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-rw-r--r--Documentation/trace/events.txt90
-rw-r--r--Documentation/trace/ftrace.txt2
-rw-r--r--Documentation/trace/power.txt17
3 files changed, 108 insertions, 1 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
new file mode 100644
index 000000000000..f157d7594ea7
--- /dev/null
+++ b/Documentation/trace/events.txt
@@ -0,0 +1,90 @@
+ Event Tracing
+
+ Documentation written by Theodore Ts'o
+ Updated by Li Zefan
+
+1. Introduction
+===============
+
+Tracepoints (see Documentation/trace/tracepoints.txt) can be used
+without creating custom kernel modules to register probe functions
+using the event tracing infrastructure.
+
+Not all tracepoints can be traced using the event tracing system;
+the kernel developer must provide code snippets which define how the
+tracing information is saved into the tracing buffer, and how the
+tracing information should be printed.
+
+2. Using Event Tracing
+======================
+
+2.1 Via the 'set_event' interface
+---------------------------------
+
+The events which are available for tracing can be found in the file
+/debug/tracing/available_events.
+
+To enable a particular event, such as 'sched_wakeup', simply echo it
+to /debug/tracing/set_event. For example:
+
+ # echo sched_wakeup >> /debug/tracing/set_event
+
+[ Note: '>>' is necessary, otherwise it will firstly disable
+ all the events. ]
+
+To disable an event, echo the event name to the set_event file prefixed
+with an exclamation point:
+
+ # echo '!sched_wakeup' >> /debug/tracing/set_event
+
+To disable all events, echo an empty line to the set_event file:
+
+ # echo > /debug/tracing/set_event
+
+To enable all events, echo '*:*' or '*:' to the set_event file:
+
+ # echo *:* > /debug/tracing/set_event
+
+The events are organized into subsystems, such as ext4, irq, sched,
+etc., and a full event name looks like this: <subsystem>:<event>. The
+subsystem name is optional, but it is displayed in the available_events
+file. All of the events in a subsystem can be specified via the syntax
+"<subsystem>:*"; for example, to enable all irq events, you can use the
+command:
+
+ # echo 'irq:*' > /debug/tracing/set_event
+
+2.2 Via the 'enable' toggle
+---------------------------
+
+The events available are also listed in /debug/tracing/events/ hierarchy
+of directories.
+
+To enable event 'sched_wakeup':
+
+ # echo 1 > /debug/tracing/events/sched/sched_wakeup/enable
+
+To disable it:
+
+ # echo 0 > /debug/tracing/events/sched/sched_wakeup/enable
+
+To enable all events in sched subsystem:
+
+ # echo 1 > /debug/tracing/events/sched/enable
+
+To eanble all events:
+
+ # echo 1 > /debug/tracing/events/enable
+
+When reading one of these enable files, there are four results:
+
+ 0 - all events this file affects are disabled
+ 1 - all events this file affects are enabled
+ X - there is a mixture of events enabled and disabled
+ ? - this file does not affect any event
+
+3. Defining an event-enabled tracepoint
+=======================================
+
+See The example provided in samples/trace_events
+
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index e362f50c496f..2a82d8602944 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -179,7 +179,7 @@ Here is the list of current tracers that may be configured.
Function call tracer to trace all kernel functions.
- "function_graph_tracer"
+ "function_graph"
Similar to the function tracer except that the
function tracer probes the functions on their entry
diff --git a/Documentation/trace/power.txt b/Documentation/trace/power.txt
new file mode 100644
index 000000000000..cd805e16dc27
--- /dev/null
+++ b/Documentation/trace/power.txt
@@ -0,0 +1,17 @@
+The power tracer collects detailed information about C-state and P-state
+transitions, instead of just looking at the high-level "average"
+information.
+
+There is a helper script found in scrips/tracing/power.pl in the kernel
+sources which can be used to parse this information and create a
+Scalable Vector Graphics (SVG) picture from the trace data.
+
+To use this tracer:
+
+ echo 0 > /sys/kernel/debug/tracing/tracing_enabled
+ echo power > /sys/kernel/debug/tracing/current_tracer
+ echo 1 > /sys/kernel/debug/tracing/tracing_enabled
+ sleep 1
+ echo 0 > /sys/kernel/debug/tracing/tracing_enabled
+ cat /sys/kernel/debug/tracing/trace | \
+ perl scripts/tracing/power.pl > out.sv