diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/events.txt | 90 | ||||
| -rw-r--r-- | Documentation/trace/ftrace.txt | 2 | ||||
| -rw-r--r-- | Documentation/trace/power.txt | 17 |
3 files changed, 108 insertions, 1 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt new file mode 100644 index 0000000..f157d75 --- /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 e362f50..2a82d86 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 0000000..cd805e1 --- /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 |
