Commit feff0839 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

perf ftrace latency: Update documentation 



Add description of 'perf ftrace latency' subcommand.

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Changbin Du <changbin.du@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20220321234609.90455-2-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 84005bb6

tools/perf/Documentation/perf-ftrace.txt

+52 −23
Original line number Diff line number Diff line
@@ -9,32 +9,24 @@ perf-ftrace - simple wrapper for kernel's ftrace functionality 
SYNOPSIS

--------

[verse]

'perf ftrace' <command>

'perf ftrace' {trace|latency} <command>



DESCRIPTION

-----------

The 'perf ftrace' command is a simple wrapper of kernel's ftrace

functionality.  It only supports single thread tracing currently and

just reads trace_pipe in text and then write it to stdout.

The 'perf ftrace' command provides a collection of subcommands which use

kernel's ftrace infrastructure.



The following options apply to perf ftrace.

  'perf ftrace trace' is a simple wrapper of the ftrace.  It only supports

  single thread tracing currently and just reads trace_pipe in text and then

  write it to stdout.



OPTIONS

-------

  'perf ftrace latency' calculates execution latency of a given function

  (optionally with BPF) and display it as a histogram.



-t::

--tracer=::

	Tracer to use when neither -G nor -F option is not

	specified: function_graph or function.

The following options apply to perf ftrace.



-v::

--verbose::

        Increase the verbosity level.



-F::

--funcs::

        List available functions to trace. It accepts a pattern to

        only list interested functions.

COMMON OPTIONS

--------------



-p::

--pid=::
@@ -43,10 +35,6 @@ OPTIONS 
--tid=::

	Trace on existing thread id (comma separated list).



-D::

--delay::

	Time (ms) to wait before starting tracing after program start.



-a::

--all-cpus::

	Force system-wide collection.  Scripts run without a <command>
@@ -61,6 +49,28 @@ OPTIONS 
	Ranges of CPUs are specified with -: 0-2.

	Default is to trace on all online CPUs.



-v::

--verbose::

        Increase the verbosity level.





OPTIONS for 'perf ftrace trace'

-------------------------------



-t::

--tracer=::

	Tracer to use when neither -G nor -F option is not

	specified: function_graph or function.



-F::

--funcs::

        List available functions to trace. It accepts a pattern to

        only list interested functions.



-D::

--delay::

	Time (ms) to wait before starting tracing after program start.



-m::

--buffer-size::

	Set the size of per-cpu tracing buffer, <size> is expected to
@@ -114,6 +124,25 @@ OPTIONS 
	  thresh=<n>   - Setup trace duration threshold in microseconds.

	  depth=<n>    - Set max depth for function graph tracer to follow.





OPTIONS for 'perf ftrace latency'

---------------------------------



-T::

--trace-funcs=::

	Set the function name to get the histogram.  Unlike perf ftrace trace,

	it only allows single function to calculate the histogram.



-b::

--use-bpf::

	Use BPF to measure function latency instead of using the ftrace (it

	uses function_graph tracer internally).



-n::

--use-nsec::

	Use nano-second instead of micro-second as a base unit of the histogram.





SEE ALSO

--------

linkperf:perf-record[1], linkperf:perf-trace[1]