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perf ftrace latency: Update documentation
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Add description of 'perf ftrace latency' subcommand.

Signed-off-by: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>
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Namhyung Kim authored and Arnaldo Carvalho de Melo committed Mar 22, 2022
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Showing 1 changed file with 52 additions and 23 deletions.
75 changes: 52 additions & 23 deletions tools/perf/Documentation/perf-ftrace.txt
Original file line number Diff line number Diff line change
Expand Up @@ -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=::
Expand All @@ -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>
Expand All @@ -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
Expand Down Expand Up @@ -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]

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