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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2015-11-03 16:37:15 -0500
committerSteven Rostedt <rostedt@goodmis.org>2015-11-03 16:37:15 -0500
commit627645fdb657dfae5fcf26bbf6a6e1b63751dbc8 (patch)
tree7c8d356aa5ba5d77def07dd5859d848c94172131 /Documentation/trace
parent54ed1444052467044e9e01334ac8123dd6345211 (diff)
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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>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/events.txt18
-rw-r--r--Documentation/trace/ftrace.txt6
2 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 75d25a1d6e42..c010be8c85d7 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -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
=================
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index db18362c14f3..f52f297cb406 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -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