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Commit 540b589e authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

tracing: Update the documentation to describe "event-fork" option 



Add documentation to the ftrace.txt file in Documentation to describe the
event-fork option. Also add the missing "display-graph" option now that it
shows up in the trace_options file (from a previous commit).

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent c37775d5

Documentation/trace/ftrace.txt

+24 −10
Original line number Diff line number Diff line
@@ -210,6 +210,11 @@ of ftrace. Here is a list of some of the key files: 
	Note, sched_switch and sched_wake_up will also trace events

	listed in this file.



	To have the PIDs of children of tasks with their PID in this file

	added on fork, enable the "event-fork" option. That option will also

	cause the PIDs of tasks to be removed from this file when the task

	exits.



  set_graph_function:



	Set a "trigger" function where tracing should start
@@ -725,16 +730,14 @@ noraw 
nohex

nobin

noblock

nostacktrace

trace_printk

noftrace_preempt

nobranch

annotate

nouserstacktrace

nosym-userobj

noprintk-msg-only

context-info

latency-format

nolatency-format

sleep-time

graph-time

record-cmd
@@ -742,7 +745,10 @@ overwrite 
nodisable_on_free

irq-info

markers

noevent-fork

function-trace

nodisplay-graph

nostacktrace



To disable one of the options, echo in the option prepended with

"no".
@@ -796,11 +802,6 @@ Here are the available options: 


  block - When set, reading trace_pipe will not block when polled.



  stacktrace - This is one of the options that changes the trace

	       itself. When a trace is recorded, so is the stack

	       of functions. This allows for back traces of

	       trace sites.



  trace_printk - Can disable trace_printk() from writing into the buffer.



  branch - Enable branch tracing with the tracer.
@@ -897,6 +898,10 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6] 
  	    When disabled, the trace_marker will error with EINVAL

	    on write.



  event-fork - When set, tasks with PIDs listed in set_event_pid will have

	       the PIDs of their children added to set_event_pid when those

	       tasks fork. Also, when tasks with PIDs in set_event_pid exit,

	       their PIDs will be removed from the file.



  function-trace - The latency tracers will enable function tracing

  	    if this option is enabled (default it is). When
@@ -904,8 +909,17 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6] 
	    functions. This keeps the overhead of the tracer down

	    when performing latency tests.



 Note: Some tracers have their own options. They only appear

       when the tracer is active.

  display-graph - When set, the latency tracers (irqsoff, wakeup, etc) will

	          use function graph tracing instead of function tracing.



  stacktrace - This is one of the options that changes the trace

	       itself. When a trace is recorded, so is the stack

	       of functions. This allows for back traces of

	       trace sites.



 Note: Some tracers have their own options. They only appear in this

       file when the tracer is active. They always appear in the

       options directory.