tracing: Add some documentation about set_event_pid

Update Documentation to include some comments about how to use
set_event_pid.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2015-11-03 16:37:15 -05:00 committed by Steven Rostedt
parent 54ed144405
commit 627645fdb6
2 changed files with 24 additions and 0 deletions

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@ -288,6 +288,24 @@ prev_pid == 0
# cat sched_wakeup/filter
common_pid == 0
5.4 PID filtering
-----------------
The set_event_pid file in the same directory as the top events directory
exists, will filter all events from tracing any task that does not have the
PID listed in the set_event_pid file.
# cd /sys/kernel/debug/tracing
# echo $$ > set_event_pid
# echo 1 > events/enabled
Will only trace events for the current task.
To add more PIDs without losing the PIDs already included, use '>>'.
# echo 123 244 1 >> set_event_pid
6. Event triggers
=================

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@ -204,6 +204,12 @@ of ftrace. Here is a list of some of the key files:
Have the function tracer only trace a single thread.
set_event_pid:
Have the events only trace a task with a PID listed in this file.
Note, sched_switch and sched_wake_up will also trace events
listed in this file.
set_graph_function:
Set a "trigger" function where tracing should start