	or use different path using 'man.<tool>.path' config option.

	pager.*::
	pager.<subcommand>::
	When the subcommand is run on stdio, determine whether it uses
	pager or not based on this value. Default is 'unspecified'.

	kmem.*::
	kmem.default::
	This option decides which allocator is to be analyzed if neither
	'--slab' nor '--page' option is used. Default is 'slab'.

	record.*::
	record.build-id::
	This option can be 'cache', 'no-cache' or 'skip'.
	'cache' is to post-process data and save/update the binaries into
	the build-id cache (in ~/.debug). This is the default.
	But if this option is 'no-cache', it will not update the build-id cache.
	'skip' skips post-processing and does not update the cache.

	diff.*::
	diff.order::
	This option sets the number of columns to sort the result.
	The default is 0, which means sorting by baseline.
	Setting it to 1 will sort the result by delta (or other
	compute method selected).

	diff.compute::
	This options sets the method for computing the diff result.
	Possible values are 'delta', 'delta-abs', 'ratio' and
	'wdiff'. Default is 'delta'.

	SEE ALSO
	--------
	linkperf:perf[1]